It is the purpose for all life. In order for living things to exists, they must learn to exist with, understand it, and adapt to it. Everything that we do is dictated by nature. Our clothing, shelter, food, jobs, and lives are all affect directly or indirectly by nature. We gain all of our knowledge form nature.
Human advancement is the result of better understanding nature and how it functions.
As we further gain an understanding of the world in which we live in, we improve our quality of living. Man's goal is to fully understand nature on every level, which is a neverending pursuit.