View source for Earth:Wetland

{{Short description|Land area that is permanently, or seasonally saturated with water}}
<noinclude>{{multiple image |perrow=2 |total_width=400 |image1=USGS_image_cropped.jpg |alt1=Upland vs. wetland vs. lacustrine zones |image2=Freshwater swamp forest in Gowainghat Sylhet Bangladesh photo taken in July 2016.jpg |alt2=Freshwater [[Earth:Swamp|swamp]] forest in Bangladesh |image3=Tourbière 03 - Parc de Frontenac - Juillet 2008.jpg |alt3= Peat bogs are freshwater wetlands that develop in areas with standing water and low [[Chemistry:Soil fertility|soil fertility]]. |image4= Remediated wetlands at the Mount Polley mine.jpg |alt4 = Mount Polley wetlands in British Columbia, Canada |footer= Wetlands come in different sizes, types, and locations. Clockwise from top left: Upland vs. wetland vs. lacustrine zones; Freshwater [[Earth:Swamp|swamp]] forest in Bangladesh; A freshwater cattail ([[Biology:Typha|Typha]]) marsh that develops with standing water and high soil fertility; Peat bogs are freshwater wetlands that develop in areas with standing water and low [[Chemistry:Soil fertility|soil fertility]].}}</noinclude>

A '''wetland''' is a distinct [[Earth:Ecosystem|ecosystem]] that is flooded or saturated by [[Chemistry:Water|water]], either permanently for years or decades or seasonally for a shorter periods. Flooding results in oxygen-free [[Earth:Anoxic waters|anoxic]] processes prevailing, especially in the soils.<ref name=Keddy2010>{{cite book |last=Keddy |first=P.A. |url=https://books.google.com/books?id=eVeaSqFy2VgC |title=Wetland ecology: principles and conservation |date=2010 |publisher=Cambridge University Press |isbn=978-0521519403 |edition=2nd |location=New York}} {{Webarchive|url=https://web.archive.org/web/20130411041256/http://www.drpaulkeddy.com/wetlandecology2.html|date=2013-04-11}}</ref> The primary factor that distinguishes wetlands from terrestrial land forms or [[Earth:Body of water|water bodies]] is the characteristic [[Biology:Vegetation|vegetation]] of aquatic plants, adapted to the unique anoxic [[Earth:Hydric soil|hydric soil]]s.<ref name=ramsar>{{cite web|title=Official page of the Ramsar Convention|url=http://www.ramsar.org/cda/en/ramsar-pubs/main/ramsar/1-30_4000_0__|access-date=2011-09-25}}</ref> Wetlands are considered among the most biologically diverse of all ecosystems, serving as home to a wide range of plant and animal species. Methods for assessing wetland functions, wetland ecological health, and general wetland condition have been developed for many regions of the world. These methods have contributed to wetland conservation partly by raising public awareness of the functions some wetlands provide.<ref name="ACADEMIC PRESS">{{Cite book |title=Wetland and Stream Rapid Assessments: Development, Validation, and Application|date=2018|publisher=Academic Press|isbn=978-0-12-805091-0|editor-last=Dorney |editor-first=J. |location=London; San Diego, CA |oclc=1017607532|editor-last2=Savage |editor-first2=R.|editor-last3=Adamus |editor-first3=P.|editor-last4=Tiner |editor-first4=R.}}</ref> [[Earth:Constructed wetland|Constructed wetland]]s are designed and built to treat municipal and industrial [[Earth:Wastewater|wastewater]] as well as to divert [[Earth:Stormwater|stormwater]] runoff. Constructed wetlands may also play a role in [[Engineering:Water-sensitive urban design|water-sensitive urban design]].

Wetlands occur naturally on every [[Earth:Continent|continent]].<ref name=Davidson2014>{{cite journal |author=Davidson, N.C.|year=2014|title=How much wetland has the world lost? Long-term and recent trends in global wetland area |journal=Marine and Freshwater Research |volume=65|issue=10|pages=934–941|doi=10.1071/MF14173|s2cid=85617334}}</ref> The water in wetlands is either freshwater, brackish or [[Earth:Seawater|saltwater]].<ref name=ramsar/> The main wetland types are classified based on the dominant [[Biology:Plant|plant]]s and/or the source of the water. For example, [[Earth:Marsh|marsh]]es are wetlands dominated by [[Biology:Aquatic plant#Emergent|emergent vegetation]] such as [[Biology:Reed (plant)|reed]]s, cattails and [[Biology:Sedge|sedge]]s; [[Earth:Swamp|swamp]]s are ones dominated by woody vegetation such as [[Earth:Tree|tree]]s and [[Biology:Shrub|shrub]]s (although reed swamps in Europe are dominated by reeds, not trees).

Examples of wetlands classified by their sources of water include [[Earth:Tidal wetland|tidal wetland]]s ([[Earth:Ocean|ocean]]ic [[Astronomy:Tide|tide]]s), [[Earth:Estuary|estuaries]] (mixed tidal and river waters), [[Earth:Floodplain|floodplain]]s (excess water from overflowed rivers or lakes), [[Earth:Spring (hydrology)|spring]]s, seeps and [[Earth:Fen|fen]]s ([[Earth:Groundwater|groundwater]] discharge out onto the surface), and [[Earth:Bog|bog]]s and vernal ponds (rainfall or [[Earth:Meltwater|meltwater]]).<ref name=Keddy2010/><ref name="water">{{cite web|date=2015 |title=US EPA|url=http://water.epa.gov/type/wetlands/what.cfm|access-date=2011-09-25}}</ref> 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,<ref name="FraserKeddy">{{cite book |url=https://books.google.com/books?id=tYeccNT_AsQC&pg=PP1 |title=The World's Largest Wetlands: Their Ecology and Conservation |date=2005 |publisher=Cambridge University Press |isbn=978-0521834049 |editor-last=Fraser |editor-first=L. |location=Cambridge, UK |editor2-last=Keddy |editor2-first=P.A.}}</ref> the [[Place:Pantanal|Pantanal]] in South America,<ref name=":1">{{cite web |title=WWF Pantanal Programme |url=http://wwf.panda.org/who_we_are/wwf_offices/bolivia/our_work/pantanal_programme/ |access-date=2011-09-25}}</ref> and the Sundarbans in the Ganges-Brahmaputra delta.<ref name=":2">{{cite journal |author=Giri, C. |author2=Pengra, B. |author3=Zhu, Z. |author4=Singh, A. |author5=Tieszen, L.L. |year=2007 |title=Monitoring mangrove forest dynamics of the Sundarbans in Bangladesh and India using multi-temporal satellite data from 1973 to 2000 |journal=Estuarine, Coastal and Shelf Science |volume=73 |issue=1–2 |pages=91–100 |bibcode=2007ECSS...73...91G |doi=10.1016/j.ecss.2006.12.019}}</ref>  

Wetlands contribute a number of functions that benefit people. These are called [[Biology:Ecosystem service|ecosystem service]]s and include [[Earth:Water purification|water purification]], [[Earth:Groundwater recharge|groundwater replenishment]], stabilization of shorelines and storm protection, water storage and flood control, processing of carbon ([[Earth:Carbon fixation|carbon fixation]], [[Medicine:Decomposition|decomposition]] and [[Earth:Carbon sequestration|sequestration]]), other nutrients and [[Earth:Water pollution|pollutants]], and support of plants and animals.<ref>{{cite web |title=Wetlands|url=https://www.nrcs.usda.gov/wps/portal/nrcs/main/national/water/wetlands/|website=USDA- Natural Resource Conservation Center|date=2023}}</ref> Wetlands are reservoirs of [[Biology:Biodiversity|biodiversity]] and provide wetland products. According to the UN Millennium Ecosystem Assessment, wetlands are more affected by environmental degradation than any other ecosystem on Earth.<ref>{{cite book |last1=Davidson |first1=N.C. |url=https://www.millenniumassessment.org/documents/document.358.aspx.pdf |title=Ecosystems and Human Well-being: Wetlands and Water Synthesis: a report of the Millennium Ecosystem Assessment |last2=D'Cruz |first2=R. |last3=Finlayson |first3=C.M. |date=2005 |publisher=World Resources Institute |isbn=978-1-56973-597-8 |location=Washington, DC |name-list-style=amp}}</ref> Wetlands can be important sources and sinks of carbon, depending on the specific wetland, and thus will play an important role in [[Earth:Climate change|climate change]] and need to be considered in attempts to [[Earth:Climate change mitigation|mitigate]] climate change. However, some [[Earth:Wetland methane emissions|wetlands are a significant source of methane emissions]] and some are also emitters of [[Chemistry:Nitrous oxide|nitrous oxide]].<ref name=":4">{{Cite journal|last=Bange|first=H. W.|date=2006 |title=Nitrous oxide and methane in European coastal waters |url=https://linkinghub.elsevier.com/retrieve/pii/S0272771406002496|journal=Estuarine, Coastal and Shelf Science |volume=70 |issue=3 |pages=361–374 |doi=10.1016/j.ecss.2006.05.042 |bibcode=2006ECSS...70..361B}}</ref><ref name=":3">{{cite journal |last1=Thompson |first1=A. J. |last2=Giannopoulos |first2=G. |last3=Pretty |first3=J. |last4=Baggs |first4=E. M. |last5=Richardson |first5=D. J. |date=2012 |title=Biological sources and sinks of nitrous oxide and strategies to mitigate emissions |journal=Philosophical Transactions of the Royal Society B |volume=367 |issue=1593 |pages=1157–1168 |doi=10.1098/rstb.2011.0415 |pmc=3306631 |pmid=22451101}}</ref> 

{{TOC level|3}}

==Definitions and terminology==
[[File:Meadowlands Lyndhurst.jpg|thumb|300px|Marshlands are often noted within wetlands, as seen here in the New Jersey Meadowlands at Lyndhurst, New Jersey, U.S.]]

===Technical definitions===
A simplified definition of wetland is "an area of land that is usually saturated with water".<ref>{{Cite web |title=Home: Oxford English Dictionary |url=https://www.oed.com/ |access-date=2022-07-08 |website=www.oed.com |language=en}}</ref> More precisely, wetlands are areas where "water covers the [[Chemistry:Soil|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".<ref name=":5" /> 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 [[Earth:Landform|landform]]s based on their [[Water level|water level]] and on the types of [[Biology:Plant|plant]]s that live within them. Specifically, wetlands are characterized as having a [[Earth:Water table|water table]] that stands at or near the land surface for a long enough period each year to support aquatic plants.<ref>{{cite web |title=Glossary of Terms |url=http://www.cvwd.net/water_glossary.htm |archive-url=https://web.archive.org/web/20120425163056/http://www.cvwd.net/water_glossary.htm |archive-date=April 25, 2012 |access-date=2012-05-23 |publisher=Carpinteria Valley Water District}}</ref><ref>{{cite web |title=Glossary |url=http://mapping2.orr.noaa.gov/portal/calcasieu/calc_html/resources/glossary.html |archive-url=https://web.archive.org/web/20120425163041/http://mapping2.orr.noaa.gov/portal/calcasieu/calc_html/resources/glossary.html |archive-date=2012-04-25 |access-date=2012-05-23 |publisher=Mapping2.orr.noaa.gov}}</ref>

A more concise definition is a community composed of [[Earth:Hydric soil|hydric soil]] and hydrophytes.<ref name="Keddy2010" />

Wetlands have also been described as [[Earth:Ecotone|ecotone]]s, providing a transition between dry land and water bodies.<ref>{{cite web |title=Glossary |url=http://www.alabamapower.com/hydro/glossary.asp |archive-url=https://web.archive.org/web/20120321233304/http://www.alabamapower.com/hydro/glossary.asp |archive-date=2012-03-21 |access-date=2012-05-23 |publisher=Alabama Power}}</ref> Wetlands exist "...at the interface between truly terrestrial ecosystems and aquatic systems, making them inherently different from each other, yet highly dependent on both."<ref name="mitsch2007">{{cite book |last1=Mitsch |first1=William J. |url=https://books.google.com/books?id=1cSKeTCi894C |title=Wetlands |last2=Gosselink |first2=James G. |date=2007-08-24 |publisher=John Wiley & Sons |isbn=978-0-471-69967-5 |edition=4th |location=New York, NY}}</ref>

In environmental decision-making, there are subsets of definitions that are agreed upon to make regulatory and policy decisions.

Under the Ramsar international wetland conservation treaty, wetlands are defined as follows:<ref>{{cite web|title=The Ramsar 40th Anniversary Message for November| publisher = Ramsar| access-date = 2011-10-10 | url = http://www.ramsar.org/cda/en/ramsar-home/main/ramsar/1_4000_0__}}</ref>
* Article 1.1: "...wetlands are areas of marsh, [[Earth:Fen|fen]], [[Earth:Peatland|peatland]] or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, [[Earth:Fresh water|fresh]], [[Earth:Brackish water|brackish]] or [[Chemistry:Saline water|salt]], including areas of marine water the depth of which at low tide does not exceed six meters."
* Article 2.1: "[Wetlands] may incorporate riparian and coastal zones adjacent to the wetlands, and [[Earth:Island|island]]s or bodies of marine water deeper than six meters at low tide lying within the wetlands."
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".<ref name="Keddy2010" />

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.'<ref>Environmental Laboratory. (1987). Corps of Engineers wetlands delineation manual. ''Tech. Rep. Y‐87–1''.</ref>

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.<ref>{{cite book |last1=Sharitz |first1=Rebecca R. |chapter=Ecology of Freshwater and Estuarine Wetlands: An Introduction |date=2019-12-31 |title=Ecology of Freshwater and Estuarine Wetlands |pages=1–22 |location=Berkeley |publisher=University of California Press |language=en |doi=10.1525/9780520959118-003 |isbn=978-0-520-95911-8 |last2=Batzer |first2=Darold P. |last3=Pennings |first3=Steven C. |s2cid=198427881}}</ref>

=== Types ===
[[File:Sunrise at viru bog.jpg|thumb|upright=1.5|Sunrise at Viru Bog, Estonia]]
Wetlands can be [[Astronomy:Tide|tidal]] (inundated by tides) or non-tidal.<ref name=":5"/> The water in wetlands is either freshwater, [[Earth:Brackish water|brackish]], [[Chemistry:Saline water|saline]], or [[Chemistry:Alkali|alkali]]ne.<ref name="ramsar" /> There are four main kinds of wetlands&nbsp;– [[Earth:Marsh|marsh]], [[Earth:Swamp|swamp]], [[Earth:Bog|bog]], and [[Earth:Fen|fen]] (bogs and fens being types of [[Earth:Mire|peatlands]] or [[Earth:Mire|mire]]s). Some experts also recognize [[Earth:Wet meadow|wet meadow]]s and [[Earth:Aquatic ecosystem|aquatic ecosystem]]s as additional wetland types.<ref name="Keddy2010" /> Sub-types include [[Earth:Mangrove swamp|mangrove forests]], [[Earth:Carr (landform)|carrs]], [[Earth:Pocosin|pocosin]]s, [[Earth:Floodplain|floodplain]]s,<ref name="Keddy2010" /> [[Earth:Mire|peatlands]], [[Earth:Vernal pool|vernal pool]]s, [[Earth:Sink (geography)|sinks]], and many others.<ref name=":0">{{Cite web|url=https://dec.vermont.gov/watershed/wetlands/what/types|title = Wetland Types &#124; Department of Environmental Conservation}}</ref>

The following three groups are used within {{wipe|Australia}} to classify wetland by type: Marine and coastal zone wetlands, inland wetlands and human-made wetlands.<ref>{{cite book|date=2001|title=A Directory of Important Wetlands in Australia: Third edition, Chapter 2: Wetland classification system, Criteria for inclusion and Data presentation|url=http://www.environment.gov.au/water/publications/environmental/wetlands/directory.html |access-date=30 March 2021|publisher=Australian Department of the Environment}}</ref> In the US, the best known classifications are the [[Biology:Cowardin classification system|Cowardin classification system]]<ref>{{Cite web|title=NPWRC :: Classification of Wetlands and Deepwater Habitats of the United States|url=https://www.fws.gov/wetlands/documents/classwet/index.html|access-date=2018-07-28|website=www.fws.gov|archive-date=2014-01-21|archive-url=https://web.archive.org/web/20140121073314/http://www.fws.gov/wetlands/Documents/classwet/index.html}}</ref> and the hydrogeomorphic (HGM) classification system. The Cowardin system includes five main types of wetlands: [[Biology:Marine habitats|marine]] (ocean-associated), [[Earth:Estuary|estuarine]] (mixed ocean- and river-associated), riverine (within river channels), lacustrine (lake-associated) and palustrine (inland nontidal habitats).

==== Peatlands ====
[[Earth:Mire|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.

=== Wetland names ===
Variations of names for wetland systems:

{{Div col|colwidth=22em}}
* [[Earth:Bayou|Bayou]]
* [[Earth:Flooded grasslands and savannas|Flooded grasslands and savannas]]
* [[Earth:Marsh|Marsh]]
** [[Earth:Brackish marsh|Brackish marsh]]
** [[Earth:Freshwater marsh|Freshwater marsh]]
* [[Earth:Mire|Mire]]
** [[Earth:Fen|Fen]]
** [[Earth:Bog|Bog]]
* [[Earth:Riparian zone|Riparian zone]]
* [[Earth:Swamp|Swamp]]
** Freshwater swamp forest
** [[Biology:Coniferous swamp|Coniferous swamp]]
** Peat swamp forest
** [[Earth:Mangrove swamp|Mangrove swamp]]
* [[Earth:Vernal pool|Vernal pool]]
{{Div col end}}

Some wetlands have localized names unique to a region such as the prairie potholes of North America's northern plain, [[Earth:Pocosin|pocosin]]s, Carolina bays and baygalls<ref name="Watson (2006)">{{cite book |author=Watson, G. E. |title=Big Thicket Plant Ecology: An Introduction |publisher=University of North Texas Press |year=2006 |isbn=978-1574412147 |edition=Third |series=Temple Big Thicket Series #5 |location=Denton, Texas}}</ref><ref name="Texas P&W">Texas Parks and Wildlife. Ecological Mapping systems of Texas: ''[https://tpwd.texas.gov/landwater/land/programs/landscape-ecology/ems/emst/woody-wetlands-and-riparian/west-gulf-coastal-plain-seepage-swamp-and-baygall West Gulf Coastal Plain Seepage Swamp and Baygall] {{Webarchive|url=https://web.archive.org/web/20200710060502/https://tpwd.texas.gov/landwater/land/programs/landscape-ecology/ems/emst/woody-wetlands-and-riparian/west-gulf-coastal-plain-seepage-swamp-and-baygall |date=2020-07-10 }}''. Retrieved 7 July 2020</ref> of the Southeastern US, mallines of Argentina, Mediterranean seasonal ponds of Europe and California, [[Earth:Turlough (lake)|turloughs]] of Ireland, [[Earth:Billabong|billabong]]s of Australia, among many others.

=== Locations ===

==== By temperature zone ====
[[File:MiddleSpring.JPG|thumb|Wetlands contrast the hot, arid landscape around Middle Spring, Fish Springs National Wildlife Refuge, Utah]]
Wetlands are found throughout the world in different climates.<ref name=":5">{{Cite web |last=US EPA |first=OW |date=2015-09-18 |title=What is a Wetland? |url=https://www.epa.gov/wetlands/what-wetland |access-date=2022-07-08 |website=US EPA |language=en}}</ref> Temperatures vary greatly depending on the location of the wetland. Many of the world's wetlands are in the temperate zones, midway between the North or South Poles and the equator. In these zones, summers are warm and winters are cold, but temperatures are not extreme. In subtropical zone wetlands, such as along the Gulf of Mexico, average temperatures might be {{convert|11|C|F}}. Wetlands in the tropics are subjected to much higher temperatures for a large portion of the year. Temperatures for wetlands on the [[Place:Arabian Peninsula|Arabian Peninsula]] can exceed {{convert|50|C|F}} and these habitats would therefore be subject to rapid evaporation. In northeastern Siberia, which has a polar climate, wetland temperatures can be as low as {{convert|−50|C|F}}. [[Earth:Peatland|Peatland]]s in arctic and subarctic regions insulate the [[Earth:Permafrost|permafrost]], thus delaying or preventing its thawing during summer, as well as inducing its formation.<ref>{{Cite web |title=PEATLANDS, CLIMATE CHANGE MITIGATION AND BIODIVERSITY CONSERVATION |url=https://www.ramsar.org/document/peatlands-climate-change-mitigation-and-biodiversity-conservation}}</ref>

==== By precipitation amount ====
The amount of precipitation a wetland receives varies widely according to its area. Wetlands in Wales, Scotland, and western Ireland typically receive about {{convert|1500|mm|in|abbr=on}} per year.{{citation needed|date=December 2022}} In some places in [[Place:Southeast Asia|Southeast Asia]], where heavy rains occur, they can receive up to {{convert|10000|mm|in|abbr=on}}.{{citation needed|date=December 2022}} In some drier regions, wetlands exist where as little as {{convert|180|mm|in|abbr=on}} precipitation occurs each year.{{citation needed|date=February 2017}}

Temporal variation:<ref>{{cite web |title=Ramsar Convention Technical Reports |url=http://www.ramsar.org/cda/en/ramsar-pubs-reports/main/ramsar/1-30-99_4000_0__}}</ref>
* [[Biology:Perennial|Perennial]] systems
* Seasonal systems
* Episodic (periodic or intermittent) systems
* Ephemeral (short-lived) systems
Surface flow may occur in some segments, with subsurface flow in other segments.

==Processes==
Wetlands vary widely due to local and regional differences in [[Earth:Topography|topography]], [[Earth:Hydrology|hydrology]], [[Biology:Vegetation|vegetation]], and other factors, including human involvement. Other important factors include fertility, natural disturbance, competition, herbivory, burial and salinity.<ref name="Keddy2010" /> When [[Earth:Peat|peat]] accumulates, [[Earth:Bog|bog]]s and [[Earth:Fen|fen]]s arise.

===Hydrology===
The most important factor producing wetlands is hydrology, or flooding. The duration of flooding or prolonged soil saturation by [[Earth:Groundwater|groundwater]] determines whether the resulting wetland has aquatic, [[Earth:Marsh|marsh]] or [[Earth:Swamp|swamp]] [[Biology:Vegetation|vegetation]]. Other important factors include soil fertility, natural disturbance, competition, herbivory, burial, and salinity.<ref name="Keddy2010" /> When [[Earth:Peat|peat]] from dead plants accumulates, [[Earth:Bog|bog]]s and [[Earth:Fen|fen]]s 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 [[Earth:Precipitation|precipitation]], surface water (saltwater or freshwater), and [[Earth:Groundwater|groundwater]]. Water flows out of wetlands by [[Earth:Evapotranspiration|evapotranspiration]], surface flows and [[Astronomy:Tide|tide]]s, and subsurface water outflow. [[Physics:Hydrodynamics|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.<ref>{{cite book|last1=Richardson|first1=J. L.|last2=Arndt|first2=J. L.|last3=Montgomery|first3=J. A.|date=2001|contribution=Hydrology of wetland and related soils|editor1-first=J. L.|editor1-last=Richardson|editor2-first=M. J.|editor2-last=Vepraskas|title=Wetland Soils|publisher=Lewis Publishers|location=Boca Raton, FL}}</ref>

Landscape characteristics control wetland hydrology and water chemistry. The [[Chemistry:Oxygen|O<sub>2</sub>]] and [[Chemistry:Carbon dioxide|CO<sub>2</sub>]] concentrations of water depend on [[Physics:Temperature|temperature]], [[Physics:Atmospheric pressure|atmospheric pressure]] and mixing with the air (from winds or water flows). Water chemistry within wetlands is determined by the [[Chemistry:PH|pH]], [[Earth:Salinity|salinity]], nutrients, [[Physics:Electrical conductivity|conductivity]], soil composition, hardness, and the sources of water. Water chemistry varies across landscapes and climatic regions. Wetlands are generally [[Earth:Minerotrophic|minerotrophic]] (waters contain dissolved materials from soils) with the exception of [[Earth:Ombrotrophic|ombrotrophic]] bogs that are fed only by water from precipitation.

Because bogs receive most of their water from the [[Astronomy:Atmosphere|atmosphere]], their water usually has low mineral ionic composition. In contrast, wetlands fed by groundwater or tides have a higher concentration of dissolved nutrients and minerals.

Fen peatlands receive water both from precipitation and ground water in varying amounts so their water chemistry ranges from acidic with low levels of dissolved minerals to alkaline with high accumulation of [[Chemistry:Calcium|calcium]] and [[Chemistry:Magnesium|magnesium]].<ref>{{cite journal|last1=Vitt|first1=D. H.|last2=Chee|first2=W|date=1990|title=The relationships of vegetation to surface water chemistry and peat chemistry in fens of Alberta, Canada|journal=Plant Ecology|volume=89|issue=2|pages=87–106|doi=10.1007/bf00032163|s2cid=25071105}}</ref>

===Role of salinity===

Salinity has a strong influence on wetland water chemistry, particularly in coastal wetlands<ref name="Keddy2010" /><ref>{{cite book|editor1-first=B. R.|editor1-last=Silliman|editor2-first=E. D.|editor2-last=Grosholz|editor3-first=M. D.|editor3-last=Bertness|date=2009|title=Human Impacts on Salt Marshes: A Global Perspective|publisher=University of California Press|location=Berkeley, CA}}</ref> and in arid and semiarid regions with large precipitation deficits. Natural salinity is regulated by interactions between ground and surface water, which may be influenced by human activity.<ref>{{cite journal|last1=Smith|first1=M. J.|last2=Schreiber|first2=E. S. G.|last3=Kohout|first3=M.|last4=Ough|first4=K.|last5=Lennie|first5=R.|last6=Turnbull|first6=D.|last7=Jin|first7=C.|last8=Clancy|first8=T.|date=2007|title=Wetlands as landscape units: spatial patterns in salinity and water chemistry|journal=Wetlands, Ecology & Management|volume=15|issue=2|pages=95–103|doi=10.1007/s11273-006-9015-5|bibcode=2007WetEM..15...95S |s2cid=20196854}}</ref>

===Soil===
[[Chemistry:Carbon|Carbon]] is the major nutrient cycled within wetlands. Most nutrients, such as [[Chemistry:Sulfur|sulfur]], [[Chemistry:Phosphorus|phosphorus]], [[Chemistry:Carbon|carbon]], and [[Chemistry:Nitrogen|nitrogen]] are found within the soil of wetlands. [[Biology:Anaerobic respiration|Anaerobic]] and aerobic respiration in the soil influences the nutrient cycling of carbon, hydrogen, oxygen, and nitrogen,<ref>{{cite book|last=Ponnamperuma|first=F. N.|date=1972|title=The chemistry of submerged soils|journal=Advances in Agronomy|volume=24|pages=29–96|doi=10.1016/S0065-2113(08)60633-1|isbn=9780120007240}}</ref> and the solubility of phosphorus<ref>{{cite journal|last1=Moore|first1=P. A. Jr.|last2=Reddy|first2=K. R.|date=1994|title=Role of Eh and pH on phosphorus geochemistry in sediments of Lake Okeechobee, Florida|journal=Journal of Environmental Quality|volume=23|issue=5|pages=955–964|doi=10.2134/jeq1994.00472425002300050016x|pmid=34872208|bibcode=1994JEnvQ..23..955M }}</ref> thus contributing to the chemical variations in its water. Wetlands with low pH and saline conductivity may reflect the presence of acid [[Chemistry:Sulfate|sulfate]]s<ref>{{cite journal|last1=Minh|first1=L. Q.|last2=Tuong|first2=T. P.|last3=van Mensvoort|first3=M. E. F.|last4=Bouma|first4=J.|date=1998|title=Soil and water table management effects on aluminum dynamics in an acid sulphate soil in Vietnam|journal=Agriculture, Ecosystems & Environment|volume=68|issue=3|pages=255–262|doi=10.1016/s0167-8809(97)00158-8|bibcode=1998AgEE...68..255M }}</ref> and wetlands with average salinity levels can be heavily influenced by calcium or magnesium. [[Chemistry:Biogeochemistry|Biogeochemical processes]] in wetlands are determined by soils with low [[Chemistry:Redox|redox]] potential.<ref>{{cite book|last=Schlesinger|first=W. A.|date=1997|title=Biogeochemistry: An Analysis of Global Change|url=https://archive.org/details/isbn_9780126251555|url-access=registration|edition=2nd|publisher=Academic Press|location=San Diego, CA|isbn=9780126251555}}</ref> Wetland soils are identified by redoxymorphic mottles (often from iron oxide rust) or low [[Munsell color system#Chroma|chroma]] intensity, as determined by the Munsell Color System.

=== Water chemistry ===
Due to the low dissolved oxygen (DO) content, and relatively low nutrient balance of wetland environments, most wetlands are very susceptible to alterations in water chemistry. Key factors that are assessed to determine water quality include:
* Major anion analysis: (HCO<sub>3</sub><sup>−</sup>,Cl<sup>−</sup>,NO<sub>3</sub><sup>−</sup>,SO<sub>4</sub><sup>2-</sup>)
* Major cation analysis (Ca<sup>2+</sup>, Mg<sup>2+</sup>, Na<sup>+</sup>, K<sup>+</sup>)
* [[Chemistry:PH|pH]]
* [[Physics:Conductivity (electrolytic)|Conductivity]]- conductivity increases with more dissolved ions in the water
* [[Biology:Turbidity|Turbidity]]
* [[Biology:Oxygen saturation|Dissolved oxygen]]
* Temperature
* [[Earth:Total dissolved solids|Total dissolved solids]]
* Gas emissions ([[Chemistry:Carbon dioxide|carbon dioxide]] and [[Chemistry:Methane|methane]]; CO<sub>2</sub> and CH<sub>4</sub>)

These chemical factors can be used to quantify wetland disturbances, and often provide information as to whether a wetland is fed by precipitation, surface water or groundwater, due to the different ion characteristics of the different water sources.<ref>{{Citation|last=Arthington|first=Angela H.|title=Environmental Flows|date=2012-10-15|pages=243–258|chapter=Wetlands, Threats, and Water Requirements|publisher=University of California Press|doi=10.1525/california/9780520273696.003.0017|isbn=9780520273696}}</ref> Wetlands are adept at impacting the water chemistry of streams or water bodies that interact with them, and can process ions that result from water pollution such as acid mine drainage or [[Earth:Urban runoff|urban runoff]].,<ref>{{Cite journal|last1=Kelman Wieder|first1=R.|last2=Lang|first2=GeraldE.|date=November 1984|title=Influence of wetlands and coal mining on stream water chemistry|journal=Water, Air, and Soil Pollution|volume=23|issue=4|pages=381|bibcode=1984WASP...23..381K|doi=10.1007/bf00284734|issn=0049-6979|s2cid=96209351}}</ref><ref>{{Cite journal|last1=Jones|first1=C Nathan|last2=McLaughlin|first2=Daniel L|last3=Henson|first3=Kevin|last4=Haas|first4=Carola A|last5=Kaplan|first5=David A|date=2018-01-10|title=From salamanders to greenhouse gases: does upland management affect wetland functions?|journal=Frontiers in Ecology and the Environment|volume=16|issue=1|pages=14–19|doi=10.1002/fee.1744|bibcode=2018FrEE...16...14J |issn=1540-9295|s2cid=90980246}}</ref>

===Biota===
The biota of a wetland system includes its plants ([[Earth:Flora|flora]]) and animals ([[Earth:Fauna|fauna]]) and [[Biology:Microorganism|microbes]] (bacteria, fungi). The most important factor affecting the biota is the hydroperiod, or the duration of flooding.<ref name="Keddy2010" /> Other important factors include fertility and salinity of the water or soils. The chemistry of water flowing into wetlands depends on the source of water, the geological material that it flows through<ref>{{cite journal|last=Bedford|first=B. L.|date=1996|title=The need to define hydrologic equivalence at the landscape scale for freshwater wetland mitigation|journal=Ecological Applications|volume=6|issue=1|pages=57–68|doi=10.2307/2269552|jstor=2269552|bibcode=1996EcoAp...6...57B }}</ref> and the nutrients discharged from organic matter in the soils and plants at higher elevations.<ref>{{cite journal|last1=Nelson|first1=M. L.|last2=Rhoades|first2=C. C.|last3=Dwire|first3=K. A.|date=2011|title=Influences of Bedrock Geology on Water Chemistry of Slope Wetlands and Headwaters Streams in the Southern Rocky Mountains|journal=Wetlands|volume=31|issue=2|pages=251–261|doi=10.1007/s13157-011-0157-8|bibcode=2011Wetl...31..251N |s2cid=14521026}}</ref> Biota may vary within a wetland seasonally or in response to flood regimes.
[[File:Temperate wetlands in Pennsylvania.jpg|thumb|Humid wetland in Pennsylvania before a rain.]]

====Flora====
[[File:Nelumbo nucifera LOTUS bud.jpg|thumb|upright|Bud of water lotus ''([[Biology:Nelumbo nucifera|Nelumbo nucifera]])'', an aquatic plant.]]

There are four main groups of hydrophytes that are found in wetland systems throughout the world.<ref>{{cite web|title=Blacktown Council wetlands |access-date=2011-09-25 |url=http://www.blacktown.nsw.gov.au/environment/educational-resources/wetlands/animals-plants-and-algae-in-wetlands.cfm |archive-url=https://web.archive.org/web/20110410125002/http://www.blacktown.nsw.gov.au/environment/educational-resources/wetlands/animals-plants-and-algae-in-wetlands.cfm |archive-date=2011-04-10}}</ref>

Submerged wetland vegetation can grow in saline and fresh-water conditions. Some species have underwater flowers, while others have long stems to allow the flowers to reach the surface.<ref>{{cite book|last1=Hutchinson|first1=G. E.|date=1975|title=A Treatise on Limnology. Vol. 3: Limnological Botany|location=New York, NY|publisher=John Wiley}}</ref> Submerged species provide a food source for native fauna, habitat for invertebrates, and also possess filtration capabilities. Examples include seagrasses and [[Biology:Vallisneria|eelgrass]].

Floating water plants or floating vegetation are usually small, like those in the [[Biology:Lemnoideae|Lemnoideae]] subfamily (duckweeds).
Emergent vegetation like the cattails (''[[Biology:Typha|Typha]]'' spp.), sedges (''[[Biology:Carex|Carex]]'' spp.) and arrow arum (''[[Biology:Peltandra virginica|Peltandra virginica]]'') rise above the surface of the water.

When trees and shrubs comprise much of the plant cover in saturated soils, those areas in most cases are called [[Earth:Swamp|swamp]]s.<ref name="Keddy2010" /> The upland boundary of swamps is determined partly by water levels. This can be affected by dams<ref>{{cite book|editor-last=Hughes|editor-first=F. M. R.|date=2003|title=The Flooded Forest: Guidance for policy makers and river managers in Europe on the restoration of floodplain forests|series=FLOBAR2, Department of Geography, University of Cambridge, Cambridge, UK}}</ref> Some swamps can be dominated by a single species, such as silver maple swamps around the Great Lakes.<ref>{{cite book|last1=Wilcox|first1=D. A|last2=Thompson|first2=T. A.|last3=Booth|first3=R. K.|last4=Nicholas|first4=J. R.|date=2007|title=Lake-level variability and water availability in the Great Lakes|series=USGS Circular 1311}}</ref> Others, like those of the [[Place:Amazon basin|Amazon basin]], have large numbers of different tree species.<ref>{{cite book|last=Goulding|first=M.|date=1980|title=The Fishes and the Forest: Explorations in Amazonian Natural History|location=Berkeley, CA|publisher=University of California Press}}</ref> Other examples include cypress (''[[Biology:Taxodium|Taxodium]]'') and [[Earth:Mangrove|mangrove]] swamps.

====Fauna====
[[File:Northern Leopard Frog (Lithobates pipiens).jpg|thumb|upright|Many species of frogs live in wetlands, while others visit them each year to lay eggs.]]
[[File:Snapping turtle 3 md.jpg|thumb|Snapping turtles are one of the many kinds of turtles found in wetlands.]]
Many species of [[Biology:Fish|fish]] are highly dependent on wetland ecosystems.<ref>{{Cite journal |last1=Colvin |first1=Susan A. R. |last2=Sullivan |first2=S. Mažeika P. |last3=Shirey |first3=Patrick D. |last4=Colvin |first4=Randall W. |last5=Winemiller |first5=Kirk O. |last6=Hughes |first6=Robert M. |last7=Fausch |first7=Kurt D. |last8=Infante |first8=Dana M. |last9=Olden |first9=Julian D. |last10=Bestgen |first10=Kevin R. |last11=Danehy |first11=Robert J. |last12=Eby |first12=Lisa |date=2019 |title=Headwater Streams and Wetlands are Critical for Sustaining Fish, Fisheries, and Ecosystem Services |url=https://onlinelibrary.wiley.com/doi/10.1002/fsh.10229 |journal=Fisheries |language=en |volume=44 |issue=2 |pages=73–91 |doi=10.1002/fsh.10229|bibcode=2019Fish...44...73C |s2cid=92052162 }}</ref><ref>{{Cite journal |last1=Sievers |first1=Michael |last2=Brown |first2=Christopher J. |last3=Tulloch |first3=Vivitskaia J. D. |last4=Pearson |first4=Ryan M. |last5=Haig |first5=Jodie A. |last6=Turschwell |first6=Mischa P. |last7=Connolly |first7=Rod M. |date=2019-09-01 |title=The Role of Vegetated Coastal Wetlands for Marine Megafauna Conservation |url=https://www.cell.com/trends/ecology-evolution/abstract/S0169-5347(19)30109-0 |journal=Trends in Ecology & Evolution |language=English |volume=34 |issue=9 |pages=807–817 |doi=10.1016/j.tree.2019.04.004 |issn=0169-5347 |pmid=31126633|hdl=10072/391960 |s2cid=164219103 |hdl-access=free }}</ref> Seventy-five percent of the United States' commercial fish and shellfish stocks depend solely on [[Earth:Estuary|estuaries]] to survive.<ref name="ramsar_a">{{cite web | title=Ramsar Convention Ecosystem Services Benefit Factsheets| access-date = 2011-09-25 | url = http://www.ramsar.org/cda/en/ramsar-pubs-info-ecosystem-services/main/ramsar/1-30-103%5E24258_4000_0__}}</ref> Tropical fish species need mangroves for critical hatchery and nursery grounds and the coral reef system for food.

[[Biology:Amphibian|Amphibian]]s such as [[Biology:Frog|frog]]s and [[Biology:Salamander|salamander]]s need both terrestrial and aquatic habitats in which to reproduce and feed. Because amphibians often inhabit depressional wetlands like prairie potholes and Carolina bays, the connectivity among these isolated wetlands is an important control of regional populations.<ref>{{Cite journal |last1=Zamberletti |first1=Patrizia |last2=Zaffaroni |first2=Marta |last3=Accatino |first3=Francesco |last4=Creed |first4=Irena F. |last5=De Michele |first5=Carlo |date=2018-09-24 |title=Connectivity among wetlands matters for vulnerable amphibian populations in wetlandscapes |url=https://www.sciencedirect.com/science/article/pii/S0304380018301686 |journal=Ecological Modelling |language=en |volume=384 |pages=119–127 |doi=10.1016/j.ecolmodel.2018.05.008 |s2cid=90384249 |issn=0304-3800}}</ref> While tadpoles feed on algae, adult frogs forage on insects. Frogs are sometimes used as an indicator of [[Biology:Ecosystem health|ecosystem health]] because their thin skin permits absorption of nutrients and toxins from the surrounding environment resulting in increased extinction rates in unfavorable and polluted environmental conditions.<ref>{{cite web|url=http://www.savethefrogs.com/why-frogs/ |title=Frogs {{!}} Bioindicators |website=Savethefrogs.com |date=2011 |access-date=2014-01-21}}</ref>

[[Biology:Reptile|Reptile]]s such as [[Biology:Snake|snake]]s, [[Biology:Lizard|lizard]]s, [[Biology:Turtle|turtle]]s, [[Biology:Alligator|alligator]]s and [[Biology:Crocodile|crocodile]]s are common in wetlands of some regions. In freshwater wetlands of the Southeastern US, alligators are common and a freshwater species of crocodile occurs in South Florida. The Florida Everglades is the only place in the world where both crocodiles and alligators coexist.<ref>{{cite journal |author=Mazzotti, F.J. |author2=Best, G.R. |author3=Brandt, L.A. |author4=Cherkiss, M.S. |author5=Jeffery, B.M. |author6=Rice, K.G. |year=2009 |title=Alligators and crocodiles as indicators for restoration of Everglades ecosystems |journal=Ecological Indicators  |volume=9 |issue=6 |page=S137−S149|doi=10.1016/j.ecolind.2008.06.008 }}</ref> The [[Biology:Saltwater crocodile|saltwater crocodile]] inhabits estuaries and mangroves and can be seen along the Eastern coastline of Australia.<ref>Messel, H. 1981. Surveys of tidal river systems in the Northern Territory of Australia and their crocodile populations (Vol. 1). Pergamon Press.</ref> Snapping turtles are one of the many kinds of turtles found in wetlands.<ref>{{Cite journal |last1=Piczak |first1=Morgan L. |last2=Chow-Fraser |first2=Patricia |date=2019-06-01 |title=Assessment of critical habitat for common snapping turtles (Chelydra serpentina) in an urbanized coastal wetland |journal=Urban Ecosystems |language=en |volume=22 |issue=3 |pages=525–537 |doi=10.1007/s11252-019-00841-1 |bibcode=2019UrbEc..22..525P |s2cid=78091420 |issn=1573-1642}}</ref>

[[Biology:Bird|Bird]]s, particularly [[Biology:Waterfowl|waterfowl]] and [[Biology:Wader|wading birds]], use wetlands extensively.<ref>{{Cite book |title=Wetland birds: habitat resources and conservation implications |last=Milton |first=W. |date=1999 |publisher=Cambridge University Press |isbn=978-0511011368 |location=Cambridge|oclc=50984660}}</ref>

[[Biology:Mammal|Mammal]]s of wetlands<ref>{{Cite book |url=http://link.springer.com/10.1007/978-3-319-24978-0 |title=Invertebrates in Freshwater Wetlands |date=2016 |publisher=Springer International Publishing |isbn=978-3-319-24976-6 |editor-last=Batzer |editor-first=Darold |location=Cham |language=en |doi=10.1007/978-3-319-24978-0 |s2cid=29672842 |editor-last2=Boix |editor-first2=Dani}}</ref> include numerous small and medium-sized species such as [[Biology:Vole|vole]]s, [[Biology:Bat|bat]]s,<ref>{{Cite journal |last1=Mas |first1=Maria |last2=Flaquer |first2=Carles |last3=Rebelo |first3=Hugo |last4=López-Baucells |first4=Adrià |date=2021 |title=Bats and wetlands: synthesising gaps in current knowledge and future opportunities for conservation |url=https://onlinelibrary.wiley.com/doi/10.1111/mam.12243 |journal=Mammal Review |language=en |volume=51 |issue=3 |pages=369–384 |doi=10.1111/mam.12243 |s2cid=233974999 |issn=0305-1838}}</ref> [[Biology:Muskrat|muskrat]]s<ref>{{Cite journal |last1=Bomske |first1=Caleb M. |last2=Ahlers |first2=Adam A. |date=2021 |title=How do muskrats Ondatra zibethicus affect ecosystems? A review of evidence |url=https://onlinelibrary.wiley.com/doi/10.1111/mam.12218 |journal=Mammal Review |language=en |volume=51 |issue=1 |pages=40–50 |doi=10.1111/mam.12218 |s2cid=224916636 |issn=0305-1838}}</ref> and [[Biology:Platypus|platypus]] in addition to large herbivorous and [[Biology:Apex predator|apex predator]] species such as the [[Biology:Beaver|beaver]],<ref>{{Cite journal |last1=Rosell |first1=Frank |last2=Bozser |first2=Orsolya |last3=Collen |first3=Peter |last4=Parker |first4=Howard |date=2005 |title=Ecological impact of beavers Castor fiber and Castor canadensis and their ability to modify ecosystems |url=https://onlinelibrary.wiley.com/doi/10.1111/j.1365-2907.2005.00067.x |journal=Mammal Review |language=en |volume=35 |issue=3–4 |pages=248–276 |doi=10.1111/j.1365-2907.2005.00067.x |hdl=11250/2438080 |issn=0305-1838|hdl-access=free }}</ref> [[Biology:Coypu|coypu]], [[Biology:Swamp rabbit|swamp rabbit]], [[Biology:Florida panther|Florida panther]],<ref>{{Cite journal |last1=Kerk |first1=Madelon |last2=Onorato |first2=David P. |last3=Hostetler |first3=Jeffrey A. |last4=Bolker |first4=Benjamin M. |last5=Oli |first5=Madan K. |date=2019 |title=Dynamics, Persistence, and Genetic Management of the Endangered Florida Panther Population |journal=Wildlife Monographs |language=en |volume=203 |issue=1 |pages=3–35 |doi=10.1002/wmon.1041 |bibcode=2019WildM.203....3V |s2cid=199641325 |issn=0084-0173|doi-access=free }}</ref> and moose. Wetlands attract many mammals due to abundant seeds, berries, and other vegetation as food for herbivores, as well as abundant populations of invertebrates, small reptiles and amphibians as prey for predators.<ref>{{cite web |url=https://www.environment.nsw.gov.au/topics/water/wetlands/plants-and-animals-in-wetlands/mammals |title=Mammals in Wetlands |work=NSW Environment, Energy and Science |publisher=Department of Planning, Industry and Environment |date=2020-02-20 |access-date=2021-10-11 |quote=Mammals live in wetlands because they are adapted to the wet conditions and there is a plentiful supply of their preferred foods. For example: The swamp rat feeds on grasses, sedges, reeds, seeds and insects. The water rat feeds on a wide range of prey including large insects, crustaceans, mussels and fishes, and even frogs, lizards, small mammals and water birds. The platypus mainly feeds during the night on a wide variety of aquatic invertebrates, free-swimming organisms such as shrimps, swimming beetles, water bugs and tadpoles, and at times worms, freshwater pea mussels and snails. The fishing bat feeds on aquatic insects, small fish and flies close to the surface of rainforest streams or large lakes and reservoirs. }}</ref>

[[Biology:Invertebrate|Invertebrate]]s of wetlands include aquatic insects (such as dragonflies, aquatic bugs and beetles, midges, mosquitoes), crustaceans (such as crabs, crayfish, shrimps, microcrustaceans), mollusks (such as clams, mussels, snails), and worms (such as polychaetes, oligochaetes, leeches), among others. Invertebrates comprise more than half of the known animal species in wetlands, and are considered the primary food web link between plants and higher animals (such as fish and birds).<ref>{{Cite book |title=Invertebrates in freshwater wetlands of North America: ecology and management |date=1999 |publisher=Wiley |last1=Batzer |first1=Darold P. |last2=Rader |first2=Russell Ben. |last3=Wissinger |first3=Scott A. |isbn= 978-0471292586 |location=New York |oclc= 39747651}}</ref> The low oxygen conditions in wetland water and their frequent flooding and drying (daily in tidal wetlands, seasonally in temporary ponds and floodplains) prevent many invertebrates from inhabiting wetlands, and thus the invertebrate fauna of wetlands is often less diverse than some other kinds of habitat (such as streams, coral reefs, and forests). Some wetland invertebrates thrive in habitats that lack predatory fish. Many insects only inhabit wetlands as aquatic immatures (nymphs, larvae) and the flying adults inhabit upland habitats, returning to the wetlands to lay eggs. For instance, a common hoverfly ''[[Biology:Syritta pipiens|Syritta pipiens]]'' inhabits wetlands as larvae (maggots), living in wet, rotting organic matter; these insects then visit terrestrial flowers as adult flies.

====Algae====
[[Biology:Algae|Algae]] are diverse plant-like organisms that can vary in size, color, and shape. Algae occur naturally in habitats such as inland lakes, inter-tidal zones, and damp soil and provide a food source for many animals, including some invertebrates, fish, turtles, and frogs. There are several groups of algae:
* [[Earth:Plankton|Phytoplankton]] are microscopic, free-floating algae. These algae are so tiny that on average, 50 of these lined up end-to-end would only measure one millimeter. Phytoplankton are the basis of the food web in many water bodies being responsible for much of the [[Earth:Primary production|primary production]] using photosynthesis to fix carbon. Filamentous algae are long strands of algal cells that can form floating mats. [[Biology:Periphyton|Periphyton]] (or epiphyton) are algae that grow as surface biofilms on plants, wood, and other substrates.<ref>{{Cite journal |last1=Wu |first1=Yonghong |last2=Liu |first2=Junzhuo |last3=Rene |first3=Eldon R. |date=2018-01-01 |title=Periphytic biofilms: A promising nutrient utilization regulator in wetlands |url=https://www.sciencedirect.com/science/article/pii/S0960852417311975 |journal=Bioresource Technology |series=1st International Conference on Ecotechnologies for Controlling Non-point Source Pollution and Protecting Aquatic Ecosystem |language=en |volume=248 |issue=Pt B |pages=44–48 |doi=10.1016/j.biortech.2017.07.081 |pmid=28756125 |bibcode=2018BiTec.248...44W |issn=0960-8524}}</ref>
* [[Biology:Chara (alga)|''Chara'']] and ''[[Biology:Nitella|Nitella]]'' algae are upright algae that look like a submerged plants with roots.<ref>{{cite web|url=http://www.blacktown.nsw.gov.au/environment/educational-resources/wetlands/animals-plants-and-algae-in-wetlands.cfm |title=Taken from Blacktown Council Wetland Inventory |publisher=Blacktown Council |access-date=2012-05-23 |archive-url=https://web.archive.org/web/20120122111725/http://www.blacktown.nsw.gov.au/environment/educational-resources/wetlands/animals-plants-and-algae-in-wetlands.cfm |archive-date=2012-01-22}}</ref>

== Disturbances and human impacts ==
Wetlands, the functions and services they provide as well as their flora and fauna, can be affected by several types of disturbances.<ref>{{Cite journal|last1=Swindles|first1=Graeme T.|last2=Morris|first2=Paul J.|last3=Mullan|first3=Donal J.|last4=Payne|first4=Richard J.|last5=Roland|first5=Thomas P.|last6=Amesbury|first6=Matthew J.|last7=Lamentowicz|first7=Mariusz|last8=Turner|first8=T. Edward|last9=Gallego-Sala|first9=Angela|last10=Sim|first10=Thomas|last11=Barr|first11=Iestyn D.|date=2019-10-21|title=Widespread drying of European peatlands in recent centuries|url=https://www.nature.com/articles/s41561-019-0462-z|journal=Nature Geoscience|language=en|volume=12|issue=11|pages=922–928|bibcode=2019NatGe..12..922S|doi=10.1038/s41561-019-0462-z|issn=1752-0908|s2cid=202908362|hdl=10871/39305|hdl-access=free}} [http://eprints.whiterose.ac.uk/151050/ Alt URL] {{Webarchive|url=https://web.archive.org/web/20200727010653/http://eprints.whiterose.ac.uk/151050/ |date=2020-07-27 }}</ref> The disturbances (sometimes termed stressors or alterations) can be human-associated or natural, direct or indirect, reversible or not, and isolated or cumulative. Disturbances exceed the levels or patterns normally found within wetlands of a particular class in a particular region. Predominant disturbances of wetlands include:<ref>{{Cite web|author=Office of Research & Development|title=Impacts on quality of inland wetlands of the United States: A survey of indicators, techniques, and applications of community-level biomonitoring data|url=https://cfpub.epa.gov/si/si_public_record_Report.cfm?dirEntryID=39147|access-date=2018-07-27|website=cfpub.epa.gov}}</ref><ref>{{Cite book|last1=Adamus|first1=Paul|url=https://www.researchgate.net/publication/323993409|title=Indicators for Monitoring Biological Integrity of Inland Freshwater Wetlands: A Survey of North American Technical Literature (1990–2000)|last2=J. Danielson|first2=Thomas|last3=Gonyaw|first3=Alex|date=2001-03-24|publisher=13214|doi=10.13140/rg.2.2.22371.86566}}</ref>

{{Div col|colwidth=22em}}
* Enrichment/[[Earth:Eutrophication|eutrophication]]
* Organic loading and reduced dissolved oxygen
* Contaminant [[Medicine:Toxicity|toxicity]]
* [[Earth:Freshwater acidification|Acidification]]
* [[Earth:Salinity|Salinization]]
* [[Sedimentation]]
* Altered solar input ([[Biology:Turbidity|turbidity]]/shade)
* Vegetation removal
* Thermal alteration
* Drying/[[Earth:Aridification|aridification]]
* Inundation/flooding
* [[Biology:Habitat fragmentation|Habitat fragmentation]]
* Other human impacts
{{Div col end}}

Disturbances can be further categorized as follows:
* Minor disturbance: Stress that maintains ecosystem integrity.<ref name="clewell2013" />
* Moderate disturbance: Ecosystem integrity is damaged but can recover in time without assistance.<ref name="clewell2013" />
* Impairment or severe disturbance: Human intervention may be needed in order for ecosystem to recover.<ref name="clewell2013" />

Just a few of the many sources of these disturbances include:<ref name="wetlands">{{cite web |title=Wetlands International works to sustain and restore wetlands for people and biodiversity |url=http://www.wetlands.org/ |access-date=2014-01-21 |publisher=Wetlands International}}</ref>
* Drainage
* Development
* Over-grazing
* Mining
* Unsustainable water use
* [[Earth:Nutrient pollution|Nutrient pollution]] (anthropogenic nitrogen inputs to aquatic systems have drastically effected the dissolved nitrogen content of wetlands, introducing higher nutrient availability which leads to [[Earth:Eutrophication|eutrophication]].<ref>{{Cite journal|last1=Finlay|first1=Jacques C.|last2=Efi Foufoula-Georgiou|last3=Dolph|first3=Christine L.|last4=Hansen|first4=Amy T.|date=February 2018|title=Contribution of wetlands to nitrate removal at the watershed scale|journal=Nature Geoscience|volume=11|issue=2|pages=127–132|bibcode=2018NatGe..11..127H|doi=10.1038/s41561-017-0056-6|issn=1752-0908|s2cid=46656300}}</ref>)
* [[Earth:Water pollution|Water pollution]]
They can be manifested partly as:
* [[Water scarcity]]
* Impacts to [[Biology:Endangered species|endangered species]]
* Disruption of wildlife breeding grounds
* Imbalance in sediment load and nutrient filtration
Biodiversity loss occurs in wetland systems through land use changes, habitat destruction, pollution, exploitation of resources, and invasive species. Vulnerable, threatened, and [[Biology:Endangered species|endangered species]] include 17% of waterfowl, 38% of fresh-water dependent mammals, 33% of freshwater fish, 26% of freshwater amphibians, 72% of freshwater turtles, 86% of marine turtles, 43% of crocodilians and 27% of coral reef-building species. Introduced aquatic plants in different wetland systems can have large impacts. The introduction of water hyacinth, a native plant of South America into Lake Victoria in East Africa as well as duckweed into non-native areas of Queensland, Australia, have overtaken entire wetland systems overwhelming the habitats and reducing the diversity of native plants and animals. This is largely due to the phenomenal growth rates of the plants and their ability to float and grow across the entire surface of the water.

=== Conversion to dry land ===
To increase economic productivity, wetlands are often converted into dry land with dykes and drains and used for agricultural purposes. The construction of dykes, and dams, has negative consequences for individual wetlands and entire watersheds.<ref name="Keddy2010" />{{rp|497}} Their proximity to lakes and rivers means that they are often developed for human settlement.<ref name="Alexander">{{cite book|last=Alexander|first=David E.|title=Encyclopedia of Environmental Science|date=1 May 1999|publisher=[[Company:Springer Science+Business Media|Springer]]|isbn=0-412-74050-8}}</ref> Once settlements are constructed and protected by dykes, the settlements then become vulnerable to land subsidence and ever increasing risk of flooding.<ref name="Keddy2010" />{{rp|497}} The Mississippi River Delta around New Orleans, Louisiana is a well-known example;<ref>{{Cite journal|last1=Keddy|first1=P.A.|last2=Campbell|first2=D.|last3=McFalls|first3=T.|last4=Shaffer|first4=G.P.|last5=Moreau|first5=R.|last6=Dranguet|first6=C.|last7=Heleniak|first7=R.|date=2007|title=The Wetlands of Lakes Pontchartrain and Maurepas: Past, Present and Future|url=http://www.nrcresearchpress.com/doi/10.1139/a06-008|journal=Environmental Reviews|language=en|volume=15|issue=NA|pages=43–77|doi=10.1139/a06-008|issn=1181-8700}}</ref> the Danube Delta in Europe is another.<ref>Gastescu, P. (1993). The Danube Delta: geographical characteristics and ecological recovery. Earth and Environmental Science, 29, 57–67.</ref>

== Ecosystem services ==
{{Further|Biology:Ecosystem service}}

Depending on a wetland's geographic and topographic location,<ref>Adamus, P.R. and L.T. Stockwell. 1983. ''A Method for Wetland Functional Assessment.'' Vol. I. Critical Review and Evaluation Concepts. FHWA-IP-82-23. Federal Highway Admin., Washington, DC.</ref> the functions it performs can support multiple [[Biology:Ecosystem services|ecosystem services]], values, or benefits. United Nations Millennium Ecosystem Assessment and Ramsar Convention described wetlands as a whole to be of [[Biology:Biosphere|biosphere]] significance and societal importance in the following areas:<ref>{{Cite book |title=Ecosystems and human well-being: wetlands and water synthesis: a report of the Millennium Ecosystem Assessment |date=2005 |publisher=World Resources Institute |author=Millennium Ecosystem Assessment |isbn=1-56973-597-2 |location=Washington, DC |oclc=62172810}}</ref>
* Water storage (flood control)
* Groundwater replenishment
* Shoreline stabilization and storm protection
* [[Earth:Water purification|Water purification]]
* [[Earth:Wastewater treatment|Wastewater treatment]] (in [[Earth:Constructed wetland|constructed wetland]]s)
* Reservoirs of [[Biology:Biodiversity|biodiversity]]
* Pollination
* Wetland products
* Cultural values
* Recreation and tourism
* [[Earth:Climate change mitigation|Climate change mitigation]] and [[Earth:Climate change adaptation|adaptation]]

According to the Ramsar Convention:{{citation needed|date=December 2022}}

<blockquote>The economic worth of the ecosystem services provided to society by intact, naturally functioning wetlands is frequently much greater than the perceived benefits of converting them to 'more valuable' intensive land use – particularly as the profits from unsustainable use often go to relatively few individuals or corporations, rather than being shared by society as a whole.</blockquote>

''Unless otherwise cited, ecosystem services information is based on the following series of references.''<ref name="ramsar_a" />

To replace these wetland [[Biology:Ecosystem services|ecosystem services]], enormous amounts of money would need to be spent on [[Earth:Water purification|water purification]] plants, dams, levees, and other hard infrastructure, and many of the services are impossible to replace.

=== Storage reservoirs and flood protection ===

Floodplains and closed-depression wetlands can provide the functions of storage reservoirs and flood protection.

The wetland system of floodplains is formed from major rivers downstream from their headwaters. "The floodplains of major rivers act as natural storage reservoirs, enabling excess water to spread out over a wide area, which reduces its depth and speed. Wetlands close to the headwaters of streams and rivers can slow down rainwater runoff and spring snowmelt so that it doesn't run straight off the land into water courses. This can help prevent sudden, damaging floods downstream."<ref name="ramsar_a" /> Notable river systems that produce wide floodplains include the Nile River, the Niger river inland delta, the Zambezi River flood plain, the Okavango River inland delta, the Kafue River flood plain, the Lake Bangweulu flood plain (Africa), Mississippi River (USA), Amazon River (South America), Yangtze River (China), Danube River (Central Europe) and Murray-Darling River (Australia).

Drainage of [[Earth:Floodplain|floodplain]]s or development activities that narrow floodplain corridors (such as the construction of [[Earth:Levee|levee]]s) reduces the ability of coupled river-floodplain systems to control flood damage. That is because modified and less expansive systems must still manage the same amount of precipitation, causing flood peaks to be higher or deeper and floodwaters to travel faster.

Water management engineering developments in the past century have degraded floodplain wetlands through the construction of artificial embankments such as [[Earth:Levee|dykes]], bunds, levees, weirs, barrages and dams. All concentrate water into a main channel and waters that historically spread slowly over a large, shallow area are concentrated. Loss of wetland floodplains results in more severe and damaging flooding. Catastrophic human impact in the Mississippi River floodplains was seen in death of several hundred individuals during a levee breach in New Orleans caused by Hurricane Katrina. Human-made embankments along the Yangtze River floodplains have caused the main channel of the river to become prone to more frequent and damaging flooding.<ref>{{Cite journal |last1=Li |first1=Luqian |last2=Lu |first2=XiXi |last3=Chen |first3=Zhongyuan |date=2007 |title=River channel change during the last 50 years in the middle Yangtze River, the Jianli reach |url=https://linkinghub.elsevier.com/retrieve/pii/S0169555X06003151 |journal=Geomorphology |language=en |volume=85 |issue=3–4 |pages=185–196 |doi=10.1016/j.geomorph.2006.03.035|bibcode=2007Geomo..85..185L }}</ref> Some of these events include the loss of riparian vegetation, a 30% loss of the vegetation cover throughout the river's basin, a doubling of the percentage of the land affected by soil erosion, and a reduction in reservoir capacity through [[Earth:Siltation|siltation]] build-up in floodplain lakes.<ref name="ramsar_a" />

===Groundwater replenishment===
Groundwater replenishment can be achieved for example by [[Earth:Marsh|marsh]], [[Earth:Swamp|swamp]], and subterranean [[Earth:Karst|karst]] and cave hydrological systems.

The [[Earth:Surface water|surface water]] visibly seen in wetlands only represents a portion of the overall water cycle, which also includes atmospheric water (precipitation) and [[Earth:Groundwater|groundwater]]. Many wetlands are directly linked to groundwater and they can be a crucial regulator of both the quantity and [[Earth:Water quality|quality of water]] found below the ground. Wetlands that have [[Earth:Permeability (earth sciences)|permeable]] substrates like [[Earth:Limestone|limestone]] or occur in areas with highly variable and fluctuating water tables have especially important roles in groundwater replenishment or water recharge.<ref>{{Cite journal |last1=van der Kamp |first1=Garth |last2=Hayashi |first2=Masaki |date=2009-02-01 |title=Groundwater-wetland ecosystem interaction in the semiarid glaciated plains of North America |journal=Hydrogeology Journal |language=en |volume=17 |issue=1 |pages=203–214 |doi=10.1007/s10040-008-0367-1 |bibcode=2009HydJ...17..203V |s2cid=129332187 |issn=1435-0157}}</ref> Substrates that are porous allow water to filter down through the soil and underlying rock into aquifers which are the source of much of the world's drinking water. Wetlands can also act as recharge areas when the surrounding water table is low and as a discharge zone when it is high. [[Earth:Karst cave|Karst]] (cave) systems are a unique example of this system and can be a connection of underground rivers influenced by rain and other forms of [[Earth:Precipitation|precipitation]] to the surface.

===Shoreline stabilization and storm protection===
{{Main|Earth:Integrated coastal zone management}}
[[Earth:Mangrove|Mangrove]]s, [[Earth:Coral reef|coral reef]]s, [[Earth:Salt marsh|salt marsh]] can help with shoreline stabilization and storm protection.

Tidal and inter-tidal wetland systems protect and stabilize coastal zones.<ref>{{Cite journal |last1=Costanza |first1=Robert |last2=Anderson |first2=Sharolyn J. |last3=Sutton |first3=Paul |last4=Mulder |first4=Kenneth |last5=Mulder |first5=Obadiah |last6=Kubiszewski |first6=Ida |last7=Wang |first7=Xuantong |last8=Liu |first8=Xin |last9=Pérez-Maqueo |first9=Octavio |last10=Luisa Martinez |first10=M. |last11=Jarvis |first11=Diane |last12=Dee |first12=Greg |date=2021-09-01 |title=The global value of coastal wetlands for storm protection |journal=Global Environmental Change |language=en |volume=70 |pages=102328 |doi=10.1016/j.gloenvcha.2021.102328 |issn=0959-3780|doi-access=free |hdl=1885/296695 |hdl-access=free }}</ref> Coral reefs provide a protective barrier to coastal shoreline. [[Earth:Mangrove|Mangrove]]s stabilize the coastal zone from the interior and will migrate with the shoreline to remain adjacent to the boundary of the water. The main conservation benefit these systems have against storms and [[Physics:Storm surge|storm surge]]s is the ability to reduce the speed and height of waves and floodwaters.

The number of people who live and work near the coast is expected to grow immensely over the next fifty years. From an estimated 200&nbsp;million people that currently live in low-lying coastal regions, the development of urban coastal centers is projected to increase the population by fivefold within 50 years.<ref name="urlUNEP-Home">{{cite web
|url=http://www.unep.org
|title=United Nations Environment Programme (UNEP) – Home page
|access-date=2011-12-11
}}</ref>
The United Kingdom has begun the concept of managed coastal realignment. This management technique provides shoreline protection through restoration of natural wetlands rather than through applied engineering. In East Asia, reclamation of coastal wetlands has resulted in widespread transformation of the coastal zone, and up to 65% of coastal wetlands have been destroyed by coastal development.<ref>{{Citation | first1 = J. | last1 = MacKinnon | first2 = Y. I. | last2 = Verkuil | first3 = N. J. | last3 = Murray | date = 2012 | title = IUCN situation analysis on East and Southeast Asian intertidal habitats, with particular reference to the Yellow Sea (including the Bohai Sea) | series = Occasional Paper of the IUCN Species Survival Commission No. 47 | page = 70 | publisher = IUCN | place = Gland, Switzerland and Cambridge, UK | isbn = 9782831712550 | url = http://www.iucn.org/asiancoastalwetlands/ | archive-url = https://archive.today/20140624015227/http://www.iucn.org/asiancoastalwetlands/ | archive-date = 2014-06-24 }}</ref><ref>{{cite journal | last1 = Murray | first1 = N. J. | last2 = Clemens | first2 = R. S. | last3 = Phinn | first3 = S. R. | last4 = Possingham | first4 = H. P. | last5 = Fuller | first5 = R. A. | date = 2014 |title = Tracking the rapid loss of tidal wetlands in the Yellow Sea| journal = Frontiers in Ecology and the Environment | volume = 12 | issue = 5 | pages = 267–272 | doi = 10.1890/130260 | bibcode = 2014FrEE...12..267M | url = http://espace.library.uq.edu.au/view/UQ:331832/UQ331832_OA.pdf }}</ref> One analysis using the impact of hurricanes versus storm protection provided naturally by wetlands projected the value of this service at US$33,000/hectare/year.<ref>{{cite web|url=http://www.fao.org/figis/servlet/static?dom=root&xml=index.xml|title=FAO|archive-url=https://web.archive.org/web/20070909042747/http://www.fao.org/figis/servlet/static?dom=root&xml=index.xml|archive-date=2007-09-09|access-date=2011-09-25}}</ref>

===Water purification===
[[Earth:Water purification|Water purification]] can be provided by floodplains, closed-depression wetlands, [[Earth:Mudflat|mudflat]], [[Earth:Freshwater marsh|freshwater marsh]], [[Earth:Salt marsh|salt marsh]], mangroves.

'''Nutrient retention:''' Wetlands cycle both sediments and nutrients, sometimes serving as buffers between terrestrial and aquatic ecosystems. A natural function of wetland vegetation is the up-take, storage, and (for nitrate) the removal of nutrients found in [[Earth:Surface runoff|runoff]] water from the surrounding landscapes.<ref>{{cite web|url=http://www.wild.org/blog/letting-nature-do-the-job|title=Letting Nature Do the Job|date=2008-08-01|website=Wild.org|archive-url=https://archive.today/20130113192135/http://www.wild.org/blog/letting-nature-do-the-job|archive-date=2013-01-13|access-date=2012-05-23}}</ref> In many wetlands, microbial processes convert soluble nutrients to a gaseous form, such as denitrification of nitrate, which then moves the nitrate to the atmosphere mostly as harmless nitrogen gas.

'''Sediment and heavy metal traps:''' Precipitation and surface runoff induces soil erosion, transporting sediment in suspension into and through waterways. These sediments move towards larger and more sizable waterways through a natural process that moves water towards oceans. All types of sediments whether composed of clay, silt, sand or gravel and rock can be carried into wetland systems through erosion. Wetland vegetation acts as a physical barrier to slow water flow and then trap sediment for both short or long periods of time. Suspended sediment can contain heavy metals that are also retained when wetlands trap the sediment. In some cases, certain metals are taken up through wetland plant stems, roots, and leaves. For example, many floating plant species such as water hyacinth (''Eichhornia crassipes''), duckweed (''Lemna'') and water fern (''Azolla'') store [[Chemistry:Iron|iron]] and [[Chemistry:Copper|copper]] found in [[Earth:Wastewater|wastewater]]; these plants also extract [[Biology:Pathogen|pathogen]]s. Fast-growing plants rooted in the soils of wetlands such as cattail (''Typha'') and [[Biology:Phragmites|reed]] (''Phragmites'') also contribute to heavy metal up-take. Animals such as the [[Biology:Oyster|oyster]] can filter more than {{convert|200|L|gal}} of water per day while grazing for food, removing nutrients, suspended sediments, and chemical contaminants in the process. On the other hand, some types of wetlands facilitate the mobilization and [[Chemistry:Bioavailability|bioavailability]] of mercury (another heavy metal), which in its [[Chemistry:Methylmercury|methyl mercury]] form increases the risk of bioaccumulation in fish important to animal food webs and harvested for human consumption.

'''Capacity:''' The ability of wetland systems to store or remove nutrients and trap sediment and associated metals is highly efficient and effective but each system has a threshold. An overabundance of nutrient input from fertilizer run-off, sewage effluent, or non-point pollution will cause [[Earth:Eutrophication|eutrophication]]. Upstream erosion from deforestation can overwhelm wetlands making them shrink in size and cause dramatic [[Biology:Biodiversity loss|biodiversity loss]] through excessive sedimentation load. Retaining high levels of metals in sediments is problematic if the sediments become resuspended or oxygen and pH levels change at a future time. The capacity of wetland vegetation to store heavy metals depends on the particular metal, oxygen and pH status of wetland sediments and overlying water, water flow rate (detention time), wetland size, season, climate, type of plant, and other factors.

The capacity of a wetland to store sediment, nutrients, and metals can be diminished if sediments are compacted such as by vehicles or heavy equipment, or are regularly tilled. Unnatural changes in water levels and water sources also can affect the water purification function. If water purification functions are impaired, excessive loads of nutrients enter waterways and cause [[Earth:Eutrophication|eutrophication]]. This is of particular concern in temperate coastal systems.<ref>{{cite journal|last1=Valiela|first1=I.|last2=Collins|first2=G.|last3=Kremer|first3=J.|last4=Lajtha|first4=K.|last5=Geist|first5=M.|last6=Seely|first6=B.|last7=Brawley|first7=J.|last8=Sham|first8=C. H.|date=1997|title=Nitrogen loading from coastal watersheds to receiving estuaries: New method and application|journal=Ecological Applications|volume=7|issue=2|pages=358–380|doi=10.2307/2269505|jstor=2269505|citeseerx=10.1.1.461.3668}}</ref><ref>{{cite journal|last=Nixon|first=S. W.|date=1986|title=Nutrients and the productivity of estuarine and coastal marine ecosystems|journal=Journal of the Limnological Society of South Africa|volume=12|issue=1–2|pages=43–71|doi=10.1080/03779688.1986.9639398}}</ref> The main sources of coastal eutrophication are industrially made nitrogen, which is used as [[Chemistry:Fertilizer|fertilizer]] in agricultural practices, as well as septic waste runoff.<ref>{{cite journal|last=Galloway|first=J.|date=2003|title=The Nitrogen Cascade|journal=BioScience|volume=53|issue=4|pages=341–356|doi=10.1641/0006-3568(2003)053[0341:tnc]2.0.co;2|s2cid=3356400 |doi-access=free}}</ref> Nitrogen is the limiting nutrient for photosynthetic processes in saline systems, however in excess, it can lead to an overproduction of organic matter that then leads to hypoxic and anoxic zones within the water column.<ref>{{cite journal|last1=Diaz|first1=R. J.|last2=Rosenberg|first2=R.|s2cid=32818786|date=2008|title=Spreading Dead Zones and Consequences for Marine Ecosystems|journal=Science|volume=321|issue=5891|pages=926–929|bibcode=2008Sci...321..926D|doi=10.1126/science.1156401|pmid=18703733}}</ref> Without oxygen, other organisms cannot survive, including economically important finfish and shellfish species.

===Wastewater treatment===
Constructed wetlands are built for wastewater treatment.{{Excerpt|Constructed wetland|paragraphs=1,2,3}}An example of how a natural wetland is used to provide some degree of [[Earth:Sewage treatment|sewage treatment]] is the East Kolkata Wetlands in Kolkata, India. The wetlands cover {{convert|125|km2|sqmi}}, and are used to treat Kolkata's sewage. The nutrients contained in the wastewater sustain fish farms and agriculture.

===Reservoirs of biodiversity===
Wetland systems' rich [[Biology:Biodiversity|biodiversity]] has become a focal point catalysed by the Ramsar Convention and World Wildlife Fund.<ref>{{Cite web |title=What is a wetland? And eight other wetland facts |url=https://www.worldwildlife.org/stories/what-is-a-wetland-and-8-other-wetland-facts |access-date=2022-11-18 |website=World Wildlife Fund |language=en}}</ref> The impact of maintaining biodiversity is seen at the local level through job creation, sustainability, and community productivity. A good example is the Lower Mekong basin which runs through Cambodia, Laos, and Vietnam, supporting over 55&nbsp;million people.

'''Biodiverse river basins:''' The Amazon holds more than 3,000 species of freshwater fish species within the boundaries of its basin.<ref>{{Cite web |title=Amazon fish |url=https://wwf.panda.org/discover/knowledge_hub/where_we_work/amazon/about_the_amazon/wildlife_amazon/fish.cfm |access-date=2022-11-18 |website=wwf.panda.org |language=en}}</ref> Fishes consuming fallen fruit, e.g., the large-bodied characid, ''Colossoma macropomum'', enter the Amazonian floodplains during annual floods egesting viable seeds thus acting as an important agent of dispersal.<ref>{{Cite journal |last1=Anderson |first1=Jill T. |last2=Nuttle |first2=Tim |last3=Saldaña Rojas |first3=Joe S. |last4=Pendergast |first4=Thomas H. |last5=Flecker |first5=Alexander S. |date=2011-11-22 |title=Extremely long-distance seed dispersal by an overfished Amazonian frugivore |journal=Proceedings of the Royal Society B: Biological Sciences |volume=278 |issue=1723 |pages=3329–3335 |doi=10.1098/rspb.2011.0155 |pmc=3177626 |pmid=21429923}}</ref> A key species which is overfished,<ref>{{Cite journal |last1=Prestes |first1=Luiza |last2=Barthem |first2=Ronaldo |last3=Mello-Filho |first3=Adauto |last4=Anderson |first4=Elizabeth |last5=Correa |first5=Sandra B. |last6=Couto |first6=Thiago Belisario D'Araujo |last7=Venticinque |first7=Eduardo |last8=Forsberg |first8=Bruce |last9=Cañas |first9=Carlos |last10=Bentes |first10=Bianca |last11=Goulding |first11=Michael |date=2022-03-02 |editor-last=Aguirre |editor-first=Windsor E. |title=Proactively averting the collapse of Amazon fisheries based on three migratory flagship species |journal=PLOS ONE |language=en |volume=17 |issue=3 |pages=e0264490 |doi=10.1371/journal.pone.0264490 |pmid=35235610 |pmc=8890642 |bibcode=2022PLoSO..1764490P |issn=1932-6203|doi-access=free }}</ref> the Piramutaba catfish, ''[[Biology:Brachyplatystoma vaillantii|Brachyplatystoma vaillantii]]'', migrates more than {{convert|3300|km|mi|abbr=on}} from its nursery grounds near the mouth of the Amazon River to its spawning grounds in Andean tributaries, {{convert|400|m|ft|abbr=on}} above sea level, distributing plant seeds along the route.

'''Productive intertidal zones:''' Intertidal mudflats have a level of productivity similar to that of some wetlands even while possessing a low number of species. The abundant invertebrates found within the mud are a food source for migratory waterfowl.<ref>{{Cite journal |last1=Jing |first1=Zhu |last2=Kai |first2=Jing |last3=Xiaojing |first3=Gan |last4=Zhijun |first4=Ma |date=2007 |title=Food supply in intertidal area for shorebirds during stopover at Chongming Dongtan, China |url=https://linkinghub.elsevier.com/retrieve/pii/S1872203207600456 |journal=Acta Ecologica Sinica |language=en |volume=27 |issue=6 |pages=2149–2159 |doi=10.1016/S1872-2032(07)60045-6}}</ref>

'''Critical life-stage habitat:''' Mudflats, saltmarshes, mangroves, and seagrass beds have high levels of both species richness and productivity, and are home to important nursery areas for many commercial fish stocks.

'''Genetic diversity:''' Populations of many species are confined geographically to only one or a few wetland systems, often due to the long period of time that the wetlands have been physically isolated from other aquatic sources. For example, the number of endemic species in the Selenga River Delta of [[Earth:Lake Baikal|Lake Baikal]] in Russia classifies it as a hotspot for biodiversity and one of the most biodiverse wetlands in the entire world.<ref>{{Cite journal |last1=Lane |first1=Charles R. |last2=Anenkhonov |first2=Oleg |last3=Liu |first3=Hongxing |last4=Autrey |first4=Bradley C. |last5=Chepinoga |first5=Victor |date=2015 |title=Classification and inventory of freshwater wetlands and aquatic habitats in the Selenga River Delta of Lake Baikal, Russia, using high-resolution satellite imagery |url=http://link.springer.com/10.1007/s11273-014-9369-z |journal=Wetlands Ecology and Management |language=en |volume=23 |issue=2 |pages=195–214 |doi=10.1007/s11273-014-9369-z |bibcode=2015WetEM..23..195L |s2cid=16980247 |issn=0923-4861}}</ref>

===Wetland products===
[[File:Broadmoor Wildlife Sanctuary marsh.jpg|thumb|Wetland at the Broadmoor Wildlife Sanctuary in Massachusetts, United States, in February]]

Wetland productivity is linked to the climate, wetland type, and nutrient availability. Low water and occasional drying of the wetland bottom during [[Earth:Drought|drought]]s (dry marsh phase) stimulates plant recruitment from a diverse [[Biology:Seed bank|seed bank]] and increases productivity by mobilizing nutrients. In contrast, high water during deluges (lake marsh phase) causes turnover in plant populations and increases open water, but lowers overall productivity. From open water to complete vegetation cover, annual net primary productivity may vary 20-fold.<ref>{{cite journal |last1=Johnson |first1=W. C.|last2=Millett|first2=B. V. |last3=Gilmanov |first3=T. |last4=Voldseth |first4=R. A. |last5=Guntenspergen |first5=G. R. |name-list-style=amp |last6=Naugle|first6=D. E. |date=2005 |title=Vulnerability of Northern Prairie Wetlands to Climate Change|journal=Bio Science|volume=10|pages=863–872}}</ref> The grasses of fertile floodplains such as the [[Place:Nile Delta|Nile]] can be highly productive, especially plants such as ''[[Biology:Arundo donax|Arundo donax]]'' (giant reed), ''[[Biology:Cyperus papyrus|Cyperus papyrus]]'' (papyrus), ''[[Biology:Phragmites|Phragmites]]'' (reed) and ''[[Biology:Typha|Typha]]'' (cattail).{{citation needed|date=November 2022}}

Wetlands naturally produce an array of vegetation and other ecological products that can be harvested for personal and commercial use.<ref>{{Cite book |title=Waterlogged wealth: why waste the world's wet places? |last=Maltby |first=E. |date=1986 |publisher=International Institute for Environment and Development |others=Earthscan |isbn=978-0905347639 |location=London |url-access=registration |url=https://archive.org/details/waterloggedwealt0000malt}}</ref> Many fishes have all or part of their life-cycle occurring within a wetland system. Fresh and saltwater fish are the main source of protein for about one billion people<ref>{{Cite journal |last1=Tidwell |first1=James H |last2=Allan |first2=Geoff L |date=2001 |title=Fish as food: aquaculture's contribution: Ecological and economic impacts and contributions of fish farming and capture fisheries  |journal=EMBO Reports |language=en |volume=2 |issue=11 |pages=958–963 |doi=10.1093/embo-reports/kve236 |issn=1469-221X |pmc=1084135 |pmid=11713181}}</ref> and comprise 15% of an additional 3.5 billion people's protein intake.<ref>{{Cite journal |last1=Béné |first1=Christophe |last2=Barange |first2=Manuel |last3=Subasinghe |first3=Rohana |last4=Pinstrup-Andersen |first4=Per |last5=Merino |first5=Gorka |last6=Hemre |first6=Gro-Ingunn |last7=Williams |first7=Meryl |date=2015-04-01 |title=Feeding 9 billion by 2050 – Putting fish back on the menu |journal=Food Security |language=en |volume=7 |issue=2 |pages=261–274 |doi=10.1007/s12571-015-0427-z |s2cid=18671617 |issn=1876-4525|doi-access=free }}</ref> Another food staple found in wetland systems is rice, a popular grain that is consumed at the rate of one fifth of the total global calorie count. In Bangladesh, Cambodia and Vietnam, where rice paddies are predominant on the landscape, rice consumption reach 70%.<ref name="ramsar b">{{cite web|url=http://www.ramsar.org/cda/en/ramsar-documents-info/main/ramsar/1-31-59_4000_0__|title=The Ramsar Information Sheet on Wetlands of International Importance|date=September 18, 2009|access-date=November 19, 2011}}</ref> Some native wetland plants in the Caribbean and Australia are harvested sustainably for medicinal compounds; these include the red mangrove (''[[Biology:Rhizophora mangle|Rhizophora mangle]]'') which possesses antibacterial, wound-healing, anti-ulcer effects, and antioxidant properties.<ref name="ramsar b" />

The nipa palm of Asia (sugar, vinegar, alcohol, and fodder) and honey collection from mangroves contribute to human diets and people's income. Coastal Thailand villages earn the key portion of their income from sugar production while Cuba relocates thousands of beehives each year to track the seasonal flowering of the mangrove ''[[Biology:Avicennia|Avicennia]]''.<ref>{{Cite book |last=Bradbear |first=Nicola |title=Bees and their role in forest livelihoods: a guide to the services provided by bees and the sustainable harvesting, processing and marketing of their products |date=2009 |publisher=Food and Agriculture Organization of the United Nations |others=Food and Agriculture Organization of the United Nations |isbn=978-92-5-106276-0 |location=Rome |oclc=427853623}}</ref> Other mangrove-derived products include fuelwood, salt (produced by evaporating seawater), animal fodder, traditional medicines (e.g. from mangrove bark), fibers for textiles and dyes and tannins.<ref>{{Cite book |last=Hogarth |first=Peter J. |title=The biology of mangroves and seagrasses |date=2015 |isbn=978-0-19-102590-7 |edition=Third |location=Oxford |oclc=907773290}}</ref>

Over-fishing is a major problem for sustainable use of wetlands. Concerns are developing over certain aspects of farm fishing, which uses natural wetlands and waterways to harvest fish for human consumption. Aquaculture is continuing to develop rapidly throughout the Asia-Pacific region especially in China where 90% of the total number of aquaculture farms occur, contributing 80% of global value.<ref name="ramsar b" /> Some aquaculture has eliminated massive areas of wetland through practices such as the shrimp farming industry's destruction of mangroves. Even though the damaging impact of large-scale shrimp farming on the coastal ecosystem in many Asian countries has been widely recognized for quite some time now, it has proved difficult to mitigate since other employment avenues for people are lacking. Also burgeoning demand for shrimp globally has provided a large and ready market.<ref>{{Cite web |title=Shrimp Market Size, Share & Growth Analysis Report, 2030 |url=https://www.grandviewresearch.com/industry-analysis/shrimp-market-report |access-date=2022-11-19 |website=www.grandviewresearch.com |language=en}}</ref>

=== Additional services and uses of wetlands ===
Some types of wetlands can serve as fire breaks that help slow the spread of minor wildfires. Larger wetland systems can influence local precipitation patterns. Some boreal wetland systems in catchment headwaters may help extend the period of flow and maintain water temperature in connected downstream waters.<ref>{{Cite journal |last1=Leibowitz |first1=Scott G. |last2=Wigington |first2=Parker J. |last3=Schofield |first3=Kate A. |last4=Alexander |first4=Laurie C. |last5=Vanderhoof |first5=Melanie K. |last6=Golden |first6=Heather E. |date=2018 |title=Connectivity of Streams and Wetlands to Downstream Waters: An Integrated Systems Framework |journal=JAWRA Journal of the American Water Resources Association |language=en |volume=54 |issue=2 |pages=298–322 |doi=10.1111/1752-1688.12631 |pmc=6071435 |pmid=30078985|bibcode=2018JAWRA..54..298L }}</ref> Pollination services are supported by many wetlands which may provide the only suitable habitat for pollinating insects, birds, and mammals in highly developed areas.<ref>{{Citation |last=McInnes |first=Robert J. |title=Managing Wetlands for Pollination |date=2016 |work=The Wetland Book |pages=1–4 |editor-last=Finlayson |editor-first=C. Max |place=Dordrecht |publisher=Springer Netherlands |language=en |doi=10.1007/978-94-007-6172-8_226-1 |isbn=978-94-007-6172-8 |editor2-last=Everard |editor2-first=Mark |editor3-last=Irvine |editor3-first=Kenneth |editor4-last=McInnes |editor4-first=Robert J.|doi-access=free }}</ref>

==Conservation==

[[File:Hommik Mukri rabas.jpg|thumb|upright=1.25|Fog rising over the Mukri bog near Mukri, Estonia. The bog has an area of {{convert|2147|ha}} and has been protected since 1992.]]
Wetlands have historically subjected to large draining efforts for development (real estate or agriculture), and flooding to create recreational [[Earth:Lake|lake]]s or generate [[Physics:Hydropower|hydropower]]. Some of the world's most important agricultural areas were wetlands that have been converted to farmland.<ref>{{cite book|first=G. P.|last=Van de Ven|date=2004|title=Man-Made Lowlands: History of water management and land reclamation in the Netherlands|location=Utrecht|publisher=Uitgeverij Matrijs}}</ref><ref>{{cite book|last=Wells|first=Samuel A.|date=1830|title=A History of the Drainage of the Great Level of the Fens called Bedford Level 2|url=https://archive.org/details/historydrainage00wellgoog|location=London|publisher=R. Pheney}}</ref><ref>{{cite web|first1=Thomas E.|last1=Dahl|first2=Gregory J.|last2=Allord|title=History of Wetlands in the Conterminous United States|url=https://water.usgs.gov/nwsum/WSP2425/history.html}}</ref><ref>{{cite journal|first=Brian|last=Lander|title=State Management of River Dikes in Early China: New Sources on the Environmental History of the Central Yangzi Region|journal=T'oung Pao|volume=100|issue=4–5|date=2014|pages=325–362|doi=10.1163/15685322-10045p02}}</ref> Since the 1970s, more focus has been put on preserving wetlands for their natural functions. Since 1900 between 65 and 70% of the world's wetlands have been lost.<ref>{{Cite journal |last=Davidson |first=Nick C. |date=2014 |title=How much wetland has the world lost? Long-term and recent trends in global wetland area |url=http://www.publish.csiro.au/?paper=MF14173 |journal=Marine and Freshwater Research |language=en |volume=65 |issue=10 |pages=934 |doi=10.1071/MF14173 |issn=1323-1650}}</ref> In order to maintain wetlands and sustain their functions, alterations and disturbances that are outside the normal range of variation should be minimized.

===Balancing wetland conservation with the needs of people===
Wetlands are vital ecosystems that enhance the livelihoods for the millions of people who live in and around them. The Millennium Development Goals (MDGs) called for different sectors to join forces to secure wetland environments in the context of sustainable development and improving human wellbeing. Studies have shown that it is possible to conserve wetlands while improving the livelihoods of people living among them. Case studies conducted in Malawi and Zambia looked at how [[Earth:Dambo|dambo]]s – wet, grassy valleys or depressions where water seeps to the surface – can be farmed sustainably. Project outcomes included a high yield of crops, development of [[Biology:Sustainable agriculture|sustainable farming]] techniques, and water management strategies that generate enough water for irrigation.<ref>{{cite web |date=2008-12-01 |title=Good practices and lessons learned in integrating ecosystem conservation and poverty reduction objectives in wetlands |url=https://www.ramsar.org/news/linking-wetland-management-and-poverty-reduction |access-date=10 May 2022 |publisher=The Ramsar Convention on Wetlands}}</ref>

===Ramsar Convention===

''The Convention on Wetlands of International Importance, especially as Waterfowl Habitat'', or Ramsar Convention, is an international treaty designed to address global concerns 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. Methods include restricting access to some wetland areas, as well as educating the public to combat the misconception that wetlands are wastelands. The Convention works closely with five International Organisation Partners (IOPs). These are: Birdlife International, the IUCN, the [[Organization:International Water Management Institute|International Water Management Institute]], [[Organization:Wetlands International|Wetlands International]] and the [[Organization:World Wide Fund for Nature|World Wide Fund for Nature]]. The partners provide technical expertise, help conduct or facilitate field studies and provide financial support. The IOPs also participate regularly as observers in all meetings of the Conference of the Parties and the Standing Committee and as full members of the Scientific and Technical Review Panel.

==Restoration==
Restoration and [[Biology:Restoration ecology|restoration ecologists]] intend to return wetlands to their natural trajectory by aiding directly with the natural processes of the ecosystem.<ref name="clewell2013">{{cite book|last1=Clewell|first1=AF|last2=Aronson|first2=J|title=Ecological restoration|date=2013|publisher=Island Press|location=Washington, DC|edition=2nd}}</ref> These direct methods vary with respect to the degree of physical manipulation of the natural environment and each are associated with different levels of restoration.<ref name="clewell2013" /> Restoration is needed after disturbance or [[Earth:Disturbance (ecology)|perturbation]] of a wetland.<ref name="clewell2013" /> Disturbances include [[Social:Exogeny|exogenous]] factors such as flooding or drought.<ref name="clewell2013" /> Other external damage may be anthropogenic disturbance caused by clear-cut harvesting of trees, oil and gas extraction, poorly defined infrastructure installation, over grazing of livestock, ill-considered recreational activities, alteration of wetlands including dredging, draining, and filling, and other negative human impacts.<ref name="clewell2013" /><ref name="mitsch2007" /> Disturbance puts different levels of stress on an environment depending on the type and duration of disturbance.<ref name="clewell2013" /> There is no one way to restore a wetland and the level of restoration required will be based on the level of disturbance although, each method of restoration does require preparation and administration.<ref name="clewell2013" />

===Levels of restoration===
Factors influencing selected approach may include<ref name="clewell2013" /> budget, time scale limitations, project goals, level of disturbance, landscape and ecological constraints, political and administrative agendas and socioeconomic priorities.

==== Prescribed natural or assisted regeneration ====
For this strategy, there is no biophysical manipulation and the ecosystem is left to recover based on the process of [[Earth:Ecological succession|succession]] alone.<ref name="clewell2013" /> The focus is to eliminate and prevent further disturbance from occurring and for this type of restoration requires prior research to understand the probability that the wetland will recover naturally. This is likely to be the first method of approach since it is the least intrusive and least expensive although some biophysical non-intrusive manipulation may be required to enhance the rate of succession to an acceptable level.<ref name="clewell2013" /> Example methods include prescribed burns to small areas, promotion of site specific soil [[Biology:Microbiota|microbiota]] and plant growth using nucleation planting whereby plants radiate from an initial planting site,<ref>{{cite journal|last1=Corbin|first1=JD|last2=Holl|first2=KD|title=Applied nucleation as a forest restoration strategy|journal=Forest Ecology and Management|date=2012|volume=256|pages=37–46|doi=10.1016/j.foreco.2011.10.013}}</ref> and promotion of niche diversity or increasing the range of niches to promote use by a variety of different species.<ref name="clewell2013" /> These methods can make it easier for the natural species to flourish by removing environmental impediments and can speed up the process of succession.

==== Partial reconstruction ====
For this strategy, a mixture of natural regeneration and manipulated environmental control is used. This may require some engineering, and more intensive biophysical manipulations including ripping of [[Earth:Subsoil|subsoil]], [[Chemistry:Agrochemical|agrichemical]] applications of herbicides or insecticides, laying of mulch, mechanical seed dispersal, and tree planting on a large scale.<ref name="clewell2013" /> In these circumstances the wetland is impaired and without human assistance it would not recover within an acceptable period of time as determined by ecologists. Methods of restoration used will have to be determined on a site by site basis as each location will require a different approach based on levels of disturbance and the local ecosystem dynamics.<ref name="clewell2013" />

==== Complete reconstruction ====
{{further|Earth:Constructed wetland}}
This most expensive and intrusive method of reconstruction requires engineering and ground up reconstruction. Because there is a redesign of the entire ecosystem it is important that the natural trajectory of the ecosystem be considered and that the plant species promoted will eventually return the ecosystem towards its natural trajectory.<ref name="clewell2013" />

In many cases constructed wetlands are often designed to treat stormwater/wastewater runoff. They can be used in developments as part of [[Engineering:Water-sensitive urban design|Water-sensitive urban design]] systems and have benefits such as flood mitigation, removing pollutants, carbon sequestration, providing habitat for wildlife and biodiversity in often highly urbanised and fragmented landscapes.<ref>{{cite book |title=Functional assessment of wetlands: towards evaluation of ecosystem services |date=2009 |publisher=Woodhead Publ. [u.a.] |location=Cambridge |isbn=978-1-84569-516-3}}</ref>

====Traditional knowledge====
Traditional ecological knowledge or local ecological knowledge is a detailed knowledge of the interactions between the environment that has been accumulated by generations of indigenous or local peoples who have shared a direct relationship with the environment. This includes expertise on flora, fauna, and natural phenomena, as well as the development of technologies needed for survival such as fishing, agriculture, and forestry.<ref>{{Cite book |title=Traditional Ecological Knowledge: Concepts and Cases |last=Inglis, J. T. |publisher=International Program on Traditional Ecological and International Development Research Centre |date=1993 |place=Ottawa, Canada |isbn=978-0-88936-683-1 |url=https://books.google.com/books?id=J2CNS64AFvsC&pg=PR4}}</ref>
The ideas from traditional ecological knowledge can be applied as a holistic approach to the restoration of wetlands. These ideas focus more on responding to the observations detected from the environment considering that each part of a wetland ecosystem is interconnected. Applying these practices on specific locations of wetlands increase productivity, biodiversity, and improve its resilience. These practices include monitoring wetland resources, planting propagules, and addition of key species in order to create a self-sustaining wetland ecosystem.<ref>{{Cite book |last=Craft |first=Christopher |url=https://books.google.com/books?id=DNhOEAAAQBAJ&dq=Creating+and+Restoring+Wetlands+From+Theory+to+Practice&pg=PP1 |title=Creating and Restoring Wetlands: From Theory to Practice |date=2022-05-12 |publisher=Elsevier |isbn=978-0-12-823982-7 |language=en}}</ref> A community of wetland plant harvesters in the Pátzcuaro wetlands used local ecological knowledge to control invasive species and protect native species present in this wetland.<ref>{{Cite journal |last=Hall |first=S. J. |date=2009 |title=Cultural Disturbances and Local Ecological Knowledge Mediate Cattail (''Typha domingensis'') Invasion in Lake Pátzcuaro, México |journal=Human Ecology |volume=37 |issue=2 |pages=241–249 |doi=10.1007/s10745-009-9228-3|doi-access=free }}</ref>

== Climate change aspects ==

=== Greenhouse gas emissions ===
In Southeast Asia, peat swamp forests and soils are being drained, burnt, mined, and overgrazed, contributing to [[Earth:Climate change|climate change]].<ref name="wetlands"/> As a result of peat drainage, the organic carbon that had built up over thousands of years and is normally under water is suddenly exposed to the air. The peat decomposes and is converted into [[Chemistry:Carbon dioxide|carbon dioxide]] (CO<sub>2</sub>), which is then released into the atmosphere. Peat fires cause the same process to occur rapidly and in addition create enormous clouds of smoke that cross international borders, which now happens almost yearly in Southeast Asia. While peatlands constitute only 3% of the world's land area, their degradation produces 7% of all CO<sub>2</sub> emissions.{{excerpt|Wetland methane emissions}}

===Climate change mitigation===

Studies have favorably identified the potential for coastal wetlands (also called [[Earth:Blue carbon|blue carbon]] ecosystems) to provide some degree of [[Earth:Climate change mitigation|climate change mitigation]] in two ways: by conservation, reducing the greenhouse gas emissions arising from the loss and degradation of such habitats, and by restoration, to increase carbon dioxide drawdown and its long-term storage.<ref name=":6">{{Cite journal |last1=Williamson |first1=Phillip |last2=Gattuso |first2=Jean-Pierre |date=2022 |title=Carbon Removal Using Coastal Blue Carbon Ecosystems Is Uncertain and Unreliable, With Questionable Climatic Cost-Effectiveness |journal=Frontiers in Climate |volume=4 |pages=853666 |doi=10.3389/fclim.2022.853666 |issn=2624-9553|doi-access=free}} [[File:CC-BY icon.svg|50px]]  Text was copied from this source, which is available under a [https://creativecommons.org/licenses/by/4.0/  Creative Commons Attribution 4.0 International License] {{Webarchive|url=https://web.archive.org/web/20171016050101/https://creativecommons.org/licenses/by/4.0/ |date=2017-10-16 }}</ref> However, CO<sub>2</sub> removal using coastal blue carbon restoration has questionable cost-effectiveness when considered only as a climate mitigation action, either for carbon-offsetting or for inclusion in Nationally Determined Contributions.<ref name=":6" />

When wetlands are restored they have mitigation effects through their ability to [[Physics:Carbon sink|sink carbon]], converting a greenhouse gas ([[Chemistry:Carbon dioxide|carbon dioxide]]) to solid plant material through the process of [[Earth:Photosynthesis|photosynthesis]], and also through their ability to store and regulate water.<ref>{{cite book |title=Synthesis of Adaptation Options for Coastal Areas |date=2009 |publisher=US Environmental Protection Agency |series=Climate Ready Estuaries Program, EPA 430-F-08-024 |location=Washington, DC}}</ref><ref>{{Cite web |date=2020-02-06 |title=Coastal Wetland Protection |url=https://drawdown.org/solutions/coastal-wetland-protection |access-date=2020-09-13 |website=Project Drawdown |language=en}}</ref>

Wetlands store approximately 44.6 million tonnes of carbon per year globally (estimate from 2003).<ref name="Chmura, G. L. 2003">{{cite journal |last1=Chmura |first1=G. L. |date=2003 |title=Global carbon sequestration in tidal, saline wetland soils |journal=Global Biogeochemical Cycles |volume=17 |issue=4 |pages=1111 |bibcode=2003GBioC..17.1111C |doi=10.1029/2002GB001917 |doi-access=free |s2cid=36119878}}{{page needed|date=January 2017}}</ref> In [[Earth:Salt marsh|salt marsh]]es and mangrove swamps in particular, the average [[Earth:Carbon sequestration|carbon sequestration]] rate is {{nowrap|210 g CO<sub>2</sub> m<sup>−2</sup> y<sup>−1</sup>}} while peatlands sequester approximately {{nowrap|20–30 g CO<sub>2</sub> m<sup>−2</sup> y<sup>−1</sup>}}.<ref name="Chmura, G. L. 2003" /><ref>{{cite journal |last=Roulet |first=N. T. |date=2000 |title=Peatlands, Carbon Storage, Greenhouse Gases, And The Kyoto Protocol: Prospects And Significance For Canada |journal=Wetlands |volume=20 |issue=4 |pages=605–615 |doi=10.1672/0277-5212(2000)020[0605:pcsgga]2.0.co;2 |s2cid=7490212}}</ref>

Coastal wetlands, such as tropical [[Earth:Mangrove|mangrove]]s and some temperate salt marshes, are known to be sinks for carbon that otherwise contribute to [[Earth:Climate change|climate change]] in its gaseous forms (carbon dioxide and methane).<ref>{{Cite journal |last1=Ouyang |first1=Xiaoguang |last2=Lee |first2=Shing Yip |date=2020-01-16 |title=Improved estimates on global carbon stock and carbon pools in tidal wetlands |journal=Nature Communications |language=en |volume=11 |issue=1 |pages=317 |bibcode=2020NatCo..11..317O |doi=10.1038/s41467-019-14120-2 |issn=2041-1723 |pmc=6965625 |pmid=31949151 |doi-access=free}}</ref> The ability of many tidal wetlands to store carbon and minimize methane flux from tidal sediments has led to sponsorship of [[Earth:Blue carbon|blue carbon]] initiatives that are intended to enhance those processes.<ref>{{cite web |title=More on blue carbon and carbon sequestration |url=http://www.earthtimes.org/climate/blue-carbon/2021/}}</ref><ref>{{Cite journal |last=Wang |first=F. |date=2021 |title=Global blue carbon accumulation in tidal wetlands increases with climate change |journal=National Science Review |volume=8 |issue=9 |pages=nwaa296 |doi=10.1093/nsr/nwaa296 |pmid=34691731|pmc=8433083 }}</ref>

=== Climate change adaptation ===
{{Further|Earth:Climate change adaptation}}

The restoration of coastal blue carbon ecosystems is highly advantageous for [[Earth:Climate change adaptation|climate change adaptation]], coastal protection, food provision and biodiversity conservation.<ref name=":6" />

Since the middle of the 20th century, human-caused [[Earth:Climate change|climate change]] has resulted in observable changes in the global [[Physics:Water cycle|water cycle]].<ref name=":8">Arias, P.A., N. Bellouin, E. Coppola, R.G. Jones, G. Krinner, J. Marotzke, V. Naik, M.D. Palmer, G.-K. Plattner, J. Rogelj, M. Rojas, J. Sillmann, T. Storelvmo, P.W. Thorne, B. Trewin, K. Achuta Rao, B. Adhikary, R.P. Allan, K. Armour, G. Bala, R. Barimalala, S. Berger, J.G. Canadell, C. Cassou, A. Cherchi, W. Collins, W.D. Collins, S.L. Connors, S. Corti, F. Cruz, F.J. Dentener, C. Dereczynski, A. Di Luca, A. Diongue Niang, F.J. Doblas-Reyes, A. Dosio, H. Douville, F. Engelbrecht, V.  Eyring, E. Fischer, P. Forster, B. Fox-Kemper, J.S. Fuglestvedt, J.C. Fyfe, et al., 2021: [https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_TS.pdf Technical Summary] {{Webarchive|url=https://web.archive.org/web/20220721021347/https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_TS.pdf |date=2022-07-21 }}. In [https://www.ipcc.ch/report/ar6/wg1/ Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change] {{Webarchive|url=https://web.archive.org/web/20210809131444/https://www.ipcc.ch/report/ar6/wg1/ |date=2021-08-09 }} [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 33–144. doi:10.1017/9781009157896.002.</ref>{{rp|85}} A warming climate makes extremely wet and very dry occurrences more severe, causing more severe floods and droughts. For this reason, some of the ecosystem services that wetlands provide (e.g. water storage and flood control, groundwater replenishment, shoreline stabilization and storm protection) are important for climate change adaptation measures.<ref name=":52">{{Cite web |title=Fact Sheet: Blue Carbon |url=https://www.american.edu/sis/centers/carbon-removal/fact-sheet-blue-carbon.cfm |url-status=live |archive-url=https://web.archive.org/web/20210428062528/https://www.american.edu/sis/centers/carbon-removal/fact-sheet-blue-carbon.cfm |archive-date=April 28, 2021 |access-date=2021-04-28 |website=American University |language=en}}</ref> In most parts of the world and under all [[Software:Climate change scenario#Emissions scenarios|emission scenarios]], water cycle variability and accompanying extremes are anticipated to rise more quickly than the changes of average values.<ref name=":82">Arias, P.A., N. Bellouin, E. Coppola, R.G. Jones, G. Krinner, J. Marotzke, V. Naik, M.D. Palmer, G.-K. Plattner, J. Rogelj, M. Rojas, J. Sillmann, T. Storelvmo, P.W. Thorne, B. Trewin, K. Achuta Rao, B. Adhikary, R.P. Allan, K. Armour, G. Bala, R. Barimalala, S. Berger, J.G. Canadell, C. Cassou, A. Cherchi, W. Collins, W.D. Collins, S.L. Connors, S. Corti, F. Cruz, F.J. Dentener, C. Dereczynski, A. Di Luca, A. Diongue Niang, F.J. Doblas-Reyes, A. Dosio, H. Douville, F. Engelbrecht, V.  Eyring, E. Fischer, P. Forster, B. Fox-Kemper, J.S. Fuglestvedt, J.C. Fyfe, et al., 2021: [https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_TS.pdf Technical Summary] {{Webarchive|url=https://web.archive.org/web/20220721021347/https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_TS.pdf |date=2022-07-21 }}. In [https://www.ipcc.ch/report/ar6/wg1/ Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change] {{Webarchive|url=https://web.archive.org/web/20210809131444/https://www.ipcc.ch/report/ar6/wg1/ |date=2021-08-09 }} [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 33–144. doi:10.1017/9781009157896.002.</ref>{{rp|85}}

== Valuation ==
The value of a wetland to local communities typically involves first mapping a region's wetlands, then assessing the functions and ecosystem services the wetlands provide individually and cumulatively, and finally evaluating that information to prioritize or rank individual wetlands or wetland types for conservation, management, restoration, or development.<ref>{{Citation |last=Emerton |first=Lucy |title=Economic Valuation of Wetlands: Total Economic Value |date=2016 |work=The Wetland Book |pages=1–6 |editor-last=Finlayson |editor-first=C. Max |place=Dordrecht |publisher=Springer Netherlands |language=en |doi=10.1007/978-94-007-6172-8_301-1 |isbn=978-94-007-6172-8 |editor2-last=Everard |editor2-first=Mark |editor3-last=Irvine |editor3-first=Kenneth |editor4-last=McInnes |editor4-first=Robert J.|doi-access=free }}</ref> Over the longer term, it requires keeping inventories<ref>{{Cite web |title=A new toolkit for National Wetlands Inventories {{!}} Convention on Wetlands |url=https://www.ramsar.org/news/a-new-toolkit-for-national-wetlands-inventories |access-date=2022-11-28 |website=www.ramsar.org}}</ref> of known wetlands and monitoring a representative sample of the wetlands to determine changes due to both natural and human factors.

===Assessment===

Rapid assessment methods are used to score, rank, rate, or categorize various functions, [[Biology:Ecosystem services|ecosystem services]], species, communities, levels of disturbance, and/or ecological health of a wetland or group of wetlands.<ref>{{Cite journal |last1=McInnes |first1=R.J. |last2=Everard |first2=M. |date=2017 |title=Rapid Assessment of Wetland Ecosystem Services (RAWES): An example from Colombo, Sri Lanka |url=https://linkinghub.elsevier.com/retrieve/pii/S221204161630417X |journal=Ecosystem Services |language=en |volume=25 |pages=89–105 |doi=10.1016/j.ecoser.2017.03.024|s2cid=56403914 }}</ref> This is often done to prioritize particular wetlands for conservation (avoidance) or to determine the degree to which loss or alteration of wetland functions should be compensated, such as by restoring degraded wetlands elsewhere or providing additional protections to existing wetlands. Rapid assessment methods are also applied before and after a wetland has been restored or altered, to help monitor or predict the effects of those actions on various wetland functions and the services they provide. Assessments are typically considered to be "rapid" when they require only a single visit to the wetland lasting less than one day, which in some cases may include interpretation of aerial imagery and [[Geographic information system|geographic information system]] (GIS) analyses of existing spatial data, but not detailed post-visit laboratory analyses of water or biological samples.

To achieve consistency among persons doing the assessment, rapid methods present indicator variables as questions or checklists on standardized data forms, and most methods standardize the scoring or rating procedure that is used to combine question responses into estimates of the levels of specified functions relative to the levels estimated in other wetlands ("calibration sites") assessed previously in a region.<ref>{{Cite web |last=Adamus |first=P. |date=2016 |title=Manual for the Wetland Ecosystem Services Protocol (WESP) |url=http://people.oregonstate.edu/~adamusp/WESP/Manual_WESP1.3_13Oct2016_Adamus.pdf |archive-url=https://web.archive.org/web/20180728191340/http://people.oregonstate.edu/~adamusp/WESP/Manual_WESP1.3_13Oct2016_Adamus.pdf |archive-date=2018-07-28 |url-status=live |access-date=July 28, 2018 |website=Oregon State University}}</ref> Rapid assessment methods, partly because they often use dozens of indicators pertaining to conditions surrounding a wetland as well as within the wetland itself, aim to provide estimates of wetland functions and services that are more accurate and repeatable than simply describing a wetland's class type.<ref name="ACADEMIC PRESS" /> A need for wetland assessments to be rapid arises mostly when government agencies set deadlines for decisions affecting a wetland, or when the number of wetlands needing information on their functions or condition is large.

===Inventory===

Although developing a global inventory of wetlands has proven to be a large and difficult undertaking, many efforts at more local scales have been successful.<ref>{{Cite web |title=Home {{!}} Ramsar Sites Information Service |url=https://rsis.ramsar.org/ |access-date=2022-11-28 |website=rsis.ramsar.org}}</ref> Current efforts are based on available data, but both classification and spatial resolution have sometimes proven to be inadequate for regional or site-specific environmental management decision-making. It is difficult to identify small, long, and narrow wetlands within the landscape. Many of today's [[Earth:Remote sensing|remote sensing]] satellites do not have sufficient spatial and spectral resolution to monitor wetland conditions, although multispectral IKONOS<ref>{{Cite journal |last1=Wei |first1=Anhua |last2=Chow-Fraser |first2=Patricia |date=2007 |title=Use of IKONOS Imagery to Map Coastal Wetlands of Georgian Bay |url=http://doi.wiley.com/10.1577/1548-8446(2007)32[167:UOIITM]2.0.CO;2 |journal=Fisheries |language=en |volume=32 |issue=4 |pages=167–173 |doi=10.1577/1548-8446(2007)32[167:UOIITM]2.0.CO;2 |issn=0363-2415}}</ref> and QuickBird<ref>{{Cite journal |last1=Cook |first1=Bruce D. |last2=Bolstad |first2=Paul V. |last3=Næsset |first3=Erik |last4=Anderson |first4=Ryan S. |last5=Garrigues |first5=Sebastian |last6=Morisette |first6=Jeffrey T. |last7=Nickeson |first7=Jaime |last8=Davis |first8=Kenneth J. |date=2009-11-16 |title=Using LiDAR and quickbird data to model plant production and quantify uncertainties associated with wetland detection and land cover generalizations |url=https://linkinghub.elsevier.com/retrieve/pii/S0034425709002119 |journal=Remote Sensing of Environment |language=en |volume=113 |issue=11 |pages=2366–2379 |doi=10.1016/j.rse.2009.06.017|bibcode=2009RSEnv.113.2366C }}</ref> data may offer improved spatial resolutions once it is 4&nbsp;m or higher. Majority of the pixels are just mixtures of several plant species or vegetation types and are difficult to isolate which translates into an inability to classify the vegetation that defines the wetland. The growing availability of 3D vegetation and topography data from LiDAR has partially addressed the limitation of traditional multispectral imagery, as demonstrated in some case studies across the world.<ref name="xu2022">{{cite journal |last1=Xu |first1=Haiqing |last2=Toman |first2=Elizabeth |last3=Zhao |first3=Kaiguang |last4=Baird |first4=John |title=Fusion of Lidar and Aerial Imagery to Map Wetlands and Channels via Deep Convolutional Neural Network |journal=Transportation Research Record |date=2022 |volume=2676 |issue=12 |pages=374–381 |doi=10.1177/03611981221095522 |s2cid=251780248 |url=https://journals.sagepub.com/doi/10.1177/03611981221095522}}</ref>

===Monitoring and mapping===

A wetland needs to be monitored<ref>{{Cite journal |last1=Stephenson |first1=P. J. |last2=Ntiamoa-Baidu |first2=Yaa |last3=Simaika |first3=John P. |date=2020 |title=The Use of Traditional and Modern Tools for Monitoring Wetlands Biodiversity in Africa: Challenges and Opportunities |journal=Frontiers in Environmental Science |volume=8 |doi=10.3389/fenvs.2020.00061 |issn=2296-665X|doi-access=free }}</ref> over time to assess whether it is functioning at an ecologically sustainable level or whether it is becoming degraded.<ref>{{Cite journal |last1=Bhatnagar |first1=Saheba |last2=Gill |first2=Laurence |last3=Regan |first3=Shane |last4=Waldren |first4=Stephen |last5=Ghosh |first5=Bidisha |date=2021-04-01 |title=A nested drone-satellite approach to monitoring the ecological conditions of wetlands |journal=ISPRS Journal of Photogrammetry and Remote Sensing |language=en |volume=174 |pages=151–165 |doi=10.1016/j.isprsjprs.2021.01.012 |bibcode=2021JPRS..174..151B |s2cid=233522024 |issn=0924-2716|doi-access=free }}</ref> Degraded wetlands will suffer a loss in water quality, loss of sensitive species, and aberrant functioning of soil geochemical processes.

Practically, many natural wetlands are difficult to monitor from the ground as they quite often are difficult to access and may require exposure to dangerous plants and animals as well as diseases borne by insects or other invertebrates. Remote sensing such as aerial imagery and satellite imaging<ref>{{Cite journal |last1=Munizaga |first1=Juan |last2=García |first2=Mariano |last3=Ureta |first3=Fernando |last4=Novoa |first4=Vanessa |last5=Rojas |first5=Octavio |last6=Rojas |first6=Carolina |date=2022 |title=Mapping Coastal Wetlands Using Satellite Imagery and Machine Learning in a Highly Urbanized Landscape |journal=Sustainability |language=en |volume=14 |issue=9 |pages=5700 |doi=10.3390/su14095700 |issn=2071-1050|doi-access=free }}</ref> provides effective tools to map and monitor wetlands across large geographic regions and over time. Many remote sensing methods can be used to map wetlands. The integration of multi-sourced data such as LiDAR and aerial photos proves more effective at mapping wetlands than the use of aerial photos alone,<ref name="xu2022" /> especially with the aid of modern machine learning methods (e.g., deep learning). Overall, using digital data provides a standardized data-collection procedure and an opportunity for data integration within a [[Geographic information system|geographic information system]].

== Legislation ==

=== International efforts ===
{{excerpt|Ramsar Convention}}

=== National efforts ===

====United States====
Each country and region tends to have its own definition of wetlands for legal purposes. In the United States, wetlands are defined as "those areas that are inundated or saturated by surface or groundwater at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions. Wetlands generally include swamps, marshes, bogs and similar areas".<ref>{{cite web|date=March 2015|title=EPA Regulations listed at 40 CFR 230.3(t)|url=http://water.epa.gov/lawsregs/guidance/wetlands/definitions.cfm|access-date=2014-02-18|publisher=US Environmental Protection Agency}}</ref> This definition has been used in the enforcement of the Clean Water Act. Some US states, such as {{wipe|Massachusetts}} and New York, have separate definitions that may differ from the federal government's.

In the United States Code, the term wetland is defined "as land that (A) has a predominance of hydric soils, (B) is inundated or saturated by surface or groundwater at a frequency and duration sufficient to support a prevalence of hydrophytic vegetation typically adapted for life in saturated soil conditions and (C) under normal circumstances supports a prevalence of such vegetation." Related to these legal definitions, "normal circumstances" are expected to occur during the wet portion of the growing season under normal climatic conditions (not unusually dry or unusually wet), and in the absence of significant disturbance. It is not uncommon for a wetland to be dry for long portions of the growing season but under normal environmental conditions, the soils will be saturated to the surface or inundated creating anaerobic conditions persisting through the wet portion of the growing season.<ref>US Government Publishing Office. (2011) [https://www.law.cornell.edu/uscode/text/16/3801 16 U.S. Code Chapter 58 Subchapter I, § 3801 – Definitions] {{Webarchive|url=https://web.archive.org/web/20170206000118/https://www.law.cornell.edu/uscode/text/16/3801 |date=2017-02-06 }}. Legal Information Institute,  Cornell Law School, Ithaca.</ref>

==== Canada ====
* The Federal Policy on Wetland Conservation<ref name="rubec2009">{{cite journal|last1=Rubec|first1=Clayton DA|last2=Hanson|first2=Alan R|title=Wetland mitigation and compensation: Canadian experience|journal=Wetlands Ecol Manage|date=2009|volume=17|issue=1 |pages=3–14|doi=10.1007/s11273-008-9078-6|bibcode=2009WetEM..17....3R |s2cid=32876048}}</ref>
* Other Individual Provincial and Territorial Based Policies<ref name="rubec2009" />

== Examples ==
The world's largest wetlands include the swamp forests of the Amazon River basin, the peatlands of the West Siberian Plain,<ref name="FraserKeddy" /> the [[Place:Pantanal|Pantanal]] in South America,<ref name=":1" /> and the Sundarbans in the Ganges-Brahmaputra delta.<ref name=":2" />

==See also==
* [[Biology:Converted wetland|Converted wetland]]
* [[Earth:Groundwater-dependent ecosystems|Groundwater-dependent ecosystems]]
* [[Earth:Paludification|Paludification]]
* [[Earth:Slough (hydrology)|Slough]]
* {{in title|wetland}}

==References==
{{Reflist|30em}}

==External links==

{{Wetlands}}
{{Aquatic ecosystem topics}}
{{Biomes}}

[[Category:Wetlands| ]]
[[Category:Aquatic ecology]]
[[Category:Environmental terminology]]
[[Category:Habitat]]
[[Category:Bodies of water]]

{{Sourceattribution|Wetland}}