Wetlands

Marshes are a relatively productive wetland in which the vegetation is dominated by tall, emergent, graminoid (that is, grass-like) plants. Typical plants of North American marshes include cattails (e.g., Typha latifolia), reeds (e.g., Phragmites communis), bulrushes (e.g., Scirpus validus), and saw-grass (Cladium jamaicense). Marshes dominated by these plants are relatively productive, because they have access to nutrients dissolved in their slowly flowing water. Wet meadows are less productive types of marshes, and are dominated by shorter graminoid plants such as sedges (Carex spp.) or a grass known as blue-joint (e.g., Calamagrostis canadensis). Salt marshes are brackish because they are periodically inundated by oceanic water. Temperate salt marshes are dominated by species of cordgrass (e.g., Spartina alterniflora).

Because they are rather productive, marshes can support relatively large populations of certain mammals, such as muskrat (Ondatra zibethicus). Birds can also be abundant in marshes. This is true of large, extensive marshes, and also of relatively small, fringing marshes around bodies of open water, such as lakes and ponds. For example, small ponds are common in the prairies of North America, where they are called "potholes." The marshy borders of potholes have historically provided important breeding habitat for most of the continent's surface-feeding ducks (these are known as "dabbling" ducks), such as mallard (Anas platyrhynchos), pintail (Anas acuta), and blue-winged teal (Anas discors). Unfortunately, most prairie potholes have been drained or filled to provide land for agriculture. This ecological conversion has increased the importance of the remaining potholes as habitat for declining populations of ducks, other animals, and native plants. Consequently, further losses of this habitat type are vigorously resisted by the conservation community, even though agricultural interests continue to encourage the drainage of these important wetlands.

Farther to the north, extensive salt marshes and freshwater fringing marshes in boreal and sub-arctic regions provide important breeding habitat for geese, especially snow goose (Chen caerulescens) and Canada goose (Branta canadensis). Historically, these migratory waterfowl wintered in extensive temperate marshes farther to the south, but now many of these birds spend much of the winter foraging for unharvested grain in agricultural fields.