Here are my suggestions:
"As you know, animals play an important part in our environment. They help maintain the biodiversity in nature. Today many animal species, however, are in danger of extinction
. The reason causing the decrease in the number of animals is mainly from human beings. It is high time we must take some measures to protect endangered animals. Where is the research supporting this?
Firstly, we should educate people from the young age about the importance of wild animals in maintain the ecosystem and biodiversity. Young people should be educated how to protect our environment in general and how to protect endangered animals in particular. They should be told about the things that threat the safety of wildlife so that they can avoid doing them. This should be included in their curriculum at school.
Secondly, the governments all over the world should set up national parks and wild-life preserves as many as possible. Thanks to these places, animals will have a suitable habitat to survive and good conditions to grow and multiply. There they can be kept in a natural and safe environment.
Last but not least, each nation must enforce stricter law with more serious punishment- capital punishment, for example- to prevent people from poaching rare and valuable animals.
In general, protecting wild animals is not a person's work but it needs the solidarity of human beings all over the world. I should think each of us has the responsibility for protecting and saving endangered species before it is too late."
Other than that, looks good. An essay like this needs more outside sources to support your assertions and make this essay more credible.