In the past hundreds of years, there have been frequent natural disasters, such as droughts floods, mud-rock flows, earthquakes, windstorms and the stretching of the new deserts.
The disasters have killed millions upon millions of people, destroyed numerable homes, and wiped out numerous pieces of fertile land. Nowadays more and more people are aware of that those disasters have much to do with what we have done to the earth. We have cut down too many trees in the forests, we have badly polluted the environment, we have shocked our own home-planet time and again with tremendously powerful explosions of nuclear bombs. As a result, climates have become warmer, rainwater rushes down hillsides angrily, and the underground energy goes up to revenge itself on us.
The earth is our only home-planet. It is urgent for us to stop damaging it. It is time for us to do our best to protect our home and make it a lovely place suitable to live in，for we have nowhere to go and survive except where we are now.