Because if people will not take care of nature then all men will live in bad environment and because of this, many will develop the disease will die animals, birds ,plants will not allocate chrolophyll and the air we breathe will clog our lungs. so we are going to drink no clean running water,a dirty and clogged with all sorts of garbage water.If we clog the ground,then we will not give tasty crops that we consume every year.So let's protect our environment.