概括法： 先概括总结文章内容涉及的现状，然后引出主题。如：

　　In recent years, while our industries and businesses have developed quickly, the number of trees in many big cities has dramatically reduced. Efforts are being made to prevent from cutting more trees, but to realize the significance of making cities greener is of importance.

　　本写法还可以从过去/历史上写，然后引伸到现在。