Assessment of Wetland Quality in Illinois Conservation Areas

John A. Crawford, Christopher A. Phillips, Andrew R. Kuhns

Research output: Book/Report/Conference proceedingTechnical report


Seasonal and semi-permanent wetlands are shallow, depressional wetlands that occur throughout the Midwestern and Eastern United States. Distribution and abundance of seasonal wetlands are regarded as an indicator of overall ecosystem health and are especially important to numerous species of plants and wildlife. In addition to their biological importance, these wetlands play critical roles in hydrology (surface water storage and groundwater exchange), biogeochemical cycling, and energy exchange (via amphibian production and dispersal) to adjacent terrestrial habitat. Despite their ecological significance within the landscape, seasonal and semi-permanent wetlands typically receive minimal regulatory protection at both the federal and state levels because they are often small and hydrologically isolated. Animals such as amphibians, semi-aquatic reptiles, and macroinvertebrates depend on wetlands for all or part of their life cycle, which means that their survival is directly linked to the presence and ecological health of wetlands. In Illinois, 32 of the 41 amphibians and 47 of the 61 reptiles are wetland dependent species, in addition to the numerous macroinvertebrate taxa found across the state. While the US loses approximately 60,000 acres of wetlands each year, wetland conversion and drainage in Illinois has been especially extensive where an estimated 90% of original wetland area has been lost; therefore assessment and protection of wetlands is a high priority within the state. Further, Action Item 3 of the Wetlands Campaign in the Illinois Wildlife Action Plan is to fill information gaps and develop conservation actions to address remaining wetlands in Illinois. Specifically, the action item calls for: 1) updated inventory of wetland habitat in Illinois; 2) research on the ecological aspects of high-quality wetland sites; and 3) assessment of the status and distribution of wetland-dependent amphibians and reptiles. The primary objectives of this project were to provide the following: 1) development of an integrated index of biological integrity (IBI) to assess wetland condition; 2) evaluation of sampling schemes; 3) establishment of reference (baseline) wetland conditions for each part of the state of Illinois; 4) identification of high quality wetland sites in Illinois; 5) identification of deficient wetland sites in Illinois; 6) identify important habitat features of high quality wetlands in Illinois; 7) report on the overall xiii health of wetlands on public lands in Illinois and provide recommendations to IDNR for areas in need of protection and restoration; and 8) contribution of information to the management plans of imperiled wetland-dependent species. In order to evaluate overall ecological health and function of seasonal and semipermanent wetlands in Illinois, we sampled 242 wetlands distributed across 45 managed lands (hereafter conservation areas) over three years (2012-2014). At each wetland, surveys were conducted during four time periods over a five month span (February-June) to increase the probability of species detection. Additionally, due to fluctuations in population sizes, variability in breeding phenologies, and suspected variability in detection rates between taxonomic groups (i.e. rare species have lower detection rates than common species), wetlands were sampled for three days per period (n =12 total samples per wetland). Each conservation area (and associated wetlands) was sampled during only one year to increase the number of overall sites sampled during the study. Wetland health and function were assessed by examining three critical components of wetlands ecosystems: 1) amphibian diversity and abundance; 2) reptile diversity and abundance; and 3) macroinvertebrate diversity and abundance. Each of these primary components was incorporated into an index of biological integrity (IBI) to determine how well the wetland was functioning within the ecosystem. As a result of this study, we have generated the following major conclusions: 1) reptiles are not good biological indicators for assessment of seasonal and semi-permanent wetland health due to low capture numbers; 2) wetland macroinvertebrate life history and distribution information is inadequate in Illinois for using macroinvertebrates as a biological indicator group; however this study is a crucial first step in providing some of that needed information; 3) amphibians are good biological indicators for assessment of seasonal and semi-permanent wetlands; however a proper sampling protocol (appropriate sample times and numbers) is critical for successful wetland evaluations; 4) high quality seasonal and semi-permanent wetlands are concentrated along the eastern side of the state (Wabash Border division) and into southern Illinois (Southern Till Plain and Coastal Plain divisions); and 5) a diversity of wetland types (physical parameters and proximity to forest) are needed for increased wildlife persistence. Lastly, we have identified 3 major areas of need for future research: 1) additional macroinvertebrate sampling in seasonal xiv and semi-permanent wetlands to fill the previously identified information gaps for this taxon; 2) assessment of anthropogenic effects on wetlands in highly urbanized environments (e.g., the Chicago region); and 3) establishment of a bank of long-term wetland monitoring sites throughout the state of Illinois to assess the impacts of climate change on wetland ecological health and function. While our distribution of sampling sites covered a large part of the state, we did not sample many properties in the northeastern part of the state. We focused on IDNR state properties for this study and the majority of public lands in the Chicago region are held by county forest preserve districts. With the dramatic effects that urbanization can have on wetlands, we believe it is imperative that wetlands in this region be sampled to set a baseline for ecological function and identify areas in need of wetland restoration and creation. Further, to fully understand the effects that climate change has had or may have on the ecological function of seasonal and semi-permanent wetlands in Illinois, a network of wetland monitoring sites is needed to collect the longitudinal datasets for climate change analyses. Ultimately, to continue to further the goals of the EPA and IDNR wetlands programs in Illinois, each of these three research items must be addressed.
Original languageEnglish (US)
PublisherIllinois Natural History Survey
StatePublished - Mar 31 2015

Publication series

NameINHS Technical Report 2015 (09)


  • INHS


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