You should save the world because you LOVE it.
You should save the world because everything you love is an integral part of it.
Everyone should do their best to save the world they live in. People that live in the world now a days should be able to continue living like that and future generations. People should start caring for their world because you never know the future. You never know if one day you will need the world's help. We all should be careful with what we do to the environment and every living thing living on it. The world is not only one person's, it is everybody's and so think about others and not only about yourself.