Wetland
[1] Wetlands form a transitional zone between waterbodies and dry lands, and are different from other terrestrial or aquatic ecosystems due to their vegetation's roots having adapted to oxygen-poor waterlogged soils.[1][4] The world's largest wetlands include the Amazon River basin, the West Siberian Plain,[5] the Pantanal in South America,[6] and the Sundarbans in the Ganges-Brahmaputra delta.The Cowardin system includes five main types of wetlands: marine (ocean-associated), estuarine (mixed ocean- and river-associated), riverine (within river channels), lacustrine (lake-associated) and palustrine (inland nontidal habitats).Anaerobic and aerobic respiration in the soil influences the nutrient cycling of carbon, hydrogen, oxygen, and nitrogen,[33] and the solubility of phosphorus[34] thus contributing to the chemical variations in its water.Frogs are sometimes used as an indicator of 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.United Nations Millennium Ecosystem Assessment and Ramsar Convention described wetlands as a whole to be of biosphere significance and societal importance in the following areas:[61] According to the Ramsar Convention:[citation needed] 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.To replace these wetland ecosystem services, enormous amounts of money would need to be spent on water purification plants, dams, levees, and other hard infrastructure, and many of the services are impossible to replace."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 does not run straight off the land into water courses.Upstream erosion from deforestation can overwhelm wetlands making them shrink in size and cause dramatic biodiversity loss through excessive sedimentation load.[73] 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.[78] Some native wetland plants in the Caribbean and Australia are harvested sustainably for medicinal compounds; these include the red mangrove (Rhizophora mangle) which possesses antibacterial, wound-healing, anti-ulcer effects, and antioxidant properties.[78] 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.Water management engineering developments in the past century have degraded floodplain wetlands through the construction of artificial embankments such as dykes, bunds, levees, weirs, barrages and dams.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.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.[90] Wetlands have historically subjected to large draining efforts for development (real estate or agriculture), and flooding to create recreational lakes or generate hydropower.Case studies conducted in Malawi and Zambia looked at how dambos – wet, grassy valleys or depressions where water seeps to the surface – can be farmed sustainably.[10] Factors influencing selected approach may include[10] budget, time scale limitations, project goals, level of disturbance, landscape and ecological constraints, political and administrative agendas and socioeconomic priorities.[10] 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 may require some engineering, and more intensive biophysical manipulations including ripping of subsoil, agrichemical applications of herbicides or insecticides, laying of mulch, mechanical seed dispersal, and tree planting on a large scale.They can be used in developments as part of 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.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.[113] However, CO2 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.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.[122] In most parts of the world and under all emission scenarios, water cycle variability and accompanying extremes are anticipated to rise more quickly than the changes of average values.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.[127] 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.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 worldwide.Remote sensing such as aerial imagery and satellite imaging[133] provides effective tools to map and monitor wetlands across large geographic regions and over time.[137] The world's largest wetlands include the swamp forests of the Amazon River basin, the peatlands of the West Siberian Plain,[5] the Pantanal in South America,[6] and the Sundarbans in the Ganges-Brahmaputra delta.