Coastal wetlands can adapt to rising oceans.Tidal marshes, which nurture marine life and reduce storm damage along many coastlines, should be able to adjust to rising sea levels and avoid being inundated and lost--if their vegetation is not damaged and their supplies of upstream sediment are not reduced, suggests a study by Duke University, Durham, N.C. Such marshes "offer great value as buffers to coastal storms in cities such as New Orleans, which is separated from the Gulf of Mexico Noun 1. Gulf of Mexico - an arm of the Atlantic to the south of the United States and to the east of Mexico Golfo de Mexico Atlantic, Atlantic Ocean - the 2nd largest ocean; separates North and South America on the west from Europe and Africa on the east by marshlands," report A. Brad Murray, associate professor of geomorphology geomorphology, study of the origin and evolution of the earth's landforms, both on the continents and within the ocean basins. It is concerned with the internal geologic processes of the earth's crust, such as tectonic activity and volcanism that constructs new and coastal processes, and doctoral student Matthew Kirwan. These coastal systems of water-tolerant plants and tidal channels "provide highly productive habitat and serve as nursery grounds for a large number of commercially important fin and shellfish," according to the researchers. Despite these benefits, a variety of environmental changes often linked to humans--including sealevel rise, sinking land, and alterations to sand and silt supplies that anchor wetland plants--are "affecting coastal marshes worldwide." However, "if the vegetation is intact, it holds the system in place and enhances the trapping of sediments and tends to minimize the erosion," Murray points out. "Up to some high level of sea-level rise, the system is going to keep itself in place because of that vegetation." It must be remembered, though, that removing some vegetation or reducing sediment supplies will set the stage for increasing water depths, a change exacerbated as the rate of rising sea levels increase. "We think that could be why marshes in the Chesapeake Bay region as well as in Louisiana are tending to deteriorate," Murray explains. "That's because those are both places with relatively high sea-level rise rates, and because of land-use changes that decrease rates of sediment delivery downstream." Such land-use alterations could include the damming of rivers and the reforestation Reforestation The reestablishment of forest cover either naturally or artificially. Given enough time, natural regeneration will usually occur in areas where temperatures and rainfall are adequate and when grazing and wildfires are not too frequent. of formerly open land. In fact, the study suggests that heavy sediment runoff during the extensive deforestation deforestation Process of clearing forests. Rates of deforestation are particularly high in the tropics, where the poor quality of the soil has led to the practice of routine clear-cutting to make new soil available for agricultural use. of America's colonial period may have created the conditions that build up today's extensive--but now probably "metastable met·a·sta·ble adj. Of, relating to, or being an unstable and transient but relatively long-lived state of a chemical or physical system, as of a supersaturated solution or an excited atom. "--marshlands along the East Coast. |
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