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A simplified definition of wetland is "an area of land that is usually saturated with water". [14] More precisely, wetlands are areas where "water covers the soil, or is present either at or near the surface of the soil all year or for varying periods of time during the year, including during the growing season". [15]
Wetlands exist on every continent, except Antarctica. [19] The water in wetlands is either freshwater, brackish or saltwater. [18] The main types of wetland are defined based on the dominant plants and the source of the water. For example, marshes are wetlands dominated by emergent herbaceous vegetation such as reeds, cattails and sedges.
Wetlands are frequently being destroyed for development, agriculture, and other uses. Wetlands have decreased by as much as 50% since 1900 and in some parts of the world by 90%. [ 19 ] [ 20 ] Inland wetlands, freshwater marshes making up about 20-25% of all freshwater wetlands globally, [ 21 ] have been decreasing approximately 1.2% each year ...
The Wetlands Geodatabase and the Wetlands Mapper, as an Internet discovery portal, provide technological tools that allow the integration of large relational databases with spatial information and map-like displays. The information is made available to an array of federal, state, tribal, and local governments and the public.
A wetland is a land area that is saturated with water, either permanently or seasonally, such that it takes on the characteristics of a distinct ecosystem. The primary factor that distinguishes wetlands from other land forms or water bodies is the characteristic vegetation of aquatic plants , adapted to the unique hydric soil .
White water lilies are a typical marsh plant in European areas of deeper water. Many kinds of birds nest in marshes; this one is a yellow-headed blackbird.. Marshes provide a habitat for many species of plants, animals, and insects that have adapted to living in flooded conditions or other environments. [1]
The degree of salinity in an estuary or delta is an important control upon the type of wetland (fresh, intermediate, or brackish), and the associated animal species. Dams built upstream may reduce spring flooding, and reduce sediment accretion, and may therefore lead to saltwater intrusion in coastal wetlands. [20]
The surface of the wetland is level with the water table. Water flows on the surface and through the subsurface of the wetland. The water table fluctuates. It may be at the surface of the wetland or a few centimeters above or below it. The wetland receives a significant amount of its water from mineral-rich groundwater or surface water. [10]