Wetlands - Habitat

Fish and wildlife use wetlands to varying degrees depending upon the species involved. Some live in wetlands for their entire lives; others require wetland habitat for at least part of their life cycle; still others use wetlands much less frequently, generally for feeding. In other words, for many species wetlands are primary habitats, meaning that these species depend on them for survival; for others, wetlands provide important seasonal habitats, where food, water, and cover are plentiful.

For example, wetlands are essentially the permanent habitat of the beaver, muskrat, wood duck, clapper rail, mud minnow, wild rice, cattail, broadleaf arrowhead and swamp rose. For other species, such as bluegill, largemouth bass, woodcock, hooded warbler, otter, raccoon, and meadow vole, wetlands provide important food, water, shelter, or nesting habitat.
Numerous birds -- including certain shorebirds, wading birds, and raptors, and many songbirds -- feed, nest, and/or raise their young in wetlands. Migratory waterfowl, including ducks, geese, and swans, use wetlands as resting, feeding, breeding, or nesting grounds for at least part of the year.

Freshwater fish, such as the northern pike, use well-flooded or ponded wetlands as breeding and nursery areas. Some fish, like the brown bullhead even subsist in wetlands that have natural low dissolved oxygen concentrations that un-adapted species cannot endure.

Rare Species Habitat

The U.S. Fish and Wildlife Service estimates that up to 43% of the federally threatened and endangered species rely directly or indirectly on wetlands for their survival.

Habitat Fragmentation

Habitat value diminishes when fragmented by barriers, which restrict wildlife migration and movement. Barriers to wildlife migration range from very small barriers such as unpaved roads and low-density housing to large hydrologic barriers such as levied roads and canals. The proximity of the wetland relative to other wetlands and native plant communities can indicate the ecosystem connectivity.

Assessing Wildlife Habitat

Wetlands support aquatic and terrestrial vertebrate and invertebrate populations during some or part of their life cycle. Wildlife species diversity is generally highest when the wetland is structurally complex. No single species, or species guild, can serve as a definitive, all-inclusive indicator of wetland habitat functions or carrying capacity.

Habitat provided by wetlands and the nearby landscape changes between years and within seasons in response to natural or human cased disturbance regimes. Given this variability, long term surveys of wildlife diversity and abundance would be required to adequately assess the faunal function. These surveys would be more appropriate as an independent, quantitative verification of this function.

Instead, structural and compositional multi-scale metrics that are less subject to these fluctuations are assessed. Emphasis is on the capacity of the wetland to maintain the habitats and resources necessary for diversity and abundance.

Minnesota Routine Assessment Method (MnRAM), Version 3.4, Minnesota Board of Water and Soil Resources

A Regional Guidebook for Applying the Hydrogeomorphic Approach to Assessing Wetland Functions of Prairie Potholes (HGM), Army Corps of Engineers

U.S. Environmental Protection Agency