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 are 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. Because of these developments, governments have passed laws to limit or reverse the threat of environmental pollution. Nearly all aspects of industrialized society lead to uncontrolled pollution that needs to be stopped
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 (Hardy 2002). 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 (Hardy 2002). A field of corn has only one dominant species, the corn plant, and is a very simple ecosystem. Drought, insects, disease, or overuse easily destroys it. 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.
The reduction of the Earth's resources has been closely linked to the rise in