23、Nature is to us what water is to fish．Yet we don’t always realize it until it is too late．With the development of modern technology, there are more and more people on the earth and fewer and fewer resources left．What’s worse, pollution is getting more and more serious and the climate is becoming warmer and warmer．So we must do something to protect not only our next generation but also ourselves．As is shown in the pictures, we plant trees and we will enjoy the shade ourselves as well as our grandchildren．If we do something good to nature, it will do more to us.