A Framework to Assess the Relative
Vulnerability of Aquatic Ecosystem
Services to Global Stressors
Prepared for:
Susan Herrod-Julius
U.S. Environmental
Protection Agency
Global Change Research Program
Prepared by:
Elizabeth Strange
Josh Lipton
Margaret Lefer
Jim Henderson
Jennifer Hazen
Stratus Consulting Inc.
PO Box 4059
Boulder, CO 80306-4059
(303)381-8000
June 13, 2002
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A FRAMEWORK TO ASSESS THE RELATIVE
VULNERABILITY OF AQUATIC ECOSYSTEM
SERVICES TO GLOBAL STRESSORS
Preparedfor:
Susan Herrod- Julius
U.S. Environmental Protection Agency
Global Change Research Program
Prepared by:
Elizabeth Strange
Josh Lipton
Margaret Lefer
Jim Henderson
Jennifer Hazen
Stratus Consulting Inc.
PO Box 4059
Boulder, CO 80306-4059
(303)381-8000
June 13,2002
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Contents
List of Figures iv
List of Tables v
Acronyms vi
Section 1 Background 1
Section 2 Existing Frameworks for Related Assessments 2
2.1 Ecological Risk Assessment 2
2.2 Natural Resource Damage Assessment 2
Section 3 Proposed Assessment Framework 3
Section 4 Conclusions 15
Literature Cited 15
Appendices
A Potential Indicators 21
B Data Sources 24
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Figures
1 Proposed assessment framework 3
2 Outline of steps in the proposed assessment process 4
3 Illustrative geographical representation of South Platte River hydrology and
associated ecosystem services 7
4 Example of a simple pathway influence diagram of relationships among water
development activities, flow alteration, and changes in riparian and stream resources
and services in the South Platte River Basin 10
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Tables
1 Example summary of risk characterization : 14
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Acronyms
DAPTF Declining Amphibian Populations Task Force
DOI U.S. Department of the Interior
EPA U.S. Environmental Protection Agency
FAO Food and Agriculture Organization of the United Nations
IWI Index of Watershed Indicators
NASQAN National Stream Quality Accounting Network
NAWQA National Water Quality Assessment
NLFWS National Listing of Fish and Wildlife Advisories
NOAA National Oceanographic and Atmospheric Administration
NRDA natural resource damage assessment
NWI National Wetlands Inventory
UV ultraviolet
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1. Background
Over the next several years, the U.S. Environmental Protection Agency's (EPA's) Global
Change Research Program will conduct a series of case studies in different regions of the United
States to evaluate potential changes in aquatic ecosystems as a result of global stressors
(U.S. EPA, 2000c). Aquatic ecosystems include inland surface waters (lakes, rivers, and
streams); wetlands; near-coastal waters (tidal rivers, estuaries, and near-shore waters); and coral
reefs. Global stressors of concern include climate change and climate variability, ultraviolet
(UV) radiation, and the development of land and water resources.
A primary interest of the case studies planned by EPA is to understand effects of global stressors
on the ecosystem services provided by aquatic resources and their supporting habitats.
Ecosystem services are the physical and biological functions performed by natural resources and
the human benefits derived from those functions. Examples of the services provided by aquatic
ecosystems include biodiversity, energy and biogeochemical cycling, food (for organisms and
humans), water storage and delivery, water purification, and the provision of recreational
opportunities that help promote human well-being (Cowling et al., 1997; Daily, 1997; Daily
et al., 1997; Ewel, 1997; Postel and Carpenter, 1997; Costanza, 1999; Ewel et al., 1999;
Holmlund and Hammer, 1999; Moberg and Folke, 1999; Roennbaeck, 1999; Quo et al., 2000).
There are several advantages of focusing EPA's aquatic case studies on ecosystem services.
First, by explicitly considering ecosystem services, EPA will ensure that case study analyses do
not become focused solely on investigators' personal research interests without consideration of
the broader ecological and sociological context. Further, ecosystem services are "cross-cutting"
indicators of ecological conditions that can be readily communicated to diverse stakeholders
(Rapport et al., 1998; Norberg, 1999). A focus on services also makes it possible to concentrate a
large amount of ecological data into a limited number of variables that are directly relevant to
environmental decision-making (de Groot, 1992). In addition, ecosystem service endpoints can
be directly linked to studies of societal preferences and values (Prugh et al., 1995; Simpson and
Christensen, 1997; Turner et al., 1998; Wilson and Carpenter, 1999; King et al., 2000; Loomis
etal.,2000).
This report describes an assessment framework designed to help case study researchers collect,
organize, analyze and communicate to diverse stakeholders relevant ecological information on
the effects of global stressors on aquatic ecosystem services. The framework is intended to
ensure that the case studies conducted for EPA's Global Change Research Program provide a
comprehensive evaluation of the potential consequences of global stressors for both aquatic
resources and the services they provide. The following sections provide an overview of existing
frameworks that can be adapted for global change research, describe the proposed framework for
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evaluating effects of global stressors on aquatic ecosystem services, and outline steps in the
proposed assessment process.
2. Existing Frameworks for Related Assessments
Elements of two existing environmental assessment approaches have been adapted and combined
to develop the process proposed herein for evaluating the potential effects of global stressors on
aquatic ecosystem services. The two approaches are the EPA ecological risk assessment
framework and the natural resource damage assessment (NRDA) process of the U.S. Department
of the Interior (DOT) and the National Oceanographic and Atmospheric Administration (NOAA).
These approaches are outlined briefly below.
2.1 Ecological Risk Assessment
EPA's ecological risk assessment framework presents a logical and systematic process for
collecting, organizing, and analyzing ecological data for the purpose of evaluating the risks
posed to natural resources by environmental stressors (U.S. EPA, 1998). The process involves
three main phases: problem formulation, analysis, and risk characterization. In addition to its
logical and coherent organizational structure, this framework has the advantage of focusing
analysis on the assessment of risk rather than exact prediction, in recognition of the uncertainty
and variability that characterize natural systems.
In addition, the framework is readily adapted to watershed-scale, multiple stressor assessments
(Serveiss, 2002). A regional scale perspective is important given the connections among
processes in different catchments and at different scales (Boughton et al., 1999; Gamier and
Mouchel, 2000; Kling et al., 2000) that influence how global stressors will influence service
flows (Bhat et al., 1998; Kurd et al., 1999; Winter, 2000).
2.2 Natural Resource Damage Assessment
The DOI and NOAA have developed approaches and promulgated regulations for conducting an
NRDA. Although the NRDA process is designed to provide for compensation for losses of
natural resources, it provides an interesting potential template for global change case studies
because it involves explicit evaluation and quantification of ecosystem services (43 CFR Part 11,
15 CFR Part 990). The injury determination phase of an NRDA includes characterization of the
pathways by which resources have been exposed to stressors, while the quantification phase
establishes the extent of the injury in terms of the loss of services provided by the injured
resources.
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3. Proposed Assessment Framework
The assessment framework proposed here combines the organizational structure and emphasis on
risk characterization of EPA's ecological risk assessment framework with the NRDA focus on
ecosystem services (Figure 1). The following sections outline each phase of the assessment
process, including some simplified examples for illustrative purposes. As indicated in Figure 1,
the assessment process should involve ongoing dialogue between researchers and stakeholders.
Communication with stakeholders is essential to ensure that researchers and decision-makers
understand what issues are of greatest concern to stakeholders, and that stakeholders understand
the scientific basis for planning decisions. Interaction with stakeholders will ensure that useful
information is developed, relevant stressors and effects are identified and investigated, and
policy-relevant results are communicated effectively.
Problem Formulation
XConceptualX ^_
( model and i
pathways to
Resource
and service
endpoints
i>
Stakeholder
Input
Analysis
pathway-influence determination
assessment endpoint responses
quantification and service response analysis
Risk Characterization
assessment endpoints
services
uncertainty analysis
communication
Figure 1. Proposed assessment framework.
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Steps in the three phases of the proposed assessment process are outlined in Figure 2 and
described below.
Phase 1: Problem Formulation
> Develop conceptual model of watershed and pathway
influence diagram
> Discuss model with stakeholders and select assessment endpoints
> Develop analysis plan
Phase 2: Analysis
> Perform data collection
> Assemble and evaluate new and existing data
> Conduct pathway influence determination
* Evaluate resource endpoints
* Evaluate service changes
> Quantify changes in resources and service flows
Phase 3: Risk Characterization
> Characterize risks to assessment endpoints and services
> Conduct uncertainty analysis
> Communicate risks to stakeholders
> Identify next steps based on stakeholder review
Figure 2. Outline of steps in the proposed assessment process.
Phase 1: Problem Formulation
In this initial phase of the assessment process, information on global stressors, physical,
chemical, and biological conditions in the watershed, natural resources potentially at risk, and
ecosystem service responses is integrated to develop a conceptual model of the watershed under
study. The objectives of this phase of the analysis are to:
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1) develop a conceptual model of the watershed and a pathway influence diagram to
provide a systematic examination of the links among stressors of concern, watershed
resources, and ecosystem services
2) discuss model with stakeholders and select assessment endpoints, including the
natural resources and associated ecosystem services that are potentially at risk
3) develop an analysis plan that provides stakeholders with a transparent identification of
the assessment endpoints that will be evaluated, the measures of change that will be
considered, and the metrics for quantification of resource and service changes.
(1) Develop conceptual model
In this step, investigators will develop a conceptual model of the watershed focusing on the
pathways that generate ecosystem services. Development of a conceptual model will ensure that
a systematic consideration of watershed structures, functions, and services is undertaken before
selecting assessment endpoints and approaches. Specific activities that should be undertaken in
the development of the conceptual model include (but are not necessarily limited to) the
following:
Describe watershed attributes. The specific
attributes of the watershed being studied
should be described in order to develop a
coherent picture of the relationships between
stressors and receptors. Box 1 provides a
simplified example of a watershed
description for a typical urbanized river, the
South Platte River Basin in Colorado.
Watershed attribute information should
include the following:
> The geographic and human setting of
the watershed, including information
on climate, landform and cover types,
ecological region, human land uses,
and general economic and
socioeconomic conditions and uses in
the watershed.
Box 1. Simplified illustration of watershed
description, South Platte River Basin
The South Platte River Basin in Colorado is typical of
urbanized watersheds throughout the arid and semi-
arid regions of the United States. In these watersheds,
climate-induced reductions in precipitation combined
with increased land and water use are expected to alter
hydrologic conditions that help generate aquatic
ecosystem services (Strange et al., 1999). The
potential effects of global stressors will vary
depending on current conditions in different parts of
the basin. The upper South Plane River Basin
provides services typical of forested uplands,
including habitat for native biota and numerous
recreational opportunities. The middle river, which
includes the Denver metropolitan area, is a major
source of water for municipal and industrial uses,
while the lower river is used to irrigate agriculture.
Global stoessors have the potential to reduce the
quantity and quality of water for all of these uses.
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> The hydrological regime, including precipitation, water recharge and flow patterns, the
timing and magnitude of flows in the basin, the watershed's drainage network, and water
uses. The illustrative example provided in Figure 3 depicts the hydrologic regime and
associated ecosystem services of the upper, middle, and lower South Platte River as a
series of input-output relationships. Inflows are the inputs to the system and flow-related
ecosystem services are the outputs. Separate representations are given for native inflows,
imported inflows (transbasin diversions), municipal treatment plant discharges, and
agricultural return flows. Ecosystem services provided by the river (represented with
rectangles, circles, and triangles) include riparian habitat, birds and fish, instream
recreation, flatwater (reservoir) recreation, dilution of contaminant concentrations,
hydropower, agricultural use, and municipal use.
> Biological attributes of the watershed, including a description of representative habitats;
taxa (including aquatic, semi-aquatic, and riparian taxa); general food-webs; threatened,
endangered, and other special status species; and commercially/recreationally important
species.
t General nutrient flows and biogeochemical cycling (e.g., relative importance of in situ
primary production versus allocthonous carbon inputs).
Develop a pathway influence diagram. The purpose of this step is to conceptually and visually
describe relationships among watershed-structures and processes so that potential receptors can
be linked causally to the stressors under consideration. This involves development of a pathway
influence diagram that outlines links among sources, stressors, resources at risk, and associated
services. This should include consideration of the complete "chain of events" that is
hypothesized to occur when considering multiple, stressor-response relationships. This will help
identify potential feedback loops that can result in "risk cascades" (Lipton et al., 1993). The
concept of risk cascades refers to ecological effects that represent a source of risk for other
system components.
It is also important to recognize that although many aquatic ecosystems are resilient and quickly
respond to changing environments, the intensity, frequency, and locations of impacts within a
given watershed may create time lags in ecosystem responses that result in long-term cumulative
effects (Stevens and Cummins 1999; Dube and Munkittrick, 2001; Schindler, 2001). The
accumulation of these direct and indirect effects may be considerable, but difficult to identify,
document, or integrate into the assessment. Although it is important to recognize complexities
such as risk cascades and cumulative effects, it is also important to make sure that the pathway
influence diagram is not so complex that response "signals" will be difficult to detect.
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Sum of Upper River
Native Inflows
Upper River
Sum of Upper River
Reservoirs
^ Sum of Upper Ri
"^ Imported Flows
r River
Sum of Middle River j
Native Inflows
Middle River Denver
^ Sum of Middle River
Imported Inflows
Municipal Treatment
Plant Discharges - / x
(RH)
Sum of Lower River ^
Native Inflows ^
M |
(RH)
Sum of Off-Stream A.
Reservoirs /FR\
Sum of Agricultural ^
Return Flows ^
-ฎ
Lower River
LA:
s.
A
T
Legend
Inflows
Consumptive Uses
Instream Uses
Reservoirs
Outflow
A = Agricultural
Outflow to
Platte River
in Nebraska
T
M = Municipal
RH = Riparian Habitat
B,F = Birds and Fish
IR = Instream Recreation
FR = Flatwater Recreation
D = Dilution
H = Hydropower
Figure 3. Illustrative geographical representation of South Platte River hydrology
and associated ecosystem services. Representations of the interactions between basin
hydrology, biological resources, and human interactions can aid investigators in
development of site conceptual models.
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At a minimum, the development of a pathway influence diagram will involve the following
steps:
> Identify and define the sources and stressors to be assessed. Investigators should
clearly identify the human activities and stressors to be assessed. Global change stressors
(e.g., land use, water development, climate change, climate variability, UV) are, by
definition, broad and subject to confusion among stakeholders. For stakeholders to
evaluate the analysis plan, it is important that the stressors of interest be clearly presented
and described. It also should be recognized
that multiple and interacting stressors may
influence ecosystem services. To the extent
feasible (and without rendering the
assessment hopelessly complex),
investigators should therefore consider both
multiple stressors and interactions among
them. ' ,
Identify natural resources of concern.
Investigators should clearly identify natural
resources (both abiotic and biotic) that are
potentially at risk.
Identify services associated with resources
of concern. After identifying the stressors
and resources of concern, investigators
should explicitly describe the ecological and
human services provided by the resources
(see example, Box 2). This will provide
stakeholders with a clear description of the
types of services associated with the stressors
being evaluated.
Identify stressor-resource-service response
relationships. In this step, investigators
should outline relationships among stressors
and the potentially affected services (as
mediated by changes in resource receptors)
(see example, Box 3). This defines the
pathways by which stressors are likely to
impact potential assessment endpoints.
Box 2. Illustration of service relationship:
Water supply for human uses
Water development and other human
activities affect the quantity and quality of
water available for a variety of ecological
and human uses. For example, in the South
Platte River Basin, increases in return flows
from irrigated farm lands, combined with
increases in stream diversions, have raised
salinity concentrations in the lower South
Platte River (Dennehy et al., 1993).
Elevated salinity can impair domestic water
supplies and the quality of irrigation water,
reducing crop production, as well as causing
toxicity to aquatic biota and altering
community composition.
Box 3. Simplified illustration of stressor-
resource-service response relationships
Water development activities
(e.g., diversions, channelization,
impoundments, groundwater pumping) are
stressors that can alter the frequency,
duration, timing, and magnitude of surface
water flows. Flow alteration can affect
numerous aquatic resources, including
instream and riparian habitat and biota. In
turn, the impairment of aquatic structures
and functions affects numerous services,
including water storage and delivery,
nutrient cycling, provision of habitat for
aquatic biota, and recreational opportunities.
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Figure 4 provides an illustrative example of a simple pathway influence diagram outlining some
of the relationships among water development activities, flow alteration, and changes in riparian
and stream resources and services in the South Platte River Basin. In the South Platte Basin,
native riparian trees such as cottonwood (Populus angustifolia) require a bare, moist substrate
produced by spring floods for seedling germination, followed by a period free from disturbance
for seedling establishment (Johnson, 1994; Shafroth et al., 1995; Friedman et al., 1997). Flow
alteration through various water development activities has decreased snowmelt peaks in the
South Platte River Basin, slowed the rate of peak flow recession, and increased summer base
flows. All of these changes have reduced recruitment of native cottonwood, resulting in less
habitat for native cavity-nesting birds (Knopf and Olson, 1984). Reduction of spring peak flows
has also allowed vegetation to establish on stream bars, reducing nesting habitat for special status
species such as the sandhill crane (Grus canadensis) (Johnson, 1994). In turn, the loss of riparian
avifauna reduces services such as bird watching. The loss of peak flows, combined with periods
of stream dewatering, also reduces instream habitat for fish as well as flows for recreational
activities such as swimming and boating. Differences in the services provided by native and non-
native species can have important economic as well as ecological consequences (e.g., Cowling
et al., 1997; Wilcox and Harte, 1997; Brismar, 2002).
(2) Meet with stakeholders to discuss model and select assessment endpoints
In this step, researchers should meet with stakeholders to present the conceptual model and
discuss potential assessment endpoints. Assessment endpoints are the natural resources and .
ecosystem services that are hypothesized to be at risk and are of concern to stakeholders.
/
(3) Develop analysis plan
The purpose of this step is to develop a clearly articulated analysis plan that will provide
stakeholders with a transparent identification of the endpoints of the assessment, the measures of
change to be used in evaluating those endpoints, available data, and metrics to be used to
quantify changes in watershed resources and services. Specific elements of the analysis plan
include the following:
> Select assessment endpoints. Based on the conceptual model, pathway influence
diagram, and stakeholder input, the specific endpoints to be examined in the assessment
should be specified. Assessment endpoints should include both resource endpoints
(e.g., flow regime) and service endpoints (e.g., agricultural water use). Selection of
assessment endpoints is based on considerations such as susceptibility to global stressors,
relevance to stakeholder priorities, and ecological importance. Selection of assessment
endpoints also should entail explicit discussion of the scale of ecological organization
being evaluated (e.g., species, community, habitat, landscape). To the extent feasible,
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Sources
Water development
Surface water
diversions
Impoundments
Channelization
Groundwater
pumping
Stressor
/ Flow \
\ alteration /
Ecological
effects
Response
endpoints
Service
endpoints
r Timing and magnitude,/^
of peak flows y^
Stream
dewatering
Cottonwood-
dependent
birds
Birdwatching
Fishing Swimming Boating
Figure 4. Example of a simple pathway influence diagram of relationships among
water development activities, flow alteration, and changes in riparian and stream
resources and services in the South Platte River Basin.
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investigators should endeavor to consider multiple organizational scales, as well as
functional connectivity within the ecosystem being assessed (e.g., migration corridors,
energy transport and biogeochemical fluxes within systems, interactions between aquatic
and terrestrial habitats).
Select measures of change. The investigators should identify and describe those specific
measures of change that will be used to evaluate assessment endpoints. For example,
changes in the timing or magnitude of peak flows might be used to evaluate the flow
regime as an assessment endpoint. In certain cases., it may be appropriate for investigators
to identify specific numerical measures that may be used (e.g., number of days on which
water temperature exceeds a lethal threshold for rainbow trout), or specific statistical
measures that may be employed in evaluating potential changes in the assessment
endpoint (e.g., 20% decrease in base flow) (e.g., Richter et al., 1996).
Describe time horizon of assessment. Global change stressors may influence ecosystem
services over lengthy time horizons. Investigators should describe the time horizon being
considered in the analysis, as well as, to the extent feasible, the anticipated relationship
between the time horizon over which ecological-responses might manifest themselves
relative to the temporal sequence of the stressor.
Select quantification metrics. In this portion of the analysis plan, the investigators
should identify the metrics that will be used to quantify changes in both resource
receptors and the services provided by the resource. This quantification step is important
because stakeholder interpretation of study results should be informed through an
understanding of the potential magnitude and extent of change rather than simply a
determination that some change may occur. Quantification metrics to be considered by
investigators might include defining the degree of potential impacts; the areal
(e.g., stream miles, number of affected acres), geographic (e.g., geographic area), and
temporal (duration, frequency, seasonality, etc.) extent of potential impacts; and the
probability of potential effects (described quantitatively or qualitatively in terms of level
of certainty).
In some cases, ecological indicators can be useful measures of stressors and effects.
EPA's Office of Research and Development defines an ecological indicator as
"a measure, an index of measures, or a model that characterizes an ecosystem or one of
its critical components" (U.S. EPA, 2000a). Considerable effort has been devoted to
developing indicators of aquatic ecosystem status and trends (U.S. EPA, 1990,2000b;
NRC, 2000), and some studies have explicitly evaluated indicators of aquatic ecosystem
services (OECD, 1993,1997; Cole et al., 1996; Revenga et al., 1998, 2000; Heinz Center,
1999; King et al., 2000; Burke et al., 2001). Indicators can be used to characterize the
current level of an ecosystem service within a watershed and to predict potential changes
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in service levels in response to particular global change scenarios. Appendix A provides a
matrix of indicators that may prove useful in evaluating service pathways.
> Identify available data, models, data/model gaps. The analysis plan should provide an
overview of available data for the watershed study and existing models that will be used
to evaluate changes, and identify data/model gaps. The plan should then describe how
data/model gaps will be filled (e.g., collection of new data, construction of new models,
reliance on certain assumptions). Appendix B lists some existing watershed databases.
t Present research plan. Finally, the analysis plan should include a defined research plan
that describes the methodological approaches to be used by the investigator. The plan
should be submitted to stakeholders for review and revised as appropriate based on
stakeholder input.
Phase 2: Analysis
In the analysis phase, the research and analysis outlined in the analysis plan are conducted. The
nature of the analysis undertaken by an investigator is necessarily case-specific and investigators
must retain the flexibility to apply a wide variety of analysis methods and approaches.
Notwithstanding this latitude, the analysis should include the following components:
> Perform data collection. Based on the analysis plan, researchers should identify existing
data sources and collect new data, if required, to fully specify the stressor-resource-
service pathways of interest. ;
> Assemble and evaluate new and existing data. The selection of study methods and the
degree of analytical sophistication will depend on the data to be evaluated.
> Conduct pathway influence determination. In this step, the investigators should
present information that provides formal consideration of whether the pathway-influence
relationships postulated in the problem formulation phase are supported and the nature of
those pathway influences.
t Evaluate resource endpoints. In this step, the investigators should determine whether
resources of concern are likely to be affected by the stressors under consideration.
Investigators should evaluate selected measures of change and describe, based on their
analysis, whether the responses in the measures of change will be linked quantitatively to
changes in the resource endpoints.
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Evaluate service changes. In this step, the investigators should provide an evaluation of
which services might be affected as a result of changes in resource endpoints. The
determination of service change should be relative to a baseline condition that reflects
those future conditions that would be expected in the absence of the global stressor being
evaluated.
Quantify changes in resources and service flows. To the extent possible, this step
should include quantitative evaluation of changes in assessment endpoints, including the
degree of change, the probability of change, and the areal, geographic, and temporal
extent of change. This quantification of change should be relative to a "future baseline"
condition. Investigators may wish to present this quantification of changes in service
flows under alternative states of nature (e.g., hypothesizing alternative future conditions),
or under alternative regulatory, mitigation, or adaptation scenarios as a means of
evaluating the relationship between service modifications and future human activities.
Phase 3: Risk Characterization
*
This final phase of the assessment involves the following steps:
> Characterize risks to assessment endpoints and services based on the results of the
analysis. Characterization of risks (described quantitatively or qualitatively) should
consider the nature of changes in assessment endpoints, including the degree of change,
the probability of change, and the spatial and temporal extent of change. In addition, the
risk characterization should describe the temporal horizon of the analysis and discuss the
sensitivity of the risk predictions relative to selection of the time horizon. The
characterization should also include, if possible, identification of potential "hot spots"
within the watershed.
EPA's Guidelines for Ecological Risk Assessment discuss in detail the components of
risk characterization, including the estimation of risk, the interpretation of the
significance of effects, and the analysis of uncertainties, assumptions, and qualifiers in
the risk assessment (U.S. EPA, 1998). Risk estimates can be developed using a variety of
techniques, including quantitative field or laboratory studies, qualitative rankings, and
mathematical models of ecological processes. The significance of risk estimates is
evaluated by considering the multiple lines of evidence obtained from such assessment
techniques.
t Conduct uncertainty analysis. Sources of uncertainty should be described and
quantified where possible. Uncertainties result from various sources, including natural
variability, imprecision in underlying data, lack of complete information, or lack of
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confidence in modeling assumptions (Finkel, 1990; Morgan and Henrion, 1990; Lipton
and Gillett, 1992; Hoffman and Hammonds, 1994; Rowe, 1994). To the extent feasible,
investigators may wish to include formal sensitivity analysis, error, or simulation analysis
into an evaluation of the uncertainties inherent in the assessment. In addition,
investigators should attempt to describe the degree of uncertainty in the "direction" of the
anticipated response, the degree of the response, and the geographic or temporal
sensitivity of the response. Finally, it may be beneficial to stakeholders to perform such
uncertainty analyses for both the assessment endpoints and the potentially affected
services (for example, the degree of uncertainty regarding the risk to a specific
assessment endpoint or species may be different than for an aggregated service).
Communicate risks to stakeholders. Once risks are fully characterized, results need to
be communicated to stakeholders.' The methods, format, and timing of communication
should be responsive to the specific needs of stakeholders and therefore may vary from
project to project depending on expressed needs. Communication may include
development of a "report card" summarizing current risks to key services (e.g., Harwell
etal., 1999).
i
Table 1 presents one simplified example of a risk summary based on a simple stressor-
response matrix. The column headings display stressor categories and the row headings
display ecosystem service categories. Each stressor-response interaction is assigned a risk
value (high, moderate, low) based on case study results. Reading across the matrix
provides an indication of the relative risk posed by the various stressors to each
ecosystem service. Reading the matrix vertically provides an indication of the relative
risk posed to the various services,by a given stressor.
Table 1. Example summary of risk characterization.
.Services
Fishing
Flood control
Boating ,
Riparian
development
Moderate
High
Low
Stressors
Flow
alteration
High
Sedimentation
High
Note: The table indicates the relative vulnerability in qualitative terms
(low, moderate, high) of different services to various stressors.
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Such a summary can help indicate which services are most vulnerable at a given case
study site and which risks are most serious. Summaries of this type are useful
communication tools for presenting assessment results and have been used in many
related applications (Harwell et al., 1999; Revenga et al., 2000; U.S. EPA, 2000c; Burke
etal., 2001; IPCC, 2001).
Discuss next steps. Based on results of the risk analysis and stakeholder review,
researchers and stakeholders should identify follow-up activities.
4. Conclusions
The assessment framework described in this report is intended to help case study researchers
make explicit the potential effects of global stressors on aquatic resources and the services they
provide. The framework is meant to be general enough to incorporate different types of data and
methods, but also specific enough that risks to aquatic ecosystem services in different geographic
areas can be compared or even aggregated across regions as appropriate.
The framework is readily adapted to watershed-scale, multiple stressor assessments. This makes
it possible to explicitly recognize that different types of aquatic ecosystems (e.g., lakes, rivers,
wetlands, riparian forests, and floodplains) are embedded within a landscape context that
determines both the amount and type of materials imported and exported, as well as their
connectivity to surrounding communities and food webs (Boughton et al., 1999; Kling et al.,
2000; Winter, 2000). . '
Details for any particular assessment will depend on site-specific considerations. Each case study
site will present unique features that will determine which assessment endpoints are most
appropriate to evaluate given the stressor scenarios of interest, available data, and stakeholder
priorities. As case study research proceeds, results will help guide further development of the
assessment process outlined here.
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Appendix A Potential Indicators
Table A-l presents a categorization scheme for aquatic ecosystem services and ecological
indicators that might be used to evaluate service pathways. Data sources for quantifying these
indicators are provided in Appendix B. Note that the categorization scheme and potential
indicators are examples only. Specific research questions will guide the selection of assessment
and measurement endpoints, as discussed in the text.
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Table A-1. Indicators that can be used to evaluate service pathways under particular global change scenarios.
Indicators
Precipitation
Air Temperature
Slope
Aspect
Landscape Type
% Forest
% Agricultural
% Urban (level of development)
Landscape Patch Size
Bank Vegetation Cover & Type
Wetland Area / Extent
Hydrodevelopment (# of dams/mi)
Channelization
Rood Control Structures
Groundwater Depletion
Annual Basin Withdraw/is
Hydrdogic Regime (Timing & Magnitude)
Runoff Rate
Infiltration
Water Temperature
Evapotranspiration
Sediment Transport
Soil Permeability
Nutrient Transport
Organic Matter Transport
Contaminant Transport
Water Levels
Water Flow (Dry Season)
Extent and Duration of Ice Cover
Water Volume (in relation to capacity)
', , ,, -i Ecosystem services
Water storage and delivery
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
1
1
i
1
1
J
1
l"
1-
X
X
X
X
X .
X
X
X .
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
r
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Hydropower
x.
X
X
X
X
X
X
X
X.
X
X
X
X
X
X
X
X.
X
X
X
X
X
X
c
I
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
5
=
ra
1
1
s.
D
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Erosion control
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Contaminant absorption and detoxification
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Nutrient cycling
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Maintenance of biodiversity
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Provision of habitat
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Production of food and raw materials
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Nearshore recreation
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
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Table A-1. (cent) Indicators that can be used to evaluate service pathways under particular global change
scenarios.
Indicators
Renewable Water Supply per Person
Residence Time of Water in Basin
Volume of Water in Aquifer Storage
Saltwater Intrusion in Aquifer
Sediment Deposition
Sediment Suspension
Dredging Expenses
Contaminant Concentrations
vlutrient Concentrations
Susoended Solids (Secchi depth)
PH
Dissolved Oxygen (hypoxia)
Biochemical Oxygen Demand (BOD)
Eutrophic Condition (Chlorophyll a, etc.)
/Vastewater Assimilative Capacity
Biological Productivity
Species Diversity
Species Richness
Threatened & Endangered Species
Endemic Species / Non-Native Species
Presence of Rare Species
Biological Distinctiveness Index
Index of Biotic Integrity
Community Index
Water Quality Standard Violations
Fish Consumption Advisories
Fisheries Catch Composition
Fisheries Catch Per Unit Effort
Beach Closures
Ecosystem services
Water storage and delivery
1
X
X
X
X
X
X
,
Hydropower
i
c
1-
5
C
1
,
-.
X
X
X
X
X
X
X
X
X
,
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Contaminant absorption and detoxification
X
X
X
X
X
X
X
X
X
X
X
X
Nutrient cycling
Maintenance of biodiversity
Provision of habitat
Production of food and raw materials
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
f
1
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Notes: Ecosystem services are indicated across the top of the table. Indicator variables are listed in the far lefthand
column. Indicator variables associated with each service are indicated by Xs in the columns.
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Appendix B Data Sources
Land cover
National Wetlands Inventory (NWI).
Water quantity
USGS gauging stations and regional hydrologic models for specific river basins provide
estimates of changes in runoff patterns (volume, timing, rates).
Water quality
EMAP (http://www.epa.gov/emap/). Data on biota (plankton, benthos, fish) and environmental
stressors (water quality, sediment quality, tissue accumulation). Among the resource groups
monitored by EMAP are estuaries, inland surface waters, and wetlands. EMAP scientists use
monitoring data to determine if statistical associations exist between condition indicators
(characteristics of the environment that provide quantitative estimates of the state of ecological
resources) and stressor indicators (characteristics of the environment that are thought to
produce changes in ecological resources).
USGS National Stream Quality Accounting Network (NASQAN) (http://water.usgs.gov/osw/)
water chemistry and sediment data for the four largest U.S. river systems (Colorado,
Columbia, Rio Grande, and Mississippi, including the Ohio and Missouri) and the National
Water Quality Assessment (NAWQA) detailed studies of 60 smaller U.S. river basins.
U.S. EPA Index of Watershed Indicators (IWI) includes 15 indicators of watershed condition and
vulnerability as reflected in overall water quality based on available data on fish consumption
advisories, sediment contamination, and other variables.
EPA Great Waters Program (http://www.epa.gov/oar/oaqps/gr8waters/) research and
reporting on deposition of hazardous air pollutants to Great Lakes, Lake Champlain, Chesapeake
Bay, and certain other coastal waters).
NOAA National Estuarine Eutrophication Assessment. CWA 303(d) lists of impaired waters
stored in EPA's TMDL Tracking Program (http://www.epa/gov/owow/tmdl/).
305b state assessments stored in EPA's National Assessment Database.
National Listing of Fish and Wildlife Advisories (NLFWA). Website:
http://www.epa.gov/OST/fish. ,: , '
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Status of Shellfish Growing Waters. Website: http://sposerver.nos.noaa.gov/projects/95register.
National Coastal Research and Monitoring Strategy. Website:
http://cleanwater.gov/coastalresearch.
EPA's National Coastal Assessment (EMAP Estuary Assessments). Website:
http://www.epa.gov/emap/nca.
PrimeNet, the EPA/NPS UV monitoring network. Website: http://www.epa.gov/uvnet.
Habitat and biota
North American Breeding Bird Survey by Patuxent Environmental Science Center. Website:
http://www.mbr.nbs.gov/bbs.
DAPTF (Declining Amphibian Populations Task Force). Website: http://www.open.ac.uk/daptf/.
DAPTF is a network of more than 3,000 scientists working in 90 countries.
Abell, R.A., D.M. Olson, E. Dinerstein, P.T. Hurley, J.T. Diggs, W. Eichbaum, S. Walters,
W. Wettengel, T. Allnutt, C.J. Loucks, and P. Hedao. 2000. Freshwater Ecoregions of North
America: A Conservation Assessment. World Wildlife Fund-United States. Washington, DC.
Musick, J.A., M.M. Harbin, S.A. Berkeley, G.H. Burgess, A.M. Eklund, L. Findley,
R.G. Gilmore, J.T. Golden, D.S. Ha, G.R. Huntsman, J.C. McGovem, S.J. Parker, S.G. Poss,
E. Sala, T.W. Schmitdt, G.R. Sedberry, H. Weeks, and S.G. Wright. 2000. Marine, esruarine, and
diadromous fish stocks at risk of extinction in North America (exclusive of Pacific salmpnids).
Fisheries 25:6-30.
Williams, J.E., I.E. Johnson, D.A. Hendrickson, S. Contreras-Balderas, J.D. Williams,
M. Navarro-Mendoza, D.E. McCallister, and J.E. Deacon. 1989. Fishes of North America:
endangered, threatened or of special concern. Fisheries.. 14:2-20.
DIAS (Database on Introduction of Aquatic Species). Available on-line at:
http://www.fao.org/fi/statist/fisoft/dias/index.htm.
USGS Non-indigenous Aquatic Species information resource.
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Food production Fisheries
FAO (Food and Agriculture Organization of the United Nations). 2000. The State of World
Fisheries and Aquaculture. FAO. Rome, Italy.
FAO (Food and Agriculture Organization of the United Nations). 1999. Projection of World
Fishery Production in 2010. Available on-line at: http://www.fao.org/fi/highligh/2010.asp.
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