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Evaluating Performance of Wetland Restoration Activities
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United States
Environmental Protection
Agency |
Office of Water
Office of Wetlands, Oceans
and Watersheds (4502-F) |
EPA843-F-98-001h
July 1998 |
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Wetland Bioassessment Fact Sheet 8
Perhaps the most commonly neglected component of wetland restoration
projects is a clearly defined approach to evaluate the success of the
restoration activities. How well do current wetland restoration techniques
work? Are they effective at restoring a balanced, adaptive community of
plants and animals? How do the conditions in restoration sites compare
to conditions in minimally impaired sites?
One way to tell if a wetland is recovering properly is to periodically
assess the condition of one or more biological assemblages, such as plants,
amphibians, or macroinvertebrates. Wetland managers can rapidly assess
the condition of an assemblage using biological assessment methods based
on a regionally appropriate index of biological integrity (IBI). An IBI
is constructed by combining at least eight attributes of an assemblage
that each show an empirical and predictable responses across a gradient
of anthropogenic disturbance (See Fact Sheet 3).
When applying an existing IBI to a new region or wetland type, make sure
to validate the metrics and calibrate the IBI scores to regional conditions.
Below are some helpful suggestions to keep in mind when using an IBI to
track the recovery of a wetland.
- Compare restoration site to reference wetlands - Reference
wetlands are minimally impaired sites that are representative of the
expected ecological conditions and integrity of other wetlands of the
same type and region. By comparing a biological assemblage (e.g., macroinvertebrates)
of a restoration site to a similar assemblage found reference sites,
wetland managers can determine the relative condition of the wetland.
Figure 1 shows a hypothetical example of comparing the IBI scores of
a restoration site to average IBI scores of reference wetlands over
ten years.
- Track both reference wetlands and restoration sites - It is
important to compare the IBI scores of the restoration site and reference
sites from the same year to identify regional trends that may effect
all wetlands in an area. For example, there may have been a drought
in Year 4, which would account for the dip in the curves on Figure 1.
- Sample during proper time of year - Bioassessment protocols
typically require that sampling be conducted within a certain time of
the year, which is often called an index period. The diversity and composition
of an assemblage can vary considerably at different times of the year.
Sampling at the wrong time of year will provide data that can not be
used. In addition, some assemblages can only be sampled at certain times
of the year because of their seasonal life cycles. For example, the
best time to sample adult frogs is during the breeding season when many
species congregate in ponds and vernal pools.
| CASE STUDY: |
USGS, Biological Resources Division, Patuxent Wildlife Research
Center
USDA Natural Resources Conservation Service, Wetlands Science Institute
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The interdisciplinary team of researchers is developing a biological
assessment method to evaluate the success of wetland restoration
activities. They are conducting research in Delmarva Bays, which
are depressional, freshwater wetlands that are common on the
Eastern Shore of Maryland. The wetlands in this study fall into
two groups. The first group includes 24 wetlands which were
previously used for agriculture and been restored during the
past 10 years. The second group includes 10 minimally impaired
wetlands, which they are using for reference wetlands. The reference
wetlands are at different successional stages to help understand
how the biological communities may change over time. Some of
the reference wetlands have open water and emergent vegetation
while others are only seasonally inundated and have trees.
For each of the restoration and reference sites, the team or
researchers is taking measurements of the following components
of the wetland ecosystems:
- Hydrology and Soil
- Water Chemistry
- Vascular Plants
- Macroinvertebrates
- Amphibians
- Birds
- Mammals
Their goal is to identify reliable indicators of wetland condition.
For each component, they are testing a variety of attributes
to identify metrics that show clear, empirical changes in value
across a gradient of disturbance, from the minimally impaired
wetlands to the most severely degraded wetlands. They intend
to develop standardized methods for gathering and analyzing
these metrics. Eventually, they intend to develop IBIs for one
or more assemblages (See Fact Sheet 5).
After developing the IBIs, they will be able to determine the
condition of other restored, depressional wetlands in the region.
They will also gain valuable information about the effectiveness
of different wetland restoration methods.
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BENEFITS OF EVALUATING PERFORMANCE
In the long run, the cost of periodically conducting biological assessments
will probably be small compared to benefits that come from such assessments.
Wetland managers will benefit by:
- Determining the effectiveness of their methods and learning how to
improve methods,
- Learning how to avoid common mistakes,
- Improving investment of restoration money and increasing ecological
return of investments,
- Avoiding the substantial financial and ecological costs of spending
money on ineffective restoration techniques and having to make second
attempts at restoring sites,
- Recording the effects of extraneous events (e.g., drought, beaver
activity) that may hinder recovery,
- Incorporating unexpected results into an adaptive management process
or simply re-evaluating restoration objectives,
- Acquiring reliable, quantitative data that can help (1) communicate
results to managers and the public, (2) resolve disputes, and (3) support
grant applications to fund future projects.
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