Some wetlands help provide clean, plentiful water supplies. For example, wetlands in Florida's Everglades help recharge the Biscayne Aquifer, the sole source of drinking water for the Miami metropolitan area. Ecological, cultural, and historic resources run abundant in our nation's wetlands, and provide countless opportunities for environmental education and public awareness programs. Although some of our wetlands have been created in as short a span as a human lifetime, many others took thousands of years to develop. Coastal wetlands also form when silt is carried down-river and deposited as it reaches the sea.
Plants then take root and hold the soil deposits firm against the force of the tide.
Wetlands form on floodplains where periodic flooding or high water tables provide sufficient moisture. Large wetlands formed when glacier' dammed rivers, scoured valleys, and reworked floodplains. Countless smaller wetlands were created when large blocks d ice left behind by receding glaciers formed pits and depressions in the land. Many of these depressions later filled with water if they had poor drainage or intersected the water table. Though trapping has greatly reduced the number of beavers in the U.S., recent wildlife protection measures have resulted in recovery of beaver populations.