GLOBAL WARMING

Examples of global exchange such as ozone depletion or global warming occur on a large scale. but what about serious environmental problems that occur in our own backyard? For example, one important urban environmental problem is chemical pollution. Until recently, people assumed that the environment can absorb any amount of pollution.

Lake Erie and other large lakes became polluted because of the assumption that they could absorb unlimited amount of industrials chemicals. Because of this incorrect assumption, pollution has often risen to a serious level. In a highly publicized example of pollution, a very large oil tanker ran aground off the coast of Alaska in 1989. Oil from the tanker heavily polluted 1,600 km(1000 mi) of coastline and injured or killed thousands of marine animals, such as the common scoter was one of the thousands of animals involve in the terrible accidents.

Despite costly and heroic cleanup efforts damage to local wildlife was extensive. This dramatic example is not an isolated occurrence, smaller oil spills and leaks that received little or no publicity account for more than 90 percent of all pollution from seepage. Many of the most disastrous incidents of pollution involve industrials chemicals that are toxic or carcinogenic(cancer-causing). Until recently, there has been relatively little regulation of the manufacture, transportation, storage, and destruction of such chemicals.

A particularly clear example of this problem occurred in Basel, Switzerland, in 1986.Fire fighters putting out a warehouse fire accidentally washed 27,000 kg(30 tons) of mercury and pesticides that were stored in the warehouse in the Rhine river. This poisons flowed from down the Rhine, through Germany and the Netherlands, and into the North Sea, killing fish and other aquatic animals and plants. Today the river is recovering, but its species diversity remains far lower than it was before the disaster.

Agricultural pollutants are among one of the major environmental pollutants in our society today. In many countries, modern agriculture introduces large amounts of chemicals into the global system. These chemicals include pesticides, herbicides, and fertilizers. Industrialized countries like United States now attempt to carefully monitor the side effects of these chemicals. Unfortunately, large quantities of many toxic chemicals that are no longer manufactured still circulate the ecosystem. The issues of pesticide pollution is just beginning to gain attention in the world agricultural system.

For example, molecules of chlorinated hydrocarbons-a class of compounds that includes the pesticide DDT, chlordane, lindane, and dieldrin-brake down slowly in the environment.* They also accumulate in the fatty tissue of animals. As these molecules pass up the trophic levels of the food chain, they become increasingly concentrated. This process is called biological magnification.

The presence of DDT in birds causes thin fragile eggshells, which can break during incubation. Because of DDT use many predatory birds in the United States and elsewhere failed to reproduce, and their numbers dwindled. In 1972, the use of DDT was restricted in the United States, and threatened bird population slowly began to increase. However, chlorinated hydrocarbons, are still manufactured in the United States and exported to other countries, where their use continues.

In conclusion. in order for us to meets the needs of an increasingly crowded world, the use of chemicals is necessary. We must learn to use them as intelligently as possible. Doing so well produce capacity of the Earth. Failure is not a rational option.