As you know, 'being green' means that you care about the environment (环境) and that you do what you can to help the Earth. Recycling (回收利用) paper and cans, reducing waste, and protecting wildlife are all examples of 'green' activities. This special green issue of National Geographic Kids is devoted to environment. In fact, you're being green simply by reading it. When you're finished, you'll know a lot of things you probably didn't know at all. And you'll be a greener citizen with a strong sense of environmental protection. In this issue(一期杂志) you will discover how you can help the Earth face its five biggest environment problems. Animal behavior. specialist Jane Goodall shares new ideas about how you can help wildlife. Answer actor Leonarde DiCaprio's call to action to help the environment. Just how green are you? Answer actor questions on Page 10 to find out. You may win a trip to Orlando, Florida. And there's a special pullout poster to hang on the wall. The writer's main purpose in writing this text is to ______.