A wetland is a distinct semi-aquatic ecosystem whose groundcovers are flooded or saturated in water, either permanently, for years or decades, or only seasonally. Flooding results in oxygen-poor processes taking place, especially in the soils. These areas form a transitional zone between waterbodies and dry lands. They differ from other terrestrial or aquatic ecosystems due to their vegetation's roots having adapted to oxygen-poor waterlogged soils. A simplified definition describes them as an area of land that is usually saturated with water. More precisely, wetlands are areas where water covers the soil, or is present at or near the surface all year or for varying periods during the year. A patch of land that develops pools after a rain storm would not necessarily be considered a wetland. Wetlands have unique characteristics based on their water level and the types of plants that live within them. Specifically, they are characterized as having a water table that stands at or near the land surface for a long enough period each year to support aquatic plants. A more concise definition identifies them as a community composed of hydric soil and hydrophytes. Under the Ramsar international wetland conservation treaty, wetlands include marshes, fens, peatlands, or waters whether natural or artificial. The treaty defines them as areas with water that is static or flowing, fresh, brackish, or salt. This includes marine waters up to six meters deep at low tide.
Global Distribution And Types
Wetlands exist on every continent, except Antarctica. The water in these environments can be freshwater, brackish, or saltwater. Marshes are wetlands dominated by emergent herbaceous vegetation such as reeds, cattails, and sedges. Swamps are dominated by woody vegetation like trees and shrubs. Reed swamps in Europe are an exception where reeds dominate instead of trees. Mangrove forests are wetlands with mangroves and halophytic woody plants evolved to tolerate salty water. Examples classified by water sources include tidal wetlands where ocean tides provide the source. Estuaries feature mixed tidal and river waters. Floodplains receive excess water from overflowed rivers or lakes. Bogs and vernal ponds rely on rainfall or meltwater sometimes mediated through groundwater springs. The world's largest wetlands include the Amazon River basin and the West Siberian Plain. The Pantanal in South America stands as another massive example. The Sundarbans in the Ganges-Brahmaputra delta completes this list of giants. Temperatures vary greatly depending on location. Many wetlands sit in temperate zones midway between poles and equator. Subtropical zone wetlands along the Gulf of Mexico experience average temperatures around twenty degrees Celsius. Tropical wetlands face much higher temperatures for large portions of the year. Wetlands on the Arabian Peninsula can exceed forty degrees Celsius causing rapid evaporation. Peatlands in arctic regions insulate permafrost delaying its thawing during summer.