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Determining cost effectiveness of active versus passive managed wetland systems
Amanda K. McLeese1, Michael Eichholz2, and Jack Nawrot3
Approximately 38% of Illinois birds and 60% of Illinois vertebrates of special concern depend on wetlands for at least part of their annual cycle; thus, the protection and restoration of wetlands is a critical component of successfully maintaining the existence of these species in Illinois. Additionally, Illinois is part of the Mississippi Alluvial Valley, an important migration and wintering area for waterfowl populations. A better appreciation of the interdependence of waterfowl requirements throughout the annual cycle has led to an understanding of the importance of wintering and migratory habitat in waterfowl conservation. Protection of migratory habitats is important to ensure that birds have sufficient nutrition to maintain energy for migration and to build body reserves for overwintering and breeding activities.
Managing wetlands for wildlife is often difficult because of the uncertainties of nature (i.e. seasonal rainfall). The hydrologic regimes and plant associations that are most beneficial to wildlife may not be those that occur naturally, or they may have been altered through habitat loss, degradation, and modification. Managers often rely on water level manipulations in order to simplify planning, ensure productive habitat, and obtain reliable, consistent results. Wetlands that rely on water level manipulations are termed “actively managed” wetlands, while those that rely on natural water cycles are termed “passively managed”.
Actively managed wetlands are characterized by constructed earthen embankments or levees, and water control structures and pumps. These structures and pumps give wetland managers the ability to control the timing, rate, and duration of flooding and drawdowns, factors which will influence plant composition, plant production, and bird use. Passively managed wetlands rely on seasonal rainfall and flood events to produce standing water and water levels are drawn down naturally through infiltration and evapotranspiration. The cost of restoring and maintaining a wetland that will be passively managed is low relative to actively managed wetlands. Although actively managed wetlands are designed to maximize wetland productivity, they are accompanied by greater costs associated with construction and management and may therefore not be the most cost efficient way to provide wetland habitat. Many programs promote wetland restoration, however, funding is still extremely limited. Managers, therefore, have the responsibility of selecting those projects that are most cost efficient. Passive management may allow for more acres of wetland habitat to be restored and may therefore produce more overall resources. The less reliable water sources, and inability to control water levels, however, makes the productivity and extent of habitat that is annually inundated less predictable than actively managed wetlands. To date, no research has compared the average productivity or cost effectiveness of actively and passively managed wetlands in southern Illinois.
The goal of this study is to compare productivity and expenses of actively and passively managed wetlands to determine which type produces more resources for wildlife per dollar spent. We will use macroinvertebrate and seed abundance and biomass as measures of productivity; and will compare bird abundance and diversity of actively and passively managed systems. Construction and maintenance costs will be projected over a 20 year period and averaged for each management strategy. Financial costs will be compared with the estimated derived benefits of each of the 2 wetland types to determine which management type provides the most resources relative to their costs.
The final report will document several ways to compare wetland productivity through a comparison of seed productivity, macroinvertebrate productivity, and bird abundance and diversity. Results will increase knowledge regarding differences in productivity and bird use of actively and passively managed wetlands. Development of a single estimate of overall productivity on a per dollar spent basis will provide researchers and managers with a way to determine what type of wetland restoration activity will allow them to most efficiently reach their objectives. Managers will be able to select cost effective design alternatives and implement habitat management decisions that maximize the production of food and habitat resources.
College of Science
Department
of Zoology
Center
For Ecology
Fisheries
& Illinois Aquaculture Center
