Phosphorus Cycle Essay

4406 WordsApr 2, 201318 Pages
GLOBLE PHOSPHORUS CYCLE: That benign-looking pond scum signifies a far-reaching shift in the global phosphorus cycle. Think of global environmental change, and you'll probably think most immediately of such sweeping atmospheric phenomena as global warming or ozone depletion. Many of the other environmental disruptions we're familiar with-toxic dumps, decimated forests, eroded fields-seem largely confined to particular localities. Yet there are some environmental changes that, while appearing to be locally confined, are in fact manifestations of worrisome global patterns. Look at the algae forming on a local farm pond, for example, and you're seeing the result of a process-the phosphorus cycle-that extends far beyond that farm. Algae thrives (literally "blooms") on runoff of waste fertilizer or other materials containing phosphorus. While human-caused changes in the closely related nitrogen cycle have been widely publicized (see "Toxic Fertility" in the March/April 2001 World Watch), impacts on the phosphorus cycle are less well known. Our research suggests, however, that the movement of phosphorus is indeed a global phenomenon-and that that patch of algae you see in the pond at your feet may be affected by changes in the soil hundreds or thousands of miles away. Both nitrogen and phosphorus are essential nutrients for plants and are therefore present in most fertilizers in addition to being present in agricultural and municipal waste products. As a result, the movement of large amounts of fertilizers around the planet can also mean the movement of excessive nutrients from one place to another. Typically, some of the fertilizer used on a farm does not stay there but moves downhill where it can get into a downstream aquatic ecosystem-a river, lake, or bay. Concentrations of excess nutrients in these bodies of water cause the patches of algae to expand prolifically.
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