Animals are considered to be endangered if the species is close to extinction throughout all or most of its environment. Animals become endangered for a variety of reasons. Some animals become endangered when their habitats contain resources for humans. For example, commercial forest cutting in the Amazon Rainforest has seriously reduced the population of many animal species and lead to the extinction of other groups. Land itself is an important resource to humans since it provides us with living space, and when people replace animal habitats with human habitats, it can lead to larger loss of natural species. Commercial and industrial operations may reduce land or water for animals and pollute their environment. Due to water pollution, the baiji, a fresh water dolphin native to China, was declared extinct, meaning it's unlikely the population can recover. Even noise pollution from human activities can lead to the disorder of animal behavior. Another cause that makes animals become endangered is over-fishing or over-hunting. Over-hunting whales led to near extinction of many species of whales. The introduction of a non-native species to a habitat may make animals become endangered. The native species may not defend against a new one, and the effects can be dangerous. In Australia, the introduction of the common house cat led to the extinction of the red-fronted parakeet and has seriously damaged the populations of several small animals. Introduced species can also bring new diseases with them. As a result, animals become endangered. Native animals may not have the power to fight against non-native diseases, and population levels can suffer. Another cause of disease is human-introduced chemicals. The use of DDT is believed to be one of the leading causes in driving the California Condor to near extinction. When animals become endangered, the entire food chain can be affected. For example, in 2008 disease seriously harmed the honeybee, which is largely responsible for pollinating   plants, including many fruits and vegetables. Without their pollination, a very large part of the human diet could be reduced. In fact, if the honeybee should become extinct, our life would be affected and billions of dollars would be lost. Therefore, many people argue that when animals become endangered it is in man's own self-interest to protect them. Why is it dangerous to introduce a non-native species to a habitat?
Native species are likely to die from the new diseases. It's hard for non-native species to survive. Non-native species will take up more space. Native species are so powerful for non-native species.