As we continue to see ever-more disturbing images on the shores of Louisiana from the gulf oil spill, it’s worth thinking again about the immense ecological importance of wetlands and why they must be protected. Oil from the leak has already filtered up from the beaches into Louisiana’s coastal wetlands, killing wildlife there. Ironically, last May was American Wetlands Month.
What are wetlands? The EPA describes them as “the vital link between the land and the water. They are transition zones where the flow of water, the cycling of nutrients, and the energy of the sun meet to produce a unique ecosystem.” Wetlands can be coastal or inland, saltwater, freshwater or brackish. In the United States they generally fall into four categories: marshes, swamps, bogs and fens.
Wetlands have sometimes been called “nurseries of life” providing safe habitat for the young of many fish, crabs and other small creatures before they are old enough to venture into open waters. In addition, wetlands provide homes for an immense diversity of plants, amphibians, reptiles, mammals and migrating waterfowl.
According the U.S. Geological Survey, coastal wetlands are among the most productive ecosystems in the world, [PDF] and among the most vulnerable to climate-change related seawater rise. Loss of wetland habitats in the last thirty years has been a leading cause of species extinction.
Aside from their inherent value to nature, what do wetlands do for us? Flood control (by acting as a “sponge” barrier to fast moving water), silt catching and erosion control (through the roots of wetland vegetation) are only a few of the most important functions. By acting as a sponge, wetlands also store water, absorbing it during the wet season and slowly releasing it during the dry season, mitigating the effect of drought.
Last but not least, wetlands purify water, through a symbiotic relationship between plant roots and periphyton—a complex of algae and microorganisms—that break down organic compounds. Natural wetlands are so good at cleaning water that they have become the model for inexpensive, cutting-edge waste management systems.
All of which makes the current crisis in the gulf all the more tragic. According to most scientists, cleaning up oil in wetlands is much more difficult than on beaches. As Marc LaSalle, a Mississippi ecologist, told the Associated Press, “When the marshlands are not being mutilated by man, they’re pretty resilient . . . A healthy marsh can tolerate a hurricane; it’s natural. But an oil spill is not natural, and the marshes have never seen oil at this level. We just have to hope they can shut this thing off quickly.”