Humans do lots of things for their own personal benefit often without thinking that harm the environment. People cut down forests for civilization, drive cars that let out pollution that's very harmful. Even smoking can be harmful to the environment. And people waste terribly, like using more than needed paper towels.
But the question doesn't specify just bad stuff. They're are tons of environmentalists who work full time helping the environment with non-violent strategies. Even at home, many people help my saving their resources. Turning of lights, using just enough paper they need, recycling, and much more.
Hope this helped!