• Federal programs encouraged destruction of wetlands during the 1800's but today seek to protect wetlands
• Wetlands are identified by the presence of hydric soils, hydrophytic vegetation, and water on or near the ground surface
• Most U.S. wetlands are freshwater wetlands but coastal wetlands are significant along the Gulf Coast
• The benefits of wetlands include improvements in water quality, ecological habitats, reducing flooding, shoreline erosion control and as recharge for groundwater

Characteristics of Wetlands
ederal programs once encouraged the infilling of wetlands, today the government joins with other nations as signatories of the Ramsar Convention, "The convention on wetlands of international importance especially as waterfowl habitat", to preserve and protect wetlands around the world. The U.S. contains twelve Ramsar sites ranging from the Alaskan coast, to a Nevada desert oasis, to Everglades National Park in southern Florida. Whether labeled bog, marsh, fen, or swamps, wetlands often represent a fuzzy transition between dry land and open water environments. The term wetland, as defined by the Clean Water Act, encompasses "those areas that are inundated or saturated by surface or groundwater at a frequency and duration sufficient to support, and under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions". Federal regulations identify wetlands by:  

1. hydrologic conditions: water is present on the land surface, or soils in the root zone are saturated during the growing season;
2. hydrophytic vegetation (e.g. cattails, willows, sawgrass, wild rice): approximately 9% of all plant species in the US and its possessions occur exclusively in wetlands;
3. hydric soils: poorly drained soils which develop anaerobic conditions during the growing season.

Two types of wetland: bottomland forested wetland (left) and fen with grasses. Images courtesy of U.S. EPA.

Wetlands can be divided into two general types:

• coastal wetlands: 5% of current wetlands, including mangrove swamps, salt marshes, e.g. Louisiana
• freshwater wetlands: 95% of wetlands including forested swamps, inland marshes, riparian (river) and lacustrine (lake) wetlands

Property-rights advocates have suggested that Clean Water Act regulations preventing the filling of wetlands represent a "taking" of private lands by the government. The U.S. constitution’s fifth amendment states that private property may not be "taken" without "just compensation". Nearly three-quarters of wetlands in the lower forty eight states are on private land. The US Army Corps of Engineers administers wetlands with the Environmental Protection Agency (EPA). The Corps is authorized to issue permits to fill wetlands where projects are in the public interest. In recent years the Corps has approved approximately 65,000 projects a year while denying about 600, less than 1%.

Benefits of Wetlands
Wetlands are recognized to have several positive functions, they can:

• improve water quality by filtering out sediment and other contaminants
• provide ecological habitats for migrating bird populations
• breeding grounds for fish and shellfish
• moderate the effects of flooding - slow run-off, especially downstream from urban centers
• shoreline erosion control - act as a buffer for coastal storms
• recreation - canoeing, hunting, fishing, birdwatching
• act as recharge areas for groundwater.

Approximately half of the US population relies on underground water sources (groundwater) for domestic water supplies and agriculture. Infiltration of water into underground aquifers is diminished when streams or storm sewers carry water away. The storage of water in wetlands acts to promote groundwater recharge as such sites act like sponges, soaking up precipitation and releasing water slowly into the groundwater system. Society has learned this lesson well and local agencies have created artificial recharge basins by diverting river waters into abandoned quarries where porous sediments (sand, gravel) allow water to pass downward into aquifers below.