When coal and oil are burned, they form acids that fall to the earth as rain. Acid rain can do a lot of damage, such as killing off living things in lakes. Scientists figured out, however, that lakes on limestone rock were less affected than others. Why? Limestone weakens acid. So as a short-term solution, scientists added lime to lakes where it doesn't occur naturally.
No single science was enough to come up with this solution -- it took experts in biology, chemistry, geology, and other sciences. If you major in environmental science, you'll learn to use the ideas and methods of a number of biological and physical sciences to tackle some of the world’s most pressing problems.