写一篇短文，论据是动物濒临绝种的危险，最重要的原因是人为因素，应包括以下内容：
1。 许多动物过去生存的地方遭到破坏。
2。 许多动物被人捕猎而死亡。
3。 许多树木被砍伐了。
4。 被污染的河流和湖泊也是引起动物死亡的原因。 Why Are Many Animals Dying out？
There are many reasons for animals dying out， but the most important one is the part that humans have played。 First， many animals have been killed for food。 Second， many of the places where animals used to live have been destroyed。 Wet land has been turned into field。
More and more trees in the forests have been cut down， but few trees are planted。 Much land has either been changed into agricultural land or used for building factories and houses。 Polluted rivers and lakes have also been a cause of death of some of the animals。