With industries and business developing quickly, the number of trees in many big cities has dramatically reduces. Efforts are being made to prevent people from cutting more trees. But a lot of trees are being destroyed by people who have never thought of the importance of green plants.Making cities greener has many advantages. First, it can make our air cleaner. Some researchers have proved that trees can reduce the amount of carbon dioxide in the atmosphere through absorption. Second, it can make our cities more beautiful. With trees and flowers everywhere, living conditions can be improved.

　　Finally, it can produce timber----an effective way to solve the problems of limited supply of natural resources.

　　Making our cities greener requires nationwide efforts. People in every field should not only know about the importance of keeping the quality of urban environment, but also take common action to plant more trees and flowers so as to improve our living conditions.