5ER&
United States
Environmental Protection
Agency
A Manager's Guide to
Indicator Selection
Humans are part of-—not apart from—ecological systems.
Individual and collective choices within a watershed determine land
use patterns, such as forested, agricultural, or urban, that in turn
affect aquatic ecosystems. As a society, we want to derive valuable
ecosystem services from our aquatic resources. These services include
drinking water, recreation, habitat, or other amenities. Conflicts
arise when social choices (land use patterns) adversely affect these
desired services. Government managers are charged with managing
the protection or achievement of these ecosystem services; to be
effective, their decision-making processes must be done within the
context of society's choices.
Photo: NOAA, Department of Comm
New Tools for Monitoring Our Waters
The original intent of the Clean
Water Act of 1972—to "restore and
maintain the chemical, physical,
and biological integrity of the
Nation's waters"—has yet to be
realized. While natural resource
and science communities have
continued to pursue this goal,
two major road blocks have
hindered their efforts: 1) a lack
of useful ecological indicators
for monitoring, diagnosing, and
predicting conditions; and 2) the
difficulty of choosing relevant
benchmarks against which to
compare their own resources. To
decrease these barriers, the U.S.
EPA Estuarine and Great Lakes
(EaGLe) Program established
five regional centers to develop
integrated ecological indicators for
use by local resource managers and
scientists (shown on page 8).
To assist resource managers and
scientists in the Mid-Atlantic
region, the Atlantic Slope
Consortium (ASC), based at
Pennsylvania State University,
has developed more than 30
biological, chemical, physical, and
socioeconomic indicators tailored
to the region's aquatic resources,
landscapes, and watersheds. The
suite of indicators can be used to
assess water resource conditions,
monitor trends, diagnose causes
of problems, and target critical
management activities. While some
indicators can be used in a variety
of ways, few indicators perform
all of these activities equally
well; therefore, understanding
the features and limitations
of indicators is critical to their
appropriate usage.
This publication describes a
framework developed by the ASC
to guide managers in selecting
ASC indicators and benchmarks
with which indicator values can
be compared. In essence, the
framework is a question-and-answer
process that defines the parameters
of a task. It incorporates factors that
are common to most managerial
situations:
• Type of question—the problem
• Spatial scale—the size of the
resource
• Temporal scale—the length
of time or timescale being
considered
• Context—the type of land use
and landscape surrounding the
resource
After considerable field testing, all
ASC indicators were categorized
according to these same factors, so
that users could readily see which
indicators and benchmarks apply to
their situation.
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A Framework for Indicator Selection
The Type of Question: defining the problem
Choosing an indicator begins with the type of question being asked. What is the problem? What
is causing it? Is management making a difference? A relevant indicator should give managers the
answers to their specific questions, and it should help them communicate the answers to the public
in an understandable and pertinent way. The ASC framework (depicted in Table 1) categorizes
managerial questions according to the following types.
Condition Assessment: What is the current condition of the resource?
Evaluation: Are management actions effective?
Stressor Diagnosis: What is causing the undesirable condition?
Communication: What will help decision makers and the public comprehend the problem?
Forecast/Restore: What will happen in the future if the problem isn't corrected? Will
restoration efforts be effective?
Table 1. Indicator Selection Framework. This table summarizes the questions that frame the selection of an
appropriate ASC indicator. Answers can then be matched with the indicators in Table 2 on pages 6-7.
Framework
Factors to Address
Criteria and Considerations
Type of Question
A relevant indicator
must be able to
address the type of
managerial question
being asked.
An indicator can
answer more than one
type of question, but
not necessarily all
types.
Condition Assessment:
What is the state of the
system?
A relevant benchmark must be chosen to indicate if a system is in
good or poor condition. For example, a forested watershed may not
provide relevant benchmarks for an urban one. Depending on the
question, more appropriate references might be drawn from
indicators derived from a restored urban river.
Evaluation:
Are management actions
effective?
This is usually a subset of a condition indicator. The indicator must
be responsive to management actions. For example, a Benthic
Index of Biotic Integrity (IBI) should reflect improvements of
in-stream habitat.
Stressor Assessment:
What is causing the problem?
For a Stressor diagnosis, the indicator should demonstrate a
cause and effect relationship with the Stressor. An example is
density of submerged aquatic vegetation with light availability.
Communication to the public:
What is the best way to
communicate status to public
and decision makers?
The indicator should encourage comprehension of the
environmental condition in a way that the public can understand,
based on concepts relevant to their own experiences and ethics.
Futures forecast or
restoration assessment:
What is the outlook for the
condition of the resource, either
with or without action?
Indicators that forecast future conditions are used mostly for large
areas over longer time periods, such as the regional impact of
climate change on agricultural production or the composition of
aquatic biological communities.
Spatial Scale
(Size)
What is the extent of the
targeted resource?
The scale of the ecosystem characteristic or process being
measured should match the scale at which management actions
are taken. For example, a Fish Index of Biotic Integrity (IBI) reflects
conditions in an entire watershed and should be responsive to
changes in land management over the entire watershed. In
contrast, the habitat value of an individual wetland is responsive to
local actions in the area immediately surrounding the wetland itself.
Temporal Scale
(Timescale)
What is the relevant timeframe
over which to monitor trends?
The selected indicator must be able to confidently detect change
over the timeframe of interest.
Context
(Land Use &
Landscape)
What is the predominant land
cover around the resource?
What type of landscape is it?
What is a useful comparison?
Measuring progress requires a realistic benchmark that is
appropriate to the type of land use and physical landscape. For
example, in an urbanized watershed, restoration to a pristine
condition is neither possible nor sustainable. What is needed is a
relevant benchmark for an urban watershed.
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Spatial Scale: how extensive is the resource?
Indicators have been developed for specific spatial scales. Therefore, it is important that
the scale of the ecological process being measured is similar to the extent of the resource
being managed. Is the resource a local lake, a small watershed, or a portion of an estuary?
Managers need to define the scale in terms that make sense, ecologically and/or politically.
The ASC indicators were developed according to the scale at which most management
decisions in the Mid-Atlantic region are made. All of the indicators can be used for
estuarine segments and small watersheds. An "estuarine segment" represents a downstream
area composed of deepwater areas, shallows, tidal marshes, creeks, and adjacent uplands. A
"small watershed" is equivalent to an upstream area that encompasses several streams and
river banks, wetlands, water bodies, and the contributing drainage basin. As can be seen
from the indicators listed in Table 2 (page 6), some are useful for smaller areas, such as sites
(for example, a riparian area along a headwater stream) or reaches (a short section of a
lower order stream).
Temporal Scale: how long and when?
Does the project in question need to look at the seasonal variations of a fish species? Does
it need to compare improvements over a 5-year period? The ASC indicators apply to the
timescales that managers most often consider—seasonal variations, annual comparisons,
and long-term trends. All indicators are developed for specific temporal scales and may not
work at other scales.
Context: land use and landscape
To determine the feasibility of
management or restoration plans, the
activities must be considered in context
with the surrounding land use and
landscape. Does the resource in question
lie in a protected forest or in a rural
watershed undergoing rapid urbanization?
Does it lie in a coastal plain or in an area
with steep hills and valleys?
The issue of context leads into the use of
ecological benchmarks. To set realistic
management goals, a resource should
be compared to a relevant benchmark,
in other words, to the best attainable
condition for the region and the type of
landscape. Traditionally, environmental
benchmarks have been taken from
systems devoid of human impact. As
most landscapes are managed with the
intention of supporting continued human
use, this is neither practical nor realistic.
When developing the ASC indicators,
the researchers determined benchmarks
for each indicator that reflect the types
of land uses, landscapes, and geological
characteristics prevalent in the Mid-
Atlantic region. Managers can refer to
Figure 1 to determine the context for
their site.
Six Land Use/Landscape Clusters
) States
C J Physiographic province
C ) Example watersheds
Landcover in Exam pie Watersheds
( ) Water
C ) Suburban
( ) Urban
J Rock
) Transitional
) Forest
(ZZ) Pasture
C 3 Row Crop
) Em rg't Wetland
) No data
Figure 1. Determining ASC Indicator Context. All small
watersheds in the region (14-digit Hydrologic Unit Code
watersheds) were classified according to land use patterns—
forested, urban, agriculture, and mixed. This information was
further delineated by additional landscape parameters (for
example, high or low slope), resulting in these six land use/
landscape clusters. ASC indicators were benchmarked according
to the land use/landscape clusters in this map of the Atlantic
Slope region.
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Photo: Donna Marie Bit
When the Fish Community Index was compared with
measures of habitat conditions, the index scores were
poorest in areas with highly altered shoreline conditions and
minimal subtidal habitat.
Putting the Framework to Work
Once users have answered the questions in the
ASC framework, they can select appropriate
indicators from the list of ASC indicators in
Table 2 (pages 6-7). The table is provided to
simplify the initial selection process. Further
information on each indicator can then be
obtained from the Atlantic Slope Consortium
website, www.asc.psu.edu.
The following hypothetical scenarios illustrate
how managers can use the ASC framework
(Table 1) and the table of indicators (Table 2)
to select indicators best suited for the resource
question at hand.
Situation #1: Professional and recreational fishers have reported declines of
fish in an estuary in a county in Maryland. The county has undergone rapid
urbanization of agricultural and forested land for the past five years. Resource
managers want to learn if and what land, use changes may be affecting nearshore
estuarinefish communities. They need to convey their findings to interested
environmental and fishing groups and local decision makers.
In this situation the managers want to answer
the following types of questions. What is the
relative biological integrity of the nearshore
environment? How will future development
affect fish communities? Can this indicator
clarify environmental connections to the
public? These questions fit into the categories
of condition assessment, futures forecast/
restore, and communication with the public,
respectively. Looking at the list of ASC
indicators in Table 2, the most applicable
indicator is the Fish Community Index for
Estuaries, since it can be used to address all
three of these questions.
It also appears that the spatial scale of the Fish
Community Index—site to small watershed—
would be appropriate, as would the temporal
scale—days to years. The initial step of the
selection process is done.
To learn more about the usefulness of the Fish
Community Index (FCI), the managers could
turn to the ASC website, where a summary and
final report of each indicator is provided. They
would learn that the FCI was developed for
application in the Chesapeake Bay watershed's
nearshore estuarine environment (< 2m
depth). The FCI incorporates measures of
fish community integrity, such as taxonomic
richness and diversity, trophic composition,
and nursery function. When the FCI was
compared with measures of habitat conditions,
such as shoreline alteration and subtidal
structures, FCI scores were lowest in areas
with highly altered shoreline conditions
and minimal subtidal habitat. In addition,
FCI scores were lower in developed and
agriculture watersheds than in watersheds
dominated by forests. In other words, biotic
responses correlated with habitat condition
measures in nearshore, shoreline, and
watershed environments.
Resource managers in this situation could
use the FCI to explore its relationship among
nearshore habitat condition and existing
shoreline conditions at specific sites or in
small watersheds in their county. They also
could use it to evaluate future development
scenarios. Additionally, the FCI would be
useful in communicating their findings to
the public, particularly since the index is
expressed as an easily understood score.
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Situation #2: The setting is a
rapidly developing semi-urban
county through which two large,
brackish rivers flow. Public
groups and environmental
managers are concerned with
declining aquatic conditions,
and the county is considering
various shoreline restoration
efforts. Project managers want
to determine which efforts would
most improve habitat condition.
In this situation, the managers need to
address the following types of questions:
What is the current status of aquatic
habitat quality? What land-use or land-
cover changes could improve aquatic
habitat condition? They have chosen
the Macrobenthic Community Indices
in Estuaries (Table 2) as one of their
assessment tools, because these indices
can be used to assess the problem
(condition assessment), to evaluate
different scenarios (forecast/restore), and
to communicate outcomes with the public
(communication). The indices also are
applicable in terms of scale and context.
A sampling of the macroinvertebrate
organisms from the nearshore benthic
environment of the Chesapeake Bay
c^moles for the Macrobenthic Community
fndTces are collected
In the summary provided on the ASC website, the managers
learned that the Macrobenthic Community Indices involves
two indices. While both indices are measures of biotic
integrity that can be correlated with habitat conditions, one
index is applicable at the site level, the other at a watershed
level. In combination, the indices can reflect ecological
thresholds of biotic response to developed land use impacts
at both the site and watershed scales. For example, the
indices' scores were significantly reduced when the amount
of developed shoreline at the site level exceeded 10%, and
when developed land use at the watershed level exceeded
12%. However, researchers also found that forests and
wetlands in the riparian zone have the potential to
diminish the effects of urban land use in localized areas.
Not only could the information provided by the Macrobenthic Community Indices help the
managers in this situation prioritize and target sites or small watersheds for restoration or protection,
it also could help them communicate goals to the public. Even so, the information provided by the
Indices is just one layer of an overall condition assessment. ASC researchers recommend adopting
an ecosystem approach incorporating various indicators that measure different scales or types of
stressors.
The impact of shoreline and watershed land use on nearshore
biotic communities is a fundamental ecosystem management
question. Shallow-water tidal habitats provide essential nursery,
spawning, and foraging areas for numerous fish, shellfish and
crustacean species. These critical resources are under intense
pressure from a variety of users. Both the Fish Community Index
and Macrobenthic Community Indices are useful assessment
tools for these areas.
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Table 2. Ecological Indicators Developed for the Mid-Atlantic Region. All ASC indicators have been categorized
according to the factors in the ASC framework. Their applicable uses are shown in the middle column below. A full list
of indicators and further information is available at: www.asc.psu.edu.
Indicator
Uses by ASC Indicator-selection Framework
Description
Abundance of
Common Reed
(Phragmites australis)
in Brackish Wetlands of
Chesapeake Bay
Type of Question: Condition assessment
Spatial Scale: Wetland and subestuary
Temporal Scale: Seasonal to annual
Context: Forested, agricultural, urban, and mixed
Correlates the abundance
of Common Reed and the
nitrate concentrations in
leaves with developed land.
Bio-optical Model
for Determining
Habitat Suitability for
Submerged Aquatic
Vegetation (SAV) in
Estuarine Segments of
Chesapeake Bay
Type of Question: Condition assessment; communication;
forecast/restore
Spatial Scale: Estuarine segment
Temporal Scale: Seasonal to annual
Context: Land-use decisions in coastal zone
Determines the level of
suspended solids that
allows SAV survival; gives
level in relationship to land
use.
Blue Crab (Callinectes
sapidus) Abundance
Type of Question: Condition assessment; communication
Spatial Scale: Shoreline segment, watershed, and regional
level
Temporal Scale: Seasonal
Context: All land covers
Correlates juvenile
crab abundance with
shoreline wetlands,
forested watersheds, and
subestuaries with average
salinity.
Fish Community Index
(FCI) for Estuaries
Type of Question: Condition assessment; communication;
forecast/restore
Spatial Scale: Site to small watershed
Temporal Scale: Days to years
Context: Low-slope forested, agricultural, urban
Biotic integrity index for fish
communities for application
in the nearshore estuarine
environment.
Index of Marsh Bird
Community Integrity
(IMBCI)
Type of Question: Community integrity assessment; stressor
diagnosis; communication
Spatial Scale: Marsh to subestuary
Temporal Scale: Years to decades
Context: Marshes within any land-cover context
Scores for marsh birds are
compared to wetland habitat
and land use to identify
wetland stressors.
Index of Waterbird
Community Integrity
(IWCI)
Type of Question: Community integrity assessment; stressor
diagnosis; communication
Spatial Scale: Subestuary
Temporal Scale: Years to decades
Context: Subestuaries and associated watersheds with any
land cover
Scores for waterbird
communities in subestuaries
are compared to indicators
of estuarine condition to
identify stressors and their
pathways.
Inverse-distance
Weighted Cropland
Type of Question: Condition assessment; stressor diagnosis
Spatial Scale: Reach to watershed
Temporal Scale: Seasons to decades
Context: Agricultural, urban, and mixed watersheds
Watershed measure that
gives greater weight to
croplands closer to water
bodies while including effect
of more distant croplands.
Inverse-distance
Weighted Developed
Land
Type of Question: Condition assessment; stressor diagnosis
Spatial Scale: Reach and watershed
Temporal Scale: Seasons to decades
Context: Urban and mixed watersheds
Watershed measure that
gives greater emphasis to
nearby developed land than
to distant developed land.
Inverse-distance
Weighted Impervious
Cover
Type of Question: Condition assessment; stressor diagnosis
Spatial Scale: Reach and watershed
Temporal Scale: Seasons to decades
Context: Urban and mixed watersheds
Watershed measure that
gives greater emphasis
to impervious land near a
resource than to distant
impervious land.
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Table 2. Continued
Indicator
Uses by ASC Indicator-selection Framework
Description
Macrobenthic
Community Indices in
Estuaries (B-IBI, W-
value)
Type of Question: Condition assessment; communication;
forecast/restore
Spatial Scale: Site to small watershed
Temporal Scale: Days to years
Context: Low-slope forested, agricultural, urban
Gives two measures of
invertebrate biotic integrity
of the nearshore estuarine
environment.
Nitrate, Total N and
Total P Concentrations
in Subestuaries of
Chesapeake Bay
Type of Question: Condition assessment
Spatial Scale: Subestuary
Temporal Scale: Short-term to seasonal
Context: Forested, agricultural, urban and mixed
Examines relationships
between watershed
characteristics and nitrate,
nitrogen, and phosphate.
Polychlorinated
Biphenyls (PCBs) in
White Perch
Type of Question: Condition assessment; communication
Spatial Scale: Watershed level
Temporal Scale: Seasonal to annual
Context: Urban
Shows probability of high
PCB levels in White Perch
in subestuaries near
commercial land.
Shoreline Condition
Type of Question: Condition assessment; stressor diagnosis;
communication; forecast/restore
Spatial Scale: Site to small watershed
Temporal Scale: Days to years, resample every 5 years to
assess change
Context: Applicable in estuarine tidal areas
Reports riparian land use,
bank characteristics, and
structural modifications
intended to reduce shoreline
erosion. GIS format allows
spatial assessment and
analysis.
Source Land
Proportion Weighted by
Inverse Riparian Buffer
Width
Type of Question: Condition assessment; stressor diagnosis
Spatial Scale: Reach to watershed level
Temporal Scale: Months to decades
Context: Agricultural, urban, and mixed watersheds
Estimates effective
proportion of land-cover
type in the watershed
draining to a stream
response point.
Source-specific Mean
Riparian Buffer Width
Type of Question: Condition assessment; stressor diagnosis
Spatial Scale: Reach to watershed
Temporal Scale: Seasons to decades
Context: Agricultural, urban, and mixed watersheds
Quantifies the potential of
riparian buffers to reduce
the impact of a specific land
cover on aquatic systems.
Spot Sampled Average
Stream Nitrate
Concentration
Type of Question: Condition assessment; performance
evaluation; stressor diagnosis
Spatial Scale: Reach to large river
Temporal Scale: Seasons to decades
Context: All watersheds
Spot sampling is a cost-
effective predictor of nitrate
and total nitrogen.
Stream-Wetland-
Riparian (SWR) Index
Type of Question: Condition assessment
Spatial Scale: Site to small watershed
Temporal Scale: Days to years
Context: All land covers
Site index of condition for
streams and associated
wetlands and riparian
areas. Average of sites in
watershed gives estimate of
watershed condition.
Wardrop, D.H., Bishop, J.A., Easterling, M., Hychka, K, Myers, W.L., Patil, G.P., and Taille, C. 2005. Characterization and classification of watersheds by
landscape and land use parameters in five mid-Atlantic physiographic provinces. Journal of Environmental an lies 12(2): 209-223.
Wardrop, D.H., Hershner, C., Havens, K, Thornton, K., and Bilkovic, D.Developing and communicating a taxonomy of ecological indicators: A case study
from the mid-Atlantic. EcoHealth (In Press).
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U.S. EPA Office of Research
and Development
Washington DC
EPA/600/S-06/002
January 2006
EPA's Science to Achieve Results (STAR)
Estuarine and Great Lakes (EaGLe) Program
I GLEI
Great Lakes Environmental Indicators Project
University of
Minnesota-Duluth
This research is funded by
U.S. EPA-Science To Achieve
Results (STAR) Program
Grant #l5ag;ia:EPH
T
- PEEIR
Pacific Estuarine
Ecosystem Indicator
Research Consortium
University of California-Davis
ASC
Atlantic Slope Consortium
Pennsylvania State University
• Smithsonian Environmental Research Center
• Virginia Institute of Marine Sciences
• East Carolina University
• Environmental Law Institute
• FTN Associates
EaGLe Program HQ
Washington DC
CEER GOM
Consortium for Estuarine
Ecoindicator Research for the Gulf of Mexico
University of Southern Mississippi
ACE INC
Atlantic Coast Environmental
Indicators Consortium
University of North Carolina—Chapel Hill
Direct and indirect effects
of human activities
have taken a toll on the
nation's estuaries, yet few direct
linkages have been identified
between human activities on
land and responses in estuarine
ecosystems. The Atlantic
Slope Consortium is one of
five national projects funded
by EPA's EaGLe program. The
goal of the EaGLe program is to
develop the next generation of
ecological indicators that can be
used in a comprehensive coastal
monitoring program.
U.S. EPA
Office of Research and Development
National Center for Environmental Research
Barbara Levinson
202-343-9720
Levinson.Barbara@epa.gov
http://es.epa.gov/ncer/centers/eagles
http://eagle.nrri.umn.edu
Atlantic Slope Consortium
Pennsylvania State University
Robert Brooks
814-863-1596
rpb2@psu.edu
www.asc.psu.edu
U.S. EPA
Mid-Atlantic Integrated Assessment
Patricia Bradley
410-305-2744
bradley.patricia@epa.gov
www.epa.gov/maia
8
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