Because of their position between dry land and water, wetlands can remove, break down or transform many of the pollutants in water that harm aquatic life in streams, rivers and lakes. Even when a wetland does not eliminate a pollutant from the water, it can prevent it from entering a stream in one big pulse, which could overwhelm the stream's delicate web of life. By holding water on the land for a short time, wetlands also help replenish ground water supplies. Besides having an important role in maintaining good water quality, wetlands themselves teem with a diversity of life, including plants, mammals, amphibians, birds, fish and insects. In fact, wetlands are some of the most diverse and productive natural communities on earth, and one third of all endangered species depend on wetlands to complete at least part of their life cycle.
Wetlands vary in how effective they are at removing pollutants.
Cleansing ability depends on how water moves through the wetland, what plants are present, the size of the wetland, the time of year, how long the water is held and many other factors. Current research is focused on learning more about how natural wetlands influence water quality. Although much needs to be learned, scientists agree on the overall importance of wetlands in regulating the flow characteristics of streams, improving surface water quality and aiding ground water recharge.