According to a study by the National Wildlife Federation, wetlands are "biological motherlodes" that help to sustain 43 percent of all the threatened and endangered species on protected lists in this country. These sodden zones provide essential habitats, breeding and feeding grounds, and resting areas for a variety of plants, fish, crustaceans, birds, mammals, reptiles, amphibians and insects. Eighty percent of America's birds, including more than half of the protected migratory species, depend on wetlands for food or sanctuary. An estimated two-thirds of the shellfish and fish harvested in this country rely on wetlands for at least part of their life cycle. But these regions are not just important for ducks, crabs, turtles and frogs, as humans benefit from them too - probably in more ways than can ever be calculated.
The Okefenokee Swamp, an almost 400,000 acre expanse of freshwater lakes and peat bog islands in southeastern Georgia, offers an example of the range of life forms to be found. The American alligator rules the swamp, along with about five poisonous snakes and 70 other reptiles. More than 200 species of birds - including herons, cranes, egrets, ibises and woodpeckers - inhabit or visit the refuge. Muskrats, river otters, foxes, black-tailed deer, black bears and other mammals abound.
But tiny wetlands can also support a diversity of life. Vernal pools, for instance, may be far smaller than a football field - ephemeral wetlands that only hold water for a few months of the year. More than 60 species of plants and animals living in the pools of California's Central Valley - including fairy shrimp and rare species of toads, salamanders and frogs - have been identified to date. Field biologists acknowledge that they've only seen a fraction of the unusual creatures that inhabit vernal pools, and many will never be identified given the rate at which the pools are disappearing. It is hard to protect these diminutive wetlands, because they attract little notice and, in the driest times of years, bear scant resemblance to the archetypal swamp.
If they were ever added up in full, small wetlands of just a few acres or less may constitute the bulk of the wetland area in this country. And for certain animals, such as frogs, toads and salamanders, small wetlands support a greater species diversity than large ones, according to a recent study in Conservation Biology. But for practical reasons, small wetlands don't receive "equal protection" in the United States - an oversight that could have grave ecological repercussions. Research by Ray Semlitsch and colleagues at the University of Missouri-Columbia showed that species increase their chances of surviving periods of drought by inhabiting several different wetlands. Their survival is imperiled, however, as small wetlands are destroyed and distances between them grow larger. This problem is especially acute for amphibians - a class of animals that is mysteriously disappearing at an alarming rate.
More than half of the wetlands in the United States have been lost to human activities and as much as 90 percent of the wetlands in states such as California and Ohio have been wiped out.