United States
Environmental Protection
Agency
EPA Science Advisory Board
1400A
Washington, DC
EPA-SAB-EPEC-02-009
June 2002
www.epa.gov/sab
&EIPA
A Framework For Assessing
and Reporting on Ecological
Condition: An SAB Report
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1 he
ic EPA Science Advisory Board (SAB) of the U.S. Environmental Protection Agency is a
body of independent experts who provide advice to the EPA Administrator on scientific and
engineering issues. The SAB was established in its present form by the Congress in 1978.
The SAB's approximately 100 members and more than 300 consultants include scientists,
engineers, and other specialists drawn from a broad range of disciplines-physics, chemistry,
biology, mathematics, engineering, ecology, economics, social sciences, medicine, and other
fields. Members are appointed by the Administrator for two-year terms. The SAB meets in
public session, and its committees and review panels are designed to include a diverse and
technically balanced range of views, as required by the Federal Advisory Committee Act
(FACA).
The SAB's principal mission is to review the quality and relevance of the scientific
information being used to support Agency decisions, review research programs and strategies,
and provide broad strategic advice on scientific and technological matters. In addition, the
SAB occasionally conducts special studies at the request of the Administrator to examine
comprehensive issues, such as anticipating future environmental risks and developing new
approaches to analyze and compare risks to human health and the environment.
Cover photo: The Experimental Lakes Area, a research facility in Ontario, Canada where a number of lakes and
watersheds have been set aside for whole-lake manipulation experiments. Photo by C.Gilmour.
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A Framework for Assessing and Reporting
on Ecological Condition
Terry F. Young and Stephanie Sanzone, Editors
Prepared by the Ecological Reporting Panel
Ecological Processes and Effects Committee
EPA Science Advisory Board
Washington, DC 20460
June 2002
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
- WASHINGTON B.C. 20460
June 28, 2002
OFFICE OF
THE ADMINISTRATOR
SCIENCE ADVISORY BOARD
EPA-SAB-EPEC-02-009
Honorable Christine Todd Whitman
Administrator
U.S. Environmental Protection Agency
1200 Pennsylvania Avenue, NW
Washington, DC 20460
Subject: A Framework for Assessing and Reporting on Ecological Condition: A
Science Advisory Board Report
Dear Governor Whitman:
The Environmental Protection Agency, both in the past and under your leadership, has
played a prominent role in informing the nation about the condition of its environment. In order
to assist you with this effort, the Science Advisory Board (SAB) is pleased to provide you with
the attached report, A Framework for Assessing and Reporting on Ecological Condition. The
purpose of the report is to offer an organizational tool that will assist the Agency systematically
to develop, assemble, and report on information about the health of ecological systems. The
proposed framework also provides a checklist of ecological attributes that should be considered
when designing ecological risk assessments, setting ecological research priorities, and
developing ecological management objectives for a broad array of Agency programs.
Driven in part by the Government Performance and Results Act (GPRA), much attention
recently has been focused on environmental reporting. At the same time, there is a general
desire to shift from reporting on government activities to reporting on the resulting
improvements in human and ecosystem health. Both your November 13, 2001 memo calling for
a "State of the Environment Report" and the SAB's 2000 report, Toward Integrated
Environmental Decision-making, underscore the need for this shift.
From our point of view, better information about ecological condition is a prerequisite
for better decision-making about ecological resources generally and Agency mandates
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specifically. For example, information about an array of ecological characteristics - in addition
to the chemical quality of air, water, and soil—can help the Agency and local groups target the
highest priority problems, rather than targeting those about which the most data have been
collected. This information also can be used by local and state decision-makers to address
environmental problems that affect Agency activities but are outside of its direct purview, such
as land use planning within watersheds. Similarly, information about ecological condition can
help the Agency predict future problems, serving as "leading indicators." The SAB is acutely
aware, however, that assessing ecological system health is scientifically complex and difficult to
accomplish with limited resources.
Reporting on ecological system health is equally complex, and few good examples
currently are available. Although hundreds of relevant ecosystem health indicators exist, little
guidance is available for distilling them into a few, credible summary statements for the public.
As a result, reports generally contain a selection of indicators that may be important, but seem
disjointed even to a casual reader and are not representative of the array of characteristics
necessary to assess ecological health. Another important impediment to good reporting is the
current dearth of ecological condition data. SAB members often have been struck by the lack of
ecological data available outside of a few categories most directly related to the Agency's
mandates. Moreover, in a number of reviews conducted by the SAB's Ecological Processes and
Effects Committee over the past decade, the Committee noted the Agency's lack of a
comprehensive and consistent list of ecological characteristics. This shortcoming has limited the
Agency's ability to achieve its program objectives.
These recurring problems, combined with the challenge of creating useful "report cards,"
provided the impetus for the attached report. A Framework for Assessing and Reporting on
Ecological Condition provides a checklist of essential ecological attributes that can be used as a
guide for designing a system to assess, then report on ecological condition. The list is organized
as a hierarchy that allows the user to judge tradeoffs when all attributes cannot be studied. This
hierarchy also provides a roadmap for synthesizing a large number of indicators into a few,
scientifically defensible categories, each of which sums up an important ecological
characteristic. These categories can then be reported on directly or used as the foundation for
extracting information related to particular environmental management goals such as the
"number of estuaries with healthy, sustainable aquatic communities." Because the framework
derives from the principles of ecology and ecological risk assessment, it provides a rigorous
basis for collecting and reporting information that covers the characteristics that are essential for
understanding and managing ecosystems.
The framework has been road-tested on three Agency programs — a public information
tool related to Clean Water Act implementation, a monitoring and assessment research program,
and an EPA-state environmental reporting program — and a monitoring program of the USD A
Forest Service. Further, the report compares the SAB framework to the suites of environmental
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indicators recently recommended by the National Research Council and The Heinz Center. The
results of these tests indicate that the SAB framework is comprehensive, that it can be used for a
variety of aquatic and terrestrial ecosystem types, and that it can be used as a template for
synthesizing information from different programs both within and outside the Agency.
In sum, the SAB framework provides a checklist of ecological attributes that should be
considered when evaluating the health of ecological systems. It also provides an organizational
scheme for assembling hundreds of individual parameters into a few understandable attributes.
We hope that the SAB framework will foster more systematic collection of ecological
information by the Agency, provide a locus for integrating that information among programs
both within and outside the Agency, and catalyze a trend towards environmental reporting that
addresses the essential attributes of ecological systems.
Ecological systems are complex, and it has proved extremely difficult to answer the
holistic questions that people ask about them - "How healthy is my watershed? Will native
species be here for my children and grandchildren to enjoy?" With this report, we provide a way
to integrate scientific data into the information necessary to answer these questions, and
ultimately to foster improved management and protection of ecological systems. We look
forward to your response to this report, and we would welcome the opportunity to discuss these
issues further with you as the Agency moves forward with a report on the state of the
environment.
Sincerely,
/Signed/ /Signed/
Dr. William H. Glaze, Chair Dr. Terry Young, Chair
EPA Science Advisory Board Ecological Reporting Panel
Ecological Processes and
Effects Committee
EPA Science Advisory Board
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NOTICE
This report has been written as part of the activities of the EPA Science Advisory Board,
a public advisory group providing extramural scientific information and advice to the
Administrator and other officials of the Environmental Protection Agency. The Board is
structured to provide balanced, expert assessment of scientific matters related to problems facing
the Agency. This report has not been reviewed for approval by the Agency and, hence, the
contents of this report do not necessarily represent the views and policies of the Environmental
Protection Agency, nor of other agencies in the Executive Branch of the Federal government, nor
does mention of trade names or commercial products constitute a recommendation for use.
Distribution and Availability: This EPA Science Advisory Board report is provided to the EPA
Administrator, senior Agency management, appropriate program staff, interested members of the
public, and is posted on the SAB website (www.epa.gov/sab). Information on its availability is
also provided in the SAB's monthly newsletter (Happenings at the Science Advisory Board).
Additional copies and further information are available from the SAB Staff [US EPA Science
Advisory Board (1400A), 1200 Pennsylvania Avenue, NW, Washington, DC 20460-0001; 202-
564-4533].
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U.S. Environmental Protection Agency
Science Advisory Board
Ecological Processes and Effects Committee
Ecological Reporting Panel
CHAIR
Dr. Terry F. Young, Environmental Defense, Oakland, CA
Also Member: Executive Committee
SAB MEMBERS
Dr. William J. Adams, Kennecott Utah Copper, Magna, UT
Member: Research Strategies Advisory Committee
Dr. Steven Bartell, Cadmus Group, Inc,. Oak Ridge, TN
Also Member: Research Strategies Advisory Committee
Dr. Kenneth Cummins, Humboldt State University, Arcata, CA
Member: Executive Committee
Dr. Virginia H. Dale, Oak Ridge National Laboratory, Oak Ridge, TN
Dr. Ivan J. Fernandez, University of Maine, Orono, ME
Dr. Cynthia Gilmour, The Academy of Natural Sciences, St. Leonard, MD
Dr. Lawrence L. Master, NatureServe, Boston, MA
Dr. Charles A. Pittinger, SoBran, Inc., Dayton, OH
Dr. William H. Smith, Professor Emeritus, Yale University
Member: Executive Committee
CONSULTANT
Dr. Frieda B. Taub, Professor Emeritus, University of Washington, Seattle, WA
SCIENCE ADVISORY BOARD STAFF
Ms. Stephanie Sanzone, EPA Science Advisory Board, Washington, DC
Ms. Mary Winston, EPA Science Advisory Board, Washington, DC
11
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TABLE OF CONTENTS
EXECUTIVE SUMMARY 1
1. THE NATIONWIDE FOCUS ON BETTER ENVIRONMENTAL REPORTING 20
1.1 A Systematic Framework for EPA 20
1.2 Terminology: Types of Environmental Measures 23
1.3 A Mandate to Report on Environmental Outcomes 26
1.4 Contents of This Document 27
2. CONSTRUCTING A REPORT ON ECOLOGICAL CONDITION 28
2.1 Reporting Architecture 28
2.2 Relationship to Other Reporting Frameworks 32
3. ESSENTIAL ECOLOGICAL ATTRIBUTES 36
3.1 Rationale for the Selected Ecological Attributes 36
3.2 Landscape Condition 39
3.3 Biotic Condition 44
3.4 Chemical and Physical Characteristics (Water, Air, Soil, and Sediment) 51
3.5 Ecological Processes 55
3.6 Hydrology/Geomorphology 60
3.7 Natural Disturbance Regimes 67
4. INDICATORS OF STRESS - THE PARALLEL UNIVERSE 71
4.1 The Role of Stressor Indicators 71
4.2 Rationale for Separating Condition and Stressor Assessments 72
4.3 The Relationship Between Ecological Condition and Stressor Indicators 73
5. APPLYING THE FRAMEWORK 77
5.1 Getting Started 77
5.2 Using the Hierarchical List of Attributes 77
5.3 Creating a Report 80
5.4 Interpreting Indicator Values 81
6. EXAMPLE APPLICATIONS OF THE REPORTING FRAMEWORK 83
6.1 Introduction 83
6.2 EMAP-West 84
6.2.1 Background 84
6.2.2 Application of the SAB Framework 85
6.3 Forest Health Monitoring Program 91
6.3.1 Background 91
in
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6.3.2 Application of the SAB Framework 92
6.4 Index of Watershed Indicators 97
6.4.1 Background 97
6.4.2 Application of the SAB Framework 97
6.5 National Environmental Performance Partnership System (NEPPS) 103
6.5.1 Background 103
6.5.2 Application of the SAB Framework 103
6.6 Conclusions 107
REFERENCES CITED R-l
APPENDIX A. THE HEINZ CENTER INDICATORS PLACED INTO THE
HIERARCHY OF ESSENTIAL ECOLOGICAL INDICATORS A-l
APPENDIX B. THE SAB REPORTING CATEGORIES ORGANIZED BY
LEVEL OF BIOLOGICAL ORGANIZATION AND BY STRUCTURE,
COMPOSITION, AND FUNCTION B-l
APPENDIX C. BIOTIC CONDITION EEA AND OTHER ESTABLISHED
SCHEMES FOR EVALUATING BIOLOGICAL INTEGRITY C-l
APPENDIX D. CONDITION INDICATORS IN THE NEW JERSEY NEPPS
AGREEMENT (FY99-2000) D-l
IV
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EXECUTIVE SUMMARY
INTRODUCTION
A wealth of environmental monitoring information has been developed since the nation
first turned its collective attention to improving environmental quality more than three decades
ago. Yet many scientists, most decision-makers, and nearly all members of the public still have
little understanding of the "health" or integrity of the nation's ecological systems. The
monitoring programs tailored to report on the implementation of environmental laws and
programs - the cleanup of pollutants, the management of public forests and rangelands, and so
forth - may accomplish the intended purpose but do not provide the information required to
assess the integrity of ecological systems in a systematic way across regions.
Recognizing this information gap, much attention has recently been focused on the
development of concise, understandable, yet accurate "environmental report cards" that
summarize the condition of ecological systems. The Environmental Protection Agency has an
important role to play in developing the missing information on the condition of the nation's
ecosystems for use in such reports. Better information about ecological condition also is a
prerequisite for better decision-making within the Agency, on issues ranging from the
development of biocriteria to the formulation of research strategies. In addition, the Agency has
mandates - as part of the Government Performance and Results Act of 1993, for example - to
report more effectively on the state of the nation's environment and the improvements resulting
from Agency programs.
To accomplish these tasks, the Agency would benefit from development of a systematic
framework for assessing and reporting on ecological condition. The framework would: help
assure that the required information is measured systematically by the Agency's programs;
provide a template for assembling information across Agency programs and from other agencies;
and provide an organizing tool for synthesizing large numbers of indicators into a scientifically
defensible, yet understandable, report on ecological condition.
The purpose of this report is to provide the Agency with a sample framework that
may serve as a guide for designing a system to assess, and then report on, ecological
condition at a local, regional, or national scale. The sample framework is intended as an
organizing tool that may help the Agency decide what ecological attributes to measure and
how to aggregate those measurements into an understandable picture of ecological
integrity.
Environmental reporting usually draws upon a range of measures, from those that capture
agency activities to those that provide information about ecological integrity or human health. In
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addition, reports can focus on economic benefits derived from ecosystems (such as flows of
goods and services), or on the condition of human health or ecological resources irrespective of
whether quantifiable economic benefits are produced. In this report, we focus exclusively on
condition measures related to ecological integrity or condition because these are a critical — and
largely missing— link in the information base upon which environmental reporting can be built.
REPORTING ARCHITECTURE
In order to foster consistent and
comprehensive assessment and reporting
on the condition of ecological resources,
the Panel proposes a framework in which
information about generic ecological
characteristics can be logically
assembled, then synthesized into a few,
scientifically defensible categories.
Information from these categories can
then be excerpted to report on a variety
of environmental management goals.
This framework for consolidating
information can be used as part of a
reporting system (Figure ES-1) that
contains the following major elements:
Goals
Objectives
Essential
Ecological
Attributes
Ecological Indicators
(Endpoints)
Measures
(Monitoring Data)
Figure ES-1. Proposed Architecture for
Assessing and Reporting on Ecological
Condition.
Goals and Objectives Ideally,
environmental management programs
begin with a process to develop goals and
objectives that articulate the desired
ecosystem conditions that will result from the program(s). Methods to develop and use goals
and objectives for environmental management have been developed extensively elsewhere and
are not part of this report.
Essential Ecological Attributes. A set of six Essential Ecological Attributes (EEAs),
along with their subdivisions, are presented in Table ES-1 and described in detail in Section 3.
The EEAs and their component categories and subcategories can be used as a checklist to help
design environmental management and assessment programs and as a guide for aggregating and
organizing information. The elements of the table and its hierarchical organization are derived
from a conceptual model of ecological system pattern and process, and incorporate ecological
structure, composition, and function at a variety of scales.
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Ecological Indicators. Ecological indicators (also called ecological endpoints) are
measurable characteristics related to the structure, composition, or functioning of ecological
systems. Multiple indicators may be associated with each subcategory in the EEA hierarchy (see
Table ES-2).
Table ES-1. Essential Ecological Attributes and Reporting Categories
Landscape Condition
• Extent of Ecological System/Habitat Types
• Landscape Composition
• Landscape Pattern and Structure
Biotic Condition
• Ecosystems and Communities
- Community Extent
- Community Composition
- Trophic Structure
- Community Dynamics
- Physical Structure
• Species and Populations
- Population Size
- Genetic Diversity
- Population Structure
- Population Dynamics
- Habitat Suitability
• Organism Condition
- Physiological Status
- Symptoms of Disease or Trauma
- Signs of disease
Chemical and Physical Characteristics
(Water, Air, Soil, and Sediment)
• Nutrient Concentrations
- Nitrogen
- Phosphorus
- Other Nutrients
• Trace Inorganic and Organic Chemicals
- Metals
- Other Trace Elements
- Organic Compounds
• Other Chemical Parameters
-pH
- Dissolved Oxygen
- Salinity
- Organic Matter
-Other
• Physical Parameters
Ecological Processes
• Energy Flow
- Primary Production
- Net Ecosystem Production
- Growth Efficiency
• Material Flow
- Organic Carbon Cycling
- Nitrogen and Phosphorus Cycling
- Other Nutrient Cycling
Hydrology and Geomorphology
• Surface and Groundwater flows
- Pattern of Surface Flows
- Hydrodynamics
- Pattern of Groundwater Flows
- Salinity Patterns
- Water Storage
• Dynamic Structural Characteristics
- Channel/Shoreline Morphology,
Complexity
- Extent/Distribution of Connected
Floodplain
- Aquatic Physical Habitat Complexity
• Sediment and Material Transport
- Sediment Supply/Movement
- Particle Size Distribution Patterns
- Other Material Flux
Natural Disturbance Regimes
• Frequency
• Intensity
• Extent
• Duration
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Measures. The measures are specific monitoring variables that are measured in the field
and aggregated into one or more ecological indicators (or endpoints).
The relationship among these components is relatively straightforward. Measures
(monitoring data) are aggregated into ecological indicators. Indicators are aggregated into the
subcategories of the hierarchy of EEAs. In theory, therefore, the framework provides a
mechanism to display the relationship between monitoring data or indicators and the
overarching conclusions that can be drawn about the condition of various important ecological
attributes.
Figure ES-1 shows a clear separation between goals and objectives in the upper half and
EEAs, indicators, and measures in the lower half, to emphasize that EEAs are a function of the
ecological systems of interest and are not derived from the goals and objectives. The EEAs are
designed to apply genetically - that is, to most aquatic and terrestrial systems at the local,
regional, or national scale. The independence of the EEA hierarchy from specific management
objectives is what makes it amenable to consistent application across many different regions and
types of programs. This independence does not mean that the EEAs and objectives are
unrelated, however. The EEAs provide an organized body of information from which one can
assess a program's success in meeting any set of objectives relating to ecological condition. In
other words, a performance measure related to a specific objective of an environmental program
will draw information from a unique subset of the EEAs.
ESSENTIAL ECOLOGICAL ATTRIBUTES
The EEAs—Landscape Condition, Biotic Condition, Chemical and Physical
Characteristics, Ecological Processes, Hydrology and Geomorphology, and Natural Disturbance
Regimes— divide up the universe of information that describes the state of an ecological system
in a logical manner that is solidly grounded in current scientific understanding. The EEAs
include three ecological attributes that are primarily "patterns" (Landscape Condition, Biotic
Condition, and Chemical/Physical Characteristics) and three that are primarily "processes"
(Hydrology/Geomorphology, Ecological Processes, and Natural Disturbance). Describing
ecological systems in terms of pattern and process has a long history in ecological science and
has been a useful construct for many years. In a nutshell, the processes create and maintain
patterns, which consist of the elements in the system and the way they are arranged; these
patterns in turn affect how processes are expressed (e.g., a riparian forest's effect on river flow
and velocity).
In order to subdivide pattern and process into EEAs, the Panel elected to highlight
ecological characteristics that often are overlooked by the Agency and by members of the public
(such as landscape structure, natural disturbance, and ecological processes). For ease of use, the
Panel grouped characteristics that generally are measured together. The EEAs and their
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component categories and subcategories are summarized below and in Table ES-2, and described
in detail in Section 3.
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TABLE ES-2. Summary of Essential Ecological Attribute Categories and Subcategories, With Example Indicators and
Measures
LANDSCAPE CONDITION
Category
Extent of Each Ecological
System/Habitat Type
Landscape Composition
Landscape Pattern/Structure
Subcategory
Example Indicators and Measures
e.g., area; perimeter-to-area ratio; core area; elongation
e.g., number of habitat types; number of patches of each habitat; size of largest patch;
presence/absence of native plant communities; measures of topographic relief, slope, and aspect
e.g., dominance; contagion; fractal dimension; distance between patches; longitudinal and lateral
connectivity; juxtaposition of patch types or serai stages; width of habitat adjacent to wetlands
BIOTIC CONDITION
Ecosystems and Communities
Species and Populations
Community Extent
Community Composition
Trophic Structure
Community Dynamics
Physical Structure
Population Size
Genetic Diversity
Population Structure
e.g., extent of native ecological communities; extent of successional states
e.g., species inventory; total species diversity; native species diversity; relative abundance of
species; % non-native species; presence/abundance of focal or special interest species (e.g.,
commonness/rarity); species/taxa richness; number of species in a taxonomic group (e.g., fishes);
evenness/dominance across species or taxa
e.g., food web complexity; presence/absence of top predators or dominant herbivores; functional
feeding groups or guilds
e.g., predation rate; succession; pollination rate; herbivory; seed dispersal
e.g., vertical stand structure (stratification or layering in forest communities); tree canopy height;
presence of snags in forest systems; life form composition of plant communities; successional state
e.g., number of individuals in the population; size of breeding population; population distribution;
number of individuals per habitat area (density)
e.g., degree of heterozygosity within a population; presence of specific genetic stocks within or
among populations
e.g., population age structure
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Organism Condition
Population Dynamics
Habitat Suitability (Focal Species)
Physiological Status
Symptoms of Disease or Trauma
Signs of Disease
e.g., birth and death rates; reproductive or recruitment rates; dispersal and other movements
measures of habitat attributes important to focal species
e.g., glycogen stores and blood chemistry for animals; carbohydrate stores, nutrients, and
polyamines for plants; hormone levels; enzyme levels
e.g., gross morphology (size, weight, limb structure); behavior and responsiveness; sores,
and tumors; defoliation
lesions
e.g., presence of parasites or pathogens (e.g., nematodes in fish); tissue burdens of xenobiotic
chemicals
CHEMICAL AND PHYSICAL CHARACTERISTICS (WATER, AIR, SOIL, SEDIMENT)
Nutrient Concentrations
Trace Inorganic and Organic
Chemicals
Other Chemical Parameters
Physical Parameters
Nitrogen
Phosphorus
Other Nutrients
Metals
Other Trace Elements
Organic Compounds
pH
Dissolved Oxygen/Redox
Potential
Salinity
Organic Matter
Other
Soil/Sediment
Air/Water
e.g. Concentrations of total N; NH4, NO3; organic N, NOx; C/N ratio for forest floor
e.g., concentrations of total P; ortho-P; particulate P; organic P
e.g., concentrations of calcium, potassium, and silicon
e.g., copper and zinc in sediments and suspended particulates
e.g., concentrations of selenium in waters, soils, and sediments
e.g., methylmercury, selenomethionine
e.g., pH in surface waters and soil
e.g., dissolved oxygen in streams; soil redox potential
e.g., conductivity
e.g., soil organic matter; pore water organic matter concentrations
e.g., buffering capacity; cation exchange capacity
e.g., temperature; texture; porosity; soil bulk density; profile morphology; mineralogy; water
retention
e.g., temperature; wind velocity; relative humidity; UV-B PAR; concentrations of particulates;
turbidity
ECOLOGICAL PROCESSES
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Energy Flow
Material Flow
Primary Production
Net Ecosystem Production
Growth Efficiency
Organic Carbon Cycling
N and P Cycling
Other Nutrient Cycling (e.g., K, S,
Si, Fe)
e.g., production capacity (total chlorophyll per unit area); net primary production (plant
production per unit area per year); tree growth or crop production (terrestrial systems); trophic
status (lakes); 14-CO2 fixation rate (aquatic systems)
e.g., net ecosystem organic carbon storage (forests); diel changes in O2 and CO2 fluxes (aquatic
systems); CO2 flux from all ecosystems
e.g., comparison of primary production with net ecosystem production; transfer of carbon through
the food web
e.g., input/output budgets (source identification-stable C isotopes); internal cycling measures (food
web structure; rate and efficiency of microbial decomposition; carbon storage); organic matter
quality and character
e.g., input/output budgets (source identification, landscape runoff or yield); internal recycling (N2-
fixation capacity; soil/sediment nutrient assimilation capacity; identification of growth- limiting
factors; identification of dominant pathways)
e.g., input/output budgets (source identification, landscape yield); internal recycling (identification
of growth- limiting factors; storage capacity; identification of key microbial terminal electron
acceptors)
HYDROLOGY AND GEOMORPHOLOGY
Surface and Groundwater Flows
Pattern of Surface Flows
(rivers, lakes, wetlands, and
estuaries)
Hydrodynamics
Pattern of Groundwater Flows
Spatial and Temporal Salinity
Patterns (estuaries and wetlands)
Water Storage
e.g., flow magnitude and variability, including frequency, duration, timing, and rate of change;
water level fluctuations in wetlands and lakes
e.g., water movement; vertical and horizontal mixing; stratification; hydraulic residence time;
replacement time
e.g., groundwater accretion to surface waters; within-groundwater flow rates and direction; net
recharge or withdrawals; depth to groundwater
e.g., horizontal (surface) salinity gradients; depth of pycnocline; salt wedge
e.g., water level fluctuations for lakes and wetlands; aquifer capacity
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Dynamic Structural Characteristics
Sediment and Material Transport
Channel Morphology; Shoreline
Characteristics; Channel
Complexity
Distribution and Extent of
Connected Floodplain (rivers)
Aquatic Physical Habitat
Complexity
Sediment Supply and Movement
Particle Size Distribution Patterns
Other Material Flux
e.g., mean width of meander corridor or alternative measure of the length of river allowed to
migrate; stream braidedness; presence of off-channel pools (rivers); linear distance of marsh
channels per unit marsh area; lithology; length of natural shoreline
e.g., distribution of plants that are tolerant to flooding; presence of floodplain spawning fish; area
flooded by 2-year and 10-year floods
e.g., pool-to-riffle ratio (rivers); aquatic shaded riparian habitat (rivers and lakes); presence of
large woody debris (rivers and lakes)
e.g., sediment deposition, sediment residence time and flushing
e.g., distribution patterns of different grain/particle sizes in aquatic or coastal environments
e.g., transport of large woody debris in rivers
NATURAL DISTURBANCE REGIMES
Example 1 : Fire Regime in a
Forest
Example 2: Flood Regime
Example 3: Insect Infestation
Frequency
Intensity
Extent
Duration
Frequency
Intensity
Extent
Duration
Frequency
Intensity
Extent
Duration
e.g., recurrence interval for fires
e.g., occurrence of low intensity (forest litter fire) to high intensity (crown fire) fires
e.g., spatial extent in hectares
e.g., length of fire events (from hours to weeks)
e.g., recurrence interval of extreme flood events
e.g., number of standard deviations from 30-year mean
e.g., number of stream orders (and largest order) affected
e.g., number of days, percent of water year (October 1- September 30)
e.g., recurrence interval for insect infestation outbreaks
e.g., density (number per area) of insect pests in an area
e.g., spatial extent of infested area
e.g., length of infestation outbreak
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Landscape Condition
A landscape is an area composed of a mosaic of interacting ecosystems, or habitat
patches. Habitat condition may reflect both abiotic features (e.g., elevation, proximity to water)
and biotic features (e.g., dominant species, presence of predators). A change in the size and
number of natural habitat patches, or a change in connectivity between habitat patches, affects
the probability of local extinction and loss of diversity of native species and can affect regional
species persistence. Patch heterogeneity also affects both biotic and abiotic landscape processes
(e.g., extent of insect infestation, surface water flows). Thus, there is empirical justification for
managing entire landscapes, not just individual habitat types, in order to insure that native plant
and animal diversity is maintained. The Panel recommends that landscape indicators be reported
in the following three categories:
Extent. The areal extent of each habitat type within a landscape is important because a
decrease in the total area of habitat available often is correlated with species decline. Extent may
be reported for broad land cover classes, for finer subunits, or both.
Landscape Composition. Landscape composition can be measured by several metrics,
including the number of landcover/habitat types, the number of patches of each habitat, and size
of the largest patch (because populations are unlikely to persist in landscapes where the largest
patch is smaller than that species' home range).
Landscape Pattern/Structure. The spatial pattern of habitat affects population viability
of native species. Recent advances in remote sensing and geographic information systems (GIS)
allow indices of pattern to be applied over large areas.
Biotic Condition
For this reporting framework, the Panel defines biotic condition to include structural and
compositional aspects of the biota below the landscape level (i.e., for ecosystems or
communities, species/populations, individual organisms, and genes). Within these biological
levels of organization, measures of composition (e.g., the presence or absence of important
elements, and diversity) and structural elements that relate directly to functional integrity (such
as trophic status or structural diversity within habitats) are considered.
Ecosystem or Community Measures. An ecological community is the assemblage of
species that inhabit an area and are tied together by similar ecological processes (e.g., fire,
hydrology), underlying environmental features (e.g., soils, geology) or environmental gradients
(e.g., elevation, temperature), and form a cohesive, distinguishable unit. In this framework,
community measures are divided into subcategories that are consistent with the concept of
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"biotic integrity" as defined by Agency guidance on biological assessment and biological
criteria.
Species or Population Level Measures. Measures of the condition or viability of
populations of species in an area are important indicators, yet monitoring the status of all species
is impossible from a practical standpoint. To address this problem, a higher taxonomic level can
be used, or a subset of species called focal species can be monitored. Focal species are selected
because they exert a disproportionately important influence on ecosystem condition or provide
information about the ability of the system to support other species. In addition, some species
(such as endangered, rare, sensitive, and game species) require attention because they relate to
biodiversity or because they are of direct interest to society for other reasons.
Individual Organism Measures. Whereas the preceding categories of biotic condition
are concerned largely with system, community, or population level measures, there are instances
when the health of particular individuals (e.g., for focal species or for species imperiled or
vulnerable to extinction or extirpation from an area) may be of interest. In addition, the health of
individuals may presage an effect on a population or related ecological process (e.g., the
presence of life-threatening birth defects in an animal population, or symptoms of disease in a
forest).
Chemical and Physical Characteristics (of Air, Water, Soil, and Sediment)
The characteristics included here are measures of chemical substances that are naturally
present in the environment and physical parameters (such as temperature and soil texture).
These environmental attributes have received substantial public attention and monitoring
because they are the subject of pollution control laws (e.g., the Clean Air Act, the Clean Water
Act). The categories listed below may be reported separately for air, for water, and so forth.
Alternatively, categories can be used to display integrated information from all environmental
compartments (air, water, soil, and sediment) at once.
Nutrient concentrations. Nutrients are those elements required for growth of
autotrophic organisms, whose ability to produce organic matter from inorganic constituents
forms the ultimate base of food webs. Concentrations of nutrients, including phosphorus,
nitrogen, potassium, and micronutrients (e.g., copper, zinc, and selenium) may be limiting if
available in too small a quantity or may lead to undesirable consequences if present in too great a
quantity.
Trace inorganic and organic chemicals. Baseline information about concentrations of
metals and organic chemicals (whether or not their concentrations are altered by pollutant
discharges) provides a foundation for assessing their ecological significance.
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Other chemical parameters. Other chemical parameters that should be reported will
differ depending on the environmental compartment (water, air, soil, and/or sediment) being
assessed. In soils and sediments, for example, measures such as total organic matter, cation
exchange capacity, and pH will be important.
Physical parameters. Physical measures, such as air and water temperature, wind
velocity, water turbidity, and soil bulk density, complement the measures of physical habitat
contained in other EEAs.
Ecological Processes
For this reporting framework, the Panel defines ecological processes as the metabolic
functions of ecosystems - energy flow, elemental cycling, and the production, consumption and
decomposition of organic matter. Biotic processes (which are included under biotic condition
for convenience) also could be included here. Many of the ecological process indicators are
taken from Ecological Indicators for the Nation, recently published by the National Research
Council. The Panel stresses, as did NRC, that adequate indicators are not yet available for all of
the key attributes of energy and material flows in ecosystems.
Energy Flow. The most basic ecosystem attribute, fundamental to life on earth, is
ecosystem productivity, or the ability to capture sunlight and convert it to high energy organic
matter (biomass), which then supports the non-photosynthetic trophic levels, including grazers,
predators, and decomposers. The balance among production, consumption, and decomposition
defines the efficiency of an ecosystem and its ability to provide the goods and services upon
which society depends.
Material Flow. Biogeochemical cycles that are key to ecosystem function include
cycling of organic matter and inorganic nutrients (e.g., nitrogen, phosphorous, and
micronutrients such as selenium and zinc). Material and energy flow are linked processes and
many indicators provide information on both.
Hydrology and Geomorphology
The hydrology and geomorphology of ecological systems reflect the dynamic interplay of
water flow and landforms. In river systems, for example, water flow patterns and the physical
interaction among a river, its riverbed, and the surrounding land determine whether a naturally
diverse array of habitats and native species are maintained. Sediment transport partially
determines which habitats occur where (both above the water and below it). The dynamic
structural characteristics — the biotic and abiotic components of the water-related habitats - are
created and maintained by both water and sediment flows.
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Water Flow. Surface and groundwater flows determine which habitats are wet or dry
and when, and water flows transport nutrients, salts, contaminants, and sediments. It is less
widely recognized, however, that the variability of water flows (in addition to their timing and
magnitude) exerts a controlling influence on the creation and succession of habitat conditions.
Dynamic structural characteristics. Structural characteristics in streambeds (or
lakebeds or bottom terrain of estuaries) and banks (or shoreline) are maintained by water flows
and sediment movement. Accordingly, measures of dynamic structural characteristics reflect the
integrity of these processes and provide direct information about the quality and diversity of
habitats. Characteristics included in this category include channel morphology and shoreline
characteristics, channel complexity, distribution and extent of connected floodplain, and aquatic
physical habitat complexity.
Sediment and other material transport. A wide variety of underwater, riparian, and
wetland habitats are maintained by the pattern of sediment and debris movement. Native species
have adapted accordingly; for example, many anadromous fish require clean gravels for
spawning, and invertebrates choose particular particle sizes for attachment or burrowing.
Natural Disturbance Regimes
All ecological systems are dynamic, due in part to discrete and recurrent disturbances that
may be physical, chemical, or biological in nature. Examples of natural disturbances include
wind and ice storms, wildfires, floods, drought, insect outbreaks, microbial or disease epidemics,
invasions of nonnative species, volcanic eruptions, earthquakes and avalanches. The frequency,
intensity, extent, and duration of the events taken together are referred to as the "disturbance
regime." Each of the disturbance regimes that is relevant to the ecological system should be
included in the assessment.
THE ROLE OF STRESSOR INDICATORS
In practice, reports about ecological condition often indiscriminately mix condition
indicators with indicators of stressors such as pollution. The framework presented here
distinguishes between ecological condition indicators and indicators of anthropogenic stressors,
and the EEAs relate only to condition. This approach is consistent with that of the National
Research Council (2000) and The Heinz Center (1999).
Other environmental reporting schemes incorporate both condition and stressor
indicators, but are careful to distinguish the two. The internationally recognized "Pressure-State-
Response" model of environmental indicators developed by the Organisation for Economic
Cooperation and Development (OECD, 1998) distinguishes pressures (i.e., stressors) from state
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(i.e., condition) variables. The ecological assessment scheme for the Great Lakes (Environment
Canada and U.S. EPA, 1999) follows the OECD format.
Distinguishing between condition indicators and stressor indicators is important because
the correlation is not one-to-one: many stressors affect more than one condition attribute, and
many condition attributes are affected by more than one stressor. Assessment of ecological
condition, therefore, shows the effects of multiple stressors acting at once and can highlight
unforeseen effects. Assessing the full array of condition indicators in parallel with an array of
stressor indicators also aids elucidation of causal mechanisms underlying compromised
ecosystem conditions. A third reason for distinguishing between condition and stressor
indicators is to avoid relying exclusively on available data - which generally focuses on
anthropogenic stressors targeted by regulations - and thereby overlooking important
characteristics relating to ecological condition (such as habitat changes or changes in water flow
patterns). The full array of condition information can help the Agency focus its efforts on the
most significant problems, rather than those about which the most data have been collected.
In short, even when the goal of an environmental program relates to the management of
stressors, it may well be necessary to assess both ecological condition and stressors, and then
assess the relationship between the two. The SAB framework can be adapted to incorporate
parallel information about stressors for this purpose (see Section 4). In addition, the array of
ecological attributes shown in Table ES-1 can be used as a checklist to identify components that
should be addressed in stressor-focused ecological risk assessments.
APPLYING THE FRAMEWORK
Designing an ecological condition assessment. One purpose of the EEA hierarchy
(Table ES-1) is to provide organizational structure for the process of selecting ecological system
characteristics that will be assessed. Once the purpose and scope of the assessment have been
determined as described in Section 5, the EEA list can be applied. The Panel recommends
beginning with a rebuttable presumption that all of the entries in Table ES-1 will be included. A
"thought experiment" can then be conducted to eliminate the subcategories and categories that
are not relevant to the assessment. When resources are limiting, the Panel generally
recommends limiting the number of subcategories for which data are collected, rather than
eliminating an entire category. Similarly, it may be preferable to limit the number of categories
assessed rather than eliminating an entire EEA.
Following the initial selection of EEA categories and subcategories, a series of checks
should be undertaken to assure that the selections accomplish the intended goals and are
scientifically defensible. For example, the list should be analyzed to assure that its components
are sufficient to address any goals and objectives that have been developed for management of
the ecological system. Similarly, components of the list should be sufficient to address questions
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of known public interest (such as the preservation of economically valuable species or the
sustainability of patches of old-growth forest). If the list falls short, then additional indicators
may be added. The final product of the design process should not only describe the assessment
and reporting scheme, but also transparently record the decision tree and professional judgments
used to develop it.
Creating a Report. Effective reporting on ecological condition requires policy
judgments and scientific understanding (to determine what to report), and it requires
communications expertise (to determine how to report it). Here, the Panel addresses only the
scientific issues.
The SAB framework provides a scientifically derived scheme for combining hundreds of
different indicators into a few ecologically related categories for reporting. Using Table ES-1 as
a guide, the information from an array of indicators can be grouped into a single subcategory and
- if desired - collapsed into a single quantitative or qualitative entry. The information within
subcategories can then be aggregated into a single category, and so forth. The discovery that
some categories lack data also is important information for both decision-makers and the public.
Depending on the level of interest and expertise of the audience, reports can be issued at
the level of individual indicators, subcategories, categories, EEAs, or the ecological system as a
whole. Many reports combine several levels of reporting. If the objective of the report is to
provide information on ecosystem integrity and sustainability, then the EEAs can be used as
reporting units (i.e., a "score" or qualitative assessment would be presented for each EEA). The
concepts behind the EEAs are fairly straightforward; for non-technical audiences, the
presentation would benefit from conversion into lay language. For example, hydrology and
geomorphology might become a description of "water flows and riverbanks" for a river basin
report.
Alternatively, the information that has been aggregated into EEAs and categories can be
extracted in order to report on a particular management objective. For example, an objective
such as "protect functional habitat types throughout the watershed" might use the extent category
of Landscape Condition to report directly on the amount of each habitat currently in existence.
In addition, a consolidated "indicator" that incorporates the Hydrology/Geomorphology,
Disturbance, Ecological Processes, and Landscape Condition EEAs might be used to report
whether these habitats are functional and likely to be maintained into the future.
The process of aggregating information from multiple indicators into a single entry for
reporting - even following the template in Table ES-1 - involves nontrivial scientific judgments.
An expansive scientific literature is available to determine appropriate methods for creating
indices and aggregating measures into endpoints, endpoints into categories, and so forth.
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Interpreting Indicator Values. To make the proposed reporting framework operational,
reference conditions should be defined against which measured values for indicators can be
compared. The reference conditions are helpful for interpreting results and are required in order
to determine how results can be normalized (qualitatively or quantitatively) for aggregation.
This normalization procedure allows various indicators to be collapsed into one result, and it
allows results from different regions to be compared. The Panel recommends that the Agency
support current efforts to develop reference conditions for this purpose.
EXAMPLE APPLICATIONS OF THE FRAMEWORK
To illustrate the proposed framework's application to programs at different geographic
scales and with different objectives, as well as to check the completeness of the framework, the
Panel selected four environmental reporting programs as case examples: an Office of Research
and Development program designed to assess condition of ecological systems; a USD A Forest
Service program designed to assess forest condition nationwide; the Office of Water's Index of
Watershed Indicators (IWI), designed to convey information to the public about watershed
condition; and a joint EPA-state reporting program designed to track progress meeting
environmental goals. The Panel, along with representatives of the programs, reviewed these case
studies to determine whether components should be added to the framework, whether the
framework provided a useful checklist for the program, and whether the framework provided a
reasonable way to organize and report on the program's indicators. The Panel appreciates the
assistance and cooperation of the programs' representatives for these road tests.
The Office of Research and Development's Environmental Monitoring and Assessment
Program (EMAP) includes a pilot project that will assess aquatic resources within streams,
landscapes, and estuaries in a twelve-state region of the western U.S. Comparison of the EMAP-
West indicators with the SAB framework indicates that all of the EMAP-West components can
be nested within the SAB framework, but that several of the categories included in the SAB
framework are omitted from EMAP-West. Landscape condition, disturbance regimes (i.e., fire,
flood, drought, volcanic activity), and ecological processes were notably lacking in coverage.
These omissions may make it more difficult for EMAP-West to accomplish its intended purpose.
In this example, therefore, it appears that use of the EEA hierarchy as a checklist provides
valuable insight that might be incorporated as the program evolves. In addition, the EEA
hierarchy could be employed to organize EMAP-West data into data systems for local groups,
thereby creating a structure into which information from other monitoring programs could be
integrated.
The USDA's Forest Health Monitoring (FHM) Program assesses the condition and health
of both public and private forests nationwide. The program focuses on sustainability of forest
system integrity and the effects of stressors thereon. Despite its initial focus on stressors,
however, the FHM metrics fit within the proposed EEA categories. Conversely, the FHM
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measures provide fairly complete coverage of the EEA hierarchy with the exception of
hydrology/geomorphology. Using the SAB reporting framework to organize and describe the
FHM indicators, therefore, helps reinforce the value of both because they are so consistent in
content. Moreover, the EEA hierarchy provides an organization scheme that could be used to
combine FHM information with monitoring data from other agencies because it can be adapted
for use in different ecosystem types at a variety of scales.
The Index of Watershed Indicators (IWI) displays information on the EPA web site about
the "condition and vulnerability" of watersheds. The Panel found that the IWI indicators are
predominantly stressor indicators and that the condition indicators that are included are notably
lacking in coverage, with the exception of the traditional Agency territory of physical and
chemical parameters. Although this is understandable given the Agency's history, it is not the
overview of watershed condition that the web site advertises nor what the public expects to find.
On the other hand, there is no reason that additional parameters cannot be added in the future in
order to provide a more balanced picture of watershed condition. The SAB framework would
provide a method to choose additional indicators, and it would provide a scientific and logical
justification for the IWFs composite indices and maps.
The National Environmental Performance Partnership System (NEPPS) uses "core
performance measures" to track the states' progress towards meeting environmental goals. The
current array of ecosystem-related core performance measures tracks only chemical and physical
characteristics and a small subset of biotic condition. Examination of a sample state NEPPS
report, however, shows far more complete coverage than the generic core performance measures
imply. The EEA hierarchy can be used profitably by the NEPPS program to determine how
ecosystem condition (or a subset such as biotic condition) can be assessed, and it offers a method
to organize and consolidate information about a variety of ecosystem types. The reporting
categories of the SAB framework appear awkward for the NEPPS core performance measures at
the present time, however, because the measures primarily are focused on reporting about
changes in pollutant levels resulting from particular legislated mandates. Measures of other
attributes — such as landscape condition, biotic condition, and hydrology that are included in the
sample state report — could be grouped into EEAs for reporting. This approach might help to
convey to the public the ecological significance of the collection of measures.
CONCLUSIONS
The framework presented here provides a valuable tool for assessing the condition
of ecological systems. In every example program tested by the Panel, the list of Essential
Ecological Attributes and associated subdivisions proved useful. In all cases, use of the EEA
hierarchy as a checklist highlighted missing elements - elements representing ecological system
characteristics broad enough in scope and importance to affect the achievement of the programs'
objectives. Recognizing that resources are always limited and that expanding a program is often
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infeasible, the EEA checklist provides a method to analyze the tradeoffs inherent in choosing
which characteristics to address. The fact that the checklist is organized hierarchically allows
the user to determine whether major characteristics (e.g., the entire array of hydrology and
geomorphology characteristics) are being eliminated from consideration in favor of a cluster of
closely-related attributes (e.g., every subcategory and indicator of biotic condition at the
community level).
In most cases, the elements that were omitted by Agency programs were those outside the
realm of biotic condition and chemical and physical characteristics. This pattern has been noted
by the SAB in the past and it is an understandable outgrowth of the issues targeted by the
Agency's legal mandates. A more complete look at ecological characteristics is key, however, to
allow the Agency to: analyze correctly the causes of environmental degradation; effectively
target corrective actions; and help address environmental problems across large geographic areas
such as watersheds.
The framework can be applied to a variety of aquatic and terrestrial systems at
local, regional, and national scales. The programs that were analyzed included both aquatic
and terrestrial systems at a variety of geographic scales. For all of these examples, the SAB
framework and EEA hierarchy provided a reasonable way to organize a broad array of
indicators. After each example was tested, the Panel was able to fine-tune the organizational
scheme by grouping characteristics into slightly different bundles at the subcategory level.
Presumably this fine-tuning will still be necessary as the SAB framework is applied to additional
programs. In no case, however, did the Panel find that important elements of condition were
missing from the framework.
The Essential Ecological Attributes and their subdivisions provide a logical method
for grouping ecologically related elements across system types (such as forests, rangelands,
and aquatic systems) and/or across programs that have different legal mandates. This
feature can be used when the Agency addresses problems that span different "media" (i.e., water,
air and land) in order to provide environmental protection for watersheds and other geographic
units. It also can be used as a unifying framework on which to map various types of ecological
assessment activities within the Agency. There is clear justification for a variety of different
programs with different purposes to exist within the Agency, among other federal agencies, and
in the private sector for the purpose of assessing ecological condition. This diversity brings
strength and depth to our understanding. It does not, by itself, insure that efficiencies among
programs are realized, that deficiencies in programs are addressed, or that the information from
one assessment is used to enhance the understanding gained from other studies. The SAB
framework provides a template that potentially could be used to foster greater integration, a
higher quality of ecological assessment, and increased efficiency among Agency programs. It
also could be used to assist the Agency to become a locus for integrating information from
different government agencies.
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The Essential Ecological Attributes and their subdivisions can be used to organize
and consolidate a large number of indicators into a few, conceptually clear categories for
reporting. One major purpose of this framework and EEA list (Table ES-1) is to help avoid
common reporting problems. For example, report authors often discover that there are numerous
relevant ecological indicators, yet there is little guidance available about how they should be
distilled into a few scientifically credible indicators for the public. Moreover, most of the easily
accessible information (e.g., water quality data regarding chemical contaminants) may be related
to past problems and reflects only part of the information required to predict future problems or
manage the ecosystem. The framework presented here can help avoid these problems by
providing a roadmap for grouping monitoring data and indicators into scientifically defensible
categories that directly relate to important characteristics of ecological condition. These
categories are straightforward, and they can therefore be explained to decision-makers,
legislators, and the public. The language used by the Panel would not, however, be suitable for
this purpose. Translation into lay language would be required.
This framework can provide the foundation for reporting on a variety of
independently-derived goals and objectives, including those mandated by legislation or
public policy. When the purpose of a report is to address questions of particular interest to the
public or address goals embodied in legislation or regulation, the SAB framework provides a
way to organize information that can then be extracted for reporting. For example, a "report
card" entry on the health of native habitats, plants, and animals would draw from the information
aggregated into the landscape condition and biotic condition EEAs. A companion report card
entry on the ability of the ecosystem to sustain healthy plants and animals into the future would
add information from each of the remaining EEAs. In some cases, however, the SAB framework
provides the requisite information but does not work well for organizing indicators into a report.
One example would be a regional water quality report for which data will be drawn from
monitoring programs designed specifically for that purpose. In this example, the SAB
framework is better used as an analytical tool than a report outline.
SUMMARY
In sum, the Panel finds that the proposed framework accomplishes its intended purpose.
The framework provides a checklist that can help identify the ecological attributes that are
important to assess in order to evaluate the health or integrity of ecological systems. It also
provides an organizational scheme for assembling hundreds of individual parameters into a few
understandable attributes. Ecological systems are complex, and it has proved extremely difficult
to answer the holistic questions that people ask about them - "How healthy is my watershed?
Will native species be here for my children and grandchildren to enjoy?" With this report, we
provide a way to integrate scientific data into the information necessary to answer these
questions, and ultimately to foster improved management and protection of ecological systems.
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1. THE NATIONWIDE FOCUS ON BETTER ENVIRONMENTAL
REPORTING
Virtually every comprehensive study on national environmental protection has called for
more coherent and comprehensive information on the state of our environment.
— William Clark, Thomas Jorling, William Merrell in Designing a
Report on the State of the Nation's Ecosystems (The Heinz Center, 1999)
Decision makers and the public need accurate information on ecological conditions and
changes for three major reasons. First, a long-term record of conditions is needed as a
reference to evaluate current conditions and trends. Second, detailed information on the
ecological effects of various human activities and natural events - such as pollution,
development, agriculture, climate change, and geomorphological events - is essential for
selecting and implementing management options to address problems successfully.
Finally, long-term ecological data are needed for society to measure the effectiveness
and efficiency of management interventions and to improve them.
— Gordon Orians, in Ecological Indicators for the Nation (National
Research Council, 2000).
1.1 A Systematic Framework for EPA
A wealth of environmental monitoring information has been developed since the nation
first turned its collective attention to improving environmental quality more than three decades
ago. Yet many scientists, most decision-makers, and nearly all members of the public still have
little understanding of the "health" or integrity of the nation's ecological systems. The
monitoring programs tailored to report on the implementation of environmental laws and
programs - the cleanup of pollutants, the management of public forests and rangelands, and so
forth - may accomplish the intended purpose but do not provide the information required to
assess the integrity of ecological systems in a systematic way across regions.
Recognizing this information gap, much attention has recently been focused on the
development of concise, understandable, yet accurate "environmental report cards" that
summarize the condition of ecological systems. The recent publication of Designing a Report on
the State of the Nation's Ecosystems by The Heinz Center (1999; in press) and Ecological
Indicators for the Nation by the National Research Council (NRC, 2000) begin to fill this gap.
There remains, however, a need to expand upon this foundation in order to create a template for
synthesizing information across different types of ecological resources. Moreover, one of the
prominent conclusions shared by both The Heinz Center and NRC reports is that much (if not
most) of the information required to assess the health of our nation's ecosystems is still
unavailable.
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In our view, the Environmental Protection Agency has an important role to play in
developing the missing information on the condition of the nation's ecosystems for use in these
and other "environmental report cards." Better information about ecological condition also is a
prerequisite for better decision-making within the Agency, on issues ranging from the
development of biocriteria to the formulation of research strategies (see, e.g., EPA Science
Advisory Board, 1994, 1997a, 1998). In addition, the Agency
has mandates - as part of the Government Performance and
Results Act of 1993 (GPRA), for example - to report more r , . ,. . .,
v ' r r Ecological integrity means the
effectively on the state of the nation's environment and the presence of structural
improvements resulting from Agency programs. compositional, and functional
characteristics within the
The inherent complexity of ecological systems, natural ran§e of variability for
, , , , , ., , . , . a particular ecological system.
however, makes both the assessment or ecological integrity
and the creation of coherent "report cards" challenging tasks.
For this reason, the Agency would benefit from development
of a systematic framework for assessing and reporting on ecological condition. The framework
would: a) help assure that the required information is measured systematically by the Agency's
programs; b) provide a template for assembling information across Agency programs and from
other agencies; and c) provide an organizing tool for synthesizing large numbers of indicators
into a scientifically defensible, yet understandable report on ecological condition (see box).
In order to accomplish these objectives, the reporting framework should be solidly
grounded in ecological principles. The reporting categories, as well as the specific measures or
indicators within each category, should be related clearly to the characteristics and functions of
ecological systems of concern. The reporting categories also should address the fundamental
structural and functional attributes of ecological systems. While the framework would
incorporate the indicators recommended by the NRC and The Heinz Center, it would encompass
a more comprehensive universe of ecological attributes and not be limited to those indicators that
are appropriate to assess at the national scale.
The purpose of this report is to provide the Agency with a sample framework for
assessing and reporting on ecological condition that:
a) identifies ecological attributes that should be measured; and
b) shows how this information may be aggregated into an understandable
picture for decision-makers.
The central feature of this framework is a list of reporting categories that is derived from
ecological principles and is organized as a nested hierarchy, much like the organizational chart
of an agency or business. This "checklist" specifies ecological attributes that should be
considered when assessing ecological condition, and it can be applied to aquatic and terrestrial
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systems at local, regional, or national scales. It also can be used to identify gaps in current
monitoring programs. The list is arranged hierarchically so that the complex array of
information can be organized and then presented in a methodical and understandable manner.
Finally, the report illustrates how the framework and reporting categories might be applied to
selected Agency programs.
Example Applications of the SAB Framework
• • As a checklist during the design of an environmental monitoring or condition assessment
effort (to ensure coverage of the essential ecological attributes of the system being assessed)
• • As a checklist during the design of watershed or site-specific ecological risk assessments (to
ensure that all significant ecological attributes are considered in the conceptual model and in
deciding what to protect)
• • As a guide for public reporting and education on ecological condition (so that environmental
indicators are assembled in coherent and meaningful ways to tell a story)
• • To set research priorities for indicator development (to fill cells in the hierarchy for which
indicators do not currently exist)
• • To set data collection priorities where indicators have been developed (to fill data gaps that
hinder environmental decision-making)
• • To integrate environmental information from multiple sources (to optimize expenditures
for monitoring and to provide a more comprehensive assessment of the condition of ecological
systems)
• • To assess progress towards environmental goals at the national, regional, or watershed
levels
• • To evaluate the collective performance of environmental protection and management
programs in a geographic area or for an ecological resource type
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1.2 Terminology: Types of Environmental Measures
Environmental reporting usually draws upon a range of measures, from those measures
that capture programmatic activities to those that portray changes in human populations or the
environment. For purposes of this report, we have adopted the definitions in a previous SAB
In a recent report, Toward Integrated Environmental Decision-Making, the SAB (2000)
recommended that EPA adopt consistent definitions and terminology for performance measures
that are relevant to the Agency. For the current report, we have adopted these definitions,
although we have renamed "process measures" to "administrative measures" to distinguish
between administrative processes and ecological processes.
a) Administrative Measures are measures of administrative effort or program actions that are
presumed to result in environmental or health improvements (e.g., number of permits issued,
number of enforcement cases pursued, number of contaminated sites cleaned up to standards).
b) Stressor Measures are measures (levels) of stressors in the environment used to determine
attainment or non-attainment of desired reductions in stressor levels; e.g., total emissions of a
pollutant, concentrations of particulates in ambient air, levels of dissolved oxygen or turbidity in
a stream, and density of roads in a watershed.
c) Exposure Measures are measures of the co-occurrence or contact between an individual or
population and environmental stressor(s) over a defined time period. The term "exposure" is
traditionally associated with chemical stressors (e.g., contaminant levels in food, concentrations
of contaminants in tissues, time-activity measures, and total exposure to a contaminant via all
routes), whereas the term co-occurrence is often used as a broader term applicable to chemical,
physical, and biological stressors.
d) Effects Measures are measures of human and/or ecological effects (e.g., asthma rates, deaths
from acute poisoning from household products or pesticides, deaths from cancer, acres of
wetlands gained or lost, local extinctions of important species). Changes in these effects
measures can be used in one of two ways: (1) to assess the impact of an environmental risk
reduction program; and/or (2) for condition assessment, in which a suite of effects measures
are evaluated and reported in combination to characterize the health or condition of an entire
population or ecosystem. Condition assessment provides a baseline against which to evaluate
the success of broad policies or multiple decisions impacting a population or geographic region.
N ___ S
report (2000) for the various types of performance measures that are relevant to the Agency:
administrative, stressor, exposure, and effects measures (see box).
These categories of performance measures comprise a spectrum (Figure 1). At one end,
the administrative measures provide important information for managing ongoing environmental
programs but provide no direct information about the state of the resource. At the other end of
the spectrum, condition measures provide information about ecological integrity or human
health. Although they do not generally relate to a single law or government program, these
condition measures:
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a) inform decision-makers and the public about the condition of various populations
or ecological systems;
b) provide the information required to design environmental management programs
(e.g., watershed management, pollution controls, pollution prevention activities);
and
c) provide information that can be used to evaluate the performance of the suite of
environmental management programs affecting the ecosystem or landscape.
Environmental
Outcomes
Administrative Stressor Exposure Effects/Condition
Measures Measures Measures Measures
activity measures pressure indicators co-occurrence adverse effects
output measures release measures health outcomes
response indicators emission measures state indicators
Least directly related Most directly related
to Environmental Outcomes to Environmental Outcomes
Figure 1. Spectrum of Environmental Performance Measures (Modified from EPA Science
Advisory Board, 2000)
Condition measures generally are defined from one of two fundamental perspectives.
The first perspective — referred to here as "sustainable flows"— evaluates flows of products
such as lumber or fish; or services, such as recreational opportunities or soil conservation. The
second perspective — referred to here as "sustainable state"— evaluates ecological health or
integrity. Figure 2 illustrates these two approaches for forest ecosystems. The second approach
provides an important underpinning for the first, because it captures information about future
products; services that are not yet recognized or measured; and characteristics with existence (or
passive use) values. The second approach also may provide earlier signals regarding changes in
relationships among ecological constituents that affect future productivity, such as might occur
as a result of global climate change. In addition to providing information about these utilitarian
(anthropocentric) values, assessments of ecological integrity also inform biocentric values.
Biocentric values incorporate the inherent worth of ecosystems that is independent of any
24
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benefits in the form of product or service flows to human societies (see, e.g., Goulder and
Kennedy, 1997 for further discussion).
While there is no "correct" evaluation strategy, it is important to recognize that the world
view underlying an assessment and reporting system influences the selection of environmental
metrics. In the case of a "sustainable flows" focus, appropriate metrics would measure the rate
and sustainability of the product/service flows from the ecological resource to humans. In the
Forest Ecosystem Health
Management Objectives
Sustainable Flows
Sustainable State
Products
e.g.,food; wood; fuel;
wildlife; forage; seeds;
biochemicals
Services
e.g., existence value;
recreation; tourism;
biodiversity; soil/nutrient
conservation; surface water
quality; pollination; carbon
storage; pollutant
sequestration
Landscape Condition
e.g., patch size; perimeter-to-area ratio
Biotic Condition
e.g., species composition, abundance, and
density; food web structure; wildlife habitat
quality; vertical stand structure; tree canopy
height; symptom/sign survey;
mortality/morbidity
Chemical/Physical Characteristics
e.g., forest floor depth; soil bulk density; soil
pH; C/N ratio of forest floor; total carbon
Ecological Processes
e.g., productivity; biomass decomposition
rate; nutrient cycling rates
Hydrology/Geomorphology
e.g., stream flow rate; debris dams; sediment
load
Natural Disturbance Regimes
e.g., frequency, intensity, duration and extent
of wind, fire, avalanche, and insect outbreaks
Figure 2. Two world views of forest system health. The "sustainable flows" view has an
anthropocentric focus and measures "health" as the ability of forest systems to provide a sustained
flow of forest products and/or forest services to human societies. The "sustainable state" view has
both an anthropocentric and a biocentric focus and measures "health" as the ability of forest systems to
sustain a certain state as defined by one or more of the ecological attributes.
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case of a "sustainable state" focus, the emphasis is on the integrity of the ecological resource.
Integrity involves the concepts of completeness (e.g., with reference to landscape, community,
and species composition) and the ability of the resource to continue into the future (i.e.,
sustainability).
In this report, we focus exclusively on condition measures related to ecological integrity
or "sustainable state" because these are a critical — and largely missing- link in the information
base upon which environmental reporting can be built.
1.3 A Mandate to Report on Environmental Outcomes
Reporting on ecological condition provides a foundation for assessing the success of the
nation's environmental protection efforts. Perhaps the most visible example of the Agency's
need to report on environmental outcomes is the Government Performance and Results Act of
1993 (GPRA), which requires federal agencies to: develop specific goals and objectives; define
performance measures to assess progress in meeting these goals and objectives; and report
annually on these performance measures. In response to this mandate, the Agency developed a
strategic plan (EPA, 1997; 2000) that defines the Agency's mission in terms of 10 environmental
goals, with associated objectives, sub-objectives, and performance measures. However, the
performance measures have tended to be administrative and stressor measures, with very few
measures of environmental outcomes — particularly ecological condition measures.
The Science Advisory Board (SAB) has long recommended to the Agency that it increase
its focus on outcome measures, including measures of ecological condition. In its review of the
Agency's draft Environmental Goals for 2000, a predecessor to the EPA Strategic Plan (1997;
2000), the SAB applauded the clear articulation of goals and measurable objectives, yet urged
the Agency to seek measures more directly related to environmental outcomes (SAB, 1997b). In
a 2000 report, Toward Integrated Environmental Decision-making., the SAB again recommended
that the Agency give increased attention to the development and application of measures of
environmental outcomes associated with regulatory and management programs (SAB, 2000).
While these recommendations are compelling in theory, they are difficult to implement in
practice. Within the National Environmental Performance Partnership System (NEPPS), for
example, both the Agency and state governments have attempted to generate a balance of
administrative and outcome measures for use as "core performance measures." (For additional
discussion of the NEPPS program as it relates to condition assessment, see Section 6.5.) In a
presentation to the Ecological Processes and Effects Committee (EPEC) of the Science Advisory
Board in July 1998, however, the Agency acknowledged the difficulty of developing these
outcome measures. Part of the challenge the Agency faces in reporting on environmental
outcomes is the dearth of condition assessments that address an appropriate array of ecological
characteristics. A number of reviews conducted by EPEC during the past decade highlighted the
26
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need for — and absence of— information about fundamental ecosystem characteristics; e.g., SAB
reviews of guidance for biological assessment of streams (1994) and lakes (1997a), landscape
assessment (1995), the Index of Watershed indicators (1997c; 1999), watershed ecological risk
assessment (1997d), and ecological research priorities (1997e; 1998). As a result, EPEC
concluded that this recurring information gap has impeded the Agency's ability not only to plan
research strategies and develop biocriteria, but also conduct ecological risk assessments and
report on watershed condition.
In short, previous SAB reviews of Agency projects and programs, as well as summaries
of the current state of regional ecological reporting, suggest a need for a generic organizational
tool that will assist the Agency to systematically develop, assemble, and report on the
fundamental characteristics of ecological systems, both regionally and nationally. The purpose
of this report is to offer assistance in designing that organizational tool.
1.4 Contents of This Document
The following report provides an overview of a generic assessment and/or reporting
system (Section 2) and a detailed list of ecological attributes that should be considered when
assessing ecological condition. The list of ecological attributes is presented as a nested hierarchy
so that it can be used to organize indicators and report on ecological condition (Section 3).
Subsequent sections discuss the relationship between assessment of condition and assessment of
stressor regimes (Section 4) and scientific issues associated with interpretation of indicator
values (Section 5). The report also presents case examples to illustrate how the attribute list and
framework might be used to strengthen Agency programs and, potentially, communication
among programs (Section 6).
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2. CONSTRUCTING A REPORT ON ECOLOGICAL CONDITION
2.1 Reporting Architecture
In order to foster consistent and comprehensive assessment and reporting on the
condition of ecological resources, the Panel proposes a reporting framework in which
information on generic ecological characteristics can be logically assembled, then synthesized
into a few, scientifically defensible categories. Information from these categories can then be
excerpted to report on a variety of
environmental management goals. This
framework for consolidating
information, which is closely derived
Goals
Objectives
Essential
Ecological
Attributes
from Harwell et al. (1999), can be used
as part of a reporting system (Figure 3)
that contains the following major
elements:
a) Goals and Objectives.
Ideally, environmental management or
restoration programs begin with a
process to develop goals and objectives
that combine societal values and
scientific understanding, then articulate
the desired ecosystem conditions that
will result from the program(s). The
proposed reporting framework can be
applied to a variety of environmental
program goals, including conservation,
restoration, or risk assessment, associated with national, regional, or watershed scale programs.
For those programs that have a less formalized procedure for developing goals, a process
analogous to the "Planning" described as part of the Agency's Guidelines for Ecological Risk
Assessment (EPA, 1998) might be used to identify the goals and objectives of the program.
b) Essential Ecological Attributes. Essential Ecological Attributes (EEAs) are the
defining attributes of an ecological system or landscape (See Section 3). A list of EEAs and
their associated subdivisions (Table 1) can be used as a checklist to help design management and
assessment programs, and used as a guide for aggregating and organizing environmental
information. The elements of the chart and its hierarchical organization are derived from a
conceptual model of ecological system structure and function. Other valid methods of
Ecological Indicators
(Endpoints)
Measures
(Monitoring Data)
Figure 3. Proposed Architecture for Assessing and
Reporting on Ecological Condition.
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categorizing ecological characteristics could be derived.
c) Ecological Indicators. Ecological indicators (also called ecological endpoints) are
measurable characteristics related to the structure, composition, or functioning of ecological
systems; i.e., indicators of condition. Multiple indicators may be associated with each element in
Table 1.
d) Measures. The measures are the specific monitoring variables that are measured in
the field and aggregated into one or more ecological indicators. Additional descriptions of the
measures and endpoints and their relationships to conceptual models are presented in Harwell, et
al. (1999). These terms are also generally analogous to the endpoints and measures defined in
the Agency's Guidelines for Ecological Risk Assessment (EPA, 1998).
The proposed reporting framework provides a template for reporting on
the success of national, regional or watershed-level environmental goals:
Example National Ecological Goals (Source: EPA Strategic Plan 2000)
By 2005, increase by 175 the number of watersheds where 80 percent or more of assessed
waters meet water quality standards, including standards that support healthy aquatic
communities.
Restore and maintain the chemical, physical, and biological integrity of the Great Lakes Basin
Ecosystem, particularly by reducing the level of toxic substances, protecting human health,
restoring vital habitats, and restoring and maintaining stable, diverse, and self-sustaining
populations.
Example Regional-Scale Restoration Program Goals (Source: CALFED Bay-Delta Program, 1999)
Rehabilitate natural processes in the Bay-Delta system to support, with minimal ongoing human
intervention, natural aquatic and associated terrestrial biotic communities, in ways that favor
native members of those communities.
Protect or restore functional habitat types throughout the watershed for public values such as
recreation, scientific research and aesthetics.
Improve and maintain water and sediment quality to eliminate, to the extent possible, toxic
impacts on organisms in the system, including humans.
Example Watershed Risk Assessment Goal (Source: EPA, 1996)
Reestablish and maintain water quality and habitat conditions in Waquoit Bay and associated
wetlands, freshwater rivers, and ponds to (1) support diverse, self-sustaining commercial,
recreational, and native fish and shellfish populations and (2) reverse ongoing degradation of
ecological resources in the watershed.
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The relationship among these components is also relatively straightforward. Measures
(monitoring data) are aggregated into ecological indicators. Indicators are aggregated into the
elements of the hierarchy of EEAs1. In theory, therefore, the framework provides a mechanism
to display the relationship between monitoring data or indicators and the overarching
conclusions that can be drawn about the condition of various important ecological attributes. It
shows transparently how a large number of detailed indicators are synthesized into a single
assessment of an ecological attribute, and it attempts to address all of the relevant attributes in a
parsimonious set. Aggregated information on EEAs is based on scientific knowledge and
judgment, yet is understandable - at least conceptually - to non-technical decision-makers and
members of the public. A more complete discussion of the Essential Ecological Attributes,
indicators, and measures - the components of the reporting system that are based on the
ecological sciences - is presented in Section 3.
This reporting architecture is based on the assumption that societal values will dominate
the selection of goals and objectives and that scientific understanding will dominate the selection
of indicators, measures, and the methods of data aggregation. Figure 3 shows a clear separation
between Goals and Objectives in the upper half and Essential Ecological Attributes, Indicators,
and Measures in the lower half, to emphasize that EEAs are a function of the ecological systems
of interest and are not derived from the Goals and Objectives. The EEAs are designed to apply
genetically - that is, to most aquatic and terrestrial systems at the local, regional, or national
scale. They may change with improved scientific understanding, but should not change with the
shorter term adjustments in objectives that are common among ecosystem management and
restoration programs. The independence of the EEA hierarchy from specific management
objectives is what makes it amenable to consistent application across many different regions and
types of programs. This independence does not mean that the Essential Ecological Attributes
and Objectives are unrelated, however. The EEAs provide an organized body of information
from which one can assess a program's success in meeting any set of objectives relating to
ecological condition. In other words, a performance measure related to a specific objective of an
environmental program will draw information from a unique subset of the Essential Ecological
Attributes.
1 How this aggregation occurs will vary among different types of programs and for different reporting
systems. Options range from a mathematical index to the selective use of representative indicators.
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Table 1. Essential Ecological Attributes and Reporting Categories
Landscape Condition
• Extent of Ecological System/Habitat Types
• Landscape Composition
• Landscape Pattern and Structure
Biotic Condition
• Ecosystems and Communities
- Community Extent
- Community Composition
- Trophic Structure
- Community Dynamics
- Physical Structure
• Species and Populations
- Population Size
- Genetic Diversity
- Population Structure
- Population Dynamics
- Habitat Suitability
• Organism Condition
- Physiological Status
- Symptoms of Disease or Trauma
- Signs of disease
Chemical and Physical Characteristics
(Water, Air, Soil, and Sediment)
• Nutrient Concentrations
- Nitrogen
- Phosphorus
- Other Nutrients
• Trace Inorganic and Organic Chemicals
- Metals
- Other Trace Elements
- Organic Compounds
• Other Chemical Parameters
-pH
- Dissolved Oxygen
- Salinity
- Organic Matter
- Other
• Physical Parameters
Ecological Processes
• Energy Flow
- Primary Production
- Net Ecosystem Production
- Growth Efficiency
• Material Flow
- Organic Carbon Cycling
- Nitrogen and Phosphorus Cycling
- Other Nutrient Cycling
Hydrology and Geomorphology
• Surface and Groundwater flows
- Pattern of Surface Flows
- Hydrodynamics
- Pattern of Groundwater Flows
- Salinity Patterns
- Water Storage
• Dynamic Structural Characteristics
- Channel/Shoreline Morphology,
Complexity
- Extent/Distribution of Connected
Floodplain
- Aquatic Physical Habitat Complexity
• Sediment and Material Transport
- Sediment Supply/Movement
- Particle Size Distribution Patterns
- Other Material Flux
Natural Disturbance Regimes
• Frequency
• Intensity
• Extent
• Duration
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2.2 Relationship to Other Reporting Frameworks
The Organization for Economic Cooperation and Development (OECD), an international
organization that works to achieve growth and stability in the world economy, has developed a
"Pressure-State-Response" (PSR) framework for environmental reporting that has been widely
adopted. The PSR framework considers that "human activities exert pressures on the
environment and affect its quality and the quantity of natural resources ("state"): society
responds to these changes through environmental, general economic and sectoral policies and
through changes in awareness and behaviour ("societal resp_onse")"(OECD, 1998).
The framework presented here relates exclusively to a subset of environmental "state",
i.e., to ecological condition assessments as defined in Section 1.2. Often, however, the goals and
objectives of environmental programs relate to the management of stressors (such as particular
chemicals or habitat alteration) in order to improve ecological condition. In these programs,
reporting on the achievement of objectives will require assessment of ecological condition, the
presence of stressors, and the relationship between the two. The framework presented here can
be adapted to incorporate parallel information on stressors for this purpose (see Section 4).
The recent, growing interest in environmental condition assessments has spawned a great
deal of work on development of indicators related to ecological condition and biotic integrity, as
well as on methods for selecting appropriate indicators. At EPA, for example, the Science to
Achieve Results (STAR) Program has awarded over 40 grants for the development of ecological
indicators, the Environmental Monitoring and Assessment Program (EMAP) has continued to
develop and test aquatic and landscape condition indicators, and EPA has released guidelines for
evaluating and selecting ecological indicators for various applications (Jackson et al., 2000).
The framework presented here attempts to show how these indicators can be assembled into a
coherent picture of sustainable ecological condition. The indicators, in short, are prerequisites
for the real-world application of this framework.
In addition, numerous local and regional ecosystem "report cards" have been developed,
such as those covering the Chesapeake Bay (EPA, 1999; Chesapeake Bay Program, 2001) and
the Great Lakes (Environment Canada and U.S. EPA, 1999). Because these efforts are tailored
to specific sites, however, they have not provided easily transferable templates that can be used
to design ecological condition assessments for other regions or other types of systems. Recent
reviews of regional environmental report cards (Myers and Sharp, 1997; see also Harwell, et al.,
1999) confirm that, although many report cards attempt to assess the status of ecological
conditions and use the best available data, none uses a systematic framework that is conceptually
based on the principles of ecology and ecological risk assessment, applies across spatial and
temporal scales and ecosystem types, and can be adapted to any set of environmental
management goals. One of the purposes of this report is to help fill this gap.
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Two recent reports have attempted to create an overarching framework for reporting on
ecological condition across the nation's ecosystems. The National Research Council, in
Ecological Indicators for the Nation (NRC, 2000), proposes a list of indicators that can be
measured reproducibly and aggregated nationwide to provide a concise snapshot of ecological
condition. (Indicators that would differ in different systems, even though they might measure an
analogous attribute, e.g., primary production, were omitted from consideration.) The report also
discusses criteria for selecting national or regional indicators and appropriate methods for
aggregating information into indicators.
Another effort to develop a framework for environmental reporting is being conducted by
The Heinz Center with the support of eight federal agencies, as well as private foundations,
corporations, and environmental advocacy groups. The Heinz Center framework will be used to
generate periodic reports on the state of the nation's ecosystems. It targets six different
ecological system types and specifies attributes for which indicators should be reported (The
Heinz Center, 1999; in press). The attributes generally are consistent across system types, but —
unlike the NRC's list — the indicators are not.
The framework presented in this report attempts to build on both the NRC and The Heinz
Center efforts. The hierarchical list of Essential Ecological Attributes includes attributes that
correspond to each of the indicators listed in the NRC report and also incorporates each of the
attributes covered by The Heinz Center, with the exception of those relating to the production of
goods and services explicitly for human use. The list presented here attempts to be more
comprehensive, relate clearly to current conceptual understanding of ecosystem structure and
function, and apply to a variety of ecological system types at several geographical scales. While
the overarching conceptual model that the Panel has used to develop the Essential Ecological
Attributes differs somewhat from those used by the NRC and The Heinz Center, the attribute
categories can be mapped onto one another in a relatively straightforward way (see Table 2).
For a more detailed analysis of the relationship of the indicators proposed by The Heinz Center
effort and the EEA reporting categories, see Appendix A.
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Table 2. Comparison of SAB Reporting Categories with NRC (2000) Indicators and The Heinz Center Indicator Categories
SAB Framework
NRC (2000)
The Heinz Center (In press) (See Appendix A for full
list of indicators recommended by The Heinz Center)
LANDSCAPE CONDITION
Extent
Landscape Composition
Landscape Pattern and Structure
BIOTIC CONDITION
Ecosystems and Communities
-Community Extent
-Community Composition
-Trophic Structure
-Community Dynamics
-Physical Structure
Species and Populations
-Population Size
-Genetic Diversity
-Population Structure
-Population Dynamics
-Habitat Suitability
Organism Condition
-Physiological Status
-Symptoms of Disease and Trauma
-Signs of Disease
ECOLOGICAL PROCESSES
Energy Flow
-Primary Production
-Net Ecosystem Production
-Growth Efficiency
Material Flow
-Organic Carbon Cycling
-N and P Cycling
-Other Nutrient Cycling
EXTENT AND STATUS OF ECOSYSTEMS
land cover
land use
ECOLOGICAL CAPITAL: BIOTIC RAW MATERIALS
total species diversity
native species diversity
ECOLOGICAL FUNCTIONING (PERFORMANCE)
land use
Productivity, including
carbon storage
net primary production
production capacity
lake trophic status
stream dissolved oxygen
soil organic matter
nutrient-use efficiency
nutrient balance
ECOLOGICAL CAPITAL: ABIOTIC RAW
MATERIALS
nutrient runoff to coastal waters
SYSTEM DIMENSIONS
Extent
Fragmentation and Landscape Pattern
BIOLOGICAL COMPONENTS
Biological Communities
Plants and Animals
Ecological Productivity
CHEMICAL AND PHYSICAL CONDITIONS
Nutrients, Carbon, Oxygen
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CHEMICAL AND PHYSICAL CHARACTERISTICS
Nutrient Concentrations
-Nitrogen
-Phosphorous
-Other Nutrients
Other Chemical Parameters
-pH
- Dissolved Oxygen
- Salinity
- Organic Matter
- Other
Trace Inorganic and Organic Chemicals
-Metals
-Other Trace Elements
-Organic Compounds
Physical Parameters
HYDROLOGY AND GEOMORPHOLOGY
Surface and Groundwater Flows
-Pattern of Surface Flows
-Hydrodynamics
-Pattern of Groundwater Flows
-Spatial and Temporal Salinity
Patterns
-Water Storage
Dynamic Structural Characteristics
-Channel/Shoreline
Morphology and Complexity
-Distribution and Extent of
Connected Floodplain
-Aquatic Physical Habitat
Complexity
Sediment and Material Transport
-Sediment Supply/Movement
-Particle Size Distribution
Patterns
-Other Material Flux
NATURAL DISTURBANCE REGIMES
Frequency
Intensity
Extent
Duration
(stream oxygen)
soil organic matter
Chemical Contaminants
Physical Conditions
HUMAN USE
Food, Fiber, and Water
Recreation and Other Services
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3. ESSENTIAL ECOLOGICAL ATTRIBUTES
3.1 Rationale for the Selected Ecological Attributes
The Essential Ecological Attributes (EEAs)—Landscape Condition, Biotic Condition,
Chemical and Physical Characteristics, Ecological Processes, Hydrology and Geomorphology,
and Natural Disturbance Regimes— summarize the major ecological features in any system by
capturing the relevant scientific information in a limited number of discrete, but not necessarily
independent categories. These six generic ecological attributes represent groups of related
ecological characteristics, as depicted in Table 1. The EEAs, categories, and subcategories are
designed to apply to all ecological systems. Various types of ecosystems are differentiated by
selecting appropriate indicators within each subcategory (or rarely, by selecting different
subcategories or categories). The values measured for these indicators can then be aggregated
either quantitatively or qualitatively to provide information about the "health" or integrity of the
attributes represented by each subcategory and category. For a very concise picture of the state
of integrity of the system as a whole, the information can be reduced to scores or qualitative
descriptors for each EEA. In short, the EEA hierarchy is intended to help determine what to
measure and then help to organize the information that is gathered.
The EEAs, categories, and
subcategories in Table 1 divide up the
universe of information that describes the
state of an ecological system in a logical
manner that is solidly grounded in current
scientific understanding. This organizational
scheme is not unique, however. In other
words, it is one way to describe ecological
systems, but other organizing principles
could legitimately have been chosen.
ECOLOGICAL
Landscape
Condition
Biotic
Condition
Chemical/
Physical
Natural
Disturbance
Hydrology/
Geomorphology
The EEAs proposed here include
three ecological attributes that are primarily
"patterns" (Landscape Condition, Biotic
Condition, and Chemical/Physical
Characteristics) and three that are primarily
"processes" (Hydrology/Geomorphology, Ecological Processes, and Natural Disturbance).
Describing ecological systems in terms of pattern and process has a long history in ecological
science and has been a useful construct for many years (e.g., Bormann and Likens, 1979). In a
nutshell, the processes create and maintain patterns, which consist of the elements in the system
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and the way they are arranged; these patterns in turn affect how processes are expressed (e.g., a
riparian forest's effect on river flow and velocity)2.
In order to subdivide pattern and process into EEAs, the Panel elected to highlight
characteristics that often are overlooked by the Agency and by members of the public (such as
landscape structure, disturbance, and ecological processes). For ease of use, the Panel grouped
characteristics that are generally measured together (such as chemical and physical
characteristics, hydrology and geomorphology, and biotic elements at a variety of hierarchical
scales). The resulting EEAs are similar to those proposed by Harwell et al. (1999).
The relationships among the EEAs are complex, and all of the EEAs are interrelated; i.e.,
changes in one EEA may affect — directly or indirectly— every other EEA. Despite this
interconnectedness, no single EEA is totally predictive of another, and no single EEA is a
sufficient predictor of the state of the system as a whole. A salient example of the first
observation is the recognition that chemical and physical characteristics alone do not predict
biotic condition. An example of the second observation is that—despite the popularity of the
proposition—measures of biotic condition cannot be used as a surrogate for ecological condition.
Changes in other components of ecological condition, such as hydrology or landscape structure,
may be significant but will not be reflected in measures of biotic condition until later.
In the Panel's view, the subdivisions of pattern and process represented by the EEAs are
critical components about which information is required to characterize the condition of any
ecological system. In order to test this assertion, the Panel conducted a few conceptual
experiments. First, the EEAs were compared to an alternative construct often used to describe
ecological systems. In addition to pattern and process, ecological systems can be described in
terms of structure, composition, and function. Moreover, each of these characteristics is
expressed at every level of ecological organization: from landscapes, to ecosystems nested
within these landscapes, to communities, and so forth down to organisms and genes. The EEAs
and their subcomponents were mapped onto structural, functional, and compositional
characteristics at a variety of scales in order to assure coverage (see Appendix B). Second, the
EEAs and their subcomponents were checked to determine whether they would be relevant at
several geographic scales (ecoregion, 1000 km2; regional landscape, 100 km2; small watershed
or ecosystem, 10 km2; reach or stand, <1 km2). In general, all of the components of Table 1 were
2The distinction between processes and patterns often is a temporal one. Processes (e.g., transfers of matter
through ecosystems, community dynamics) may follow an element of pattern (chemicals, numbers of
species) through time. Because of this relationship, patterns sometimes are measured as surrogates for
processes, which often are more difficult to measure directly. For example, the biomass of invertebrates
over space and time (a pattern) may be measured as an indicator of secondary production (a process).
37
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relevant to each geographic scale3. Finally, the Panel determined that the EEAs and their
subcomponents were applicable to a variety of ecological system types (see Section 6 and
Appendix A).
For the most part, the reporting categories contain attributes that are altered directly by
humans. Attributes generally not affected directly by humans-e.g., weather and large
topographic features-may be included indirectly under Landscape Condition as measures of
habitat extent and landscape structure.
Exceptions occur, however. For example, very small geographic scales may not include landscape
patterns.
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3.2 Landscape Condition
The biotic elements of ecological condition are organized as a nested hierarchy with
several levels—landscape, ecosystem or ecological community, species/population, organism,
and genetic/molecular level-each of which should be incorporated in an assessment of condition
(Noss, 1990; Angermeier and Karr, 1994). Within these
categories of biological organization, it is useful to report on
diversity, composition and other attributes of condition. In the ^ landscape is an area
proposed reporting framework, the Panel addresses the composed of a mosaic of
, , ., „ ,- • • T^ A 1 1 interacting ecosystems or
landscape attributes or condition in a separate EEA, rather than habitat oatches
grouping landscape measures with other measures of Biotic
Condition, primarily to draw attention to an often under-
reported aspect of ecological condition. The separation also recognizes that abiotic factors are
important determinants of landscape structure and composition.
A landscape is an area composed of a mosaic of interacting ecosystems, or habitat
patches (Forman and Godron, 1986), with the heterogeneity among the patches significantly
affecting biotic and abiotic processes in the landscape (Turner,
1989). Habitat condition may reflect both abiotic features (e.g., Habitat refers to the set
slope, aspect, elevation, proximity to water) and biotic features (e.g., of conditions that make
dominant species, presence of predators). A change in the size and a site suitable for
number of natural habitat patches, or a change in connectivity particular species (or
between habitat patches, affects the probability of local extinction
and loss of diversity of native species and can affect regional species
persistence (Fahrig and Merriam, 1985). Thus, there is empirical justification for managing
entire landscapes, not just individual habitat types, in order to insure that native plant and animal
diversity is maintained (McGarigal and Marks, 1993).
Patches comprising a landscape are usually composed of discrete areas of relatively
homogeneous environmental conditions (McGarigal and Marks, 1993) and must be defined in
terms of the organisms of interest. For example, in a landscape composed of equal parts of
forest and pasture, a photophilic butterfly species would perceive the pasture areas as suitable
habitat whereas a shade-tolerant species would prefer the forest. The concept of habitat quality
for focal species is discussed further under Biotic Condition. At the landscape scale, the extent
of broad land cover classes (e.g., forest, agriculture, urban/suburban, surface waters) can serve as
surrogates of habitat extent for broad classes of species. When particular species or ecological
communities are of interest, these broad land cover classes should be divided into finer subunits.
For example, forests can be subdivided into types such as those delineated by the Society of
American Foresters (e.g., jack pine, balsam fir, and aspen in boreal forest regions; Eyre, 1980).
The National Research Council recently recommended the refinement of a land cover surrogate
that could be used nationwide (NRC, 2000).
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Both landscapes and habitat patches are dynamic and occur on a variety of spatial and
temporal scales that vary as a function of each animal's perceptions (McGarigal and Marks,
1993). For instance, a long-lived and far-ranging bird will view its environment at broader
spatial and temporal scales than a short-lived, flightless insect. These differences can be
incorporated and used in landscape analyses by changing the spatial or temporal resolution of a
database or model.
The Panel recommends that landscape indicators be reported in the following three
categories: extent of each ecological system type; landscape composition; and landscape
pattern/structure. The categories are summarized in Table 3 and discussed below.
a) Extent. The areal extent of each habitat type within a landscape is important because
a decrease in the total area of habitat available often is correlated with species decline (Wilson,
1988; Saunders et al., 1991). Extent may be reported for broad land cover classes, for finer
subunits, or both. In addition to area, the shape of habitat patches is an important consideration
for many (e.g., edge-sensitive) species. Measures of habitat shape include the ratio of perimeter-
to-area, core area, and elongation. Changes in landscape extent through fragmentation or
aggregation of natural habitats can alter patterns of abundance for single species and entire
communities (Quinn and Harrison, 1988; Bierregaard et al., 1992), and may pose a threat to
biodiversity (Whitcombe et al., 1981; Skole and Tucker, 1993).
Habitat extent is often reported as a simple gain or loss. A more sophisticated method of
assessing the importance of habitat is based on the needs of
focal species (see Section 3.3). Through monitoring, the
Focal species are a subset of habitat needs of focal species can be analyzed and projections
,t , can be made to determine the type and amount of habitat
presence/absence and J r
abundance can indicate the needed for the species to have self-sustaining populations well-
functioning (condition) of an distributed throughout its range. The habitat created or
ecological system. maintained under any management scenario may be compared
with the habitat needed for the viability of each focal species.
The less adequate the habitat for each focal species, the greater
the risk to other native species and to ecological integrity.
b) Landscape Composition. Landscape composition can be measured by several
metrics. The number of landcover or habitat types can serve as a discrete measure, but requires a
clear definition of each type in such a way that they are not overlapping (e.g, forested land,
agricultural lands, and edges between the two). It also is important to note the absence of
habitats or native communities (e.g., early success! onal stages in a jack pine matrix ecosystem)
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that would have been expected on the basis of ecoregional characteristics4. Information on the
largest patch size may provide insight into long-term population viability because populations
are unlikely to persist in landscapes where the largest patch is smaller than that species' home
range. Traditional diversity indices such as the Shannon Index and Simpson Index quantify
diversity of habitat types. These indices first gained popularity as measures of plant and animal
diversity and are easily applied to landscape diversity (O'Neill et al., 1988). Unfortunately, these
indices convey no information about the structure and arrangement of patches within the
landscape. For instance, a landscape composed of 90% forest and 10% pasture would yield the
same landscape diversity index value as a landscape of 10% forest and 90% pasture. In addition,
these diversity indices combine patch evenness and richness information, although these
components are often more useful when considered separately. Evenness in the context of
landscape diversity refers to the distribution of area or abundance among patch types. Richness,
on the other hand, refers to the number of patch types present. Because many organisms are
associated with a single type, patch richness may correlate well with species richness (McGarigal
and Marks, 1993). Following this line of reasoning, Stoms and Estes (1993) outline a remote
sensing agenda for mapping and monitoring biodiversity which focuses almost exclusively on
species richness.
Recently ecologists have been mapping biophysical units or ecological land types in an
effort to better define landscapes relevant to predicting the distribution of species and ecosystems
(Anderson et al., 1998). These units draw upon digital data layers for three primary factors:
elevation, topography (from digital elevation models), and lithology. Geology (parent material or
substrate), elevation, slope, aspect, and moisture all are important factors in determining the
di stributi on of vegetati on.
c) Landscape Pattern/Structure. While some minimum area of native habitats in a
landscape is necessary for maintaining population viability of native species, the spatial pattern
of habitat also is important. Changes in pattern can occur
either by natural processes (e.g., wildfires, windthrows) or as rrL•„.,/• . „• i.
Habitat fragmentation results
a result of human activities (e.g., urbanization, agricultural wjien w area Wjtj1 one
expansion). Natural fragmentation generally results in habitat continuous land cover or
patches with more irregular edges than human-created patches habitat type is altered to a
(Krummel et al., 1987). This pattern is clearly evident when mosaic of different types.
one compares square agricultural fields to heterogeneous
shapes of patches created by small fires. Natural disturbance and forest management practices
can interact with existing landscape pattern to dramatically affect the risk of species loss
(Gardner et al., 1993). Species that are most vulnerable are ones that become isolated as a result
of landscape fragmentation and are also restricted to specific habitat types. Land management
"Often, native or dominant plant communities are used to identify habitats (e.g., in Gap analysis).
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practices that increase the degree of landscape fragmentation can change the competitive balance
among species, further jeopardizing the maintenance of regional native species diversity
(Gardner et al., 1993).
Changes in ecosystem structure and function often depend as much on what happens in
the area around the habitat of concern as they do on the size of the habitat and its relationship to
other similar habitat. Indices that represent the spatial arrangement of habitat patches within a
landscape have been developed from theoretical work in landscape ecology (e.g., Baker and Cai,
1992; Gardner and O'Neill, 1991; Gustafson and Parker, 1992; Krummel et al., 1987; O'Neill et al.,
1988; Plotnick et al., 1993). Recent advances in remote sensing and geographic information
systems (GIS) allow these methods to be readily applied over large areas.
Because no single index can capture the full complexity of the spatial arrangement of
patches, a set of indices are frequently evaluated. Three of the more common indices are
dominance, contagion, and fractal dimension (O'Neill et al., 1988).
Dominance, which is the complement of evenness, provides a measure of how common one
land cover is over the landscape. Its value indicates the degree to which species dependent on a
single habitat can pervade the landscape (e.g., the endangered Karner blue butterfly depends on the
presence of its single host plant, wild blue lupine; Kirtland warblers are dependent on early
success!onal patches of Jack pine). The contagion index measures the extent to which land covers
are clumped or aggregated. Contagion is a useful metric for those species that require large
contiguous areas of a particular land cover (e.g., carrion beetles which are affected by forest
fragmentation; Klein, 1989). Fractal dimension uses perimeter-to-area calculations to provide a
measure of complexity of patch shape. Natural areas tend to have a more complex shape and a
higher fractal value, whereas human-altered landscapes have more regular patch structure and a
lower fractal dimension (Krummel et al., 1987). This difference can influence the diversity of
species that inhabit edges or require multiple habitats (e.g., large herbivores require both forests for
cover and open fields for forage; Senft et al., 1987). The spatial arrangement of habitat patches
also can be measured by the mean, minimum or maximum distance between patches. For some
organisms such distance measures are critical determinants of the organisms' ability to cross
between patches (Dale et al., 1994), although the type of intervening habitat is often critical to such
movement or dispersal (e.g., presence of suitable "corridors").
In addition to landscape structure and composition, it is important to assess landscape
function or habitat quality. As previously noted, habitat quality or suitability is an attribute that is
assessed for particular species of interest and thus is discussed under the next section, Biotic
Condition. For certain purposes, however, habitat quality also may be used as a screening device
for reporting on habitat extent; only habitats that exhibit a certain degree of integrity or function
would be reported.
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Table 3. Landscape Condition
Category
Example Indicators and Measures
Extent of each ecological
system/habitat type
e.g., area; perimeter-to-area ratio; core area;
elongation
Landscape Composition
e.g., number of habitat types; number of patches of
each habitat; size of largest patch; presence/absence
of native plant communities; measures of
topographic relief, slope, and aspect
Landscape Pattern/Structure
e.g., dominance; contagion; fractal dimension;
distance between patches; longitudinal and lateral
connectivity; juxtaposition of patch types or serai
stages; width of habitat adjacent to wetlands
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3.3 Biotic Condition
For the purposes of this reporting framework, we define Biotic Condition to include
structural and compositional aspects of the biota below the landscape level (i.e., for ecosystems
or communities, species/populations, individual organisms, and genes). Within these biological
levels of organization, measures of the presence or absence of important elements, other aspects
of composition, diversity, and structural elements relating directly to functional integrity (such as
trophic status or structural diversity within habitats) are considered. Although many genetic
characteristics are important to biodiversity, rates of evolutionary change, and fitness of
individuals and populations (e.g., Landweber and Dobson, 1999), a detailed assessment of
genetic characteristics presently is beyond the scope of most ecosystem management or
assessment programs. Thus, only genetic diversity within populations of targeted species is
included within the reporting framework.
a) Ecosystem or Community Measures. An ecological community is the assemblage of
species/tara5 that inhabit an area and are tied together by similar ecological processes (e.g., fire,
hydrology), underlying environmental features (e.g., soils, geology)
or environmental gradients (e.g., elevation, temperature), and form _,
Taxa are any systematic
a cohesive, distinguishable unit. Indicators of biotic condition at groupings of organisms
the ecosystem or community level include measures of community (e.g., species, genera,
extent, community composition, trophic structure, community families, orders).
dynamics, and physical structure. These categories are consistent
with the concept of "biotic integrity" as defined by Karr and
Dudley (1981; Karr, 1991; 1993) and the Agency's guidance on biological assessment and
biological criteria (e.g., EPA, 1996b; 1998b) (see Appendix C).
1. Community Extent. The spatial extent6 of native ecological communities may be
determined from satellite imagery and aerial videography. To enhance mapping and
sharing of data on extent, the Federal Geographic Data Committee has adopted standard
classification systems for different community types (e.g., for wetlands and deepwater
habitats, Cowardin et al., 1979; for terrestrial vegetation, Grossman et al., 1998). Extent
data also may be presented for non-vegetative communities of interest (e.g., coral reefs,
oyster bars).
5In many cases, individual organisms cannot be identified to the species level (e.g., because a great number
of species have not yet been described, because reference specimens are not available, or because of a lack
of taxonomic expertise). Thus, reporting on biodiversity often will be at the level of taxa, rather than
species.
6The absence of native communities may be included here, if this information has not already been
incorporated in the metrics relating to landscape composition.
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2. Community Composition. A starting point for reporting on community composition
is an inventory of the species/taxa found in the ecological system. Useful measures of
composition include the total number of species or taxonomic units, their relative
abundance, presence and abundance of native and non-native species, and information on
the presence and abundance of focal or special interest species. Focal species are a
subset of species whose presence/absence and abundance can indicate the functioning
(condition) of an ecological system. The characteristics of focal species are discussed
further under Species and Population Level measures of condition.
Both total species diversity and native species diversity should be reported (e.g., see
NRC, 2000). Species/taxa richness often is used as a measure of community condition
but must be used cautiously so as to identify or exclude the non-native species
component. The contribution of non-native (introduced) species to richness should be
evaluated because, for example, an increase in disturbance often leads to an increase in
the number of invasive species, possibly leading to an increase in the total of number of
species. Even when evaluating the richness of native species, it is important to consider
the species composition. Fragmentation and an increase in edge in a community, for
example, can lead to increased richness of edge-tolerant species and/or to a decrease in
edge sensitive species, with a net loss of biodiversity on a regional basis. Sample
measures of species composition and abundance related to non-native species would be
the percent cover of naturalized exotics (e.g., forage grasses) or the percent cover of
invasive species.
3. Trophic Structure refers to the distribution of species/taxa and functional groups
across trophic levels. Measures of trophic structure include food web complexity and the
presence/absence of top predators or dominant herbivores. One technique of ecosystem
functional analysis uses functional feeding groups of aquatic invertebrates to characterize
biotic integrity. The invertebrates are clustered across taxonomic lines according to their
morphological and behavioral adaptations for acquiring a food resource. Relative
proportions of different functional groups can serve as surrogates measures of ecosystem
processes; for example, autotrophic state of a stream habitat is reflected in the
invertebrate functional groups that utilize primary producers as their food resource (algal
scrapers, vascular hydrophyte shredders, and algal piercers; Cummins and Klug, 1979).
These food resource-based ecosystem attributes are very sensitive to land use changes.
4. Community Dynamics include inter-specific interactions such as competition,
predation, and succession. Measures of biotic interactions (e.g., levels of seed dispersal,
pollination rates, herbivory, and prevalence of disease in populations of focal species)
provide important information about community condition. For example, unnaturally
high levels of deer browsing in forested ecosystems may lead to decreased nesting
success of ground nesting birds (e.g., deCalesta, 1994).
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5. Physical Structure refers to the distribution of both biotic and abiotic physical
structures within a habitat. In terrestrial systems, such measures usually will focus on
physical attributes of the plant community (e.g., vertical stand structure, tree canopy
height, and the presence of snags in forest systems). In aquatic systems, physical habitat
structure may result from the presence of macrophytes (e.g., eel grass beds, marsh
grasses) or abiotic structures (e.g., large woody debris in streams7). Although physical
habitat structure is a characteristic observable at the landscape scale, smaller scale
within-habitat structural attributes also are important for many species. For example,
birds are particularly attuned to the size and branching patterns of trees within their
habitats and numerous studies have shown low bird species diversity in even-aged forest
stands relative to natural stands with greater structural complexity.
b) Species or Population Level Measures. Measures of the condition or viability of
populations of species in an area are important indicators of biotic condition, yet monitoring the
status of all species is impossible from a practical standpoint. To address this problem, some
higher taxonomic level can be used, or a subset of species called focal species can be monitored.
In addition, some "special status" species (such as threatened and endangered species, game
The Role of Focal Species in Ecological Systems
Focal species may be selected for a variety of reasons. For example, keystone species
have disproportionate influences on ecological processes and other species and their
absence or removal may have a cascading affect on other processes and species (Mills et
al., 1993; Power et al, 1996). Examples include top predators (Paine, 1974; Terborgh,
2000), dominant herbivores (Naiman, 1988), and ecological engineers (e.g., beavers,
prairie dogs, gallery-forming insects in large wood on the forest floor), all of which alter
habitats and affect the fates and opportunities for other species (Jones et al., 1994;
Naiman and Rogers, 1997). Umbrella species are species whose range of occupied
habitats overlaps those of a disproportionate number of other species. Various
indicators—such as range extent, sensitivity to disturbance, habitat selectivity, and
rarity-have been developed to select umbrella species (e.g., Fleishman et al., 2000), but
the application of this concept across taxonomic groups and regions may not be reliable
(Andelman and Fagen, 2000). Link species are species that play a critical role in
ecosystem processes such as flows of materials or energy within complex foodwebs
(Dale and Beyeler, 2001).
7Aspects of aquatic physical habitat complexity associated with stream channel morphology (e.g., the
presence of pools and riffles) also may be reported under Hydrology and Geomorphology.
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species, sensitive species, and those that are vulnerable because of their rarity) should be
monitored, whether or not they would otherwise be considered focal species8.
Measures of condition at the species or population level include population size; genetic
diversity within or among populations; population structure; population dynamics; and habitat
suitability for focal species.
1. Population Size is one of the key measures of population health. Often, population
size must be estimated by combining density estimates for samples of known size and
proportion (of the area), stratified as needed to reflect spatial differences in density.
Usually only adult population size is measured, due to difficulties in including juveniles
in the estimates.
2. Genetic Diversity measures are important in assessing population condition because
small population size can lead to inbreeding within a population, and this inbreeding can
lead to an increase in the manifestation of deleterious and lethal mutations within a
population. Various measures, such as the degree of heterozygosity, can be used to
assess the genetic condition or health of a population. For example, reduced levels of
heterozygosity and an increase in deleterious mutations led to poor breeding success in
Florida panthers and a decision to bring in pumas from the western states to improve the
genetic fitness and viability of the remaining population.
3. Population Structure includes demographic information such as population age
structure and composition (e.g., number of juveniles or fledglings) and percentage of the
population that is of reproductive age. These measures, combined with information on
population dynamics (e.g., reproductive characteristics such as age at first reproduction)
are used to estimate population viability by modeling population trends through time. A
method used in fisheries involves comparing minimum reproductive size in a population
with mean individual size; as the mean size in the population approaches the minimum
reproductive size, the population is at severe risk of collapse. Changes in population
patterns occur as a result of inter- and intra-specific interactions (community and
population dynamics) and changes in physical and chemical aspects of the environment.
For example, a large population of long-lived mussels below a dam may be composed
entirely of mature individuals that are not able to reproduce because of changes in
hydrology, water temperature, and/or other species (e.g., host fish) since the population
was established in that location.
8 Species that are imperiled or vulnerable to extinction or extirpation from an area may or may not be on official federal or state list;
threatened species. For example, some states have no endangered species legislation and some species groups (e.g., plants and inv
listed in proportion to their endangerment. Lists of vulnerable species are maintained by state natural heritage programs and non-g
(e.g., NatureServe, International Union for the Conservation of Nature or IUCN).
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4. Population Dynamics includes measures of reproductive output (e.g., frequency of
reproduction, litter size, fledgling success) and survivorship (e.g., of different age
classes). Although population viability can be measured from time series data on
population size alone, increasingly accurate predictions of viability can be obtained by
using information on population structure and dynamics. Population dynamics also are
influenced by the processes of emigration and immigration, and these processes are
influenced in turn by geographic isolation. Populations may be usefully be characterized
as "sink" or "source" populations, depending on whether they are net exporters of
propagules or depend on emigration.
5. Habitat Suitability. The characteristics that define habitat suitability will differ
depending on the organism(s) of interest. However, parameters of habitat suitability
should reflect the basic needs of a species for food, water, cover, reproduction, and, in
some cases, social interactions. For example, important variables for fish habitat would
include water temperature and flow velocity, dissolved oxygen level, shading, the
presence of certain substrate types, and access to available food. Grassland bird habitat
parameters might include grass stem height and density, and the extent of residual
vegetation. Alligator habitat might be characterized by the availability and depth of open
water in marsh areas and the degree of substrate exposure under low water conditions.
Habitat suitability is a critical component of efforts to predict the occurrence of species.
Habitat analysis is used routinely in assessing the extent of mitigation required when
wetlands are taken out of service, and for assessing the environmental impacts of
proposed land and water development projects (see, for example, Fish and Wildlife
Service, 1981). Habitat assessment models exist for various types offish and wildlife
species, including over 150 Habitat Suitability Index models published by the U.S. Fish
and Wildlife Service. Because of the array of habitat requirements exhibited by species of
interest, habitat quality measures may be reported under a variety of EEA categories.
However, information on habitat quality for particular species of concern should be
considered in assessing the viability of populations of those species in an area.
c) Individual Organism Measures of Biotic Condition Whereas the preceding
categories of biotic condition are concerned largely with system, community, or population level
measures, there are instances when the health of particular individuals (e.g., for focal species or
for species imperiled or vulnerable to extinction or extirpation from an area) may be of interest.
In addition, the health of individuals may presage an effect on a population or related ecological
process (e.g., the presence of life-threatening birth defects, or symptoms of disease in a forest).
Measures in this category are primarily physiological, lexicological, or molecular in nature and
have been divided into physiological status, and symptoms and signs of disease or trauma.
Impaired organism condition indicates biological resources at risk due, for example, to
insufficient food supply, sub-lethal exposure to contaminants, or disease or parasites.
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1. Physiological status is the general condition of an organism, including the
functioning of tissues and organs. Example measures
include respiratory rate; growth rate; enzymatic activity „. . , , , . ,
r J ' ° ' J J Disease is abnormal physiology
(including biomarkers, such as induction of detoxification caused by biotic, chemical, or
enzyme activity, that signal exposure to toxicants); and physical agents.
measures of nutritional status. In fisheries, the ratio of
mass to length often is used as a measures of individual condition, as compared to the
mean of a population at large.
2. Symptoms of disease or trauma include the
responses of target organisms to stress, infection,
infestation, orinjury. Examples of important r^^a is a condition of abnormal
' J •> r r anatomy or morphology caused by
symptoms include changes in behavior and/or gross physical, chemical, or biotic agents.
morphology, the presence of tumors and lesions,
and defoliation and crown die-back (for trees).
Examples of trauma include the presence of scarring on manatees from collisions with
boat propellers and scarring of tree trunks by harvesters.
3. Signs of disease are evidence of the presence of agents capable of causing abnormal
physiology in the target organism. Example measures include the presence of pathogens
(e.g., bacteria, fungi, protozoa, nematodes) and insects on or in target organisms, and
tissue burdens of xenobiotic chemicals (i.e., organic compounds that are foreign to the
organism being sampled). Some naturally occurring substances, such as copper and
selenium, are required for normal physiological function in many organisms; yet, in
excess, these substances may cause physiological dysfunction. Tissue concentrations of
these essential substances may be considered either measures of physiological status or
as a sign of disease, depending on whether nutritional deficiency or toxicity is the
relevant concern.
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Table 4. Biotic Condition
Category
Ecosystems and
Communities
Species and Populations
Organism Condition
Subcategory
Community Extent
Community Composition
Trophic Structure
Community Dynamics1
Physical Structure
Population Size
Genetic Diversity
Population Structure
Population Dynamics1
Habitat Suitability (Focal
Species)
Physiological Status
Symptoms of Disease or
Trauma
Signs of Disease
Example Indicators and Measures
e.g., extent of native ecological communities; extent of
successional states
e.g., species inventory; total species diversity; native
species diversity; relative abundance of species; % non-
native species; presence/abundance of focal or special
interest species (e.g., commonness/rarity); species/taxa
richness; number of species in a taxonomic group (e.g.,
fishes); evenness/dominance across species ortaxa
e.g., food web complexity; presence/absence of top
predators or dominant herbivores; functional feeding
groups or guilds
e.g., predation rate; succession; pollination rate;
herbivory; seed dispersal
e.g., vertical stand structure (stratification or layering in
forest communities); tree canopy height; presence of
snags in forest systems; life form composition of plant
communities; successional state
e.g., number of individuals in the population; size of
breeding population; population distribution; number of
individuals per habitat area (density)
e.g., degree of heterozygosity within a population;
presence of specific genetic stocks within or among
populations
e.g., population age structure
e.g., birth and death rates; reproductive or recruitment
rates; dispersal and other movements
measures of habitat attributes important to focal species
e.g., glycogen stores and blood chemistry for animals;
carbohydrate stores, nutrients, and polyamines for plants;
hormone levels; enzyme levels
e.g., gross morphology (size, weight, limb structure);
behavior and responsiveness; sores, lesions and tumors;
defoliation
e.g., presence of parasites or pathogens (e.g., nematodes
in fish); tissue burdens of xenobiotic chemicals
1 Also may be reported under Ecological Processes
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3.4 Chemical and Physical Characteristics (Water, Air, Soil, and Sediment)
The Chemical and Physical characteristics included here are measures of physical
parameters (such as temperature) and concentrations of chemical substances that are naturally
present in the environment. These attributes have received substantial public attention because
they are the subject of pollution laws (Clean Air Act, Clean Water Act, and the like) that place a
great deal of emphasis on measurement and reporting of key physical and chemical parameters
within ecosystems. For example, under Section 305(b) of the Clean Water Act, states are
required to report annually on the status of their surface waters. Water quality criteria are used
to determine whether a given water body or stream meets the designated use or is "impaired."
Similarly, National Ambient Air Quality Standards established under the Clean Air Act are used
to judge the quality of ambient air. The advantages of such systems are that they utilize data that
are reasonably easy to collect and for which there are standardized measurements and
consistency of interpretation. As a result, standard lists of parameters have been developed and
are routinely reported by each state, the importance of each parameter has been well researched,
and data may be available9. We point out, however, that chemical measurements by themselves
do not provide a comprehensive picture of ecosystem integrity.
In general, the parameters listed under this EEA are standard components of monitoring
programs, because they are natural components of ecosystems
within certain ranges, and they are pollutants (stressors) at other
concentration ranges. Monitoring for pollution control usually "A stressor is any physical,
covers many man-made chemicals (xenobiotic compounds) in chemical, or biological entity
addition to the parameters listed here; these may legitimately be that can mduce an adverse
j rv • i j j • j-4- >. response." (EPA, 1998)
and often are included in condition assessments. ^
The proposed reporting framework includes reporting
categories for nutrients, trace inorganic and organic chemicals, other chemical parameters, and
physical parameters. Because legislative mandates and monitoring programs are separated by
environmental compartments (air, water, sediment, soils), many assessments and reports will
include a separate section for each compartment. In other words, all of the categories would be
reported for air, then all categories would be reported for water, and so forth. On the other hand,
a report that integrates the various compartments also may provide insights.
9The Panel notes, however, that the U.S. General Accounting Office recently reported that only 19 percent
of the nation's flowing waters were assessed in the most recent Clean Water Act 305(b) national water
quality inventory (GAO/RCED-00-54). Additional information soon will be available from the USGS
National Ambient Water Quality Assessment Program for about one-half of the conterminous United
States.)
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Although the categories in Table 5 are generally applicable, the specific
chemical/physical parameters that should be included in a particular reporting scheme will vary
depending on the spatial scale of the assessment and on whether the system being assessed is
fundamentally aquatic, terrestrial, or a mosaic of different ecosystem types. Note that chemical
fluxes and mass balance indicators are reported under the Ecological Processes EEA. Similarly,
descriptors of physical habitat quality and type are included in the Hydrology and
Geomorphology and/or the Biotic Condition EEAs.
a) Nutrient concentrations. Nutrients are elements required by plants and animals to
carry out their life functions. The establishment of a food web starts with autotrophic
organisms, who have the ability to produce organic matter from inorganic constituents, among
which are the essential elements we call "nutrients." Concentrations of nutrients, including
phosphorus, nitrogen, and potassium, and micronutrients (e.g., copper, zinc, and selenium)
provide important information about the condition of environments as these chemical
constituents may be limiting if available in too small a quantity and may lead to undesirable
consequences if present in too great a quantity. Phosphorus, for example, is often the limiting
nutrient in lakes. In estuarine and coastal ecosystems, nitrogen is often a limiting nutrient and
anthropogenic loadings of nitrogen may lead to over-enrichment and eutrophication. Similarly,
nitrogen is most often the limiting mineral nutrient in terrestrial ecosystems. In addition, the
balance between the amount of carbon (the energy currency) and nitrogen (the nutrient
availability currency) is a key parameter (C/N ratio) in determining the status of ecosystems and
their productivity. Measures of nutrient cycling are discussed under the Ecological Processes
EEA.
b) Trace inorganic and organic chemicals. This reporting category includes metals and
other trace inorganic chemicals, as well as organic chemicals10. Assessing the ecological
significance of chemicals in the environment requires an understanding of naturally occurring
levels of specific chemicals in an ecological system. Therefore, obtaining baseline information
on a broad spectrum of metals and organic chemicals in environmental samples is an important
step in ecological assessments, whether or not their concentrations are elevated by pollutant
discharges. For some chemicals, attention also should be given to specific fractions known to be
of greatest ecological importance (e.g., measures for trace metals should include both total and
acid extractable metals to provide insights on bioavailability and availability shifts over time).
As noted above and in Section 4, ecological condition assessments may include or exclude
xenobiotic chemicals and chemicals targeted because of their potential toxicity, persistence,
and/or tendency to bioaccumulate in the tissues of organisms and biomagnify in a food web. If
included, such parameters logically would be incorporated into this subcategory.
10Some chemicals in this category (e.g., zinc and copper) are essential in trace amounts and also may be
included in the nutrients subcategory, particularly if their concentrations may be limiting.
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c) Other chemical parameters. Other chemical parameters that should be reported will
differ depending on the environmental compartment (water, air, soil, and/or sediment) being
assessed. In soils and sediments, for example, measures such as total organic matter, cation
exchange capacity, and pH will be important. In aquatic environments, measures might include
alkalinity, biochemical oxygen demand (BOD), dissolved organic carbon (DOC), and water
transparency.
d) Physical parameters: Physical measures, many of which have been routinely
collected for years, are an important complement to other measures of physical habitat.
Examples are provided for soil and sediment environments, as well as for aquatic environments
and air.
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Table 5. Chemical and Physical Characteristics (Water, Air, Soil, and Sediment)
Category
Nutrient Concentrations
Trace Inorganic and
Organic Chemicals
Other Chemical
Parameters
Physical Parameters
Subcategory
Nitrogen
Phosphorus
Other Nutrients
Metals
Other Trace Elements
Organic Compounds
pH
dissolved oxygen/redox
potential
salinity
organic matter
other
soil/sediment
air/water
Example Indicators and Measures
e.g., concentrations of total N; NH4, NO3;
organic N, NOx; C/N ratio for forest floor
e.g., concentrations of total P; ortho-P;
particulate P; organic P
e.g., concentrations of calcium, potassium,
and silicon
e.g., copper and zinc in sediments and
suspended particulates
e.g., concentrations of selenium in waters,
soils, and sediments
e.g., methylmercury, selenomethionine
e.g., pH in surface waters and soil
e.g., dissolved oxygen in streams; soil redox
potential
e.g., conductivity
e.g., soil organic matter; pore water organic
matter concentrations
e.g., buffering capacity; cation exchange
capacity
e.g., temperature; texture; porosity; soil bulk
density; profile morphology; mineralogy;
water retention
e.g., temperature; wind velocity; relative
humidity; UV-B PAR; concentrations of
particulates; turbidity
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3.5 Ecological Processes
In this reporting framework, we define Ecological Processes as the metabolic functions of
ecosystems - energy flow, elemental cycling, and the production, consumption and
decomposition of organic matter- at the ecosystem or landscape level. In the proposed reporting
scheme, biological processes at the species, population and community levels, including gene
flow associated with community and population dynamics, are grouped with other biological
measures under Biotic Condition because these processes generally are assessed together.
Biological processes, however, legitimately may be incorporated under the Ecological Processes
EEA.
The most basic ecosystem attribute, fundamental to life on earth, is ecosystem
productivity, or the ability to capture sunlight and convert it to high energy organic matter
(biomass), which supports the non-photosynthetic trophic levels, including grazers, predators,
and decomposers. The balance among production, consumption and decomposition defines the
efficiency of an ecosystem, and its ability to provide the goods and services upon which society
depends. Using Lindemann's (1942) trophodynamic model of ecology, the metabolic
functioning of ecosystems can be conceptually divided into flows of energy and flows of
materials (including organic and inorganic matter). The balance between these flows evolves in
ecosystems to obtain "a self-correcting homeostatis..." (Odum, 1969). Condition reporting that
includes ecological processes allows us to examine how human perturbation of ecosystems has
affected this ecological integrity.
Although conceptual models of ecosystem functioning have included flows of energy and
materials for over 100 years (Forbes, 1887), these ecosystem processes are used less often in
environmental reporting than are static measures (like standing stock of biomass or chlorophyll)
because of the inherent difficulty in capturing rate measurements in summary-type, integrative
metrics. Process-level measurements also often have inherently higher variability than static
measurements, and cost more to obtain.
Notwithstanding these complications, improved reporting of ecosystem processes will
require increased use of material and energy budgets, rather than simply concentration
measurements. Some indicators of material and energy flow are amenable to repeated sampling
through time of a number of statistically-chosen individual sites-the approach taken by EPA's
EMAP. Characterizing and reporting on ecological processes often is best accomplished using
multi-tiered monitoring systems in which integrative ecosystem-level measures are coupled with
detailed examination of processes at smaller spatial scales (e.g., Hubbard Brook Experimental
Forest and other National Science Foundation Long Term Ecological Research sites, Canada's
Experimental Lakes Area). A multi-tiered approach has been advocated by the White House's
Committee on Environment and Natural Resources (CENR) and incorporated into some EMAP
programs. A commitment to small-scale, intensive, long-term process-based monitoring
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programs within larger monitoring studies will continue to strengthen the scientific basis for
indicators11.
The key attributes of energy and material cycling in ecosystems are gross and net
ecosystem productivity, the efficiency of energy transfer through food webs, and flows of carbon
and nutrients (commonly referred to as biogeochemical cycling). Many of the examples listed
below and in Table 6 are taken from the NRC's recent publication, Ecological Indicators for the
Nation (NRC, 2000). However, the Panel stresses, as did NRC, that adequate indicators are not
yet available for all of the key attributes of commonly held conceptual models for energy and
material flows in ecosystems.
a) Energy Flow. The flow of energy between trophic levels and the interaction between
heterotrophic and autotrophic components are universal features of ecosystems (Odum, 1969).
Thus energy flow includes the concepts of both productivity and growth efficiency. Production
can be conceptualized and reported in a variety of ways. Gross primary production is the amount
of carbon fixed by an ecosystem as a result of photosynthesis. Net primary production is the
difference between energy capture (photosynthesis) and metabolic processes (respiration) in
plants alone. Net ecosystem production subtracts energy loss through the metabolism of
heterotrophic organisms, including decomposers and consumers. In general, indicators of
ecosystem production are fairly mature relative to indicators for other ecosystem processes.
1. Primary Production. Measures of gross and net primary production are diverse in
scale and methodology, and range from estimates of production made from standing
chlorophyll stocks or nutrient concentrations, to direct measurements of primary
production in enclosed containers.
2. Net ecosystem production is the difference between whole-ecosystem primary
production and respiration. Estimates of net ecosystem production indicate whether an
ecosystem is self- supporting via primary production within the system boundary or
whether organic matter must be imported across the system boundary in order to sustain
biological integrity. NRC (2000) recommended that net ecosystem production be
assessed through net ecosystem organic carbon storage, or the change in the total amount
of organic carbon in an ecosystem per unit time. Measures of carbon storage (e.g.,
carbon sequestered in soils and vegetation) are critical to calculating CO2 loading of the
atmosphere and associated alteration of global climate. In forested ecosystems, the
1 'The choice of scales is of key importance in the examination of ecological condition and, therefore, in the
design of indicator programs for ecological processes (NRC, 2000). Estimates of metabolic function must
be made on temporal and spatial scales that are appropriate to the growth rate and spatial distribution of the
organisms driving the process (often microorganisms with rapid growth rates), and to disturbance regimes
that affect those organisms (cf. Hutchinson, 1967).
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change in the standing stock of trees (in non-harvested forests) plus the change in organic
matter content of soils provides a measure of net ecosystem production. Key ecosystem
products (e.g., wood, fishery yields, or crop production) also traditionally have been used
as measures of ecosystem production. Although these are valuable indicators for
ecological products that are desirable to humans, they should not serve as sole surrogates
for measures of whole-system net production. In aquatic ecosystems, production-to-
respiration (P/R) ratios are commonly obtained from the change in oxygen or carbon
dioxide fluxes over light/dark cycles. Local and satellite-based measures of CO2 flux
from ecosystems are somewhat less well developed, but may provide excellent integrated
measurements of net ecosystem production.
3. Growth Efficiency. Ecosystem growth efficiency is a fundamental attribute of
ecosystems, defining how well energy and carbon are transferred through food webs. The
concept of growth efficiency arises from Lindemann's (1942) model of the efficiency of
energy and material transfer between trophic levels, i.e. from primary producers to top
consumers. It also includes the efficiency of energy and material transfer through
decomposition and microbial grazers (i.e., the microbial loop; Azam et al., 1983). By
comparing primary production with net ecosystem production, a measure of net
ecosystem growth efficiency can be obtained.
Integrative indicators are needed to show how production is translated and distributed
among trophic levels. In aquatic ecosystems, for example, high productivity at the
bottom of the food web without translation to higher trophic levels may result in
ecosystems that are less desirable to humans (e.g., more algae, fewer fish). Measures of
growth efficiency often are confined to upper trophic level production, especially
production of organisms with direct value to humans (e.g., game fish). These measures
should be broadened to include wider measures of energy transfer within food webs.
b) Material Flow. Key materials in ecosystems include organic matter, and inorganic
nutrients (e.g., nitrogen and phosphorus) and micronutrients (such as selenium and zinc). The
flows of these materials in ecosystems are often referred to as biogeochemical cycles. Material
and energy flow are linked processes and many indicators provide information on both,
especially for carbon flow.
1. Organic Carbon Cycling. All known life is based on carbon, and carbon
cycling—from carbon dioxide, to algal or plant biomass, higher trophic levels, and
microbial decomposition pathways— is a fundamental ecological process.
Characterization of carbon cycling would include input/output budgets, gross and net
organic carbon production, and efficiency of organic carbon transfer through the food
web. Net ecosystem production (see above) is a commonly used, but incomplete
indicator of organic matter cycling. Increased attention is being given to the quantity and
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quality of organic matter in ecosystems, and the influence of organic matter quality on
ecosystem integrity. The Panel encourages the development of integrative measures of
organic carbon quality and trophic transfer. Additionally, we recommend that, for the
many aquatic systems that depend on allocthonous sources of organic carbon, organic
carbon inputs should be included in materials budgets along with measures of nutrient
inputs.
2. Nutrient Cycling. Concentrations of nutrients are commonly measured in ecosystems
but the content of nutrients in various ecosystem compartments, the rates of transfer
among ecosystem compartments, and the mechanisms governing those transfers are less
often examined. Additions to the ecosystem and losses from the ecosystem over time are
critical parameters to define in order to evaluate ecological integrity and sustainability.
Highly complex pathways of nutrient cycling for elements like nitrogen underscore the
need to define rates of nutrient cycling with attention to the importance of time. Nitrogen
concentrations in plant tissues can vary over the life of the plant, over the growing
season, and among years for perennial vegetation. Knowing a single concentration at one
point in time provides limited information on the status of nitrogen accumulation or
depletion in the ecosystem. Forests can at once accumulate nitrogen in the soil and forest
floor while simultaneously becoming more nitrogen limited for forest growth. Measuring
the "available" pool of either a macronutrient or micronutrient in the soil does not
provide information on what total pools of these constituents might be present or how
that availability might change (either providing more of a needed nutrient or creating
conditions of detrimental excess) if environmental conditions change. In short,
understanding nutrient cycling rates illuminates both the condition of an ecosystem and
its potential response to disturbance. Defining the bounds of the ecosystem measured is a
critical component of defining nutrient budgets and cycling.
Outputs from one environment (habitat) can affect the receiving environment (habitat);
for example, nitrogen outputs from the Mississippi River drainage enter the Gulf of
Mexico and are associated with hypoxic events caused by phytoplankton growth and
decay. The feasibility and utility of input-output studies were demonstrated in the
Hubbard Brook studies, which used the properties of rivers to converge into a single
output stream to monitor a watershed's outputs. By comparing precipitation inputs to
outputs of harvested and intact forests, the researchers discovered acid precipitation.
Measures of nutrient cycling should include input/output mass balance (e.g., for nitrogen,
phosphorus, and other nutrients), identification of dominant nutrient cycling pathways,
and nutrient use/efficiency balance. Seitzinger et al. (2000) have developed large-scale
nutrient budgets, based on inputs from rivers and coastal areas to the oceans, that will
provide a basis for examining global and regional changes in nutrient cycling.
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Table 6. Ecological Processes
Category
Subcategory
Example Indicators and Measures
Energy Flow
Primary Production
e.g., production capacity (total chlorophyll per
unit area); net primary production (plant
production per unit area per year); tree growth
or crop production (terrestrial systems);
trophic status (lakes); 14-CO2 fixation rate
(aquatic systems)
Net Ecosystem Production
e.g., net ecosystem organic carbon storage
(forests); diel changes in O2 and CO2 fluxes
(aquatic systems); CO2 flux from all
ecosystems
Growth Efficiency
e.g., comparison of primary production with
net ecosystem production; transfer of carbon
through the food web
Material Flow
Organic Carbon Cycling
e.g., input/output budgets (source
identification-stable C isotopes); internal
cycling measures (food web structure; rate and
efficiency of microbial decomposition; carbon
storage); organic matter quality and character
N and P Cycling
e.g., input/output budgets (source
identification, landscape runoff or yield);
internal recycling (N2-fixation capacity;
soil/sediment nutrient assimilation capacity;
identification of growth-limiting factors;
identification of dominant pathways)
Other Nutrient Cycling (e.;
K, S, Si, Fe)
e.g., input/output budgets (source
identification, landscape yield); internal
recycling (identification of growth-limiting
factors; storage capacity; identification of key
microbial terminal electron acceptors)
Biological Processes
(Note: Also may be reported
under Biotic Condition)
Community Dynamics
e.g., predation rate; successional state;
pollination rate; herbivory
Population Dynamics
e.g., birth and death rates; reproductive or
recruitment rates; dispersal and other
movements
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3.6 Hydrology/Geomorphology
The hydrology and geomorphology characteristics of ecological systems reflect the
dynamic interplay of water flow and landforms. In river systems, for example, attributes such as
water flow patterns and the physical interaction among a river, its riverbed, and the surrounding
land determine whether a naturally diverse array of habitats and native species are maintained
and whether the natural succession or transition from one habitat type to another is maintained.
These underlying physical processes are disrupted when rivers are dammed, streambeds are
channeled into concrete banks, and large percentages of flow are taken out of the river for human
use.
The geomorphic pattern of stream/river habitat and the hydrology that sets, maintains,
and reforms it serve as the physical template upon which the life cycles of running water
organisms are overlain. That is, the deterministic life cycles of aquatic organisms are adapted to
the most probable states of a stochastic system. For example, some aquatic insects have evolved
such that the time of their most vulnerable life stages coincides with the most probable period of
stable flows over the long term. Further, females of many aquatic species deposit their eggs in
areas where re-aeration keeps water well-oxygenated, thereby enhancing egg survival. Thus,
changes in hydrology and geomorphology provide important information about future Biotic
Condition and Landscape Condition.
In this sample hierarchy, Hydrology and Geomorphology are divided into three
interrelated components: water flow; dynamic structural characteristics, and sediment transport.
Water flow regimes affect sediment movement and patterns of erosion and deposition. Sediment
transport partially determines which habitats occur where (both above the water and below it).
The dynamic structural characteristics — the biotic and abiotic components of the water-related
habitats - are created and maintained by water and sediment flows. They also influence water
flow patterns and availability of sediment for transport. While the three-part division is to some
extent arbitrary, it is a useful construct to assure that essential water-related habitats (e.g.,
gravelly riffles, deep pools, nearshore shaded areas, floodplains) and the dynamic physical
processes that sustain them are not overlooked in ecosystem assessments. Some categories
included in Hydrology/Geomorphology—such as pattern of surface flows, channel complexity,
and distribution and extent of connected floodplain-also may be reported as elements of
Landscape Condition.
a) Water Flow. Surface and groundwater flows determine which habitats are wet or dry
and when, and water flows transport nutrients and contaminants. It is less widely recognized,
however, that the variability of water flows (in addition to their timing and magnitude) exerts a
controlling influence on the creation and succession of habitat conditions. The category of
surface and groundwater flows therefore includes the amount, timing, flow direction, and
variability of water flows.
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1. Pattern of surface flows. In rivers, a natural flow regime "organizes and defines river
systems" (Poff et al., 1997). Even where water flows are regulated, maintaining a natural
pattern of variability - if not flow magnitude - helps to support native species and a
diverse array of habitats. Patterns of flow variability also are directly related to aquatic
community structure and help maintain native species. Detailed indicators of the
magnitude, frequency, duration, timing, and rate of change of river flows have been
developed (Richter et al. 1996; see also Poff et al., 1997 and Richter et al., 1997 for a
discussion of the underlying conceptual model). Although simpler surrogates may be
used, particularly for other aquatic (non-riverine) and terrestrial systems, an effort should
be made to capture the low-flow and high-flow amount, timing, and variability of surface
flows. Note that periodic floods (which maintain habitat diversity, affect sediment
particle size distributions in the channels and in the floodplains, and provide the
disturbances that generally favor native species) are also treated under Natural
Disturbance Regimes and could reasonably be reported in either category.
2. Hydrodynamics. The velocity and direction of water flows determine the movement
of nutrients and contaminants in both surface and groundwater systems and have led to
numerous adaptations of attachment and feeding among running water organisms. In
estuaries, circulation and mixing are controlling physical processes that determine
residence times of pollutants and nutrients, affect the biomass and community
composition of plankton, and help determine the distribution of aquatic and wetland
habitats.
3. Pattern of groundwater flows. Groundwater is of interest because it supplies water
and chemicals to terrestrial and aquatic systems. It is also becoming more widely
recognized as an important ecosystem in its own right. Relevant attributes therefore
include the transfer of groundwater to surface systems, the mass balance of groundwater
in an aquifer, and the rate and direction of water movement within an aquifer.
4. Spatial and temporal salinity patterns. In brackish systems such as estuaries and
brackish wetlands, patterns of salinity are determined by water flows and mixing
characteristics (by-products of hydrodynamics and geomorphology) and in turn
determine habitat suitability for biotic communities. Ideally, salinity patterns should
remain within natural ranges and should vary through time in a pattern consistent with
natural conditions. This parameter may be incorporated within the Chemical/Physical
EEA, but is cross-listed here in order to highlight its importance in certain system types.
5. Water storage. Water storage refers to the amount of water in a lake or aquifer. For
lakes, wetlands, and aquifers, water storage integrates surface and groundwater flows. In
the surface systems, fluctuations in water storage determine the area inundated and
influence shoreline and wetland vegetation patterns. In aquifers, water storage
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determines the extent of surface water ponding, in addition to flow rate and direction. In
extreme circumstances, depletion of water in an aquifer can cause the supporting
structure to collapse, destroying the aquifer's storage capacity.
b) Dynamic structural characteristics. Maintenance of the diversity of natural habitats
in aquatic systems is a dynamic process involving variations in water flow, erosion and
deposition of sediments, and transport of other materials. Where these processes continue to
operate, specific structural patterns can be observed in the streambed (or lakebed or bottom
terrain of estuaries) and banks (or shoreline). Accordingly, dynamic structural characteristics
reflect the maintenance of these underlying processes, and they provide direct information about
the quality and diversity of habitats.
Dynamic structural characteristics overlap to some degree with the more stable structural
characteristics included under Landscape Condition. The dynamic characteristics are grouped
with hydrology here, because hydrology and fluvial geomorphology are closely related in
aquatic systems and are often neglected in assessments of ecosystem condition. In terrestrial
systems, however, the attributes of habitat complexity, connectivity, and topographic relief tend
to be more stable and may logically be included (and aggregated with other attributes) under the
Landscape Condition category.
Although the structural characteristics are divided here into several subcategories, they
can be assessed as a group and combined with information on material transport, as in EPA's
Rapid Bioassessment Protocols (Barbour et al., 1999), the EMAP, and the National Ambient
Water Quality Assessment Program (NAWQA) program of the USGS.
1. Channel morphology and shoreline characteristics Shoreline and channel
characteristics are significant indicators of habitat quality for aquatic organisms. The
inside of bends - where banks and channel bottom are eroded and sediment is
transported away — provide deep water areas for passage or temporary refuge for
organisms, such as migrating salmonid fishes; the outside of bends — where flows are
reduced and sediments are deposited — provide areas for establishment of organisms with
longer residence times. As the inside bends continue to erode, oxbows and backwaters
can develop which contribute significantly to channel complexity (see below). The
relationship of the vegetation on the banks, the riparian zone, to the stream channel is a
critical feature of aquatic habitats. The vegetation can provide shade that limits aquatic
plant growth and moderates water temperatures; the roots contribute, along with the
nature of the soil material, to bank stability; and large wood derived from bank
vegetation can provide some of the best in-channel habitat available to organisms. In
fact, in active channels dominated by fine sediments, large wood may constitute the only
stable habitat available to invertebrates.
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2. Channel complexity. Stream islands, their associated point bars, and braids12
constitute channel complexity that often confers important biotic diversity on a river
system. Islands and braids result from differential cutting of the channel and deposition
of sediment downstream from obstructions such as patches of exposed bed rock, large
boulders, or woody debris. Both islands and braids increase the edge habitat where
terrestrial or semi-aquatic vegetation can significantly influence the community structure
of the aquatic biota. For example, braids essentially extend riparian plant cover found
along smaller headwater channels to larger, wider river reaches. Channel complexity in
marshes and river floodplains increases the amount of edge habitat and allows for the
interface of different plant assemblages and invertebrates that require the different flow
regimes that occur on the inside vs. outside of meanders in such channels.
3. Distribution and extent of connected floodplain For many aquatic organisms, the
off-channel or seasonally wetted habitats can be of utmost importance. These areas of
interface between aquatic and terrestrial habitats provide such qualities as refugia of
reduced flow during high discharge periods in streams and rivers, and reproduction (e.g.,
fish spawning) or feeding areas for aquatic animals when access from the main water
body is available. Isolation of rivers, lakes, or estuaries from their associated floodplains
or wetlands by diking can greatly reduce productivity of the aquatic biota. Connected
floodplains also are important for attenuation of the impact of peak water flow on
downstream areas, recharge of groundwater aquifers, and deposition of sediment.
Similarly, coastal wetlands connected to estuarine environments provide natural
attenuation of tidal and storm surge energy, reducing coastal flooding and erosion.
4. Aquatic physical habitat complexity. In aquatic systems, several specific structural
characteristics are associated with instream habitat type and condition. These include, for
example, areas of shaded riparian habitat (that moderate temperature, reduce aquatic
primary production, and provide carbon inputs from dropping leaves), presence of large
woody debris (that provides areas to rest and hide), and alternating patterns of riffles,
runs and pools (that may provide clean spawning gravels and feeding areas).
Maintenance of these features can be critical to support of native communities.
c) Sediment and other material transport. A wide variety of underwater and near-
shore habitats (e.g., wetlands, early successional states in riparian areas) is maintained by the
pattern of sediment and debris movement, and native species have adapted accordingly.
12Point bars are composed of coarse sediments deposited in areas of reduced water velocity, e.g., on the
down-stream side of islands. Braids are secondary channels connected to or part of the main flow channel.
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1. Sediment supply and movement. The transport and storage of sediment are major
forces that determine the distribution of instream and wetland habitats. Biologically
healthy rivers are usually characterized by an approximate balance between scour and
deposition of sediments. If deposition significantly exceeds transport, then reliable,
stable habitat for sessile invertebrates may be buried and gravels where eggs are
deposited by spawning fish may become silty. On the other hand, excessive scour can
remove the very sediment required to support the attachment or spawning activities.
2. Particle size and distribution. Sediment particle size has been shown repeatedly to
have significant influences on aquatic organisms. Coarse sediments are used for
attachment by many aquatic invertebrates, the intermediate sizes are important for many
spawning fish, the fine sizes are selected for burrowing and tube construction by
invertebrates, and very fine sediments (silts and clays) may be ingested by many
invertebrates that derive nutrition by digesting the bio-films that adhere to the particle
surfaces. The sediments of the channel bed are distributed in accordance with the
hydraulic conditions that deposited them, with coarse sediments in areas of higher flow
and finer particles in lower velocity drop zones. The aquatic organisms will be
distributed in accordance with their predictable sediment particle size requirements.
3. Other fluxes. Habitat complexity and productivity in rivers, lakes, wetlands and
estuaries are maintained, in part, by fluxes of water, sediments, nutrients, organic matter
(in allocthanous systems), and large woody debris. This category is designed as a catch-
all for the items, such as large woody debris and other carbon inputs, that may not be
captured elsewhere in the reporting hierarchy.
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Table 7. Hydrology and Geomorphology
Category
Subcategory
Example Indicators and Measures
Surface and Groundwater Flows
Pattern of Surface Flows
(rivers, lakes, wetlands, and
estuaries)
e.g., flow magnitude and variability,
including frequency, duration, timing, and
rate of change; water level fluctuations in
wetlands and lakes
Hydrodynamics
e.g., water movement; vertical and
horizontal mixing; stratification; hydraulic
residence time; replacement time
Pattern of Groundwater Flows
e.g., groundwater accretion to surface
waters; within-groundwater flow rates and
direction; net recharge or withdrawals;
depth to groundwater
Spatial and Temporal Salinity
Patterns (estuaries and
wetlands)
e.g., horizontal (surface) salinity gradients;
depth of pycnocline; salt wedge
Water Storage
e.g., water level fluctuations for lakes and
wetlands; aquifer capacity
Dynamic Structural
Characteristics
Channel Morphology;
Shoreline Characteristics;
Channel Complexity
e.g., mean width of meander corridor or
alternative measure of the length of river
allowed to migrate; stream braidedness;
presence of off-channel pools (rivers);
linear distance of marsh channels per unit
marsh area; lithology; length of natural
shoreline
Distribution and Extent of
Connected Floodplain (rivers)
e.g., distribution of plants that are tolerant
to flooding; presence of floodplain
spawning fish; area flooded by 2-year and
10-year floods
Aquatic Physical Habitat
Complexity
e.g., pool-to-riffle ratio (rivers); aquatic
shaded riparian habitat (rivers and lakes);
presence of large woody debris (rivers and
lakes)
Sediment and Material Transport
Sediment Supply and
Movement
e.g., sediment deposition, sediment
residence time and flushing
Particle Size Distribution
Patterns
e.g., distribution patterns of different
grain/particle sizes in aquatic or coastal
environments
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Other Material Flux
e.g., transport of large woody debris
(rivers)
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3.7 Natural Disturbance Regimes
Over sufficient time scales, all ecological systems are dynamic in nature. This dynamism
results in part from discrete and recurrent disturbances that may be physical, chemical, or
biological in nature. Examples of natural disturbances include wind and ice storms, wildfires,
floods, drought, insect outbreaks, microbial or disease epidemics, nonnative invasive species
introduction, volcanic eruptions, earthquakes and avalanches.
White and Pickett (1985) define a disturbance as "any relatively discrete event in time
that disrupts ecosystem, community, or population structure and changes resource, substrate
availability, or the physical environment." Given sufficient knowledge of the natural history of a
region, patterns of natural disturbance regimes can be described. The frequency, intensity (i.e.,
degree of disturbance), extent (i.e., spatial coverage), and duration of the events taken together
are referred to as the "disturbance regime." An assessment or report on the condition of an
ecological system should address each of the disturbance regimes relevant to that system.
Disturbances are ecologically important when the imprint they leave on the ecological
system is large in area or persists for a very long time, or when the disturbance is an integral part
of the ecological system. Both species and ecosystems may be adapted to either frequent or large
disturbances (Grime, 1977). Harper (1977) argues that the evolution of attributes that enable a
species to respond to a disturbance relate to the frequency of the disturbance events, relative to
the life span and pattern of the life cycle (e.g., the aquatic insect species that have a terrestrial
adult stage that overlays the normal periods of flooding) of the organism of concern. The size of
the disturbance also influences the characteristics of species which inhabit a site. In some cases,
a large disturbance event may even be the dominant force structuring the system, creating the
template upon which subsequent ecological processes and interactions among species occur.
Large crown fires in boreal forests, for example, create a mosaic of stands of varying ages that
may persist for several centuries (Romme and Knight, 1982). Volcanic eruptions create a spatial
structure for vegetation patterns that may endure for millenia.
Disturbances typically do not result in extensive areas of uniform impact (Turner et al.,
1998). Rather, they create complex heterogeneous patterns across the landscape in which the
disturbances have affected some locations but not others. For example, exposed ridges are more
susceptible to damaging winds than sheltered coves (Boose et al., 1994), and even very large
fires leave some stands unscathed because of wind shifts or natural fire breaks (Turner and
Romme, 1994). The disturbance-generated mosaic has important influences on biotic structure
and ecosystem processes. Understanding the nature of these landscape patterns and the factors
controlling them is essential for understanding and predicting ecosystem dynamics and
vegetation development, and for developing guidelines for natural resource management (Dale et
al., 1998).
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Natural disturbance regimes are not the equivalent of environmental stressors as the term
is used in ecological risk assessment (see, e.g., EPA, 1998). However, human-induced changes
to natural disturbance regimes (e.g., changes to fire regimes as a result of human fire-suppression
activities; changes to flood regimes as a result of damming or channeling a river; changes in
local weather patterns as a result of urbanization or forest removal) would be considered
stressors to ecological systems. As with other parameters that are included in ecosystem
condition reports, therefore, interpretation of data on disturbance variables requires comparison
to "reference conditions" (in this case historical disturbance patterns) in order to detect changes
that might indicate current or future change to ecological system function and sustainability (see
Section 5).
a) Frequency of a disturbance refers to its return or recurrence interval. Some events,
such as spring rains and snow melts that result in local flooding, occur annually or every few
years and are not considered disturbances. On the other hand, rare and extreme flood events are
generally considered to be those in which the area inundated, water depth, or water volume is
beyond two standard deviations of the mean. For example, the 1993 floods in the midwestern
U.S. were well beyond two standard deviations of the 30-yr averages for both depth and duration
of summer flooding (Sparks and Spink, 1998). A frequency distribution of disturbance events
(e.g., a 200-year flood) can be used to identify disturbances.
b) Intensity of a disturbance refers to the effects of the disturbance on the biota, rather
than the energy released or force exerted by the disturbance, and it includes both the severity and
magnitude of impact. Disturbance intensity is important in its own right; for example, hurricanes
of the same spatial extent may have highly variable severities, which strongly influence
ecological responses. The relationship between disturbance size and intensity is complex. The
heterogeneity created by disturbances refers to the spatial distribution of disturbance intensities
across the system. In the case of rivers, channel configuration is, on average, driven by
intermediate level flow events; average annual flows being too small to create much physical
alteration and very large events being rare (Wolman and Miller, 1960).
c) Extent is the spatial coverage of the disturbance event. Disturbance extent can be
identified by statistical distributions (Turner and Dale, 1998), such as the mean and standard
deviation. In landscapes affected by crown fires, a size distribution indicates that 1-3% of fire
events account for 97-99% of the area burned (Bessie and Johnson, 1995). Thus, these few fire
events are both infrequent and very extensive.
Alternatively, disturbance extent may be defined by perception of the event relative to a
human scale or to the lifespan and attributes of the organisms in the ecosystem. For example, the
1980 eruption of Mount St. Helens was neither excessively large nor rare when considered in
geologic time (Harris, 1986), but it was large when considered from the perspective of humans
and the organisms that inhabited the area. It is important to recognize that "large" may well be a
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function of the relative size of the organisms. For example, a storm-induced disturbance patch of
35 to 100 m2 in the intertidal zone may seem small from the human perspective, but it is large
relative to the organisms that reside there. What is considered infrequent also must be
considered relative to the lifespan of the affected organisms.
d) Duration refers to the temporal scale of the disturbance event, which may range from
minutes/hours (e.g., earthquakes and some weather events) to days/weeks (e.g., some fire events)
to months or years (e.g., some insect outbreaks). Long-running disturbances tend to have the
greatest ecological impact. For example, droughts of several years can result in soil loss and
local changes in species composition.
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Table 8. Examples of Natural Disturbance Regimes
Example 8a: Fire Regime in a Forest
Category
Frequency
Intensity
Extent
Duration
Example Indicators and Measures
e.g., recurrence interval for fires
e.g., occurrence of low intensity (forest litter fire) to hig
fires
i intensity (crown fire)
e.g., spatial extent in hectares
e.g., length of fire events (from hours to weeks)
Example 8b: Flood Regime
Category
Frequency
Intensity
Extent
Duration
Example Indicators and Measures
e.g., recurrence interval of extreme flood events
e.g., number of standard deviations from 30-year mean
e.g., number of stream orders (and largest order) affected
e.g., number of days, percent of water year (October 1- September
30)
Example 8c: Insect Infestation
Category
Frequency
Intensity
Extent
Duration
Example Endpoints and Measures
e.g., recurrence interval for insect infestation outbreaks
e.g., density (number per area) of insect pests
in an area
e.g., spatial extent of infested area
e.g., length of infestation outbreak
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4. INDICATORS OF STRESS - THE PARALLEL UNIVERSE
4.1 The Role of Stressor Indicators
In practice, reports about ecosystem condition often combine condition indicators with
stressor indicators, at times indiscriminately. For the reasons outlined below, the SAB
framework distinguishes between (natural) ecological condition indicators and (anthropogenic)
stressor indicators, and the Essential Ecological Attributes and example indicators relate only to
condition. This approach is consistent with the National Research Council's decision to "focus
its recommendations on national indicators that inform about the status and trends in ecosystem
extent, condition, and functioning, rather than focusing specifically on indicators of the stressors
themselves" (NRC, 2000). The focus on condition indicators is also consistent with The Heinz
Center's Report on the State of the Nations's Ecosystems (The Heinz Center, 1999; in press).
Other environmental reporting schemes incorporate both condition and stressor
indicators, but are careful to distinguish the two. The internationally recognized "Pressure-State-
Response" model of environmental indicators used by the Organisation for Economic
Cooperation and Development (OECD, 1998), distinguishes pressures (i.e., stressors) from state
(i.e., condition) variables, as does the Harwell et al. (1999) proposal for a report card framework.
The ecological assessment and reporting scheme for the Great Lakes (Environment Canada and
U.S. Environmental Protection Agency, 1999) also includes both pressure and state indicators.
Ultimately, the decision on whether (and how) to include stressors in an ecological condition
assessment may depend primarily on the purpose of the assessment. Because the framework
proposed here may be used in a scheme that also includes the "parallel universe" of
anthropogenic stressors, this section discusses how stressor variables relate to the framework of
EEAs, categories, and subcategories presented in Section 3.
One category of environmental assessments ™ , . , . ,
Ecological risk assessment is a process
that often will include information on both that evaluates the ilkeilhood that adverse
condition and stressor measures is that of ecological ecological effects may occur or are
risk assessment. Although risk assessments are occurring as a result of exposure to one or
generally focused on understanding the effects of more stressors... Changes often considered
Al . 1 • 1 ^ ^1 undesirable are those that alter important
anthropogenic stressors on ecological systems, the . , ,, , , . . ..
^ ° ° J ' structural or functional characteristics or
framework proposed here may provide a useful components of ecosystems." (EPA, 1992)
reference scheme for such assessments.
Specifically, the array of ecological attributes
presented in Table 1 may be used as a checklist to help formulate conceptual models related to
ecosystem structure and function, and as a checklist to identify the assessment endpoints that
should be evaluated to detect adverse effects.
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4.2 Rationale for Separating Condition and Stressor Assessments
Distinguishing ecological condition indicators from anthropogenic stressor indicators has
a number of advantages. First, it more clearly differentiates natural variations from human-
induced variations. This distinction facilitates environmental remediation and natural resource
management in those situations where managers do not intend to alter natural variations,
including those caused by natural disturbance regimes. Increasingly, society has recognized that
altering natural disturbance regimes (e.g., restricting the frequency of forest fires or altering the
course of rivers) may have serious long-term adverse effects.
Second, addressing anthropogenic stressors separately enables more systematic
assessment of the relationships between these stressors and ecosystem impacts. Anthropogenic
stressors may have both direct and indirect effects upon one or more Essential Ecological
Attributes. Assessing the complete array of condition indicators, as well as stressor indicators,
can aid the analysis of the causal mechanisms underlying compromised ecosystem conditions.
In addition, as Harwell et al. (1999) recognized, stressors often can be characterized more easily
and rapidly than their effects because there may be a significant lag time between the stressor
and the effect.
A third reason for the distinction between indicators of condition and of stress is to
encourage indicator selection criteria to be based upon fundamental environmental attributes and
processes, rather than current data availability. Reports on ecosystem condition often focus
primarily or exclusively on anthropogenic stressors because data of this type (e.g., on emissions,
criteria exceedances, or incidents) already are collected through conventional regulatory
processes. This focus on select data creates potential for overlooking important ecosystem
characteristics and prioritizing environmental risks and protection needs inappropriately.
Last, distinguishing condition and stressor indicators can be helpful in allocating
management responsibilities among public and private institutions, depending upon their
charters and regulatory domains. An assessment and reporting framework that separates, yet
clearly links, stressor and condition measures may lead to more comprehensive, cross-agency
and cross-media coordination of environmental management functions.
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4.3 The Relationship Between Ecological Condition and Stressor Indicators
Figure 4 illustrates the relationship between common anthropogenic stressors and one or
more of the Essential Ecological Attributes. Stressors were qualitatively identified with one or
more of the EEAs on the basis of how their effects are mediated, reflecting the multiple
mechanisms by which stressors may affect different aspects of ecological systems. The Panel
concluded that each EEA (and each category, each subcategory, and many indicators) may be
affected by more than one stressor. Conversely, each stressor may directly (and/or indirectly)
affect more than one EEA (and category and subcategory). For example, habitat conversion may
fa
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H abitat fragme ntation
Climate chanse
Invasive non-native species
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Hydrologic alteration
Habitat conversion
H abitat fragme ntation
Climate change
Over-harvesting of vegetation
Large-scale invasive
species introductions
Large-scale disease/pest outbreaks
Pesticides \ ' ,."
1 Habitat conversion
Disease/pest outbreaks d „, . . ,
T Climate change
Nutrient pulses /-, 7 ^ * *•
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Metals ~ . < , ,
Disease/pest outbreaks
Dissolved oxygen depletion Landscape Alteredf ire regime
Ozone (troposphenc) Condition Altered flood regime
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Figure 4. Sample stressors and the Essential Ecological Attributes they affect.
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alter groundwater and surface flows, and the change in groundwater levels may then alter the
intensity and extent of fires. In short, a one-to-one correlation between a particular attribute and
a single stressor may occur, but often may be a misleading oversimplification.
In general, stressors fall into one of two categories: a) unnatural and adverse
perturbations of ecological attributes; or b) the introduction of a foreign agent - physical,
chemical or biological — into an ecosystem at a level that interferes with essential ecological
processes.
In the first category, the stressor indicator is a significant and adverse departure "beyond
reference conditions" assumed for the ecological indicator. Thus, it is important to define the
natural range of variability in environmental conditions, to which ecological systems presumably
are adapted, as distinguished from extreme or atypical variations induced by human activities.
(See Section 5 for discussion of reference conditions.) In the case of chemical or physical
attributes, condition measures may have the same units as measures used to report on
anthropogenic stressors. For example, dissolved oxygen and pH are measures of water
chemistry that are useful for describing both pristine and impacted surface waters. Natural
variation in these environmental parameters defines in part the types of organisms adapted to
those waters. On the other hand, anthropogenic stressors (e.g., high organic loadings or acid
deposition) may introduce excursions and deviations in dissolved oxygen and pH beyond natural
ranges and cycles, thus altering the resident biological communities.
Stressors in the second category may require a different set of measures (e.g.,
concentration of a xenobiotic chemical; infestation of an introduced pest species) than those
chosen as the ecological indicator or measure. A comparison of condition indicators and stressor
indicators for hydrology and geomorphology characteristics, for example, illustrates this point
(see Table 9). Both Table 9 and Figure 4 tend to underplay the fact that most stressors do not
have a one-to-one relationship with ecological condition attributes. Ecological risk assessments
use conceptual models to relate each major stressor to its potential effects on multiple condition
parameters. Conversely, assessment of ecological condition shows the effects of multiple
stressors and highlights unforeseen effects.
The distinction between condition and stressor indicators is to some extent a subjective
judgment. The Heinz Center report (in press), for example, includes concentrations of
xenobiotic chemicals as condition indicators. In other cases, a measure may legitimately be
considered both a condition and stressor measure; for example, tissue burdens of pesticides
may be a condition measure (for the organism) and a stressor measure (for the organism's
consumers). The decision to report levels of xenobiotic chemicals in the environment as
indicators of condition (or even as indicators of stress) may be controversial, however, because
of the difficulty in determining what levels of such chemicals may be associated with
environmental effects. For example, recent monitoring studies have reported low
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concentrations of many xenobiotic compounds (e.g., pharmaceutical chemicals, personal care
products, and agrochemicals) in multiple environmental media (Kolpin et al., 2002), but the
implications of these findings for environmental condition are unclear. After considerable
debate, the Panel concluded that chemical concentrations in the environment logically could be
reported as either condition or stressor measures, depending on whether and how the chemical
impacts the ecological system. In some cases, it may be necessary or appropriate to report on
levels of xenobiotic chemicals as indicators of prior exposure or potential vulnerability. In other
cases, xenobiotic chemicals may be listed as condition indicators in order to reflect their
dominant effect or control on the system. Alternatively, xenobiotic chemicals (or introduced
species) may be reported as stressor indicators when they are associated with adverse ecological
effects. In the latter case, an interpretive guideline (e.g., a water quality criterion, a soil
screening level, or an effects threshold in a bioassay) may be required to establish causality or
severity. Finally, the Panel notes that, in highly managed or modified ecosystems, stressors may
be introduced intentionally to maintain the ecosystem in its desired state (e.g., herbicides in
agricultural plots, introduced species of game fish in a lake). In these cases, the definition of
stressor vs. condition indicators is highly subjective and will be determined by the context and
the authors' judgment.
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Table 9. Comparison of Condition Indicators and Stressor Indicators: Examples for
Hydrology and Geomorphology
Essential
Ecosystem
Attribute
Hydrology and
Geomorphology
Category
Surface and
Groundwater
Flows
Dynamic
Structural
Characteristics
Sediment and
Material
Transport
Subcategory
pattern of
surface flows
pattern of
ground water
flows
channel
morphology;
shoreline
characteristics
sediment
supply and
movement
Example Ecological
Condition
Indicators
flow magnitude and
variability, including
frequency, duration,
timing, and rate of
change
groundwater
accretion to surface
waters; net recharge
or withdrawals
mean width of
meander corridor;
length of natural
shoreline
sediment deposition;
sediment residence
time and flushing
Example Stressor
Indicators
number of dams
per 100 miles;
percent of flows
diverted; stream
bed scouring due to
extreme runoff
amount of
impervious surface;
number of
irrigation wells
number of river
miles channelized
or rip-rapped;
extent of hardened
lake shoreline
amount of soil
erosion from
agricultural fields
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5. APPLYING THE FRAMEWORK
5.1 Getting Started
Although the framework and the hierarchical list of Essential Ecological Attributes
presented here are straightforward, we recommend that an initial design process be used to
define how the framework will be tailored to fit the program at hand. The final product of the
design process should not only describe the assessment and reporting scheme, but also record the
decision tree and professional judgments used to develop it.
Substantial information already is available from other sources regarding the
development of goals and objectives, the selection of indicators, and the design of monitoring
programs (see, e.g., Cairns et al., 1993; EPA, 1998; NRC, 2000; McDaniels, 2000; Dale and
Beyeler, 2001). Accordingly, this section will focus on the use of the EEA list to either plan an
assessment of the condition of an ecological system or report the results of such an assessment.
5.2 Using the Hierarchical List of Attributes
The purpose of the attribute list (Table 1) is to provide organizational structure for the
process of selecting ecological system characteristics for assessment and/or reporting. The first
step in this process is to define the context of the ecological condition assessment. Relevant
considerations include the purpose of the assessment (e.g., ecosystem management, informing
general land-use decisions, public information, feedback regarding the success of environmental
protection efforts), and whether the assessment is a one-time, synoptic study, a longer term
evaluation of trends, or both. The level of resources available for the assessment and the
existence of data from other studies or ongoing monitoring programs also will affect tailoring of
the framework. However, during this preliminary program design, critical data needs for
condition and stressor assessment should be the principal focus. Additionally, the decision
should be made either to limit the assessment to ecological system condition (as did the NRC
and Heinz Center efforts) or to include a parallel assessment of stressors (as did the Great Lakes
State of the Lakes Ecosystem Conference [SOLEC] and Chesapeake Bay reports).
Preliminary design work also will include the definition of the geographic scope and an
inventory of the type(s) of ecosystems and habitat types that will be included. For assessments
that cover large geographic areas and incorporate many ecological regions, design work may
require the development of a hierarchical typology or classification scheme (see, e.g., Levy et al,
in press) that divides the ecological system into workable subunits for analysis.
Some characteristics of ecological systems-e.g., topography, geology, and dominant
weather patterns-do not change except on very long (e.g., geologic) time scales. These
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relatively stable attributes generally have not been included in the description of the EEAs, and
yet are relevant to the interpretation of assessment results. These stable attributes also may be
summarized as contextual background.
Once the purpose and scope of the condition assessment have been determined, the
hierarchical list of Essential Ecological Attributes can be used to guide the selection of
characteristics that will be assessed. To determine which characteristics are appropriate for the
assessment, the Panel recommends beginning with a rebuttable presumption that all of the entries
in Table 1 will be included. A "thought experiment" can then be performed to eliminate
subcategories and categories that are not relevant to the ecological system or to the purpose of
the assessment. When resources (i.e., time, personnel, funding) are limiting, the Panel generally
recommends limiting the number of subcategories for which data are collected, rather than
eliminating an entire category. Similarly, it may be preferable to limit the number of categories
included, rather than eliminate an entire EEA. When exceptions are made, consideration may be
given to reinserting the category or EEA during ongoing adaptive management.
In short, the list of characteristics and indicators to be included in an assessment
ultimately will be defined by the attributes of the system itself and by the contextual factors
mentioned above. To the extent feasible within these constraints, however, the Panel
recommends using the elements of the hierarchy presented in Table 1 so that the assessment will
incorporate the array of components required to characterize ecological condition.
Part of the utility of the hierarchical EEA list is that an assessment can be planned even
in the absence of a conceptual ecological model of the system. It is preferable, however, to
develop a conceptual model that displays the interactions among the characteristics
(subcategories, categories, and/or EEAs) chosen for assessment. The conceptual model, which
will be used to inform the initial selection of characteristics to be assessed, should reflect the
latest scientific understanding of the inherent properties (i.e., patterns and processes) of that
ecosystem type, rather than focusing on management objectives or stressor response. The
conceptual model and the hierarchical list of EEAs and subsidiary characteristics are
complementary tools that help assure that the assessment will include all characteristics that
define the ecological system.
Following the initial selection of EEA categories and subcategories, a series of checks
should be undertaken to assure that the selections accomplish the intended goals and are
scientifically defensible. For example, the components selected should be sufficient to address
any goals and objectives that have been developed for management of the ecosystem. Similarly,
components of the list should be sufficient to address questions of known public interest (such as
the preservation of particular species or the sustainability of patches of old-growth forest). If the
list falls short, then additional subcategories and indicators may be added. Development of a
conceptual model that graphically illustrates the relationship between various management
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objectives (or public interest issues) and the elements of the EEA hierarchy will be useful during
this design phase and will help non-scientists understand the relationships between the
ecosystem components and the objectives.
An additional check of the preliminary list of EEAs, categories, and subcategories to be
included in the assessment should assure that the list addresses the structure, composition, and
function of the system at all relevant hierarchical levels. (See Appendix B for additional detail.)
It also is advisable to survey the temporal characteristics of the list, to assure that some of the
indicators will respond in a reasonably short time frame and some will represent long-term
dynamics. Some of the EEAs will exhibit change over several time scales (e.g., annual,
decadal), but for each category there is generally a time scale over which to observe both natural
variation and changes outside the normal range.
Following the selection of indicators and measures, an iterative review of the attribute list
generally should be undertaken. At this point, it may be possible to trim the list of attributes
and/or indicators (based on their potential to respond to and represent changes in the focus
system and their ability to collectively represent the system) to eliminate redundancies and create
a parsimonious set.
The final product of this portion of the design process would include:
a) relevant information about the context of the assessment;
b) the hierarchical list of attributes (and ideally, indicators) selected for the
assessment;
c) the rationale behind these selections and the underlying conceptual model;
d) the rationale for omitting other attributes or indicators that were considered; and
e) the proposed process for collapsing the indicator data into subcategories,
categories, and EEAs for reporting.
In addition to this detailed technical record, a summary of the design process should be included
in the public report.
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5.3 Creating a Report
Effective reporting on ecological condition requires policy judgments and scientific
understanding (to determine what to report), and it requires communications expertise (to
determine how to report it). Here, the Panel addresses only the scientific issues.
One major purpose of this framework and EEA list (Table 1) is to help avoid common
reporting problems. First, report authors often discover that there are numerous relevant
ecological indicators, yet there is little guidance available about how they should be distilled into
a few scientifically credible indicators for the public. Faced with this problem, many report
authors select a small subset of indicators they judge to be important. Although their reasoning
may be sound (e.g., select indicators that are of interest and understandable to the public), the
resulting report often appears to be a disjointed collection of facts that does not adequately
characterize ecological condition or effectively address other goals developed by society for
ecosystem management. Second, many report authors confine their reporting to information
that is readily available. Yet most easily accessible information (e.g., water quality data
regarding chemical contaminants) is related to past problems and is only part of the information
required to predict future problems or manage the ecosystem. This approach also reinforces a
somewhat circular public policy: people care about what they learn about via reports; and reports
contain information that the authors think people care about. Information that might lead to
more informed decisions -wherein protective or corrective actions are targeted at the most
important problems— may be left out of this circular loop.
The framework presented here can help avoid these problems by providing a roadmap for
grouping monitoring data and indicators into scientifically defensible categories that directly
relate to important characteristics of ecological condition. Using Table 1 as a guide, the
information from an array of indicators can be grouped into a single subcategory and, if desired,
collapsed into a single quantitative or qualitative entry. The information within subcategories
can then be aggregated into a single category, and so forth. The discovery that some categories
lack data is also important information for both decision-makers and the public.
Depending on the level of interest and expertise of the audience, reports can be issued at
the level of individual indicators, subcategories, categories, EEAs, or the ecological system as a
whole. Many reports, such as the Chesapeake Bay report card (Chesapeake Bay Program, 2001),
combine several levels of reporting. If the objective of the report is to provide information on
ecosystem integrity and sustainability, then the EEAs can be used as reporting units (i.e., a
"score" or qualitative assessment would be presented for each EEA). The concepts behind the
EEAs are fairly straightforward; the presentation, however, likely would benefit from conversion
into understandable lay language. For example, hydrology and geomorphology might become a
description of "water flows and riverbanks" for a river basin report.
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Alternatively, the information that has been aggregated into EEAs and categories can be
extracted in order to report on a particular management objective. For example, an objective
such as "protect functional habitat types throughout the watershed" might use the extent category
of Landscape Condition to report directly on the amount of each habitat currently in existence.
In addition, a consolidated "indicator" that incorporates the Hydrology/Geomorphology, Natural
Disturbance, Ecological Processes, and Landscape Condition EEAs might be used to report
whether these habitats are functional and likely to be maintained into the future.
The process of aggregating information from multiple indicators into a single entry for
reporting - even following the template in Table 1 - involves both policy decisions and
nontrivial scientific judgments. An expansive scientific literature is available to determine
appropriate methods for creating indices and aggregating measures into endpoints, endpoints into
categories, and so forth. The procedure does not have to be complicated; in many cases, simple
algorithms or qualitative ranks can be used. It is important to record why particular aggregation
methods are chosen and then explain clearly any value judgments or applications of expert
opinion that affect the aggregation methods or weighting schemes.
5.4 Interpreting Indicator Values
To make the proposed reporting framework operational, reference conditions should be
defined against which measured values for indicators can be compared. The reference
conditions are helpful for interpreting results and are required in order to determine how results
can be normalized (quantitatively or qualitatively) for aggregation. This normalization procedure
allows various indicators or indices to be collapsed into a single aggregated result. Reference
conditions should be established for each ecoregion, resource type, or other ecological unit
addressed in the assessment. In this way, normalized results for the same characteristic may be
compared to results from different ecoregions. (For example, biotic condition in one area can be
compared to biotic condition in another area, even though the underlying measurements or
indicator values are different in the two locations.)
Often, environmental conditions are defined along a spectrum - with conditions at one
end representing an ecosystem with a high degree of integrity and those at the other end
representing an ecosystem that is highly degraded. The spectrum defines a scale for normalizing
and interpreting measured values for indicators. This is the general approach used to develop
several common indices of biotic integrity. First, a list of species population, community,
habitat, or landscape characteristics is assembled that is thought to represent ecological state.
Second, an evaluation scale for normalizing each measured characteristic is developed (generally
using qualitative assessments such as "excellent", "good", "fair", or "poor"). Third, the
information for the multiple metrics is combined into a single index or score. Some examples of
this approach are the diversity indices (e.g., Cao et al., 1996), indices of biotic integrity (e.g.,
Karr and Chu, 1999), benthic indices of biotic integrity (e.g., Engle et al., 1994; Weisberg et al.,
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1997), and functional group analysis (e.g., Merritt and Cummins, 1996; Waters, 2000). The
Agency's Rapid Bioassessment Protocols (Barbour et al., 1999), which address biological and
geomorphological characteristics of rivers, also employ this approach.
Reference conditions that attempt to define a "healthy" ecological system are often
derived from either the conditions that existed prior to anthropogenic disturbance or conditions
in a relatively undisturbed but comparable system in the ecoregion. Alternatively, reference
conditions can be inferred from a combination of historical data, a composite of best remaining
regional conditions, and professional judgment. In previous reviews, the SAB has recommended
that hypothetical reference conditions be established (using information from actual sites,
historical data, empirical models, and expert opinion), rather than actual reference locations that
may exhibit changing environmental conditions over time (EPA Science Advisory Board,
1997a).
Ecosystems are dynamic and variable, and each set of reference conditions should
address this fact. The "historic range of variability" of ecosystem attributes characterizes the
variation and distribution of ecological conditions occurring in the past. The term "historic
range of variability" often refers to natural conditions occurring over a period of centuries; in
this context, it may represent conditions of high ecological integrity. If the historic range of
variability of ecological conditions includes anthropogenic disturbance, then it would simply
represent a long-term baseline. Such a baseline could still be used to develop a scale for
interpreting measured values of indicators; however, the users should be aware of the
anthropogenic disturbances that are included in the long-term record.
The definition of reference conditions that represent a high degree of ecological integrity
is largely a scientific endeavor. Selection of reference sites, for example, should be a science-
based activity. In contrast, development of benchmarks that serve as goals for ecosystem
management or restoration will be a combined effort of scientists, ecosystem managers, and the
public. Management or regulatory benchmarks should be developed based on scientific
understanding of the environmental state likely to be achievable under current or proposed
stressor regimes, but ultimately will reflect societal decisions about desired uses of the resource.
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6. EXAMPLE APPLICATIONS OF THE REPORTING FRAMEWORK
6.1 Introduction
To illustrate the proposed framework's application to programs at different geographic
scales and with different objectives, as well as to check the completeness of the framework, the
Panel selected four environmental reporting programs as case examples: an EPA Office of
Research and Development program designed to assess current condition and long-term trends of
ecological systems; a USDA Forest Service program designed to assess forest condition
nationwide; an EPA Office of Water program designed to convey information about watershed
health to the public; and a joint EPA-state reporting program designed to track progress toward
meeting environmental goals. At public meetings in July 1998 and September 2000, the Panel
received briefings from representatives of the selected programs. The following case examples
include brief program descriptions (based on briefings and materials provided to the members of
the Panel and on prior SAB reviews) and a discussion of how the proposed framework might be
applied to the program. The discussion of the example programs does not constitute a formal
SAB review of the programs. In conducting these analyses, the Panel considered the following
questions:
a) Does the program include measures that do not fit within the categories or
subcategories of the proposed SAB framework? If so, can these measures be included?
b) Has the program missed something that is included in the proposed SAB framework?
c) Does the EEA hierarchy provide a sensible way to organize the program's indicators?
d) Would the proposed SAB framework and EEA hierarchy make it easier to convey the
importance and context of the program to others (either within or outside the Agency)?
e) Does the Panel have any other general insights or recommendations for the program
with regard to reporting on ecological condition?
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6.2 EMAP-West
6.2.1 Background
The Agency's Environmental Monitoring and Assessment Program (EMAP) was
developed to provide a description of the current status and longer term trends of ecological
attributes in terrestrial and aquatic systems nationwide. An associated purpose of the program is
to track changes in ecological health tied to environmental legislation, including the Clean Water
Act. EMAP data also may be used to prospectively characterize risks posed by large-scale
environmental stresses, such as acid deposition and climate change.
The EMAP is distinguished by its use of a spatially tessellated statistical sampling design
that provides for random sampling of the nation's ecological resources. EMAP includes both
ecological condition measures and stressor measures.
One aspect of the EMAP is a series of regional-scale demonstration projects such as the
Mid-Atlantic Integrated Assessment (MAIA), which collected and integrated environmental
information for a region from southern New York to northeastern North Carolina (e.g., Jones et
al., 1997). A second regional pilot, referred to as EMAP-West, was begun in 1999 to develop
baseline descriptions for aquatic resources in western landscapes, streams, and estuaries in a
twelve-state region (EPA, 2001). EMAP-West will be implemented in partnership with a variety
of state, tribal, and federal agencies (e.g., NOAA and USGS). Data and information collected
during the EMAP-West pilot will be used to support environmental assessments at local, state,
and regional levels; establish a long-term archive of data in STORET; provide data for general
public use; and help develop data systems that then can be maintained by local and state groups.
The Panel chose EMAP-West as its first case study for application of the proposed framework.
The EMAP-West contains three components: Coastal Waters, Surface Waters, and
Landscapes. The indicators specified for each of these components are discussed below and
summarized in Table 10.
Coastal Waters: The Western Pilot for estuaries will complete a statistically based,
unbiased, and representative sampling of more than 700 sites in Washington, Oregon, and
California. Particularly intensive sampling will occur in the Northern Rivers area in California
and the Tillamook Bay, Oregon. The Western estuaries EMAP will use the sampled systems as
biological integrators of environmental stress, provide for aggregation of data across local, state
and regional levels, and generate cost-effective information for describing ecological condition
in these estuaries. Selected estuarine indicators include a description of the benthic community
assemblage, fish assemblage, measures offish pathologies, fish tissue contamination, mapping
of submerged aquatic vegetation, sediment measures (e.g., grain size, total organic carbon,
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chemical characteristics, and sediment toxicity), and water column parameters (e.g., nutrients,
temperature, salinity, depth, dissolved oxygen, pH, and chlorophyll).
Surface Waters: The stream study entails a statistically based sampling of 900 locations
in 12 states, including 18 ecologically distinct western ecoregions. Fifteen percent of the
locations for both streams and rivers will be revisited in the sampling effort. The objective of the
study is to develop criteria for ecological reference sites to allow comparisons of ecosystem
condition. The EMAP surface water indicators to be characterized for each site include
descriptions offish assemblage, fish tissue contamination, periphyton community structure,
macroinvertebrate assemblage, physical habitat descriptors (e.g., riparian zone, woody debris,
canopy cover, gradient), and physico-chemical parameters (e.g., nutrients, temperature,
alkalinity, dissolved oxygen, and heavy metal concentrations).
Landscapes: The EMAP-West Landscape Study will focus on watershed scale
indicators, riparian descriptors, and biophysical measures. The watershed indicators include a
human use index, a measure of agriculture on steep slopes, a natural cover type index, human
population density, and the number of roads that cross streams. The percentage of stream miles
with different types of land cover will be used as an indicator of riparian condition. Average
watershed slope and the Palmer Drought Severity Index have been selected as representative
biophysical indicators.
6.2.2 Application of the SAB Framework
One direct way to evaluate the potential application of the SAB reporting framework to
the EMAP-West pilot is to compare EMAP-West's indicators with the EEA hierarchy (Table 1)
that summarizes the attributes comprising ecological condition. As Table 10 shows, all of the
condition measures included in the EMAP-West pilot can be incorporated into the SAB
framework. On the other hand, EMAP-West will collect data that pertain to several, but
certainly not all, of the categories contained in the SAB's proposed reporting framework.
The landscape component of EMAP-West includes information about natural land cover,
but focuses primarily on inferential measures of human impacts (i.e., stressor measures) and
drought potential. While the inclusion of these watershed-scale indicators is an improvement
from earlier EMAP studies, it is not clear to the Panel how this information might be used to
evaluate landscape pattern and structure, landscape composition, or the remaining extent of
different types of habitats. Conversely, however, EMAP-West highlights the fact that the
Landscape Condition EEA should be interpreted to include human-dominated land uses such as
urban and intensively managed agricultural areas.
The data collected for streams and rivers incorporates most of the categories included in
the Physical/Chemical Characteristics and Biotic Condition EEAs, as well as important elements
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of the Hydrology and Geomorphology EEA. Genetic diversity, however, is a notable omission
from the biotic condition assessment in light of the need to manage endangered salmon stocks.
Similarly, ecological processes and disturbance regimes are not covered. In a region where
wildfires, droughts, floods, and even volcanic eruptions shape the ecology, the omission of
disturbance regimes will make it more difficult to interpret data and define reference conditions.
In this example, therefore, it appears that use of the EEA hierarchy (Table 1) as a
checklist provides valuable insight that might be used to expand the program and/or aid the
interpretation of the results. In addition, the EEA hierarchy could be used as a way to organize
EMAP-West data into data systems for local groups and provide a structure within which to
incorporate information from other monitoring programs to fill gaps in the EMAP-West
indicator list. Even when these additional data are not based on the EMAP's statistical sampling
design, they can provide useful input to the anticipated environmental assessments.
In the Panel's opinion, EMAP-West is not atypical in its omission of ecological
processes. This is one reason that ecological processes are highlighted as a separate EEA in the
proposed framework. EMAP-West could incorporate ecological process measurements by
expanding its GIS-based spot sampling design to a tiered system, similar to that used by the
Forest Health Monitoring Program (See Section 6.3). In a tiered approach, intensive process-
based studies of a small number of representative areas, plus integrated measures for whole
ecosystems, are coupled with the widespread randomized spot sampling. Long-term intensive
study of selected plots provides process information that helps explain the patterns measured
across the rest of the monitoring sites.
The EMAP-West estuaries study emphasizes physical and chemical attributes of the
water column and sediments, coupled with measures offish (i.e., representative organism)
condition. Other aspects of biotic condition include community composition and the physical
habitat structure provided by submerged aquatic vegetation. Although the sampling design
reflects one of the pilot's objectives - to correlate certain stressors with biological characteristics
- comparison with the SAB framework shows that critical ecosystem characteristics that
influence biotic condition have been omitted. The missing characteristics may be candidates for
later addition, particularly to the extent that they help explain correlations (or lack thereof)
between chemical or physical data and biotic condition. As mentioned above for the streams and
rivers section of the pilot, the EEA hierarchy could provide a classification scheme for
organizing data from other monitoring programs along with EMAP data to provide a more
comprehensive assessment of estuarine condition.
In sum, it appears that the EEA hierarchy does provide a sensible way to organize
EMAP-West's indicators in order to determine what elements have been omitted from the pilot.
In the Panel's view, the ability to highlight missing elements such as genetic characteristics (in
view of the endangered salmon controversies) and disturbance regimes (in view of the
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importance of fire, drought, and volcanic eruptions in the area) is a valuable asset. The EEA
hierarchy also provides an organizational scheme for integrating the EMAP-West data with data
from other programs; presenting the combined information to the local, state, and regional
groups who will use the EMAP results; and helping to explain how each of the indicators is
relevant to ecological condition. In addition, it seems likely that using the EEA hierarchy as an
organizing scheme could help the Office of Research and Development highlight the utility of
EMAP to other parts of the Agency.
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Table 10. EMAP-West Indicators Organized Using the SAB Framework
SAB Reporting Categories and Subcategories
Landscape Condition
Extent of ecological system/habitat types
Landscape Composition
Landscape Pattern/Structure
Biotic Condition
Ecosystems and Communities
Community Extent
Community Composition
Trophic Structure
Community Dynamics
Physical Structure
Species and Populations
Population Size
Genetic Diversity
Population Structure
Population Dynamics
Habitat Suitability (focal species)
Organism Condition
Physiological Status
Symptoms of Disease or Trauma
Signs of Disease
Chemical and Physical Characteristics (Water, Air, Soil,
Sediment)
EMAP Western Pilot: Coastal (c) and Surface Waters (Rivers and
Streams) (s) and Landscapes (1) (EPA, 2001)
Condition Measures
submerged aquatic vegetation
(SAV) abundance (c)
occurrence of submerged aquatic
vegetation (c), occurrence of
macroalgae (c), riparian vegetation
(s), average slope of watershed
natural cover type index (1)
benthic community assemblage (c),
stream macroinvertebrate
assemblages, fish community
assemblage (c, s), periphyton
assemblage (s), phytoplankton
(rivers)
submerged vegetation (c), riparian
habitat/land use (s)
fish pathologies (c)
fish parasites (c), fish tissue
residues of metals and organic
contaminants (c), Hg in fish tissues
(s)*, persistent organic
contaminants in fish tissue (s)*
Stressor (or Stressor
Surrogate) Measures
human use index (1);
agriculture on steep slopes (1);
population density (1);
roads crossing streams (1);
% of stream miles with different
types of land cover (1)
fecal coliform (surrogate
indicator of microbial
pathogens)(c)
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Nutrient Concentrations
Nitrogen
Phosphorus
Other Nutrients
Trace Inorganic and Organic Chemicals
Metals
Other Trace Elements
Organic Compounds
Other Chemical Parameters
PH
Dissolved Oxygen/Redox Potential
Salinity
Organic Matter
Other
Physical Parameters
soil/sediment
water/air
Ecological Processes
Energy Flow
Primary Production
Net Ecosystem Production
Growth Efficiency
Material Flow
Organic Carbon Cycling
N and P Cycling
Other Nutrient Cycling
Hydrology and Geomorphology
Surface and Groundwater Flows
Pattern of Surface Flows
Hydrodynamics
Pattern of Groundwater Flows
Salinity Patterns
Water Storage
Dynamic Structural Characteristics
Channel/Shoreline Morphology and Complexity
nutrients (c)
total N, nitrate, ammonium (s)
total P (s)
silica (s)
metals in sediments (c)
organic contaminants in sediments
(c)
pH (s, c)
dissolved oxygen (c)
salinity (c)
sediment total organic carbon (c),
dissolved organic carbon (c, s)
cations and anions (s), dissolved
inorganic carbon (s), acid
neutralizing capacity (s)
substrate/grain size (c, s), silt/clay
percent (c)
temperature (c, s), water depth (c),
turbidity and suspended sediments
(c,s)
chlorophyll (c), algal pigment
abundance (c)
microbial abundance (c)
river discharge (c), stream
discharge (s)
channel morphology (s)
sediment toxicity (c)
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Extent and Distribution of Connected Floodplain
Aquatic Physical Habitat Complexity
Sediment and Material Transport
Sediment Supply and Movement
Particle Size Distribution Patterns
Other Material Flux
Natural Disturbance Regimes
Frequency
Intensity
Extent
Duration
submerged vegetation (c), fish
cover (s), large woody debris (s)
Palmer drought severity index (1)
*If additional funds become available (EPA, 2001)
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6.3 Forest Health Monitoring Program
6.3.1 Background
The Forest Health Monitoring (FHM) Program is a monitoring and assessment program
of the USD A Forest Service initiated in 1991 and currently operating in 48 states with an annual
budget of approximately $9 million. At inception in 1991, the FHM was a joint effort of the
EPA EMAP and the Forest Service, and the program uses the EMAP probability based sampling
design. (Recently, the FHM program was integrated with the Forest Inventory and Analysis
(FIA) program of the Forest Service; FHM ground plots are now Phase 3 of the FIA plot
network.) The objectives of the FHM program are to evaluate the status and trends in forest
condition and health across the U.S., including both public and private forested lands. The
program is a tiered effort with a) a national status and trends detection component; b) an
intensive evaluation component for areas where serious problems are detected; and c) an
intensive site monitoring component co-located with National Science Foundation Long Term
Ecological Research (LTER) sites. The latter component of the program allows hypothesis
testing via field experimentation and is a critical component of the effort.
The FHM program utilizes the Santiago Declaration Criteria and Indicators for
Conservation and Sustainable Management of Temperate and Boreal Forests
(www.fs.fed.us/1 and/sustain_dev/sd/sfmsd.htm) as a framework for sustainability assessment and
reporting. Forest health indicators are analyzed and reported by the ecoregion section as defined
by Bailey (1995).
The FHM provides ready public access to both summary information and quality-assured
data through its web site (www.na.fs.fed.us/spfo/fhm/index.htm), which is an important aspect of
any program intended to assess ecological condition. Because the program is spatially explicit,
map products are being developed as a powerful and effective means of summarizing results in a
way that is readily understood by both the scientific community and the public. In addition to
maps, tabular summary data are provided by ecoregion and subunits within these landscape
units.
The focus of the FHM program is to derive measures of forest "sustainability" and the
effects of stressors (e.g., exotic species, management, climate, air pollution, extreme natural
events). Sustainability is defined in terms of productivity, carbon cycling, water conservation,
soil conservation, diversity, and forest vitality. Because of fiscal constraints, the FHM program
has focused almost exclusively on aboveground tree metrics, primarily symptomology (e.g.,
crown density, percent crown dieback) along with species composition, stand structure, and
productivity. In recent years, however, other indicators of forest condition have been
implemented, including lichen assemblages and soil properties. Most recently, there have been
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increased efforts to utilize GIS and remote sensing capabilities in spatial extrapolation and
interpretation of data.
The FHM program currently is monitoring a variety of indicators including symptom
indicators (mortality, dieback, tree crown transparency, ozone damage on foliage), species
composition (trees, lichens, exotic species presence), and process indicators (productivity). The
program also is making efforts to provide cost-effective linkages with other ecological and
environmental data, such as networks that define precipitation chemistry (i.e., acid deposition),
air quality (e.g., ozone levels), and meteorology (e.g., precipitation and temperature).
6.3.2 Application of the SAB Framework
Despite its initial focus on stressors, the FHM metrics map directly to the EEA hierarchy.
All of the condition measures of the FHM program fit within the proposed EEA categories
(Table 11). Conversely, the FFCVI measures provide fairly complete coverage of the EEA
hierarchy; the exceptions are hydrology and geomorphology, and information about disturbance
regimes (which is inferred by evidence of tree damage rather than being characterized explicitly,
as proposed by the SAB). The fact that the FFCVI measures cover many of the condition
categories in the proposed SAB framework is a testament to the recognition by the U.S. Forest
Service that maintenance of forest ecosystem integrity is an important component of forest
management, whether on public or private lands.
The tiered evaluation approach used by the FHM program could serve as a template for
establishing a hierarchy of measurements within the Ecological Processes EEA. The hierarchy
would distinguish indicators appropriate at the whole-ecosystem scale from indicators that could
be used to more intensively monitor smaller scale plots (e.g., to monitor energy cycling). Use
of the SAB reporting framework as a checklist also could be useful to the FFCVI program over
time to guide decisions on additions or deletions of metrics; for example, the SAB framework
emphasizes the need to continue developing forest ecosystem-level assessments (rather than just
mensurational data such as tree size and wood volume) and process measurements.
The Panel also hopes that use of the EEA hierarchy to describe the FHM indicators could
provide a tool for combining data from the FHM program with data from programs in other
agencies. By providing a single organizational scheme that can be used for different ecosystem
types and geographic scales, the SAB framework can be used to integrate information from a
variety of different agencies, which then can be used for a variety of purposes.
Within the Forest Service, for example, information routinely collected at FIA plots
(including slope, aspect, soil depth, soil drainage characteristics, and amount and severity of tree
injury) and FIA landscape level measures (e.g., the extent of forest types and forest
fragmentation) may be integrated and reported with FHM data to provide a more comprehensive
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assessment of forest condition. The SAB framework also provides a means of relating FHM
data to data on rainfall, climate, and disturbances (e.g., insects, fire, ice or wind storms) that are
collected by other programs and entities. For example, annual aerial and ground surveys
conducted by FFDVI partners map and quantify tree mortality and damage caused by forest
insects, pathogens, and extreme weather events.
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Table 11. FHM Indicators Organized Using the SAB Framework
SAB Reporting Categories and Subcategories
Landscape Condition
Extent of ecological system/habitat types
Landscape Composition
Landscape Pattern/Structure
Biotic Condition
Ecosystems and Communities
Community Extent
Community Composition
Trophic Structure
Community Dynamics
Physical Structure
Species and Populations
Population Size
Genetic Diversity
Population Structure
Population Dynamics
Habitat Suitability
Organism Condition
Physiological Status
Symptoms of Disease or Trauma
Signs of Disease
Forest Health Monitoring Program and Forest
Inventory and Analysis (FIA) Parameters1
Condition Measures
remote sensing of extent of
forest/non-forest land uses
(FIA)
forest types (FIA)
forest fragmentation (FIA)
tree community
composition, lichen
community composition,
presence of exotics
stand structure, down
woody debris, slope
stand age
regeneration; growth rates
growth rates, tree size class
tree mortality, dieback, tree
crown transparency, ozone-
damaged foliage
Stressor (or Stressor
Surrogate) Measures
urbanization, rates of land
use change, distance to
roads (FIA)
presence of exotics, lichen
community composition
(bioindicator of exposure
to N- and S-based air
pollutants)
evidence of damage (from
insects, disease, fire,
animals, weather, or
logging) (FIA)
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Chemical and Physical Characteristics (Water,
Air, Soil, Sediment): SOIL
Nutrient Concentrations
Nitrogen
Phosphorus
Other Nutrients
Trace Inorganic and Organic Chemicals
Metals
Other Trace Elements
Organic Compounds
Other Chemical Parameters
pH
Dissolved oxygen/Redox Potential
Salinity
Organic Matter
Other
Physical Parameters
soil/sediment
water/air
Ecological Processes
Energy Flow
Primary Production
Net Ecosystem Production
Growth Efficiency
Material Flow
Organic Carbon Cycling
N and P Cycling
Other Nutrient Cycling
total soil nitrogen
plant-available
(extractable) phosphorus
exchangeable cations
(e.g., Ca, Mg, and K)
extractable metals
soil pH
carbonates
soil organic matter content,
total organic carbon, forest
floor measures
soil texture, depth of litter,
percentage of soil
compaction
timber/wood volume
(calculated from tree height
and diameter measures)
(FIA)
carbon storage in tree
biomass
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Hydrology and Geomorphology
Surface and Groundwater Flows
Pattern of Surface Flows
Hydrodynamics
Pattern of Groundwater Flows
Salinity Patterns
Water Storage
Dynamic Structural Characteristics
channel/shoreline morphology and
complexity
extent and distribution of connected
floodplain
aquatic physical habitat complexity
Sediment and Material Transport
sediment supply and movement
particle size distribution patterns
other material flux
Natural Disturbance Regimes
Frequency
Intensity
Extent
Duration
(for insects, pathogens and
extreme weather events:
inferred from annual
surveys of tree mortality and
damage)
'The table includes only a subset of the FIA parameters that relate closely to forest condition.
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6.4 Index of Watershed Indicators
6.4.1 Background
The Index of Watershed Indicators (IWI), developed by the Agency's Office of Water, is
advertised as a snapshot of the "health of aquatic resources." The IWI provides a website
(www. epa. gov/i wi) that allows members of the general public to obtain information about any
watershed. Its easy accessibility and understandable graphic format (watershed and national
maps) make it a powerful potential tool for public education about watershed condition. The
IWI was originally conceived as a method for highlighting the water quality assessments
generated by states to report on their progress towards meeting requirements of the Clean Water
Act13. To the average user, however, the IWI appears to offer an overall assessment of the
condition of the watershed and its vulnerability to future insult.
The IWI currently provides scores for watershed condition and vulnerability based on an
algorithm that combines values from 16 indicators. One set of indicators is used to assess
"watershed condition" and another set of indicators is used to assess "watershed vulnerability."
Based on these two assessments, watersheds are grouped into categories by condition (i.e., better
water quality, water quality with less serious problems, or water quality with more serious
problems) and by vulnerability (i.e., high or low). In previous reviews of the IWI, the SAB has
recommended enhancements to the suite of indicators included in the Index, and commented on
data integration issues associated with the development of the IWFs component indicators and
the final watershed scores (EPA Science Advisory Board, 1999; 1997c).
6.4.2 Application of the SAB Framework
Comparison of the IWI indicators to the proposed SAB framework for reporting on
ecological condition provides a useful assessment of the coverage provided by the IWI (Table
12). This exercise is particularly appropriate for the IWI, since the website describes itself as a
source of information on watershed condition. Of the 16 indicators or composite indicators
included in the IWI, only 5 provide direct information on the condition of ecological resources
other than chemical and physical characteristics. A sixth indicator, the indicator that reports on
the attainment of designated uses, is based in part, in some states, on an assessment of biological
community diversity, composition and structure. In the majority of states, however, the
determination of designated use attainment is based on physical and chemical water quality
parameters.
"Section 305(b) of the Clean Water Act (Public Law 92-500) requires states to assess the condition of their
surface waters and report their assessments to EPA every two years. The section also requires EPA to
summarize the state assessments in a biennial report to the Congress on the quality of the nation's waters.
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In short, with the exception of the traditional Agency territory of chemical and physical
parameters, the IWI indicators are notably lacking in coverage of the many other important
aspects of condition.
Moreover, the IWI includes a preponderance of stressor rather than condition indicators
(see Table 12). As discussed in Section 4, information on stressor levels is important for
interpreting changes in ecological indicators and for designing and assessing the effectiveness of
environmental management approaches. Stressor indicators, however, generally do not provide
direct information about the condition or "health" of ecological systems. In the Panel's judgment,
therefore, the suite of indicators included in the IWI does not provide a basis for reporting on
'whether rivers, lakes, streams, wetlands, and coastal areas are "well" or "ailing"' (quote
excerpted from the description of the IWI at www.epa.gov/iwi).
On the other hand, there is no reason that additional data layers cannot be added. Even if
data are not currently available nationwide for particular parameters, highlighting indicators with
no data serves two purposes: to educate members of the public regarding the importance of
often-overlooked elements of ecological condition (such as hydrology and landscape pattern);
and to create public support for the collection of the information. Given the website's popularity
and accessibility, and given the fact that it advertises a snapshot of watershed condition, it seems
that a more comprehensive list of condition indicators should be used. The EEA checklist could
be used to choose these supplemental indicators.
As the IWI indicator and composite indicator list is expanded, it will become increasingly
important to have an organizing framework that groups the indicators into understandable
categories for presentation. Similarly, it will become increasingly important to have a
scientifically and logically justifiable explanation for the composite indicators and maps. The
EEA hierarchy can be used for this purpose.
The EEA hierarchy also provides a vehicle for integrating information collected or
managed by entities other than EPA. In fact, the current suite of IWI indicators includes a
number that are based on data from state programs (e.g., the extent to which waters are meeting
designated uses, the existence offish consumption advisories), other federal agencies (e.g., the
estuarine vulnerability data from NOAA, the inventory of dams maintained by the U.S. Army
Corps of Engineers), or non-governmental organizations (e.g., data on aquatic species at risk
from the Heritage Network). The proposed SAB reporting framework might be used to facilitate
and organize a similar integration of information from a variety of data sources to provide an
assessment of the condition of ecological systems in watersheds around the country.
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Table 12. The IWI Indicators Organized Using the SAB Framework
SAB Reporting Categories
and Subcategories
Landscape Condition
Extent of ecological
system/habitat types
Landscape Composition
Landscape
Pattern/Structure
Biotic Condition
Ecosystems and
Communities
Community Extent
Community
Composition
Trophic Structure
Community
Dynamics
Physical Structure
Species and Populations
Population Size
Genetic Diversity
Population Structure
Population Dynamics
Habitat Suitability
Organism Condition
Physiological Status
Symptoms of Disease
or Trauma
Signs of Disease
Chemical and Physical
Characteristics (Water, Air,
Soil, Sediment)
Nutrient Concentrations
EPA's Index of Watershed Indicators
Condition Measures
% loss of wetlands
number of aquatic or
wetland-dependent species
at risk3
existence of state fish
consumption advisories4
Stressor (or Stressor Surrogate) Measures1
% impervious surface
% of waters that meet designated uses2
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Nitrogen
Phosphorus
Other Nutrients
Trace Inorganic and
Organic Chemicals
Metals
Other Trace Elements
Organic Compounds
Other Chemical
Parameters
pH
Dissolved
Oxygen/Redox
Potential
Salinity
Organic Matter
Other
Physical Parameters
sediment
water
Ecological Processes
Energy Flow
Primary Production
presence of contaminated
sediments5
presence of contaminated
sediments5
% exceedances of national reference levels for
conventional pollutants (ammonia, phosphorus, pH,
and dissolved oxygen) in ambient water6
conventional pollutant loads over permit limits
(includes biochemical oxygen demand, total
suspended solids, nutrients and others)
estuarine pollution susceptiblity index (includes
predicted concentrations of N and P)
presence of contaminated sediments5
% exceedances of ambient water quality criteria for
4 toxics [Cu, Cr(VI), Ni, Zn]6
toxic loads exceed permit limits (including Cd, Cu,
Pb, Hg, and others)
presence of contaminated sediments5
% exceedances of national reference levels for
conventional pollutants (ammonia, phosphorus, pH,
and dissolved oxygen) in ambient water6
conventional pollutant loads over permit limits
(includes biochemical oxygen demand, total
suspended solids, nutrients and others)
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Net Ecosystem
Production
Growth Efficiency
Material Flow
Organic Carbon
Cycling
Nitrogen and
Phosphorus Cycling
Other Nutrient
Cycling
Hydrology and
Geomorphology
Surface and Groundwater
Flows
Pattern of Surface
Flows
Hydrodynamics
Pattern of
Groundwater Flows
Salinity Patterns
Water Storage
Dynamic Structural
Characteristics
Channel/Shoreline
Morphology and
Complexity
Extent and
Distribution of
Connected
Floodplain
Aquatic Physical
Habitat Complexity
Sediment and Material
Transport
atmospheric deposition of
total N (estimated)
reservoir impoundment
volume
sediment runoff potential from cropland and
pastureland (simulated)-indirect indicator of
organic matter flux associated with erosion and
sediment transport
potential nitrogen runoff from farm fields;
atmospheric deposition of total N (estimated)
% impervious surface
reservoir impoundment volume (indirect measure of
hydrologic modification)
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Sediment Supply and
Movement
sediment runoff potential from cropland and
pastureland (simulated); estuarine pollution
susceptibility index (includes particle retention
efficiency for estuaries, based on capacity to inflow
ratio)
Particle Size
Distribution Patterns
Other Material Flux
Natural Disturbance Regimes
Frequency
Intensity
Extent
Duration
Notes:
1 Human population change, which is included in the IWI, is a driver that affects a number of stressors and
indirectly affects a number of condition parameters.
2 Designated uses are established by states in their water quality standards, and may include aquatic life uses.
3 Includes species that are classified by the Heritage Network as critically imperiled, imperiled, or vulnerable, or
are listed under ESA as threatened or endangered
4 Fish consumption advisories are developed by states based on a determination of potential risk to humans from
consumption of fish or shellfish due to metals, pesticides, PAH, PCBs, dioxins, or other bioaccumulative
chemicals.
5 Screening-level assessment based on existing sediment chemistry and biological data compared to various
environmental criteria or effects thresholds.
6 Although reporting on % exceedences of various effects-based benchmarks does not provide direct information
on environmental condition, the underlying data on ambient concentrations in air, water, sediment, or soil could be
reported as condition indicators.
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6.5 National Environmental Performance Partnership System (NEPPS)
6.5.1 Background
The National Environmental Performance Partnership System (NEPPS) is a joint state-
EPA effort to negotiate environmental priorities and strategies, and to track progress toward
environmental protection goals. The goal areas covered in the NEPPS agreements are derived
from the Agency's Strategic Plan (EPA, 2000), which in turn closely tracks the Agency's legal
mandates. A keystone of NEPPS is reporting on a set of core performance measures, including
program "output" measures, "outcome" measures, and "environmental indicators" (loosely
correlated with administrative, stressor/exposure, and condition measures, as defined in Figure
1). The 1997 agreement initiating the NEPPS program notes that "EPA and the states will strive
to reduce the number of core program output measures in favor of outcome measures and
environmental indicators" (EPA, 1997). The agreement goes on to say, "As we gain experience
with core performance measures, states and EPA believe that we can reduce our emphasis on
traditional output reporting requirements as the primary performance indicator of a state or
federal program. We believe that progressive core measures that chart environmental progress
and program outcomes will help us reduce our dependence on simply counting the things we
do." (EPA, 1997)
The program guidance also notes that the core measures are intended to serve as a
minimum set, and in fact the EPA-state agreements negotiated under NEPPS program contain a
number of additional reporting measures beyond the required core measures. To date, 35 states
have entered into NEPPS agreements with EPA. The initial description of core measures (EPA,
1997) has been updated for many of the EPA goal areas (EPA, 2000).
6.5.2 Application of the SAB Framework
The SAB framework can reasonably be compared to the subset of NEPPS measures that
report on goals related to ecological condition (Table 13). For these four goals, only three Core
Environmental Measures directly measure ecological condition. Two measures address portions
of the SAB's Chemical and Physical Characteristics EEA; many of these chemicals are naturally
occurring compounds that may be categorized as condition and/or pollutant (stressor) measures,
depending on their concentrations. The remaining measure - percent of assessed rivers and
estuaries with healthy aquatic communities - addresses a subset of the SAB's Biotic Condition
EEA. Tables 1 and 4 provide a list of characteristics that should be assessed in order to
determine the condition of biological communities, and this checklist could be compared to the
measures in individual state NEPPS agreements that will be used to report progress toward the
core performance measure.
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A more complete view of the NEPPs program emerges when a state agreement is
analyzed, because the individual state agreements include many indicators beyond the minimum
list required by the Agency. An example of this sort of analysis is presented using the New
Jersey NEPPS agreement for FY99-2000 (Appendix D). In the New Jersey example, several
additional Essential Ecological Attributes are included, as well as additional categories within
the Biotic Condition and Chemical/Physical Characteristics EEAs.
Would the proposed SAB framework enhance the ability of the NEPPS program to
communicate with the public, and would the SAB framework be a sensible way to organize the
program's indicators? Although there are several ways in which the NEPPS program could
profitably use the SAB framework, the Panel concludes that the SAB reporting scheme would be
awkward for NEPPS to adopt at the present time. The current reporting categories for NEPPS
generally are derived directly from legal mandates, and the NEPPS indicators correlate closely
with these mandates. As a result, rearranging the NEPPS indicators into EEA (Table 1)
groupings appears strained, particularly for air pollutants. On the other hand, the New Jersey
indicators for landscape and biotic condition, hydrology and geomorphology could be grouped
effectively into EEAs in order to highlight their ecological significance.
As the NEPPS program evolves towards more measures of environmental quality and
fewer measures of administrative effort, the SAB framework can provide greater benefits. If the
program moves towards adopting goals such as "maintain healthy watersheds" or "restore
natural ecological processes to support native communities," then the SAB framework will
provide some direction for the selection of appropriate indicators. At that point, the SAB
framework might also provide a useful way to organize the results for reporting.
In the meantime, the SAB framework can provide a useful checklist function for the
NEPPS program. For example, with respect to the current indicator that measures the number of
estuaries and rivers with healthy aquatic communities, the SAB's Biotic Condition EEA offers a
list of important parameters that should be measured. This list may help ensure that metrics are
assessed for both biological communities and focal species, and that measures of physical
structure are used to determine whether habitat conditions are conducive to sustaining these
communities and species. Similarly, the checklist within the Hydrology and Geomorphology
EEA relates to processes that maintain the habitats for the aquatic communities in the long term.
Reporting on these additional attributes serves an important educational function, in addition to
providing a more representative picture of the presence and sustainability of "healthy aquatic
communities".
The EEA hierarchy (Table 1) also offers a method to consolidate information from a
variety of different programs and/or resource types (i.e., lakes and rivers, forests, rangelands).
Using the categories in the Landscape Condition EEA, for example, a state could track the
changes in extent and fragmentation of various habitat types, and highlight those habitat types
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for which information is missing. Moreover, cataloging the NEPPS indicators within the Table 1
categories highlights some areas where the goal-driven indicators are disjointed ecologically
(e.g., measures of wetland acreage, without corresponding information on wetland community
types; information on benthic communities, without corresponding measures of aquatic physical
habitat complexity).
If the states envision the NEPPS reporting program as a planning tool, the SAB
framework can be used to highlight useful information that may be missing from current
monitoring programs. For example, in a river where aquatic biotic condition is unacceptable,
information on water flows and aquatic physical habitat complexity may indicate that changes in
these parameters override the improvements expected from decreasing chemical contamination.
This information would improve the targeting of environmental protection resources. Similarly,
information about the extent and distribution of connected floodplain, coupled with information
about the distribution of levees (i.e., channel morphology and complexity) and pattern of surface
flows, can help explain and predict flood behavior. This information, in turn, provides insight
into the effects of additional development in floodplains and riparian areas.
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Table 13. NEPPS Core Environmental Indicators for Environmental Goals Associated
with Ecological Resources
Goal/Program Area
Clean Air
Criteria Air Pollutants 1
(ozone, carbon monoxide,
paniculate matter, lead,
nitrogen dioxide, sulfur
dioxide)
Air Toxics
Clean Waters
watershed restoration and
protection
Waste Management and
Restoration of Abandoned Waste
Sites
Store, treat, and dispose of
waste in ways that prevent
harm to the natural
environment.
Ensure that communities, work
places, and ecosystems are safe
from pollution.
Ground water protection
program
Condition Measures
trends in air quality for each of 6
criteria air pollutants
% of assessed rivers and estuaries
with healthy aquatic communities
% change in selected substances
found in surface waters
To Be Developed: indicators of
change in the condition of the
soil, shallow groundwater, or
ecosystems
Exposure/Stressor Measures
trends in air quality for each of 6
criteria air pollutants
trends in emissions of toxic air
pollutants
% of assessed waterbodies that
support healthy aquatic life use
designations (chemical water quality
criteria)
% change in selected substances
found in surface waters
groundwater releases controlled
Trends in pesticide residues in ground
water at several representative
locations.
1 National Ambient Air Quality Standards (NAAQS) include Primary Standards to protect public health and
Secondary Standards to protect public welfare (e.g., visibility, impacts on agricultural crops, and materials
damage). Nonetheless, levels of some criteria air pollutants also have been linked to ecological effects, so
changes in ambient levels of these pollutants may effect the condition of ecological resources.
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6.6 Conclusions
a) The framework presented here provides a valuable tool for assessing the
condition of ecological systems.
In every example program tested by the Panel, the list of Essential Ecological Attributes
and associated subdivisions (Table 1) proved useful. In all cases, use of the EEA hierarchy as a
checklist highlighted missing elements - elements representing ecological system characteristics
broad enough in scope and importance to affect the achievement of the programs' objectives.
Recognizing that resources are always limited and that expanding a program is often infeasible,
the EEA checklist provides a method to analyze the tradeoffs inherent in choosing which
characteristics to address. The fact that the checklist is organized hierarchically allows the user
to determine whether major characteristics (e.g., the entire array of hydrology and
geomorphology characteristics) are being eliminated from consideration in favor of a cluster of
closely-related attributes (e.g., every subcategory and indicator of biotic condition at the
community level).
In most cases, the elements that were omitted by Agency programs were those outside the
realm of biotic condition and chemical and physical characteristics. This pattern has been noted
by the SAB in the past, and it is an understandable outgrowth of the issues targeted by the
Agency's legal mandates. A more complete look at ecological characteristics is key, however, to
allow the Agency to: analyze correctly the causes of environmental degradation; effectively
target corrective actions; and help address environmental problems across large geographic areas
such as watersheds.
b) The framework can be applied to a variety of aquatic and terrestrial systems
at local, regional, and national scales.
The programs that were analyzed included both aquatic and terrestrial systems at a
variety of geographic scales. For all of these examples, the SAB framework and EEA hierarchy
provided a reasonable way to organize a broad array of indicators. After each example was
tested, the Panel was able to fine-tune the organizational scheme by regrouping characteristics at
the subcategory level. Presumably this fine-tuning will still be necessary as the SAB framework
is applied to additional programs. In no case, however, did the Panel find that important
elements of condition were missing from the framework.
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c) The Essential Ecological Attributes and their subdivisions provide a logical
method for grouping ecologically related elements across system types (such
as forests, rangelands, and aquatic systems) and/or across programs that
have different legal mandates.
This feature can be used when the Agency addresses problems that span different
"media" (e.g., water, air, and land) in order to provide environmental protection for watersheds
and other geographic units. It also can be used as a unifying framework on which to map various
types of ecological assessment activities within the Agency. There is clear justification for a
variety of different programs with different purposes to exist within the Agency, among other
federal agencies, and in the private sector for the purpose of assessing ecological condition. This
diversity brings strength and depth to our understanding. It does not, by itself, insure that
efficiencies among programs are realized, that deficiencies in programs are addressed, or that the
information from one assessment is used to enhance the understanding gained from other studies.
The SAB framework provides a template that potentially could be used to foster greater
integration, a higher quality of ecological assessment, and increased efficiency among Agency
programs. It also could be used to assist the Agency to become a locus for integrating
information from different government agencies.
d) The Essential Ecological Attributes and their subdivisions can be used to
organize and consolidate a large number of indicators into a few,
conceptually clear categories for reporting.
One major purpose of this framework and EEA list (Table 1) is to help avoid common
reporting problems. For example, report authors often discover that there are numerous relevant
ecological indicators, yet there is little guidance available about how they should be distilled into
a few scientifically credible indicators for the public. Moreover, most of the easily accessible
information (e.g., water quality data regarding chemical contaminants) may be related to past
problems and reflects only part of the information required to predict future problems or manage
the ecosystem. The framework presented here can help avoid these problems by providing a
roadmap for grouping monitoring data and indicators into scientifically defensible categories that
directly relate to important characteristics of ecological condition. These categories are
straightforward, and they can therefore be explained to decision-makers, legislators, and the
public. The language used by the Panel would not, however, be suitable for this purpose.
Translation into lay language would be required.
e) This framework can provide the foundation for reporting on a variety of
independently derived goals and objectives, including those mandated by
legislation or public policy.
When the purpose of a report is to address questions of particular interest to the public or
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address goals embodied in legislation or regulation, the SAB framework provides a way to
organize information that can then be extracted for reporting. For example, a "report card" entry
on the health of native habitats, plants, and animals would draw from the information aggregated
into the landscape condition and biotic condition EEAs. A companion report card entry on the
ability of the ecosystem to sustain healthy plants and animals into the future would add
information from each of the remaining EEAs. In some cases, however, the SAB framework
provides the requisite information but does not work well for organizing indicators into a report.
One example would be a regional water quality report for which data will be drawn from
monitoring programs designed specifically for that purpose. In this example, the SAB
framework is better used as an analytical tool than a report outline.
In sum, the Panel finds that the proposed framework accomplishes its intended purpose.
The framework provides a checklist that can help identify the ecological attributes that are
important to assess in order to evaluate the health or integrity of ecological systems. It also
provides an organizational scheme for assembling hundreds of individual parameters into a few
understandable attributes. Ecological systems are complex, and it has proved extremely difficult
to answer the holistic questions that people ask about them - "How healthy is my watershed?
Will native species be here for my children and my grandchildren to enjoy?" With this report,
we provide a way to integrate scientific data into the information necessary to answer these
questions, and ultimately to foster improved management and protection of ecological systems.
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rivers and estuaries - effects of extreme hydrologic events. Regul. Rivers res. Manage.
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Stoms, D.M. and I.E. Estes. 1993. A remote sensing research agenda for mapping and monitoring
biodiversity. International Journal of Remote Sensing 14(10): 1839-1860.
Terborgh, J., J. A. Estes, P. Paquet, K. Rails, D. Boyd-Heger, B. J. Miller, R. F. Noss. 1999. The
role of top carnivores in regulating terrestrial ecosystems. Pp 39-64 In M. E. Soule and J.
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measurements for Croplands, Forests and Coasts and Ocenas. The H. John Heinz III
Center, Washington, DC. www.us-ecosystems.org
The Heinz Center. In press. The State of the Nation's Ecosystems: Measuring the Lands,
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U.K.
Turner, M.G. 1989. Landscape ecology: The effect of pattern on process. Annual Review of
Ecology and Systematics, 20:171-197.
Turner, M.G. and Dale, V.H. 1998. What have we learned from large, infrequent disturbances?
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EPA/630/R-92/001, February 1992. EPA Risk Assessment Forum, Washington, DC.
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APPENDIX A. THE HEINZ CENTER INDICATORS PLACED INTO THE
HIERARCHY OF ESSENTIAL ECOLOGICAL INDICATORS
The following table sorts the indicators developed by The Heinz Center (in press)
according to the hierarchical list of ecosystem attributes summarized in Table 1. To prepare its
overview of the state of the nation's ecosystems, The Heinz Center developed a framework for
selecting indicators (summarized in Table 2) with associated decision rules, convened a
committee for each of six ecosystem types, requested each committee independently to select
indicators according to the framework, and produced a consolidated list of indicators that relate
to all ecosystem types. For many of the indicators, data are not yet available.
As the following table shows, the draft set of indicators being recommended by The
Heinz Center correspond fairly well with the components of the EEA hierarchy, although all
ecosystem types are not represented in all EEAs or categories (e.g., in The Heinz Center report,
floods in aquatic systems are not included as disturbances). Thus, use of the EEA hierarchy as a
checklist can help to identify potential candidates for future inclusion in The Heinz Center's
reports. In addition, the reporting categories embedded in the EEA hierarchy provide a useful
structure for grouping The Heinz Center indicators from different ecosystem types, as shown
below.
The list of indicators developed by The Heinz Center contains many that would have
been considered stressors by some members of the SAB Panel, even though The Heinz Center
excluded stressors from consideration. This difference highlights the various schools of thought
regarding the definition of stressors versus condition indicators where chemical and physical
parameters are concerned.
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SAB Reporting Categories and
Subcategories
Landscape Condition
Extent of ecological
system/habitat types
Landscape Composition
Landscape Pattern/Structure
Biotic Condition
Ecosystems and Communities
| Community Extent
List of Indicators Recommended by The Heinz Center (In press)
Area of six ecosystem types and their major subunits
Area of more detailed subunits of these ecosystem types (four
coastal habitats; six land uses in grasslands; five land uses in
farmland ecosystems; size and shape of natural habitat patches in
farmlands; acreage of forest cover types; five forest management
categories; five shoreline types; total impervious area in urban and
suburban regions).
Area of ecosystem types or habitats meeting certain quality criteria
(altered freshwater ecosystems; vegetated stream bank; percent of
all systems that are physically altered or otherwise disturbed)1
Extent of forest in various patch sizes; area and sizes of patches in
grasslands and shrublands; patch sizes of natural areas within urban
and suburban regions
Presence of particular communities: forest community types with
reduced area; % of freshwater plant communities rare or at-risk
Fragmentation and landscape pattern at the national level;
fragmentation of farmlands by development
A-2
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Community Composition
Trophic Structure
Community Dynamics
Physical Structure
Species and Populations
Population Size
Genetic Diversity
Population Structure
Population Dynamics
Habitat Suitability
Organism Condition
Physiological Status
Symptoms of Disease or
Trauma
Signs of Disease
Chemical and Physical
Characteristics (Water, Air,
Soil, Sediment): SOIL
Nutrient Concentrations
Nitrogen
Index of biotic integrity for freshwater animal communities
nationwide and for urban streams in particular; benthic index for
coastal waters; soil biological condition, as Nematode Maturity
Index
% non-native cover in non-cropped farmland areas; % non-native
cover in forests and grass- and shrublands; % native (or non-native)
animal species in freshwater systems; number of non-native species
and their ranges in coastal systems; population trends in native and
invasive non-native bird species; population trends in selected
disruptive species in urban and suburban areas
Number of plant and animal species at-risk in forests, freshwater
systems, grass- and shrublands, marine waters, and in the nation as a
whole; number of "original" species at risk or absent in urban and
suburban areas, status of selected wildlife species in farmlands
forest age
animal deformities and deaths in freshwater systems; marine
mortalities
chemicals in fish tissue nationwide
nitrate in streams and groundwater in farmlands, forests , grass- and
shrublands, urban and suburban areas
A-3
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Phosphorus
Other Nutrients
micronutrients
Trace Inorganic and Organic
Chemicals
Metals
Other Trace Elements
Organic Compounds
Other Chemical Parameters
pH
Dissolved oxygen/Redox
Potential
Salinity
Organic Matter
Other
Physical Parameters
soil/sediment
water/air
Ecological Processes
Energy Flow
Primary Production
Net Ecosystem Production
Growth Efficiency
Material Flow
Organic Carbon Cycling
N and P Cycling
Other Nutrient Cycling
Hydrology and Geomorphology
phosphorous in freshwater systems, and separately in farmland
streams, and urban and suburban areas
Trace chemicals and contaminants in streams, fish tissue,
groundwater, and sediments nationwide, and specifically in coastal
sediments and urban streams and soils
Pesticides in streams and groundwater of farmlands
Dissolved oxygen in coastal waters
Soil salinity in farmlands
Soil organic matter in farmlands
Ozone levels in urban and suburban air
Stream temperature in urban and suburban regions, sea surface
temperature
Water clarity in freshwater systems
Plant growth index; production capacity, as chlorophyll
concentrations in coastal systems
Carbon storage in forests and grass- and shrublands
nitrogen yields from watersheds and loads from rivers nationwide
A-4
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Surface and Groundwater
Flows
Pattern of Surface Flows
Hydrodynamics
Pattern of Groundwater
Flows
Salinity Patterns
Water Storage
Dynamic Structural
Characteristics
channel/shoreline
morphology and
complexity
extent and distribution of
connected floodplain
aquatic physical habitat
complexity
Sediment and Material
Transport
sediment supply and
movement
particle size distribution
patterns
other material flux
Natural Disturbance Regimes
Frequency
Intensity
Extent
Duration
changes in streamflows nationwide; number and duration of no-flow
periods in grass- and shrublands
depth to groundwater in grass- and shrublands
groundwater levels nationwide
index of riparian conditions in grass- and shrublands; index of
stream habitat quality in freshwater systems generally and
specifically in farmlands
erosion in coastal systems and farm soils
fire frequency index in forests and grass- and shrublands
areal extent of forest disturbance from several sources
'Although each of The Heinz Center's indicators is listed only once, many contain components that
inform additional subcategories, as well. These indicators, for example, may contain elements that can
be extracted to describe the structural diversity of a particular habitat, which is included as a subcategory
within the Biotic Condition EEA.
A-5
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APPENDIX B. THE SAB REPORTING CATEGORIES ORGANIZED BY
LEVEL OF BIOLOGICAL ORGANIZATION AND BY STRUCTURE,
COMPOSITION, AND FUNCTION
This figure depicts the EEA categories in which aspects of structure, composition, and
function at various hierarchical levels would be reported and assessed in the system proposed in
this report. Noss (1990) presented the idea of categorizing biodiversity attributes in a nested
hierarchy that included composition, structure, and function at the landscape,
community/ecosystem, population/species, and genetic levels of biological organization. More
recently, Dale and Beyeler (2001) proposed broadening the scheme to include all attributes
related to ecological integrity. The EEA hierarchy presented in this report does not explicitly
subdivide ecological integrity attributes according to structure, function, and composition at a
variety of scales; it does, however, encompass each of these subdivisions as shown in the figure.
The EEAs relating to process span a number of hierarchical scales. Both Landscape Condition
and Biotic Condition incorporate structural and functional attributes.
B-l
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STRUCTURE | COMPOSITION
~l
LANDSCAPES Landscape Condition j
ECOSYSTEMS
AND
COMMUNITIES
SPECIES AND
POPULATIONS
|
i
Landscape Pattern/Structure Extent, \
Landscape \
Composition |
1
L J
Chemical and i i Biotic Condition i
Physical i i i
\ 1
FUNCTION
~l 1
Ecological Natural . . Hydrology and
Processes
Disturbances i i Geomorphology
i i
Energy and Frequency, \ \ Surface and Ground Water
Material flows Intensity, Extent, \ \ Flows, Dynamic Structural
Duration | | Characteristics,
i i Sediment and Material
Energy and
Material flows
J \ \ \
Characteristics i i i i
I | Physical Community \ Tl
Nutrients, Trace
Inorganic and
f)
Organic
Chemicals, Other
Chemical
Parameters,
Physical
Parameters
Nutrients, Trace
Inorganic and
Organic
Chemicals, Other
Chemical
Parameters,
Physical
Parameters
1
ORGANISMS
Structure, Extent,
Trophic Community
Structure Composition
Population Population Size
Structure
L ,
GENES I Genetic Diversity \
\ \
\ 1
Community Dynamics
\
\
Population
Dynamics
|
Physiological Status,
Symptoms of Disease
or Impairment,
Signs of Disease i
i i Transport
| |
Frequency, • • Surface and Ground Water
Intensity, Extent, . , Flows, Dynamic Structural
Duration . . Characteristics,
Sediment and Material
Frequency,
Intensity, Extent,
Duration
Frequency,
Intensity, Extent,
Duration
Frequency,
Intensity, Extent,
| Duration |
Transport
Surface and Ground Water Flows,
Dynamic Structural Characteristics,
Sediment and Material Transport
Surface and Ground Water Flows,
Dynamic Structural Characteristics,
Sediment and Material Transport
Surface and Ground Water Flows,
Dynamic Structural Characteristics,
Sediment and Material Transport
B-2
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APPENDIX C. BIOTIC CONDITION EEA AND OTHER ESTABLISHED
SCHEMES FOR EVALUATING BIOLOGICAL INTEGRITY
Biotic Condition EEA
Ecosystems and Communities
Community Extent
Community Composition
Trophic Structure
Community Dynamics
Physical Structure
Species and Populations
Population Size
Genetic Diversity
Population Structure
Population Dynamics
Habitat Suitability (focal
species)
Organism Condition
Physiological Status
Symptoms of Disease or
Trauma
Signs of Disease
Index of Biotic Integrity
(IBI) Metrics
total number of species;
abundance of certain
species; species composition
(% of particular species; %
tolerant species; number of
species in specific
categories)
trophic composition
(% omnivores/ insectivores/
top carnivores)
EPA Streams Biocriteria
Guidance1
community structure
(taxa richness; relative
abundance; dominance)
taxonomic composition
(taxa identity; sensitivity;
rare/endangered/key taxa)
predation rate;
recruitment rate; trophic
dynamics; productivity
metabolic rates
disease; anomalies
contaminant levels
EPA Lakes Biocriteria
Guidance: Reservoir
Biological Assemblage
Index2
species richness;
species abundance
trophic composition
reproductive composition
disease; anomalies
IFrom Figure 2-2 (Attributes that should be incorporated into biologial assessment) in EPA, 1996b.
2In addition to biological assessment, the assessment includes information on dissolved oxygen, chlorophyll concentration,
and sediment quality. (EPA, 1998b)
C-l
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APPENDIX D. CONDITION INDICATORS IN THE NEW JERSEY NEPPS
AGREEMENT (FY99-2000)1
SAB Reporting Categories and Subcategories
Landscape Condition
Extent of ecological system/habitat
types
Landscape Composition
Landscape Pattern/Structure
Biotic Condition
Ecosystems and Communities
Community Extent
Community Composition
Trophic Structure
Community Dynamics
Physical Structure
Species and Populations
Genetic Diversity
Population Size
Population Structure
Population Dynamics
Habitat Suitability
Organism Condition
Physiological Status
Symptoms of Disease or
Impairment
Environmental Condition Indicators in the New
Jersey NEPPS Agreement for FY99/2000
wetlands acreage (freshwater and coastal); statewide
forest acreage
% tree cover (canopy) in urban/suburban areas; types
of land cover
land cover change; acreage of fragmented forest
benthic macroinvertebrate communities (non-tidal
waters); tree species composition and species diversity
(forest, including urban forest); number, type, and
extent of noxious invasive exotic plant species
statewide
fish and shellfish population measures; tree species
population and distribution; endangered species
populations statewide; priority landscape species;
horseshoe crab egg density and migratory bird
populations; beach nesting bird populations
tree species growth rate and mortality; adverse
reproductive outcomes in raptors and selected
waterbirds
D-l
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Signs of Disease
Chemical and Physical Characteristics: AIR
Nutrient Concentrations
Nitrogen
Phosphorus
Other Nutrients
Trace Inorganic and Organic
Chemicals
Metals
Other Trace Elements
Organic Compounds
Other Chemical Parameters
pH
Dissolved Oxygen/Redox
Potential
Salinity
Organic Matter
Other
Physical Parameters
Chemical and Physical Characteristics:
WATER (Surface and Ground Water)
Nutrient Concentrations
Nitrogen
Phosphorus
Other Nutrients
Trace Inorganic and Organic
Chemicals
Metals
Other Trace Elements
Organic Compounds
Other Chemical Parameters
|pH
fish tissue concentrations of bioaccumulative
chemicals that are toxic to humans (e.g., mercury,
PCBs, dioxin and certain pesticides)
NO2 levels in ambient air
concentrations of air toxics (metals associated with
suspended particulate matter)
VOC levels in ambient air
ozone levels in ambient air
particulate matter in ambient air
nitrate levels in ground water; total N, ammonia, and
nitrate in streams
total P in streams
metal levels in ground water
VOC levels in ground water; pesticides concentrations
in ground water; detectable pesticide residues in
ground and surface waters (monitored)1
D-2
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Dissolved Oxygen/Redox
Potential
Salinity
Organic Matter
Other
Physical Parameters
Chemical and Physical Characteristics:
SEDIMENT
Nutrient Concentrations
Nitrogen
Phosphorus
Other Nutrients
Trace Inorganic and Organic
Chemicals
Metals
Other Trace Elements
Organic Compounds
Other Chemical Parameters
pH
Dissolved Oxygen/Redox
Potential
Salinity
Organic Matter
Other
Physical Parameters
Chemical and Physical Characteristics: SOIL
Nutrient Concentrations
Nitrogen
Phosphorus
Other Nutrients
Trace Inorganic and Organic
Chemicals
Metals
Other Trace Elements
Organic Compounds
Other Chemical Parameters
|pH
in-stream dissolved oxygen
chloride in ground water
radioactivity in ground water, and in surface water
discharge at nuclear power plants
sediment contaminants
radioactivity in tidal sediments
D-3
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Dissolved Oxygen/Redox
Potential
Salinity
Organic matter
Other
Physical Parameters
Ecological Processes
Energy Flow
Primary Production
Net Ecosystem Production
Growth Efficiency
Material Flow
Organic Carbon Cycling
N and P Cycling
Other Nutrient Cycling
Hydrology and Geomorphology
Surface and Groundwater Flows
Pattern of Surface Flows
Hydrodynamics
Pattern of Groundwater Flows
Salinity Patterns
Water Storage
Dynamic Structural Characteristics
Channel/Shoreline
Morphology and Complexity
Extent and Distribution of
Connected Floodplain
Aquatic Physical Habitat
Complexity
Sediment and Material Transport
Sediment Supply and
Movement
Particle Size Distribution
Patterns
Other Material Flux
Natural Disturbance Regimes
| Frequency
trophic status of public lakes
stream flows, including base flow levels and flood
flows
water levels in reservoirs; ground water supplies
shoreline changes
D-4
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Intensity
Extent
Duration
'Some of the indicators included in the NJ NEPPS set of condition indicators~e.g., those relating to xenobiotic
chemicals- are classified as stressor indicators under the SAB framework but are included as condition indicators
by The Heinz Center.
Sources: NJ DEP. 1998. Environmental Indicators Technical Report: National Environmental Performance
Partnership System (NEPPS). June 1998.
Environmental Indicators in the FY99-2000 New Jersey NEPPS Performance Partnership Agreement. (At
www.state.nj.us/dep/dsr/nepps.htm).
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