Modern agriculture has vastly increased the amount of food that farms are capable of producing with great gains in efficiency, but it can also have a major negative impact on the environment. Large-scale farms are vital for keeping the world fed, but they can devastate local ecosystems through clearcutting and runoff, which often releases methane, ammonia and other toxic chemicals into the environment.
In order to grow crops, the natural flora of an area must first be removed. This can lead to habitat destruction and a major change in the ecological balance. Much of the destruction of the rain forests is due to the expansion of agricultural operations. Removing old-growth plants and trees can also increase erosion, remove nutrients from the soil and spur flooding. The dust storms that plagued the Midwest in the 1930s were, in part, due to over-farming of the land and clearing of natural plant cover.
Runoff from farming operations can often include toxic substances. Pesticides and ammonia are common pollutants leftover from industrial farming operations, and they may find their way into the water table through the natural water cycle. In addition, livestock farms can be a massive source of methane and other pollutants from animal waste, and if this runoff enters lakes and streams, it can trigger dangerous algae blooms and kill fish and other wildlife.