Wetlands face destruction due to threats such as commercial development, industry, urbanization, agriculture, invasive species, pollution, climate change and dams. It is estimated that approximately half of the world's wetlands have disappeared since 1900. The loss or alteration of wetlands is believed to contribute to global warming.
Wetlands are a type of ecosystem characterized by either a seasonal or permanent saturation of land by water, which can either be fresh, brackish or salt. Aquatic plants and other vegetation specific to wetlands are another defining characteristic, as they are fully adapted to the exclusive hydric soil. Wetlands are useful to the environment due to their ability to purify water, provide stability to shorelines, serve as a home for a variety species and act as a buffer for floods. Examples of wetlands include swamps, bogs, marshes and fens. Climate varies based on location, but wetlands are present on every continent with the exception of Antarctica. Of all ecosystems, it is believed that wetlands face the most environmental degradation.
Around half of the world's human population relies on wetlands for their freshwater needs. Wetlands also serve as a significant source of protein and are often used as fisheries. Conservation efforts within the United States are centered around building artificial wetlands to offset the loss of those from industry and commercial interests.