Wetlands and the Environment

Wetlands cover less than ten percent of the earth's surface but are the source of almost one-quarter of the world's productivity. For example, saltwater wetlands provide nursery habitat for most of the fish and shellfish that we eat. As these habitats are destroyed, the ability of fish populations to replenish themselves is also destroyed. What effect do you think this could have on our food supply in the future?

Emergent palustrine wetland on the Palouse, Idaho. Photo: © Penelope Morgan 2004

Wetlands are so productive because of the amount of vegetation they contain. Abundant plants constantly photosynthesize, converting carbon dioxide to oxygen and producing energy and food. Nutrients produced by the plants are distributed widely through floods, storms, and tides. And the dead and dying plants (detritus) form the base of food webs: protozoa, bacteria, fungi, and larvae consume the detritus; fish, worms, birds, and insects consume the detritus-consumers; and so on.

The dense vegetation of wetlands creates a natural water-treatment system that surpasses anything that humans have created. As water enters a wetland, it slows. Sediment settles out and is trapped by the wetland plants and their roots. The plants also absorb almost two-thirds of the nitrate and phosphorus commonly carried in stormwater runoff and floods, especially that which comes from agricultural areas and their heavy loads of fertilizer. Bacteria in the water and soil also can neutralize wastes, including the body wastes of animals and humans.

The slowed, cleansed water of a wetland may pass into another waterway, but much of it percolates into the ground and recharges groundwater supplies. Such supplies provide a majority of the drinking water in many areas in the U.S.. For example, one wetland in Massachusetts was found to recharge a shallow aquifer with more than 240 million gallons per month.

In addition to slowing and cleansing water, in coastal areaas the wetland's dense vegetation creates a tough buffer zone that can deflect waves and other heavy water surges that might otherwise erode shorelines and threaten people's homes.

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