By Ron Divelbiss
Some swamps produce up to eight times as much plant matter as an average wheat field. Wetlands, wild half-worlds between land and water, occupy some six percent of the world's land surface, their ever-changing patterns of floating vegetation, solid ground, and open water providing plenty of opportunities for a wide range of plants and animals.
Wetlands are found throughout the world, in a wide range of climates, and vary from swaying cattail swamps and steamy forests to desolate peat bogs. They are among the most threatened habitats in the world.
Wetlands form where water gathers. They occur at the edges of lakes, for example, and where rivers reach the sea. Plants grow out into the open water; once established, they slow the flow of water and trap soil; the silt is then invaded by more vegetation, and the open water is itself gradually taken over. The type of wetland formed by this process is swamp or marsh, and is often dominated by species such as cattails, reeds or swamp cypress.
Another important type of wetland is bog, which is typically dominated by sphagnum moss; such vegetation usually develops in closed basins, where rainfall is high but evaporation of surface water is relatively low.
Temperate cattail swamps are one of the most familiar types of wetland. Cattails are very well adapted to the wetland environment. They can tolerate a high water table, and their new shoots grow quickly upward to reach the light above the water. There they grow tall and dense, and although other plants grow beneath them, few can overtop them. The cattails provide a habitat for wildlife throughout the year. Together with other wetland plants, the cattails also provide food for the wetland animals. Moth larvae eat the leaves of the cattails, and other herbivorous insects bore their way into the cattail stems.
The smaller flying insects fall prey to such hunters as dragonflies. Drangonfly larvae develop in the water, spending up to a year submerged as nymphs. They then climb cattail stems to emerge from their larval skins as adults, and find plenty of food among the vegetation. Amphibians such as newts and frogs also feed on insects. Small birds feed on the insects too, and when the insect abundance ends with the passing of the summer, these birds leave.
The open water provides food for many species that shelter in the cattail swamp itself. Vegetations, water invertebrates, and fish provide food for ducks, water shrews, voles, and raccoons.
But wetlands are easily damaged and destroyed by drainage and pollution. Swampy areas, so vital to many types of wildlife, are widely regarded as wastelands, and are always under threat of reclamation. Bogs suffer a different type of damage; they are exploited for their peat.