The functions of wetlands

Wetlands provide many benefits to society -- such as fishand wildlife habitats, natural water quality improvement, floodstorage, shoreline erosion protection, opportunities for recreation andaesthetic appreciation, and natural products for our use at little orno cost. Protecting wetlands can, in turn, protect our health and safety by reducing flood damage and preserving water quality.

Wetlands are among the most productive ecosystems in the world, comparable to rain forests and coral reefs. They also are a source of substantial biodiversityin supporting numerous species from all of the major groups oforganisms – from microbes to mammals. Physical and chemical featuressuch as climate, topography (landscape shape), geology, nutrients, andhydrology (the quantity and movement of water) help to determine theplants and animals that inhabit various wetlands. Wetlands in Texas,North Carolina, and Alaska, for example, differ substantially from oneanother because of their varying physical and biotic nature.

You can read more here:

http://www.epa.gov/owow/wetlands/functions.html