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A SYNTHESIS OF THE EMAP INLAND WETLANDS APPROACH
EXECUTIVE SUMMARY
By
Mark T. Brown
Center for Wetlands
University of Florida
Gainesville, Fl 32611
for
Office of Research and Development
U.S. Environmental Protection Agency
October 1989
(CFW-89-10)
A SYNTHESIS OF THE EMAP INLAND WETLANDS APPROACH
By
Mark T. Brown
Center for Wetlands
University of Florida
Gainesville, Fl 32611
Introduction
The purposes of this synthesis report are to:
1. Summarize core and developmental indicators that have been selected for immediate use and
pilot testing by EMAP Inland Wetlands
2. explain the choices of indicators of ecological status by enumerating valued ecological qualities
and perceptions of ecological status by the public
3. explain the causal pathways of potential stressors to develop a clear picture of nominal and
subnominal ecological status, probable causes of subnominal status, and conflicting evidence of ecological
status;
4. establish critical research needs for EMAP Inland Wetlands over the next several years to
first test the suite of indicators of ecological status and then to further refine the indicator suite and
sampling protocols to meet overall EMAP goals and objectives.
Synthesis
EMAP Inland Wetlands Indicators
The overall goals and objectives of EMAP are designed to answer the following four questions:
1. What is the current extent of terrestrial and aquatic resources at risk from loss, alteration,
or damage from anthropogenic stresses at the regional and national scale?
2. What is the current status of these ecological resources?
3. What is the most probable diagnosis for resources in subnominal condition?
4. Are there regional or national trends in the condition of ecological resources?
The near term goals of the EMAP -Inland Wetlands effort are to: (1) identify indicators that are
appropriate for determining status and trends of ecological condition of the nation's wetlands, (2) field
A SYNTHESIS OF THE EMAP INLAND WETLANDS APPROACH
By
Mark T. Brown
Center for Wetlands
University of Florida
Gainesville, Fl 32611
Introduction
The purposes of this synthesis report are to:
1. Summarize core and developmental indicators that have been selected for immediate use and
pilot testing by EMAP Inland Wetlands
2. explain the choices of indicators of ecological status by enumerating valued ecological qualities
and perceptions of ecological status by the public
3. explain the causal pathways of potential stressors to develop a clear picture of nominal and
subnominal ecological status, probable causes of subnominal status, and conflicting evidence of ecological
status;
4. establish critical research needs for EMAP Inland Wetlands over the next several years to
first test the suite of indicators of ecological status and then to further refine the indicator suite and
sampling protocols to meet overall EMAP goals and objectives.
Synthesis
EMAP Inland Wetlands Indicators
The overall goals and objectives of EMAP are designed to answer the following four questions:
1. What is the current extent of terrestrial and aquatic resources at risk from loss, alteration,
or damage from anthropogenic stresses at the regional and national scale?
2. What is the current status of these ecological resources?
3. What is the most probable diagnosis for resources in subnominal condition?
4. Are there regional or national trends in the condition of ecological resources?
The near term goals of the EMAP -Inland Wetlands effort are to: (1) identify indicators that are
appropriate for determining status and trends of ecological condition of the nation's wetlands, (2) field
test measurement techniques of indicators and develop protocols, and (3) test a suitable suite of indicators
to determine their applicability to a national EMAP Design.
While the program goals of EMAP Inland Wetlands are obviously identical to the overall EMAP
goals, the near term goals and objectives are more related to developing and testing indicators and suites
of indicators to assure that the meet the overall program goals. To this end we have developed a
methodology and systematic review process to select a suite of potential indicators that seem to be
appropriate to begin testing immediately. We have also identified a set of indicators that may be added
to the indicator suite at a later time (from one to several years) once sufficient confidence related to their
application and appropriateness to EMAP has been demonstrated. The lack of confidence stems from
either one or both of the following two issues:
measurement techniques have not been thoroughly standardized or tested, or
their is some question whether they are sensitive enough or applicable to all wetland
types and conditions.
Field testing in a pilot program will provide needed information on methodologies and
standardized protocols for those indicators where techniques are weak, and analysis of data and
comparison with other indicators and known stressors will reveal whether indicators are appropriate
and sensitive for determining status and trends of end points of concern.
In addition, we have identified a third set of potential indicators that are further from
implementation (3-5 years), but that deserve testing and development because they may have great
potential in providing essential information not covered by other indicators.
The following list of proposed EMAP Inland Wetland indicators by class is ordered in a rough
confidence ranking that is based on (1) their ability to provide meaningful information, and (2)
developmental status.
Core Indicators
1. Regional changes in acreage, type diversity and spatial patterns
2. Hydroperiod
3. Direct measurement of nutrients
4. Direct measurement of pollutants
5. Vegetation patterns, abundance, biomass, and species composition
6. Sedimentation and Organic Matter accretion
7. Waterbird abundance and species composition.
Developmental indicators (well developed)
1. Bioaccumulation
2. Macroinvertebrate abundance, biomass, and species composition
3. Leaf area, greenness, and per cent light transmittance
Developmental Indicators (poorly Developed)
1. Microbial community structure
2. Bioassays
3. Biomarkers
Wetland Indicators Not Selected
In the literature concerning the state of the art of indicators of ecological status (sometimes
termed "bioindicators") there are numerous suggestions of extensive lists of components or pathways of
energy exchange that might be candidates for indicators. The lists were seriously considered, and
narrowed to those mentioned above as the most promising. Several proposed indicators that were not
chosen deserve mentioning to explain, in light of their public viability, why they have been discarded.
The three most common are fish, herpetofauna, and mammals.
In most cases, the public sees wetlands as wildlife habitat, and thus the use of visible wildlife
species as indicators of ecological status would seem to make good sense. They are widely known, the
public recognizes the connections between wildlife and habitat to some extent, and they are an important
"endpoint." Yet they present special difficulties in sampling that resultfrom the pulsing hydrology of most
wetland systems that effect spatial and temporal distributions and life habits which, in turn, cause
fluctuations in populations that may not be related to changes in wetland ecological status.
Variation in normal seasonal distributions of wildlife and fish within wetlands are compounded
by other pulsing events like wet and dry seasons or periods of extreme rainfall and drought. For instance,
many herpetofauna key reproduction to dry seasons or rainfall events that may vary considerably from
one year to the next. Fish populations within wetland ecosystems are extremely variablefrom year toyear,
and wetland to wetland. Viable populations within isolated wetlands depend on standing surface water
throughout the year; a condition that may vary from one year to the next. Fish populations in flowing
water wetland systems depend on conditions in contributing streams and rivers that have little or no
relation to the status of the associated wetland. Sampling schemes in the simplest of programs that are
designed to sample fish and herpetofauna quickly become cumbersome as a result accounting for these
factors; a national or regional program would be unwieldy.
Mammals are mobile species, the larger the animal, the more mobile. Many spend only portions
of yearly life cycles within wetland systems since they integrate over broad landscapes of uplands and
wetlands. Some species are affected by hunting pressure, or because of their mobility, are subject to
accidental death on roadways. These anthropogenic pressures result in fluctuations in populations that
are unrelated to ecological status. In addition, temporal variability in mammal populations is
compounded by wetland hydrologic pulses that can drive some species to higher ground during the wet
season or unusual rainfall events, or drive them to other wetlands where drought has not adversely
affected food supplies.
In all, the use of fish, herpetofauna, and mammals as indicators of ecological status of wetlands
was judged to present significant difficulties when proposed within the regional character of the sampling
scheme for EMAP Inland Wetlands. Required sampling frequency, and spatial resolution that would
be necessary to account for within region, temporal, and within wetland variability precludes their use in
the program. The use of mammals and to some extent herpetofauna as indicators of ecological status on
a larger scale (i.e. the landscape scale) may be a fruitful approach and probably should be pursued as a
means of accounting for status and trends in regional biodiversity.
Endpoints of Wetland Ecological Status
Ecological qualities or endpointss" valued by the public are related to four broad categories of
ecological functions: (1) water quality functions, (2) Water quantity hydrologicc) functions, (3) Wildlife
support, and (4) socio-cultural values. Each of these functions has one or more facets that are often
considered separately as endpoints depending on type of wetland, regional characteristics, and other
public perceptions as follows:
Water Quality Functions:
Two primary sources: (1) wetlands provide quality improvement through
sedimentation and immobilization, and limited uptake of various pollutants/ nutrients
carried in flowing waters, and (2) organic substrate acts as filter to immobilize substances
as they pass from surface waters through wetland soils to ground waters.
Hydrologic Functions
Water storage and flood abatement.
Wetland water storage acts as buffer against flooding by storing storm
water and releasing slowly to minimize flood peaks and maintain base flow.
Ground Water Recharge and Discharge
Wetlands are areas where ground waters either discharge or infiltrate.
Often, in individual wetlands bi-directional flow is characteristic during different
portions of the year.
Life Support
Primary Production and Food Chain Support
Wetland productivity is often greater than surrounding ecological
communities by virtue of their role as areas of landscape concentration. Internal
food chains and those where production is often exported are sustained by the
higher production.
Wildlife habitat.
As a result of higher production, and structural characteristics wetlands
offer habitat features not found in other community types.
Socio-Cultural values
Uniqueness and scarcity
Wetlands represent only about 20% of the total landscape, in some areas
they represent a very small percentage. Often wetlands are the last vestiges of a
wild landscape.
Cultural values.
Research,and educationalvalues,aestheticvalues,waste and stormwater
recycle, wood and wood products, sustained yield agricultural production.
Public Perceptions of Ecological Status
Public perceptions of ecological status are less complex than are the qualities for which wetlands
are valued. While there are over half a dozen qualities judged important and valuable, most are not easily
perceived. As a result there are three main indicators of wetland ecological status that are easily
understood and have often been shown to garner public concern. They include (in order of perceived
public importance): (1) loss of wetland area, (2) decline in viable populations of wildlife, and (3)
noticeable (rapid) changes in species composition.
The loss of acreage has been elevated in the minds of the public in recent years to an extent that
acreage in and of itself has become synonymous with wetland ecological status. While trends in the loss
of acreage are often blamed for decreases in wildlife populations, the actual loss is of great public
concern. As a result, the foremost important indicator of EMAP Inland Wetlands is measurement of
changes in acreage, type diversity and spatial patterns of wetlands across regions and among wetland
types.
Loss of wetland area, and to a lessor extent, declines in the quality of wetland habitat have been
suggested as the causes of decline in viable populations of wildlife. Many species of threatened birds and
mammals have been shown to be wetland dependent species; terminology that has become increasingly
important to the public. Public perceptions regarding losses of birds, mammals and fish (probably in that
order) as they relate to the spatial extent of inland wetlands is relatively high.
Rapid changes in species composition 'r in the condition of plant species present in wetland
ecosystems is often attributed to exogenous impacts by the public. Invasions of exotic species and species
considered noxious, as well as noticeable shifts in species composition are often quite apparent and
garner public attention. However, much of the public does not associate the changes in species
composition with functional impacts like loss of wildlife habitat and food chain support. The change in
species composition, in and of itself, is sufficient evidence for most of the public to suggest changes in
ecological status have occurred.
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EMAP -Inland Wetlands Indicator Strategy
Determining Ecological Status
EMAP is being designed to provide information on a region by region basis concerning the
ecological status of the Nation's ecosystems. The chosen suite of indicators for each class of ecosystems
(inlandwetlands, agro-ecosystems,forests,near coastal systems, etc.) need provide information regarding
the percent of the target population that is nominal or subnominal, distinguish between contradictory
indications of status among the various indicators, and provide probable cause of the subnominal
condition. The suite then, must contain indicators of stress origins, exposure, and response.
Stressor Indicators Stressor indicators are economic, social,and environmental engineering data that
can be used to confirm diagnoses and determine most probable sources of exposure or as ancillary data
that may help in interpretation of diagnoses. Indicators that are of interest to EMAP Inland Wetlands
include: population, land use, changes in land use, drainage density of canals and ditches, ground water
and surface water withdrawals, sewage treatment methods and quantities, etc. Some of these data are best
complied from aerial photography, some from recent census information, and some from regional or local
engineering sources. While an important component of the EMAP Inland Wetlands program, these data
are required by each of the ecosystem teams and will be provided and maintained by the EMAP
characterization group as part of the Geographic Information Base for each sample location.
Response Indicators Response indicators are biological measurements that quantify the overall
condition of the ecosystem. Examples include gross pathology of species present, presence or absence
of "sentinel" species, and community structure. Response indicators can be used to separate the population
of wetlands into nominal and subnominal classes of condition. They tend to integrate the effects of all
stressors acting on a wetland system over time, but provide ambiguous diagnostic evidence.
Core indicators that are classed as response indicators include: (1) vegetation patterns,
abundance, biomass, and species composition; (2) waterbird abundance and species composition, and (3)
organic matter accretion.
Measurements of leaf area, percent light transmittance, and greenness, as well as
macroinvertebrate abundance, biomass, and species composition, once further developed may offer
advantages in increasing resolution of determination in nominal and subnominal classes and contribute
to resolving conflicting indicators.
Exposure Indicators Exposure indicatorsare physical,chemical, and biological measurements that can
be related to habitat degradation, pollutant exposure, or other causes of poor condition. Examples include
direct measurement of pollutant concentrations, bioaccumulation of toxins in tissue, bioassays using test
organisms, and measurement of habitat condition. Exposure indicators are used to partition the
subnominal fraction of the population into sources of exposure.
Core indicators that are classed as exposure indicators include: (1) regional changes in acreage,
type diversity, and spatial patterns; (2) hydroperiod; (3) direct measurement of pollutant; (4) direct
measurement of nutrients; and (5) sedimentation. Measurements of bioaccumulation is a developmental
indicator that may offer significant advantages for indicating exposure.
Setting the Nominal/Subnominal Boundaries '
Determination of the ecological status of wetlands within regions of the Nation requires
that someyardstick be developed thatindicateswhat is normalforvarious measured parameters, andwhat
is abnormal. For the purposes of EMAP, these two classes have been termed nominal and subnominal.
Separating the entire population of wetlands into nominal and subnominal may be accomplished by
deriving criteria values from reference sites, or by statistically classifying the population of sampled
wetlands where outlier or certain categories of measured parameters are considered subnominal.
The approach to setting the nominal/subnominal boundary that promises to be most fruitful in
the short run (considering the wide variation in parameters of wetland ecosystems) and that may provide
needed baseline data for statistical classification is the use of reference wetlands. Wetlands selected as
part of the overall sampling frame will be further subclassified based on surrounding landscape attributes
into a continuum of landscape development intensities from "relatively pristine" to highly developed.
Those wetlands in the relatively pristine classes will be used to determine nominal characteristics for
measured parameters, and subnominal characteristics established as some statistic (percent confidence
interval, for instance) of the nominal classes. Obviously, the entire population of wetlands must first be
classified by type and region to account for the extreme variability in measured parameters between
wetland types and regions.
Stressors and Wetland Ecological Status
Exogenous stressors on wetland ecological status can be ordered into two broad groups: a) those
resulting from changes in driving forces and b) and those associated with inputs of pollutants and toxins.
Changes in driving forces of wetland ecological systems include:
alterationsofhydroperiods resultingfrom manipulations of groundwater, surface
water, and stormwater that will lead to changes in biota and potential loss of
wetland dependent wildlife species.
loss of habitat and wetland conversion resulting from increased demands for wood,
peat, and other wetland "products".
Global climate changes causing increases or decreases in rainfall, and surface
water elevations resulting in changes in biota
Invasion by exotic and nuisance species that shift species richness, losses of
indigenous species, and declines in wildlife habitat suitability.
Changes associated with exogenous inputs of pollutants and toxins include:
Changes in salinity resultingfrom increased surface runoff from agricultural and
urbanized landscapes resulting in loss of wetland integrity and changes in species
composition.
Increased concentrations of nutrientsfrom agricultural and urbanized landscapes
resulting in changes in floral species composition and concurrent faunal
composition.
Increased concentrations of organic, metals, and pesticides etc. resulting in
declines or loss of faunal components and negative impacts of bio-accumulation.
Chosen response indicators (Vegetation, waterbirds, and organic matter accretion, as well as
future use of macroinvertebrates, measures of canopy closure and photosynthetic potential) cover the
most important community responses that result from exogenous stressors. However, it is quite obvious
that characteristic responses, like changes in species composition, or percent cover, can be caused by an
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one of several of the stressors acting independently or in concert. The chosen exposure indicators will
help to determine most probable cause of subnominal behavior in one of the response indicators.
The suite of indicators has been chosen to illuminate the differences between these stressors and
identify probable causes for subnominal categorization. The single most important exposure indicator
that will have the greatest influence on separating causal influences is hydroperiod. Hydroperiod is by
far the most significant driving force that shapes wetland structural and functional organization, and is
the driving force most often manipulated by humans. Changes in hydroperiod have significant effects on
species composition, nutrient pathways and rates of cycling, habitat quality, and gross production.
Without simultaneous measurement of hydroperiod alongwith the response indicators, separation of the
subnominal population of wetlands by stressor will be hindered.
Other important exposure indicators that must be measured to interpreted the subnominal
population are direct measurement of pollutants, nutrients, and sedimentation. Once hydroperiod is
accounted for and subnominal responses are indicated by one or more of the indicators, the most probable
stressor can be identified using systems diagrams of pathways of energy and matter (see next section) and
then direct measurements of the appropriate exposure indicator can be made.
Resolving Conflicting Indications of Status
It is quite reasonable to assume that different response indicators can and will give conflicting
indications of ecological status. There are two things that contribute to this situation. First, stressors act
differentially in hierarchically organized systems affecting some compartments more than others,
depending on the quality and quantity of the stressor. Second, as a result of time lags, responses in some
compartments (those with rapid turnover times for instance) will be quicker than in other compartments.
Thus measurements in response in different hierarchical levels within an ecosystem can easily
demonstrate conflicting evidence. With time however, the conflicting evidence may resolve itself as
internal pathways of energy and mater exchange reorganize under the new influences. Annual or biennial
measurements on a population of wetlands in a dynamic landscape should exhibit significant conflicting
evidence of ecological status, but where change is not so rapid, conflicts should be minor.
The possibility of conflicting indicator situations where one of more measurements of response
indicators suggest that a portion of a regional population of wetlands is subnominal while one or more
suggest it is nominal, is difficult to resolve without a larger scale understanding of ecosystem structural
properties and stress action and response pathways. Systems diagrams like that given in Figure 1 showing
pathways of energy and matter exchange can be used to trace stressor actions and illuminate community
level responses. In this way, systems diagrams with sufficient detail can not only be used to resolve
conflicting response indications, but can be used to identify probable stressors, since not all stressors, act
along the same pathways to cause the same response. For example stressors that act at the "top end" of
an ecological community, like pesticides, will show responses in waterbird abundance first before lower
organisms and vegetation show significant responses; or on the other hand, "bottom end" stressors, like
nutrient enrichment will cause responses relatively quickly in vegetation compartments with delays in
cascading responses in higher order compartments.
Conflicting responses provide important information that can be used to determine probable
stressors, and while the situation may suggest difficulties in measurement techniques or interpretation
of data, it can easily be used to benefit the overall objectives of the program. With adequate analysis of
data and an overall system level perspective, conflicts can be resolved through tracing backwards from
the response indicator in the diagram to probable causal agents. Direct measurement of the agent can
then be done to confirm or deny the qualitative assessment using the systems diagram.
Research Needs for EMAP Inland Wetlands
There are three critical areas of research needed to help meet the objectives of EMAP and to
increase the efficiency and reliability of the suite of indicators in identifying sub classes of wetland
ecological resources that have experienced more damage than others. First, in the near term, a pilot
program that will test whether the suite of indicators can give unambiguous information will be conducted.
At this time measurement techniques and field protocols, and data analysis techniques and protocols will
be tested. Also developmental indicators will be further developed with preliminary testing conducted
to help move them toward implementation within 1 to 3 years.
Second, in the near term, analysis of landscape scale indicators measured from remotely sensed
data need development and testing. A proposed index called the Landscape Development Intensity (LDI)
index that is a measure of the level of developmental impact and therefore a possible indicator of potential
ecological impacts may provide a quick and cost effective method of identifying populations of wetlands
that are most likely to be subnominal. Further, the LDI may allow for landscape scale classification that
will quickly and economically allow for the targeting of resources within regions. The LDI has been
applied in some preliminary work in Florida and has showed some promise in stratifying populations of
wetlands in urbanizing landscapes. Further testing is needed to expand its applicability through
incorporating additional variables in the index.
Third, in the long term, much system level research on the structural organization of wetland
ecological resources is needed to better understand stress action pathways and the self-design
reorganization than occurs in ecological communities in response to varying quantities and qualities of
stressors. AS this research is accomplished significant advances can be made regarding development of
indicators of ecological status, refinement of boundaries between nominal and subnominal, and efficiency
of detection of subnominal populations.
Figure 1. Energy diagram of a forested wetland showing components and causal pathways of energy and matter exchange.
Systems diagrams can be used to illuminate community level responses, solve conflicting response indicators,
and identify probable stressors.
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