You can do things that mildly effect the environment. I'm aware of the trash that we produce that get clogged in the oceans or landfills. However, there is no actual scientific evidence that we (humans) cause major changes in the overall changes the Earth goes through and has been going through for thousands of years. And just so you know, I'm saying thousands of years instead of billions, because I believe the Earth to be only 6-7 thousand years old.