Trees are useful to man in three important ways: they provide him with wood and other products, they give him shade, and they help to prevent drought(干旱) and floods. Unfortunately, in many parts of the world man has...Trees are useful to man in three important ways: they provide him with wood and other products, they give him shade, and they help to prevent drought(干旱) and floods. Unfortunately, in many parts of the world man has cut down a large number of trees every year.展开更多
文摘Trees are useful to man in three important ways: they provide him with wood and other products, they give him shade, and they help to prevent drought(干旱) and floods. Unfortunately, in many parts of the world man has cut down a large number of trees every year.