Pollution Interception - Pollution in a watershed might include industrial effluents, fertilizers, sewage, and city storm runoff. Left untreated or free in the water, high levels of these nutrients cause eutrophication, an initial explosion of algal growth followed by a precipitous decline in plant life. Wetlands handle pollutants in several ways. Plants take up and filter some. Others settle into the anaerobic soil strata and are chemically reduced over time. Still more are processed by bacterial action. When wetlands are lost, pollutants they would have rendered harmless remain at large, free to move on into other aquatic systems.

Toxic Residue Processing - In developed areas wetlands receive their share of toxic residues. When heavy metal toxins such as lead wash down the watershed, they are often destined for a wetland stop. These residues, like pollutants, can be buried and neutralized in soils, taken up by reeds, rushes, and other plants; and reduced through ion exchange. While wetlands play a crucial part in protecting watersheds from toxins, their capacity and long-term ability to do so is limited.

Waste Treatment - Wetlands can be remarkably effective in treating controlled amounts of human and animal wastes. Several factors contribute to wetlands' performance in processing waste:

1. A high rate of biological productivity that leads to a large capacity for consuming waste
2. Heavy deposition of sediments that bury waste

3. A high level of bacterial activity in sediment layers that breaks down and neutralizes waste

Cities like Philadelphia and Calcutta, India, have incorporated wetlands into their wastewater treatment schemes for decades, with persuasive results. While it is important to pay attention to a wetland's capacity, these urban wastewater treatment wetlands have removed coliform bacteria and suspended solids, reduced the turbidity of wastewater by nearly half, and added tons of oxygen to the water every day on a sustained basis.

Physical/Hydrological Functions

Chemical Functions

Biological Functions

Socioeconomic Functions/Benefits