Environmental problems are becoming more and more serious all over the world.For example,cars have made the air unhealthy for people to breathe and poisonous gas is given off by factories.Trees on the hills have been cut down and waste water is being poured continuously into rivers.Furthermore,wherever we go today,we can find rubbish carelessly disposed.Pollution is,in fact,threatening our existence.The earth is our home and we have the duty to take care of it for ourselves and for our later generations.Fortunately,more and more people have realized these problems.Measures have been taken to cope with these problems by the government.Laws have been passed to stop pollution.I hope the problem will be solved in the near future and our home will become better and better.To everyone on our planet,Over the past years,floods,droughts,landslides,and dust-storms have frequented our planet,the only habitat of human beings.Several days ago,tsunami(海嘯) has swept the Southeast Asia,which has caused enormous damage.All these have sounded an alarm to human beings.The destruction which is caused by human beings has aroused people’s concern all over the world.If we pay no heed to the present destructive human activities,our planet will become of tomb instead of cozy home.What’s more,we should realize that only from our planet can we obtain our sheltering,food,cloth and so forth.Counter-measures must be taken to curb the destruction caused by human beings.Most importantly,laws must be established to punish those who are involved in destructive conducts.