Wetland 102024 224355169 2008-07-08T14:12:11Z OCPE 5186797 /* Further reading */ {{pp-semi-protected|small=yes}} {{globalize}} [[Image:Floridacrocodile1.JPG|thumb|240px|A subtropical wetland in [[Florida]], [[United States|USA]], with an endangered [[American Crocodile]].]] A '''wetland''' is an area of [[land]] consisting of [[soil]] that is [[saturated]] with [[moisture]], such as a [[swamp]], [[marsh]], or [[bog]]. As defined in terms of [[physical geography]], a wetland is an environment "at the interface between truly [[terrestrial ecoregion|terrestrial]] [[ecosystems]] and [[aquatic habitat|aquatic]] systems making them inherently different from each other yet highly dependent on both"<ref name="mitsch2007">{{cite book |last=Mitsch |first=William J. |coauthors=James G. Gosselink |title=Wetlands |edition=4th edition |date=2007-08-24 |publisher=John Wiley & Sons |location=New York |isbn=978-0471699675 |pages=p. ? |chapter=?}}</ref>. In essence, wetlands are [[ecotone]]s. Wetlands often host considerable [[biodiversity]] and [[endemism]]. In many locations such as the [[United Kingdom]] and [[United States]] they are the subject of [[Conservation movement|conservation]] efforts and [[Biodiversity Action Plan]]s. The [[United States Army Corps of Engineers]] and the [[United States Environmental Protection Agency]] jointly define wetlands as "those areas that are inundated or saturated by surface or ground water at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetations typically adapted for life in saturated soils. Wetlands generally include swamps, marshes, bogs, and similar areas."<ref>Definition from Corps of Engineers, Wetlands Delineation Manual, by Environmental Laboratory, U.S. Army Corps of Engineers, Waterways Experiment Station, 3909 Halls Ferry Road, Vicksburg, MS 39180-6199</ref><ref>42 Federal Register 37125-26, 37128-29. [[1977-07-19]]. via {{cite web |url=http://www.nrb.state.vt.us/wrp/rulemaking/wetlands/vtransproposal.pdf |title=VTrans Proposal |accessdate=2008-01-19 |last=Gingras |first=Glenn |date=2006-08-21 |format=PDF}}</ref> ==Characteristics== ===Soils=== Wetlands are found under a wide range of [[hydrology|hydrological]] conditions, but at least some of the time water [[water content|saturate]]s the [[soil]]. The result is a [[hydric soil]], one characterized by an absence of free oxygen some or all of the time, and therefore called a "[[reducing environment]]." ===Vegetation=== [[Plants]] (called [[hydrophytes]] or just wetland plants) specifically adapted to the reducing conditions presented by such soils can survive in wetlands, whereas species intolerant of the absence of soil oxygen (called "upland" plants) cannot survive. Adaptations to low soil oxygen characterize many wetland species. There are many types of vegetation in wetlands. There are plants such as [[typha|cattails]], [[Scirpus|bulrushes]], [[Cyperaceae|sedges]], [[Sagittaria|arrowhead]], [[Nymphaeaceae|water lilies]], [[Iris versicolor|blue flag]], and floaters like common [[Lemnaceae|duckweed]]. [[Potamogeton|Pondweed]] is also another type of plant that grows in wetlands, but it is not easily seen. [[Peat]]land can be dominated by [[Acer rubrum|red maple]], [[Acer saccharinum|silver maple]], and [[elm]] trees. Some types of trees in peatland can exhibit lower trunks and roots that have adapted to the wet surroundings by forming buttresses,like the [[cypress]], enlarged root bases to better support the trees in the mucky soil. Trees can also form knees, raised roots that allow for gas exchange. Swamps can also have [[Chamaecyparis thyoides|whitecedar]], [[Tamarack Larch|tamarack, and [[Eastern White Pine|white pine]]. Below the [[Canopy (forest)|canopy]], there are often limited amounts of shrubs such as [[Alnus incana|speckled alder]], [[Holly|Winterberry]], and [[Myrica gale|sweet gale]]. [[Mangrove]]s are a species of plant which typically thrive in [[salt marsh|coastal wetlands]] (called marine or estuarine environments). They are a special tree taxon that can survive in salty wetland water. Mangroves also provide the base for the wetland food chain. They are the producers in the wetland environment. Because mangroves add [[sulfur]] to the wetlands, it makes the water more acidic, therefore allowing decomposed matter in the water to biodegrade faster than it normally would, which in turn, provides more food for the organisms in the wetland ecosystem. ===Hydrology=== Generally, the hydrology of a wetland is such that the area is permanently or periodically inundated or saturated at the soil surface for a period of time during the growing season. The presence (or absence) of water is not necessarily a good method for identifying wetlands because the amount of water generally fluctuates depending on such things as rainfall patterns, snow melt, dry seasons, longer droughts, and tidal patterns. Often the same wetland can appear to be an open body of water sometimes and a dry field at other times because of significant fluctuations in water levels. The three water sources that contribute to wetlands are: *[[precipitation]] falling within the wetland *[[groundwater]] moving up or out from the subsurface of the wetland *surface flow from the surrounding [[watershed]] or nearby water bodies ([[lake]]s, [[stream]]s, [[ocean]]s, etc.) Location determines which of these sources will be contributing water to a wetland. ===Topography=== Generally, wetlands are located within topographic features that are lower in elevation that the surrounding landscape such as depressions, valleys, and flat areas. Topography plays an important role in determining the size and shape of a wetland by controlling where the water goes and how long it stays there. ==Classification== Below are terms used for various types of wetlands: *A [[bog]] or [[muskeg]] is [[Acid|acidic]] [[peat]] land (peat bog). *A [[Moorland|moor]] was originally the same as a bog but has come to be associated with this soil type on hill-tops. *A [[moss (habitat)|moss]] is a raised bog in [[Scotland]] *A [[fen]] is a freshwater peat land with chemically [[Base (chemistry)|basic]] (which roughly means [[Alkali|alkaline]]) ground water. This means that it contains a moderate or high proportion of [[hydroxyl]] ions ([[pH]] value greater than 7). *A carr is a fen which has developed to the point where it supports trees. It is a European term, mainly applied in the north of the UK. *A freshwater [[Marsh|marsh's]] main feature is its openness, with only low-growing or "emergent" plants. It may feature [[Poaceae|grasses]], [[Juncaceae|rushes]], [[Phragmites|reeds]], [[typha]]s, [[Cyperales|sedges]], and other herbaceous [[plant]]s (possibly with low-growing woody plants) in a context of shallow [[water]]. It is an open form of fen. *A [[vernal pool]] ( or ephemeral) is a shallow, freshwater pond that is seasonal, having water during rainy months and drying up completely during the remainder of the year. One distinctive characteristic is the lack of fish species in the pool. *A coastal [[salt marsh]] may be associated with [[Estuary|estuaries]] and along waterways between coastal [[barrier island]]s and the inner coast. The plants may extend from reed in mildly brackish water to [[salicornia]] on otherwise bare marine mud. It may be converted to human use as [[pasture]] ([[salting]]) or for salt production ([[Sea salt|saltern]]). *A [[swamp]] is wetland with more open water surface and deeper water than a marsh. In North America, it is used for wetlands dominated by trees and woody bushes rather than grasses and low herbs, but this distinction does not necessarily apply in other areas, for instance in [[Africa]] where swamps may be dominated by [[papyrus]]. *A [[dambos|dambo]] is a shallow, grass-covered depression of the central and southern African plateau which is waterlogged in the rainy season and usually forms the headwaters of a stream or river. It is marshy at the edges and at the headwater but maybe swampy in the centre and downstream. *A [[Mangrove|mangrove swamp]] or mangal is a salt or brackish water environment dominated by the [[Mangrove#Species|mangrove species of tree]], such as ''Sonneratia''. *A paperbark wetland is a fresh or brackish water environment dominated by the [[Melaleuca]] tree. *A [[bayou]] or [[slough (wetland)|slough]] is a [[southern United States]] terms for a creek amongst swamp. In an [[India|Indian]] mangrove swamp, it would be called a [[Creek (tidal)|creek]]. *A [[constructed wetland]] is artificially contrived wetland, intended to absorb [[flash flood]]s, clean [[sewage]], enhance [[wildlife]] or for some other human reason. *A [[pocosin]] is a bog-like wetland dominated by fire-adapted shrubs and trees, found mainly in the southeastern United States on the [[Atlantic Coastal Plain]]. *Seasonally flooded basins or flats. *Inland fresh meadows. *Inland shallow fresh water. The [[U.S. Fish and Wildlife Service]]'s [[National Wetlands Inventory]] (NWI) produces and provides information on the characteristics, extent, and status of U.S. wetlands and deepwater habitats and other wildlife habitats. The NWI also produces periodic reports on the status and trends of wetlands in the conterminous U.S. The NWI website includes a [http://wetlandsfws.er.usgs.gov/NWI/index.html Wetlands Mapper]. ===Hydrogeomorphic classes=== The Hydrogeomorphic (HGM) Approach is a system developed by the [[United States Army Corps of Engineers]] to classify all wetlands based on three factors that influence how they function: position in the landscape (geomorphic setting), water source (hydrology), and the flow and fluctuation of the water once in the wetland (hydrodynamics). There are seven classes (types) of wetlands in this system: *riverine *depressional *slope *mineral soil flats *organic soil flats *estuarine fringe *lacustrine fringe This approach also intends to develop subclasses of wetlands to account for specific conditions of various regions. [[Image:Atchafalaya basin.gif|right|frame|Time lapsed animation of basin from 1956 to 1993.]][[Image:Pt_Pelee_Marsh_Boardwalk.jpg|thumb|center|Marsh in [[Point Pelee National Park|Point Pelee]], Ontario, Canada|600px]] ===Wetlands in drylands=== In contrast to wetlands in other [[biomes]] (usually permanent and fresh water), wetlands in drylands are more diverse in their composition, depending on the local climate and other particularities of the surroundings. They can be fresh or saline, permanent, seasonal or temporary, filling intermittently or regularly. Wetlands in drylands can be attributed all values and uses of wetlands found in other biomes. However, given the stark contrast to their dry surroundings, many of these values are enhanced. This applies to the water balance where gradual release and storage of rainwater by wetlands amid drylands is crucial because of the unpredictability and incalculability of rain. During dry seasons, wetlands in drylands are also pivotal as refugia for wildlife, livestock and people. Moreover, biodiversity levels are higher than in wetlands in other major biomes, in particular because of the accessibility of water amid an otherwise very dry environment. ===Intertidal wetlands=== In intertidal wetlands the majority of natural stress comes from salinity and [[tide|tidal movements]]. The intertidal wetlands must be able to survive extreme conditions of mainly salt water at high tide, fresh water at low tide and times of flood and brackish water at other times. The saline water is a very difficult condition for plants to survive in. The grey mangrove accomplishes this by excluding salt in the root system, salt glands in the leaf, and waxy leaves to minimize water loss. However it is vulnerable to changes in salinity levels. Changes to tidal movements through increased run-off or altered drainage can cause the roots of mangroves to be inundated for longer than normal periods affecting their pneumatophones. It can also be pushed past its threshold level if water quality is changed. Thus even healthy ecosystems are vulnerable to change. Some species such as [[oyster]]s and [[mollusk]]s have been used as [[indicator species]], with any decline in their numbers indicating the ecosystem is under stress. A change in nutrient levels may also affect primary productivity and thus bring about change. ==Functions== [[Image:Mokrady_Srby_2.jpg|thumb|right|160px|Home of water birds in wetland near [[:cs:Tuchlovice|Tuchlovice]], [[Czech Republic|Czech Rep.]] ]] ===Hydrologic=== Hydrologic functions include long term and short term water storage, subsurface water storage, energy dissipation, and moderation of groundwater flow or discharge. By absorbing the force of strong [[wind]]s and tides, wetlands protect terrestrial areas adjoining them from [[storm]]s, [[floods]], and tidal damage. ===Biogeochemical=== Nutrient cycling, retention of particulates, removal of imported elements and compounds, and the import and export of organic carbon are all biogeochemical functions of wetlands. Wetlands remove nutrients from surface and ground water by filtering and by converting nutrients to unavailable forms. [[Denitrification]] is arguably the most important of these reactions because humans have increased [[nitrate]] worldwide by applying [[fertilizer]]s. Increased nitrate availability can cause [[eutrophication]], but denitrification converts biologically available nitrogen back into nitrogen gas, which is biologically unavailable except to nitrogen fixing bacteria. Denitrification can be detected in many soils, but denitrification is fastest in wetlands soils<ref name="ullaha2006">{{cite journal |last=Ullaha |first=Sami |coauthors=S.P. Faulkner |date=2006-11-30 |title=Denitrification potential of different land-use types in an agricultural watershed, lower Mississippi valley |journal=Ecological Engineering |volume=28 |issue=2 |pages=131–140 |publisher=Elsevier |issn=0925-8574 |doi=10.1016/j.ecoleng.2006.05.007 |url=http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VFB-4KHC351-1&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=b9658a4af09bafdf4d6f3400bad4f27a |accessdate=2008-01-19 |quote=Low-elevation clay soils in wetlands exhibited 6.3 and 2.5 times greater DP compared to high-elevation silt loam and low-elevation clay soils in croplands, respectively.}}</ref>. Intertidal wetlands provide an excellent example of invasion, modification and succession. The invasion and succession process is establishment of seagrasses. These help stabilize sediment and increase sediment capture rates. The trapped sediment gradually develops into mud flats. Mud flat organisms become established encouraging other life forms changing the organic composition of the soil. ===Habitat=== Wetland provide a safe and lush environment for many different species of fish, birds, and insects. It includes the [[mallard duck]], the [[Sickleback fish]], mangroves, and [[water moccasins]]. Like animals, there are many plant communites that will only survive in the unique environmental conditions of a wetland. In the continental U.S. wetlands account for only 5% of the total land area, but over 30% of the nation's vascular flora occur in wetlands. Mangroves establish themselves in the shallower water upslope from the mudflats. Mangroves further stabilize sediment and over time increase the soil level. This results in less tidal movement and the development of salt marshes. (succession) The salty nature of the soil means it can only be tolerated by special types of grasses e.g. saltbush, rush and sedge. There is also changing species diversity in each succession. ===Value to humans=== While many of the functions above are directly or indirectly beneficial to humans and society, wetlands are specifically valuable to people as places for recreational and educational activities such as hunting, fishing, camping, and wildlife observation. Wetlands are often filled in to be used by humans for everything from [[agriculture]] to parking lots, in part because the economic value of wetlands has only been recognized recently: the [[shrimp]] and [[fish]] that breed in salt water marshes are generally harvested in deeper water, for example. Humans can maximize the area of healthy, functioning wetlands by minimizing their impacts and by developing management strategies that protect, and where possible rehabilitate those ecosystems at risk. [[Image:Wetland-marshall-county-indiana.jpg|thumb|250px|left|Small wetland in [[Marshall County, Indiana|Marshall County]], [[Indiana]] in the United States.]] Wetlands are sometimes deliberately created to help with water reclamation. One example is [[Green Cay Wetlands]] in [[Boynton Beach, Florida]], in the United States. [[Image:Turtle-on-log-green-cay-florida-mar08.jpg|thumb|right|300px|Turtle on a log at [[Green Cay Wetlands]], a water reclamation facility in [[Boynton Beach, Florida]] in the United States.]] ==Protection and rehabilitation== [[Image:Wetland500.JPG|thumb|A temperate wetland in [[United Kingdom|Britain]], with shallow open water and reedbeds.]] Historically, humans have made large-scale efforts to drain wetlands for development or to flood them for use as recreational lakes. Since the 1970s, more focus has been put on preserving wetlands for their natural function—sometimes also at great expense. One example is the project by the U.S. Army Corps of Engineers to control flooding and enhance development by taming the [[Everglades]], a project which has now been reversed to restore much of the wetlands as a natural habitat and method of flood control. The creation of the treaty known as the [[Ramsar Convention]] (1971), or more properly "The Convention on Wetlands of International Importance, especially as Waterfowl Habitat", demonstrates the global concern regarding wetland loss and degradation. The primary purposes of the treaty are to list wetlands of international importance and to promote their wise use, with the ultimate goal of preserving the world’s wetlands. ;Exclusion: Those responsible for the management of wetland areas often facilitate public access to a small, designated area while restricting access to other areas. Provision of defined boardwalks and walkways is a management strategy used to restrict access to vulnerable areas, as is the issuing of permits whilst visiting. ;Education: In the past, wetlands were regarded as wastelands. Education campaigns have helped to change public perceptions and foster public support for the wetlands. Because of their location in the catchment area, education programs need to teach about total catchment management programs. Educational programs include guided tours for the general public, school visits, media liaison, and information centers. ===United States=== [[Image:SlatMarshBLUE1602.jpg|thumb|200px|among the Salt Marsh Nature Center, in [[Brooklyn]], NY]] [[Image:HackensackWEtlands.JPG|thumb|200px|Wetlands in the state of New Jersey]] In the United States, some wetlands are regulated by the federal government under the [[Clean Water Act]]. Determining the boundary between regulated wetlands and non-regulated lands therefore can be contentious. In reality, there is no natural boundary between the classes that humans define on these gradients (wetland/upland), and this issue is highlighted by the [[U.S. Fish and Wildlife Service]]'s definition from Classification of Wetlands and Deepwater Habitats of the United States, which defines wetlands as "lands transitional between terrestrial and aquatic systems." Regulations to protect water quality and highway safety require that we create arbitrary boundaries within those gradients, but these boundaries are scientifically definable, and consist of areas where three criterion of the presence of [[hydric soil|hydric soils]], the presence of [[wetland vegetation]], and the presence of appropriate [[hydrology]]. Such regulations must be predictable, reproducible, and enforced. Otherwise, we will sacrifice clean water for development in the case of wetlands regulation (or vice versa), or sacrifice safe travel for quick travel (or vice versa) in the case of speed limits. Determining which wetlands are regulated under section 404 of the clean water act<ref>{{cite web |url=http://www.epa.gov/owow/wetlands/facts/fact11.html |title=Section 404 of the Clean Water Act: How Wetlands are Defined and Identified |accessdate=2008-01-19 |date=2006-02-22 |work=Wetlands fact sheet |publisher=EPA}}</ref> or section 10 of the rivers and harbors act is termed "jurisdictional determination". Determining the boundary of wetland, whether jurisdictional under sections 404 or 10, or not jurisdictional but still meeting the technical definition of a wetland, that is having the soils, vegetation and hydrology criterion met is called a "wetland delineation", and generally is performed by college graduates with natural science or biology degrees working for engineering firms or environmental consulting firms who are familiar with the 1987 U.S. Army Corps of Engineers Wetland delineation manual. [[Image:Overly Protected Wetlands.jpg|thumb|left|200px|Wetlands protected by steel fence, [[San Francisco]], CA]] Defining a boundary depends upon soil and vegetation characteristics; it is easier to do where the slope of the land is steeper. Deciding if a wetland is a regulated wetland depends on classifying the water in it as "water of the United States" or not. Classifying water as "of the U.S." or "not of the U.S." for purposes of enforcing the Clean Water Act suggests a natural boundary that probably does not exist in nature, and one that was not created regarding air for purposes of enforcing the Clean Air Act. Indiana Wetlands are the focus of the U.S. [[National Wetlands Coalition]], which in turn has become the focus of some controversy over "false fronts," a form of political [[camouflage]]. {{seealso|National Wetlands Research Center|Wetlands Reserve Program}} ==See also== *[[Asmat Swamp]] (in Indonesia) *[[Bog]] *[[Cardiff Bay Wetlands Reserve]] (in [[Wales]] UK) *[[Flooded grasslands and savannas]] *[[Freshwater swamp forest]] *[[Marsh]] *[[Peat swamp forest]] *[[Salt marsh]] *[[Slough (wetland)|Slough]] *[[Swamp]] ==References== {{Reflist}} ==Further reading== *Ghabo, A. A. (2007) [http://www.terranuova.info/file_download/51 Wetlands Characterization; Use by Local Communities and Role in Supporting Biodiversity in the Semiarid Ijara District, Kenya]. Terra Nuova East Africa. Wetlands in drylands. *[http://www.cpe.rutgers.edu/brochures/pdfs/1987-Army-Corps-Wetlands-Delineation-Manual.pdf 1987 U.S. Army Corps of Engineers Wetland delineation manual] ==External links== *[http://www.articlemyriad.com/37.htm Wetlands: The Ecological Effect of Loss (Research article)] *[http://www.esterosdelibera.com/ Marshlands of Iberá] (in English and Spanish) *Federal Register (1996-08-16). [http://www.wetlands.com/coe/fr16au96.htm "National Action Plan to Develop the Hydrogeomorphic Approach to Assessing Wetland Functions] *[http://www.fws.gov/nwi/plants.htm National Wetland Inventory] (USA) *Brinson, M. M., Hauer, F. R., Lee, L. C., Nutter, W. L., Rheinhardt, R. D., Smith, R. D., and Whigham, D. (1995). [http://el.erdc.usace.army.mil/wetlands/pdfs/wrpde11.pdf"A guidebook for application of hydrogeomorphic assessments to riverine wetlands"] Technical Report WRP-DE-11, U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS. NTIS No. AD A308 365. *[http://www.cpe.rutgers.edu/programs/wetlands.html Rutgers University Wetland Delineation and Wetland Education Courses] [[Category:Wetlands| ]] [[cs:Mokřad]] [[da:Vådområde]] [[de:Feuchtgebiet]] [[et:Märgala]] [[el:Υγροβιότοπος]] [[es:Humedal]] [[eo:Malsekejo]] [[fa:تالاب]] [[fr:Zone humide]] [[ko:습지]] [[it:Zona umida]] [[lt:Šlapynė]] [[nl:Drasland]] [[ja:湿地]] [[no:Våtmark]] [[pl:Mokradło]] [[pt:Zona úmida]] [[sl:Mokrišče]] [[fi:Kosteikko]] [[sv:Våtmark]] [[th:พื้นที่ชุ่มน้ำ]] [[zh:湿地]]