范文：
　　Recent efforts toward the greening of our cities have achieved much, although the results are still far from satisfactory. In recent years many trees have been planted in the cities and much care has been taken of the planted trees. In spite of all this, the greening process is relatively slow compared with cities in many other countries. For example, the green space available on average to each Shanghai citizen is only 0.4 Mu while every Londoner has more than 20 Mu.
　　We can benefit much from making our cities greener by planting trees. First, trees absorb carbon dioxide to produce oxygen which is essential to the health of human beings. Second, trees and other greenery make our cities more beautiful. Third, trees can also improve the climate of the cities.
　　Since we can get so much from making our cities greener, we should spare no effort to do that. We should plant more trees and take better care of them. We also should not cut down the trees. In a word, we should do everything to add to the greening of our cities.