Unit 3 Chapter 1: Enered Species Like individual animals, animal species' also ually die out. It is estimated that, until the 18th century, one species disappeared from the Earth every four years. By the 19th century, this had increased to one species per year. By 1975, it was 1,000 species per year, and today animals are disappearing at the appalling rate of more than 40,000 species per year. Most species are threatened by pollution, habitat destruction, and unreasonable exploitation caused by humans. The International Union for Conservation of Nature has created a number of categories that describe the er level of animal species: ·A species that has died out completely is called extinct. Examples are the dinosaurs and the dodo bird. ·Species that only live in zoos or on farms, etc, fall into the category extinct in the wild, for example, various horse species. ·A species is labeled cicallyl enered when it is in immediate er of dying out completely. Its numbers are erously low, and it needs protection in order to survive. The Siberian tiger and the snow leopard are two examples. ·Species that have a high, but not immediate, risk of dying out are simply labeled enered. The giant panda is a famous example. ·A vrlnerable species is in less trouble than an enered one, but its numbers are still certainly declining. The cheetah and the African elephant are vulnerable species. ·Animal species that aren't particularly enered and have high numbers of individuals are labeled less concern. There are many factors that can cause an animal or plant species to become enered. The main cause of species enerment is humanity's destruction of both water and land habitats. Deforestation and soil, air, and water pollution can all destroy habitat. This can then cause a large number of animals or plants to die. The critically enered Sumatran orangutan has seen a 50% decline in its population over the last eight years as farmers clear more and more forests for agriculture. Another cause of enerment is the unreasonable exploitation of animals. Uncontrolled hunting of whales in the last century, for example, resulted in many whale species becoming critically enered. The very high demand for animal parts for use in certain foods or medicines is another example. The horn of the rhinoceros can be sold at a high price in some places where it is thought to be medicinal: a price so high that people will kill the animals even though it is against the law. Introducing a non native species to an environment can also cause species enerment. A native species is one that develops naturally in a particular area, and has done so for a long time. A non-native species might be introduced into a new environment by humans, either intentionally or by accident. The brown tree snake, unknowingly introduced by cargo2 ships stopping at Guam, has managed to kill off ten of the eleven species of birds native to the island's forests. In Florida, large pet snakes such as the anaconda and the python have been released into the large Everglades swamp. The snakes have been quite sccessful, and now compete with and even threaten the swamp's alligators. Organizations such as the World Wildlife Fund and the International Union for Conservation of Nature try to raise awareness of threatened animals and plants. These organizations work with government agencies to save threatened or enered species, and to make new laws that will protect these species. Many of these plans work, but some do not. Public awareness of this issue is important. To preserve the quality of our lives and the lives of future gencrations, we must also protect plant and animal species now and in the future.