Читать книгу Wetlands Conservation - Группа авторов - Страница 17

The wetland ecosystem is a very sensitive aspect of the ecological landscape. The health of flora and fauna species is associated with the conditions and distribution of the wetlands. Any change on a small and large scale in the wetland ecological system impacts the biodiversity and habitat of the species. The changes in wetlands leads to changes in number of species, distribution of the species, alteration in migratory bird routes, and changes in community structures and species interconnection (Erwin 2009). Rapid changes in population dynamics or any other environmental or climate change often result in wetland encroachment due to increasing demand for ecosystem services in wetlands (Mitchell 2013; Davidson 2014; Dixon et al. 2016). These wetlands are increasingly degraded, and the provision of wetlands services is at serious risk. Based on an analysis of 189 reports on change in wetlands system, Davidson outlined in 2014, that ‘over a long period wetlands have been converted to other land‐use practices and have lost more than 50% since 1900 AD and more than 87% since the beginning of the 18th century’. Trustworthy information on the spatial distribution of wetlands would help academics, policymakers, scientists, and environmental conservationists understand the location, area, distribution and current physio‐biological status of global wetlands and develop efficient conservation policies measures and management plans. However, globally (Davidson 2014; Dixon et al. 2016) and at regional levels some work has been done on recent changes in global wetlands, distribution, loss and status.

Wetlands are currently at higher risk of climate change for example alternations have been noted in coral reefs, mangroves and tropical forests, sub‐arctic forests, prairies and arctic/alpine areas. Inland freshwater wetlands are likely to be affected mainly by precipitation patterns and more frequent or intense droughts, storms and floods. Changes in rainfall patterns and volume entering river systems would change water availability to coastal wetlands including deltas and estuaries, affecting salinity and sediment and nutrient supply. Melting will cause mountain snowfields and glaciers that feed many of the world's largest river and wetland systems will disappear. Water quality will be harmed as a result of rising water temperatures, floods, and droughts, which will exacerbate various forms of pollution. Many semi‐arid regions are uniquely vulnerable to climate change impacts and are expected to undergo severe anthropogenic and natural pressures for water resources and wetlands. There may be many other minor hazards specific to different wetlands, such as deterioration and loss of habitat, conversion for agriculture and infrastructure development, changing land use and land cover, urbanisation, pollution from agricultural runoff, sewage and solid waste disposal, encroachment and remediation of wetlands, degradation of wetlands, the infestation of weeds and alien species invasions, poaching of wildlife and man‐wildlife conflict.

Xu et al. (2019) has identified 2414 sites of international importance wetlands covering 254543972 ha and have been recognized globally significant. According to Xu et al. (2019), 2303 wetlands of global significance are distributed unevenly across the globe's continents. Many wetlands have been damaged and degraded due to rapid farming and urbanisation in North America and Europe, leading to loss of most floodplain regions (Tockner and Stanford, 2002). Increasing pressure on water resources by population is also very dominant in these regions, which increases biodiversity loss. Such adverse impacts on wetlands are high in developing countries in the continents of Asia and Africa (Vorosmarty et al., 2010). Some parts of South America, Australia and Northern Europe have remained less affected by the controlled and regulating anthropogenic activities as compared to other parts of the globe. As a result of greater water regulation for agricultural growth and urban and industrial expansion, ecological qualities have deteriorated in recent decades in Australia (Finlaysonet et al., 2013). Based on 153 reports published in 63 different journals, Kandus et al. 2018 found that most wetlands in South America have been conserved and are in relatively excellent condition. China's wetlands cover 53.42x106 acres, accounting for 10% of worldwide wetlands and 5.58 % of the country's total land area. Multiple contributing variables are constantly putting China's wetlands at jeopardy. Since the 1950s, a considerable number of wetlands have been lost or damaged. 33% of China’s total wetlands have been lost in the time span of 1978 ‐2008. Cropland expansion has majorly led to the loss of vegetated wetlands in China during 1990 to 2010 (Mao et al. 2021).

Loss of vegetation due to invasive species has resulted in the spread and displacement of native species. Adversely vegetation loss is also affected by coastal wetlands due to anthropogenic pressure and climate change impacts. Global warming and climate change are of serious concern to coastal and high‐altitude wetlands. Flood plains are no longer considered wetlands when flood management control fails. Other factors, such as agricultural development, land use, land cover changes, urbanisation, infrastructure development and desertification, are also equally responsible for the degradation of wetlands. According to a study by Zelder and Kercher (2005), reported over 5000 km² of wetland is lost annually in Asia due to agriculture, dam construction, and other factors, and about 50% of the global wetland area has been lost as a result of human activity. Over the last 100 years, most continents have experienced significant wetland losses. A study conducted by Xu et al. (2019) on the basis 2303 wetlands of international importance found that largest numbers of wetlands are located in Europe, and Africa has the largest area of land; out of these study locations, more than 50% of the locations are influenced by contamination (54%), biological resource use (53%), natural system alteration (53%) and farming and aquaculture (42%). Major wetlands depend on fish, water birds and tortoises in severe decline, with 1/4th of them threatened extinction, especially in the tropics and wetlands site in United Kingdom and Irelands are least affecting among all over the continents (Xu et al. 2019). According to the Global Wetlands Outlook (2018) since, 1970, 81% of inland wetland populations and 36% of coastal and marine species have declined and more than >10 percent of inland species are subject to global risk assessment from the IUCN Red List. The highest degree of the global threat of extinction are marine turtles (100% globally threatened), wetland‐depend mega fauna (62%), freshwater reptiles (40 %), marine molluscs (37%), amphibians (35%), corals (33%) and crabs and crayfish (32%): coral reef‐dependent parrotfish and surgeonfish (2%), and dragonflies (8%) have low globally threatened status (Global Wetlands Outlook, 2018). Loss of vegetation due to invasive species has resulted in the spread and displacement of native species. Vegetation loss is also affected by coastal wetlands.

Wetlands are linked to malaria and have been drained for this reason as well. Water quality of the wetlands has also deteriorated due to increasing pollution, drainage, weed infestation and siltation. It's expected to deteriorate further. The main sources of pollution are untreated industrial waste, waste and wastewater from power plants, chemical, fertiliser and pesticide runoff from agricultural land, etc. Eutrophication causes algal blooms, which reduces the water's oxygen content, leading to the extinction of other species. Salinity has also been increased due to pollution. At least 5.25 trillion persistent plastic particles are afloat in the World's oceans and have enormous impacts on coastal waters (Ramsar Convention on Wetlands, 2018). Successive droughts have led to the early departure of many migratory birds.

Finlayson and Valk (1997) claim that the decrease of wetlands coincides with growing scientific evidence of their value to humans, biodiversity, and the environment's quality. At present, the poor consciousness of the significance of the wetland ecosystem by decision‐makers and underestimating the values and benefits of wetlands are also a major concern. The protection of wetlands is now becoming a problem and challenging task. It complicates attempts to establish strategies to reduce risks and protect these important resources. Promoting a wetland wise use initiative is crucial to human livelihoods and survival. Finlayson and Valk (1997) argue that the decline in wetlands coincides with increasing scientific evidence of their importance to people, wildlife, and the environment's quality. The protection of wetlands is also difficult. It complicates attempts to establish strategies to reduce risks and preserve these important resources. Promoting the wetland wise use programme is crucial to human livelihoods and survival.