The primary concerns of people nowadays are the economy, technology and their living conditions. But there is an unfair phenomenon in the present world, on the one hand, the human population is growing and their living conditions are improving, while on the other hand, many wild lives are on the verge of distinction and the disappearance of their habitats is accelerating. The shortage of foods and living spaces has eliminated some species of plants and animals naturally and they were replaced by newer species that are more adaptable to the acute living conditions. Other species are near extinct due to the environmental changes or natural disasters; but the fundamental factor that causes the present outcome is human, they either directly go after the animals for their resources or the animals' habitats where natural resources can be exploited. In addition, there are other human activities which indirectly contribute to the present grave situation and the list of endangered animals is growing. To sum up, humans are responsible for the extinction of animals. The popular consensus is that the most important cause of animal extinction is the loss of their habitats. Presently rapid destructions are underway in many habitats of abundant species. As a matter of fact, about two-thirds of tropical species of animals and plants, particularly those in the humid tropical forests are in the list of endangered species. According to some researches, generally, 50% of the species in a habitat would be lost if 90% of it was to be eliminated; It is understood that species have chosen to disappear and the decision is never random. The tigers back in ancient times had always evoked awe in the hearts of people. They were the symbol of courage and strength; but unfortunately, this was the same reason why hunters and wildlife traders went after the tigers. In the past century, at least three sub-species of tigers had been wiped out by these criminal activities. The statistics show that there were once 100,000 tigers in Asia, but they remain fewer than 3000 today. What a remarkable number and unbelievable consequence! Most people are never involved in the evil animal trade, but they support it unwittingly in the form of purchasing endangered species as souvenirs every year. Animals are our close friends and good companions; the world will be a terrible place without them. But if we continue to allow people to exploit animals for fashion, traditional medicines, souvenirs and hunting pleasure without taking any preventive actions, the future generations may only see animals in the museums in a few years from now. Finally, other than the above reasons, there are yet other factors contributing to the extinction of animals. However, these factors are caused by human activities too. For example, the green house effect which is the result of carbon emission by humans which has caused global warming and this may affect animals in many different ways. 【英语牛人团】