Environmental Science is the study of organisms and the their surroundings. The goal of environmentalists is to create a sustainable society where humans can live in good conditions without depleting resources and doom our future generations.
There are many problems with society right now. We have various forms of pollution, overpopulation, over-harvesting our resources, global warming, and much more.
In order for humans to survive in the long run, and not be the source of its own undoing, we must figure out ways to live sustainably.