indicated above are pictures that show trees play a vital role in water and soil conservation. in the left hand picture, people are fleeing from voracious sand dunes because they cut down all the trees. the caption reads, "as the sand advances, we retreat." in the right hand picture, the people have returned carrying tools, water and samplings for the reforestation of the land. we are informed that, "as we advances, the sand retreats."it seems that the cartoonist is sending a message about the significance of trees in water and soil conservation and the need for everyone to fight against the danger of the desertification. in fact, what he is saying is if we do not fight against the sand, it will drive us away from the land. if we let this situation go as it is, our environment will suffer a great destruction.

　　the best way to fight back against the greedy desert is made clear in the second picture. there the local people are vigorously setting about the task of planting trees to reclaim the land and make it fertile. the fact that there are three people in the picture, each with a different job suggests that cooperative efforts is one of the keys to success in the battle against soil erosion and only in this way can desertification be finally defeated.