Wetlands Biome

0 views

Skip to first unread message

Concordia Zentner

unread,

Aug 3, 2024, 5:13:01 PM8/3/24

to emchomacal

Forbidding Fens
From Swamp Thing to Wuthering Heights, wetlands are traditional settings for myths and ghost stories. One of the earliest written stories in the English language, Beowulf, takes place near a fen, or bog, in Scandinavia. One of the main characters in Beowulf, the monster Grendel, lives in a cave beneath the fen.

Ghost Airport
In the 1970s, Floridas Miami-Dade Aviation Department planned to build a 101-square-kilometer (39-square-mile) airport complex and transportation corridor in the southern Florida wetlands. The Everglades Jetport would have blocked the flow of water into the Everglades, causing untold environmental damage. A group of activists, helped by the first-ever environmental impact study, successfully stopped the venture.

Soggy Cities
Some of the biggest cities in the U.S. were built on top of wetlands, including Boston, Massachusetts; San Francisco, California; and Washington, D.C. In fact, the "tidal basin" in front of the Jefferson Memorial in Washington, D.C., often floods the surrounding sidewalks with water from the Potomac River.

The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit. The Rights Holder for media is the person or group credited.

For information on user permissions, please read our Terms of Service. If you have questions about how to cite anything on our website in your project or classroom presentation, please contact your teacher. They will best know the preferred format. When you reach out to them, you will need the page title, URL, and the date you accessed the resource.

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 for a shorter periods. Flooding results in oxygen-poor (anoxic) processes taking place, especially in the soils.[1] Wetlands form a transitional zone between waterbodies and dry lands, and are different from other terrestrial or aquatic ecosystems due to their vegetation's roots having adapted to oxygen-poor waterlogged soils.[2] They are considered among the most biologically diverse of all ecosystems, serving as habitats to a wide range of aquatic and semi-aquatic plants and animals, with often improved water quality by the plants removing excess nutrients such as nitrates and phosphates.

Wetlands exist on every continent, except Antarctica.[3] The water in wetlands is either freshwater, brackish or saltwater.[2] The main wetland types are classified 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. Swamps are dominated by woody vegetation such as trees and shrubs (although reed swamps in Europe are dominated by reeds, not trees). Mangals are wetlands with halophytic woody plants known as mangroves, which have evolved to tolerate salty water.

Examples of wetlands classified by the sources of water include tidal wetlands (where the water source is ocean tides), estuaries (water source is mixed tidal and river waters), floodplains (water source is excess water from overflowed rivers or lakes), and bogs and vernal ponds (water source is rainfall or meltwater).[1][4] Some wetlands have multiple types of plants and are fed by multiple sources of water, making them difficult to classify. The world's largest wetlands include the Amazon River basin, the West Siberian Plain,[5] the Pantanal in South America,[6] and the Sundarbans in the Ganges-Brahmaputra delta.[7]

Wetlands contribute many functions that benefit people. These are called ecosystem services and include for example water purification, stabilization of shorelines, storm protection and flood control. In addition, wetlands also process and condense carbon (in processes called carbon fixation and sequestration), and other nutrients and water pollutants. Wetlands can act as a sink or a source of carbon, depending on the specific wetland. If they function as a carbon sink, they can help with climate change mitigation. However, wetlands can also be a significant source of methane emissions due to anaerobic decomposition of soaked detritus, and some are also emitters of nitrous oxide.[8][9]

Methods exist for assessing wetland functions and wetland ecological health. These methods have contributed to wetland conservation by raising public awareness of the functions that wetlands can provide.[10] Constructed wetlands are a type of wetland that can treat wastewater and stormwater runoff. They may also play a role in water-sensitive urban design. Environmental degradation threatens wetlands more than any other ecosystem on Earth, according to the Millennium Ecosystem Assessment from 2005.[11]

A simplified definition of wetland is "an area of land that is usually saturated with water".[12] 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".[13] A patch of land that develops pools of water after a rain storm would not necessarily be considered a "wetland", even though the land is wet. Wetlands have unique characteristics: they are generally distinguished from other water bodies or landforms based on their water level and on the types of plants that live within them. Specifically, wetlands 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.[14][15]

Wetlands have also been described as ecotones, providing a transition between dry land and water bodies.[16] Wetlands exist "...at the interface between truly terrestrial ecosystems and aquatic systems, making them inherently different from each other, yet highly dependent on both."[17]

An ecological definition of a wetland is "an ecosystem that arises when inundation by water produces soils dominated by anaerobic and aerobic processes, which, in turn, forces the biota, particularly rooted plants, to adapt to flooding".[1]

Sometimes a precise legal definition of a wetland is required. The definition used for regulation by the United States government is: 'The term "wetlands" means those areas that are inundated or saturated by surface or ground water at a frequency and duration to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions. Wetlands generally included swamps, marshes, bogs, and similar areas.'[19]

For each of these definitions and others, regardless of the purpose, hydrology is emphasized (shallow waters, water-logged soils). The soil characteristics and the plants and animals controlled by the wetland hydrology are often additional components of the definitions.[20]

The following three groups are used within Australia to classify wetland by type: Marine and coastal zone wetlands, inland wetlands and human-made wetlands.[22] In the US, the best known classifications are the Cowardin classification system[23] and the hydrogeomorphic (HGM) classification system. The Cowardin system includes five main types of wetlands: marine (ocean-associated), estuarine (mixed ocean- and river-associated), riverine (within river channels), lacustrine (lake-associated) and palustrine (inland nontidal habitats).

Peatlands are a unique kind of wetland where lush plant growth and slow decay of dead plants (under anoxic conditions) results in organic peat accumulating; bogs, fens, and mires are different names for peatlands.

Some wetlands have localized names unique to a region such as the prairie potholes of North America's northern plain, pocosins, Carolina bays and baygalls[24][25] of the Southeastern US, mallines of Argentina, Mediterranean seasonal ponds of Europe and California, turloughs of Ireland, billabongs of Australia, among many others.

The amount of precipitation a wetland receives varies widely according to its area. Wetlands in Wales, Scotland, and western Ireland typically receive about 1,500 mm (59 in) per year.[citation needed] In some places in Southeast Asia, where heavy rains occur, they can receive up to 10,000 mm (390 in).[citation needed] In some drier regions, wetlands exist where as little as 180 mm (7.1 in) precipitation occurs each year.[citation needed]

Wetlands vary widely due to local and regional differences in topography, hydrology, vegetation, and other factors, including human involvement. Other important factors include fertility, natural disturbance, competition, herbivory, burial and salinity.[1] When peat accumulates, bogs and fens arise.

The most important factor producing wetlands is hydrology, or flooding. The duration of flooding or prolonged soil saturation by groundwater determines whether the resulting wetland has aquatic, marsh or swamp vegetation. Other important factors include soil fertility, natural disturbance, competition, herbivory, burial, and salinity.[1] When peat from dead plants accumulates, bogs and fens develop.

Wetland hydrology is associated with the spatial and temporal dispersion, flow, and physio-chemical attributes of surface and ground waters. Sources of hydrological flows into wetlands are predominantly precipitation, surface water (saltwater or freshwater), and groundwater. Water flows out of wetlands by evapotranspiration, surface flows and tides, and subsurface water outflow. Hydrodynamics (the movement of water through and from a wetland) affects hydro-periods (temporal fluctuations in water levels) by controlling the water balance and water storage within a wetland.[28]

Landscape characteristics control wetland hydrology and water chemistry. The O2 and CO2 concentrations of water depend upon temperature, atmospheric pressure and mixing with the air (from winds or water flows). Water chemistry within wetlands is determined by the pH, salinity, nutrients, conductivity, soil composition, hardness, and the sources of water. Water chemistry varies across landscapes and climatic regions. Wetlands are generally minerotrophic (waters contain dissolved materials from soils) with the exception of ombrotrophic bogs that are fed only by water from precipitation.