Endanger Species are those whose population have been so reduced that they are threatened with extinction. Thousand of species are included in category. The International Union for the conservation of Nature and Nature Resources (head quartered in
Causes of Extinction
During the millions of years that preceded the appearance of human life, extinction of organisms was linked to large scale geologic and climatic changes, the effects of which were translated into major alteration of the environment. Environmental change is still the primary cause of the extinction of animals, but now the changes are greatly accelerated by human activity. Clearing land for farms and towns, lumbering, mining, building dams, and draining wetlands all alter the environment so extensively that ecosystem may be completely destroyed. With a burgeoning human population requiring food, shelter, and clothing and constantly demanding more energy-using devices, the temptation to exploit land for human use without regard for consequences is great.
Frequently, several forms of environmental change are responsible for the disappearance of species. For example, as tropical forest are cut down, primates have progressively smaller feeding and living spaces. They also become more accessible to hunters, who kill monkeys for food and trap zoo specimens. Some animal species may move into human communities when their own are destroyed. Extermination of marauding monkeys, roaming tigers, or foraging deer is easy to justify by people whose livelihood is threatened.
Many species of birds lay thin-shelled or shell-less eggs as a result of ingesting degradation products of DDT and other chemicals that enter the food chain. Species of salamanders in
Many species have been exterminated or endangered because people have killed the animals for food, fur, hides, or feathers. As a result of whaling, some whale species are close to extinction. Claim and fish are endangered by varying combination of naturally changing environments, population, and over harvesting.
Many endangered species received a measure of relief in 1973, when the 80 nations that originally participated in the Convention on International Trade in Endangered Species of Wild Flora agreed to half imports of endangered species. The International Whaling Commission forbids the hunting of blue, bowhead, humpback, gray, and right whales; it set a moratorium on all commercial whaling, effective in 1986, but