Since the earliest times,trees have always been very useful and important to man who made use of them in many ways.Even today trees continue to serve man in so many ways.
Trees provide man with fruits and building materials in the form of wood.Without trees it would be impossible to build houses,boats and even bridges.Furniture such as tables,chairs and beds is made of wood.
In the tropics (热带地区) where it is very hot throughout the year,trees protect man from the terrible heat.They are also useful in preventing good and rich top soil from being washed away during heavy rains which are so common in the tropics.
If there were no trees or vegetation (植被) of some kind to hold back the soil with their roots,heavy rain would wash away the rich surface soil that is so important and necessary to agriculture.The result is that the land becomes a desert.
There are so many desert areas in the world.A long time ago these desert areas must have been very rich fertile (肥沃的) areas,but since our ancestors (祖先) in the distant past did not have enough knowledge about science of nature,they cut down all the trees in the areas where they lived and never planted new ones.By and by,the rich surface soil was blown away and washed away by strong winds and heavy rains.In the end the land was turned into useless deserts where nothing could grow.