Efforts to improve the standard of living for humans--through the control of nature and the development of new products--have also resulted in the pollution, or contamination, of the environment. Much of the world's air, water, and land is now partially poisoned by chemical wastes. Some places have become uninhabitable. This pollution exposes people all around the globe to new risks from disease. Many species of plants and animals have become endangered or are now extinct. As a result of these developments, governments have passed laws to limit or reverse the threat of environmental pollution.
Ecology and Environmental Deterioration
The branch of science that deals with how living things, including humans, are related to their surroundings is called ecology . The Earth supports some 5 million species of plants, animals, and microorganisms. These interact and influence their surroundings, forming a vast network of interrelated environmental systems called ecosystems. The arctic tundra is an ecosystem and so is a Brazilian rain forest. The islands of Hawaii are a relatively isolated ecosystem. If left undisturbed, natural environmental systems tend to achieve balance or stability among the various species of plants and animals. Complex ecosystems are able to compensate for changes caused by weather or intrusions from migrating animals and are therefore usually said to be more stable than simple ecosystems. A field of corn has only one dominant species, the corn plant, and is a very simple ecosystem. It is easily destroyed by drought, insects, disease, or overuse. A forest may remain relatively unchanged by weather that would destroy a nearby field of corn, because the forest is characterized by greater diversity of plants and animals. Its complexity gives it stability.
Population Growth and Environmental Abuse
The reduction of the Earth's resources has been closely linked to the rise in human population. For many thousands of years people lived in relative harmony with their surroundings. Population sizes were small, and life-supporting tools were simple. Most of the energy needed for work was provided by the worker and animals. Since about 1650, however, the human population has increased dramatically. The problems of overcrowding multiply as an ever-increasing number of people are added to the world's population each year.
Factories and transportation depend on huge amounts of fuel--billions of tons of coal and oil are consumed around the world every year. When these fuels burn they introduce smoke and other, less visible, by-products into the atmosphere. Although wind and rain occasionally wash away the smoke given off by power plants and automobiles, the cumulative effect of air pollution poses a grave threat to humans and the environment.
Although the release of toxic chemicals into the atmosphere is against the law in most countries, accidents can happen, often with tragic results. In 1984, in Bhopal, India, a pesticide manufacturing plant released a toxic gas into the air that within a few hours caused the deaths of more than 2,000 people.
Since the beginning of civilization, water has been used to carry away unwanted refuse. Rivers, streams, canals, lakes, and oceans are currently used as receptacles for every imaginable kind of pollution. Water has the capacity to break down or dissolve many materials, especially organic compounds, which decompose during prolonged contact with bacteria and enzymes. Waste materials that can eventually decompose in this way are called biodegradable. They are less of a long-term threat to the environment than are more persistent pollutants such as metals, plastics, and some chlorinated hydrocarbons. These substances remain in the water and can make it poisonous for most forms of life. Even biodegradable pollutants can damage a water...