We don't build houses or factories in swamps, bogs, or marshes, and we don't plant wheat or many other crops on land submerged in water. To do so is a serious mistake. Wetlands act like giant sponges, soaking up rain and snowmelt and slowly releasing water in drier seasons. Thus, they help to reduce floods and to ease the worst effects of drought. Draining ponds, sloughs, and marshes often lowers the water table and dries up wells.
Wetlands also reduce soil erosion by checking or slowing the runoff from storms and thaws.
Without wetlands we would no longer have a ready supply of fresh drinking water. Much like our kidneys, wetlands filter the waters of our lakes, rivers, and streams, reducing pollution. The vegetation in wetlands removes phosphates and other plant nutrients washed in from the surrounding soil, thereby retarding the growth of algae and aquatic weeds. This growth is a serious problem in some of Canada's major waterways where dead and decaying algae rob the deeper waters of their oxygen. Wetlands are also the homes for at least some part of the year for many fish, birds, and other animals, meeting essential breeding, nesting, nursery, and feeding needs.