Wetlands

Wetland systems that are made of permeable sediments like limestone or occur in areas with highly variable and fluctuating water tables especially have a role in groundwater replenishment or water recharge. Wetlands can also act as recharge areas when the surrounding water table is low and as a discharge zone when it is too high.

Karst cave systems are a unique example of this system and are a connection of underground rivers influenced by rain and other forms of precipitation. Groundwater is an important source of water for drinking and irrigation of crops. Unsustainable abstraction of groundwater has become a major concern. In the Commonwealth of Australia , water licensing is being implemented to control use of water in major agricultural regions.

Wetlands ( film) - Wikipedia

On a global scale, groundwater deficits and water scarcity is one of the most pressing concerns facing the 21st century. Mangroves , coral reefs , salt marsh. Tidal and inter-tidal wetland systems protect and stabilize coastal zones.

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Coral reefs provide a protective barrier to coastal shoreline. Mangroves 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 storm surges is the ability to reduce the speed and height of waves and floodwaters.

The sheer number of people who live and work near the coast is expected to grow immensely over the next fifty years. This management technique provides shoreline protection through restoration of natural wetlands rather than through applied engineering. Wetlands cycle both sediments and nutrients balancing terrestrial and aquatic ecosystems.

A natural function of wetland vegetation is the up-take, storage, and for nitrate the removal of nutrients found in runoff from the surrounding soil and water. 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 which may be composed of clay, sand, silt, and rock can be carried into wetland systems through this process. Wetland vegetation acts as a physical barrier to slow water flow and trap sediment for short or long periods of time.

Suspended sediment often contains heavy metals that are retained when wetlands trap the sediment. In some cases, certain metals are taken up through wetland plant stems, roots, and leaves. Many floating plant species, for example, can absorb and filter heavy metals. Water hyacinth Eichhornia crassipes , duckweed Lemna and water fern Azolla store iron and copper commonly found in wastewater. Many fast-growing plants rooted in the soils of wetlands such as cattail Typha and reed Phragmites also aid in the role of heavy metal up-take.

On the other hand, some types of wetlands facilitate the mobilization and bioavailability of mercury another heavy metal , which in its methyl mercury form increases the risk of bioaccumulation in fish important to animal food webs and harvested for human consumption. 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 eutrophication.

Upstream erosion from deforestation can overwhelm wetlands making them shrink in size and cause dramatic 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 eutrophication. This is of particular concern in temperate coastal systems.

An example of how a natural wetland is used to provide some degree of sewage treatment is the East Kolkata Wetlands in Kolkata, India. The nutrients contained in the wastewater sustain fish farms and agriculture. The function of most natural wetland systems is not to manage wastewater. However, their high potential for the filtering and the treatment of pollutants has been recognized by environmental engineers that specialize in the area of wastewater treatment. These constructed wetland systems are highly controlled environments that intend to mimic the occurrences of soil, flora, and microorganisms in natural wetlands to aid in treating wastewater effluent.

Constructed wetlands can be used to treat raw sewage, storm water, agricultural and industrial effluent. They are constructed with flow regimes, micro-biotic composition, and suitable plants in order to produce the most efficient treatment process. Other advantages of constructed wetlands are the control of retention times and hydraulic channels. Constructed wetland systems can be surface flow systems with only free-floating macrophytes , floating-leaved macrophytes, or submerged macrophytes; however, typical free water surface systems are usually constructed with emergent macrophytes.

Wetland systems' rich biodiversity is becoming a focal point at International Treaty Conventions and within the World Wildlife Fund organization due to the high number of species present in wetlands, the small global geographic area of wetlands, the number of species which are endemic to wetlands, and the high productivity of wetland systems.

Hundred of thousands of animal species, 20, of them vertebrates, are living in wetland systems. The discovery rate of fresh water fish is at new species per year. The impact of maintaining biodiversity is seen at the local level through job creation, sustainability, and community productivity. The Amazon holds 3, species of freshwater fish species within the boundaries of its basin, whose function it is to disperse the seeds of trees. Intertidal mudflats have a level of productivity similar to that of some wetlands even while possessing a low number of species.

The abundance of invertebrates found within the mud are a food source for migratory waterfowl. 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. 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 Lake Baikal in Russia classifies it as a hotspot for biodiversity and one of the most biodiverse wetlands in the entire world. Evidence from a research study by Mazepova et al. Its species of free-living Platyhelminthes alone is analogous to the entire number in all of Eastern Siberia. The 34 species and subspecies number of Baikal sculpins is more than twice the number of the analogous fauna that inhabits Eurasia. One of the most exciting discoveries was made by A. Shoshin who registered about species of free-living nematodes using only six near-shore sampling localities in the Southern Baikal.

Biodiversity loss occurs in wetland systems through land use changes, habitat destruction, pollution, exploitation of resources, and invasive species. Introduced hydrophytes in different wetland systems can have devastating results. 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 suffocating the wetlands and reducing the diversity of other plants and animals.

This is largely due to their phenomenal growth rate and ability to float and grow on the surface of the water. Wetland productivity is linked to the climate, wetland type, and nutrient availability. Low water and occasional drying of the wetland bottom during droughts dry marsh phase stimulate plant recruitment from a diverse seed bank and increase productivity by mobilizing nutrients. In contrast, high water during deluges lake marsh phase causes turnover in plant populations and creates greater interspersion of element cover and open water, but lowers overall productivity.

During a cover cycle that ranges from open water to complete vegetation cover, annual net primary productivity may vary fold. Wetlands naturally produce an array of vegetation and other ecological products that can be harvested for personal and commercial use. 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.

Food converted to sweeteners and carbohydrates include the sago palm of Asia and Africa cooking oil , the nipa palm of Asia sugar, vinegar, alcohol, and fodder and honey collection from mangroves. More than supplemental dietary intake, this produce sustains entire villages. Coastal Thailand villages earn the key portion of their income from sugar production while the country of Cuba relocates more than 30, hives each year to track the seasonal flowering of the mangrove Avicennia.

Over-fishing is the major problem for sustainable use of wetlands. Concerns are developing over certain aspects of farm fishing, which uses natural waterways to harvest fish for human consumption and pharmaceuticals. This practice has become especially popular in Asia and the South Pacific. Its impact upon much larger waterways downstream has negatively affected many small island developing states. 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 check in absence of other employment avenues for people engaged in such occupation.

Also burgeoning demand for shrimps globally has provided a large and ready market for the produce.

Threats to rice fields mainly stem from inappropriate water management, introduction of invasive alien species, agricultural fertilizers, pesticides, and land use changes. Industrial-scale production of palm oil threatens the biodiversity of wetland ecosystems in parts of southeast Asia, Africa, and other developing countries. Over-exploitation of wetland products can occur at the community level as is sometimes seen throughout coastal villages of Southern Thailand where each resident may obtain for themselves every consumable of the mangrove forest fuelwood, timber, honey, resins, crab, and shellfish which then becomes threatened through increasing population and continual harvest.

Some types of wetlands can serve as fire breaks that help slow the spread of minor wildfires.

The Importance of Wetlands

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. Pollination services are supported by many wetlands which may provide the only suitable habitat for pollinating insects, birds, and mammals in highly developed areas. It is likely that wetlands have other functions whose benefits to society and other ecosystems have yet to be discovered.

Wetlands perform two important functions in relation to climate change. They have mitigation effects through their ability to sink carbon , converting a greenhouse gas carbon dioxide to solid plant material through the process of photosynthesis , and also through their ability to store and regulate water.

The ability of many tidal wetlands to store carbon and minimize methane flux from tidal sediments has led to sponsorship of blue carbon initiatives that are intended to enhance those processes. However, depending on their characteristics, some wetlands are a significant source of methane emissions and some are also emitters of nitrous oxide [67] [68] which is a greenhouse gas with a global warming potential times that of carbon dioxide and is the dominant ozone -depleting substance emitted in the 21st century.

Data on nitrous oxide fluxes from wetlands in the southern hemisphere are lacking, as are ecosystem-based studies including the role of dominant organisms that alter sediment biogeochemistry. Aquatic invertebrates produce ecologically-relevant nitrous oxide emissions due to ingestion of denitrifying bacteria that live within the subtidal sediment and water column [86] and thus may also be influencing nitrous oxide production within some wetlands.

In Southeast Asia, peatswamp forests and soils are being drained, burnt, mined, and overgrazed, contributing severely to climate change. It decomposes and turns into carbon dioxide CO 2 , which is released into the atmosphere. Peat fires cause the same process to occur and in addition create enormous clouds of smoke that cross international borders, such as happens every year in Southeast Asia.

Through the building of dams, Wetlands International is halting the drainage of peatlands in Southeast Asia, hoping to mitigate CO 2 emissions. Concurrent wetland restoration techniques include reforestation with native tree species as well as the formation of community fire brigades. This sustainable approach can be seen in central Kalimantan and Sumatra , Indonesia.

What Are Wetlands?

Wetlands, the functions and services they provide as well as their flora and fauna, can be affected by several types of disturbances. The disturbances sometimes termed stressors or alterations can be human-associated or natural, direct or indirect, reversible or not, and isolated or cumulative. When exceeding levels or patterns normally found within wetlands of a particular class in a particular region, the predominant ones include the following [88] [89].

Just a few of the many sources of these disturbances are [87].

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Wetlands have historically been the victim of large draining efforts for real estate development , or flooding for use as recreational lakes or hydropower generation. Some of the world's most important agricultural areas are wetlands that have been converted to farmland. In order to maintain wetlands and sustain their functions, alterations and disturbances that are outside the normal range of variation should be minimized.

Wetlands are vital ecosystems that provide 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. A three-year project carried out by Wetlands International in partnership with the International Water Management Institute found 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 dambos — wet, grassy valleys or depressions where water seeps to the surface — can be farmed sustainably to improve livelihoods.

Mismanaged or overused dambos often become degraded, however, using a knowledge exchange between local farmers and environmental managers, a protocol was developed using soil and water management practices. Project outcomes included a high yield of crops, development of sustainable farming techniques, and adequate water management generating enough water for use as irrigation. Before the project, there were cases where people had died from starvation due to food shortages. By the end of it, many more people had access to enough water to grow vegetables. A key achievement was that villagers had secure food supplies during long, dry months.

They also benefited in other ways: Mangrove leaves and roots provide nutrients that nourish plankton, algae, fish and shellfish. Mangroves are also home to many birds and mammals — such as mangrove monkeys in South Asia. These wetlands include rivers, swamps, and lakes and springs that dry up for portions of the year. These wetlands are essential for farmers, pastoralists who graze animals, and the livelihoods of people who fish and collect plants.

They are also important to millions of waterbirds that breed in Europe and Asia, such as waders and herons. High altitude wetlands store water from rain and glacial melt, feed groundwater stores, trap sediments and recycle nutrients, enhancing both the quantity and quality of water. These wetlands are important stopping points for migratory birds and breeding grounds for birds, fish and amphibians. Their ability to promote vegetation growth lessens soil erosion and buffers water flow, providing a steady flow of water downstream while reducing the severity of disasters such as landslides, floods and droughts.

Arctic wetlands store enormous amounts of greenhouse gases and are critical for global biodiversity. They are also the main source of livelihoods for local indigenous peoples. Arctic wetlands offer unique habitats to both plants and animals. For many migratory species the Arctic provides indispensable breeding and feeding areas. Over four million people, including more than 30 different indigenous groups, live in the Arctic. People living in the Arctic depend on wetlands for fish and waterfowl hunting, harvesting of plants and as pastures for grazing.

They provide habitat for animals and plants and many contain a wide diversity of life, supporting plants and animals that are found nowhere else. Wetlands provide an important range of environmental, social and economic services. Many wetlands are areas of great natural beauty and many are important to Aboriginal people.

Wetlands also provide important benefits for industry. For example, they form nurseries for fish and other freshwater and marine life and are critical to Australia's commercial and recreational fishing industries. Australia currently has 65 Ramsar wetlands that cover more than 8.