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Editorial Articles


Volume-46, 15-21 February 2020

Wetlands: Significance and conservation

 

Dr. Abhishek Swami

Wetlands are areas where water covers the 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. Water saturation (hydrology) largely determines how the soil develops and the types of plant and animal communities living in and on the soil. Wetlands may support both aquatic and terrestrial species. The prolonged presence of water creates conditions that favor the growth of specially adapted plants (hydrophytes) and promote the development of characteristic wetland (hydric) soils.

Wetlands occur naturally on every continent. The main wetland types are swamp, marsh, bog, and fen; sub-types include mangrove forest, floodplains, mire, vernal pool, sink, and many others. Many peat lands are wetlands. The water in wetlands is either freshwater, brackish, or saltwater. Wetlands can be tidal (inundated by tides) or non-tidal. The largest wetlands include the Amazon River basin, the West Siberian Plain, the Pantanal in South America, and the Sundarbans in the Ganges-Brahmaputra delta. The UN Millennium Ecosystem Assessment determined that environmental degradation is more prominent within wetland systems than any other ecosystem on Earth. Constructed wetlands are used to treat municipal and industrial wastewater as well as stormwater runoff. They may also play a role in water-sensitive urban design.

Categories of Wetlands

Wetlands vary widely because of regional and local differences in soils, topography, climate, hydrology, water chemistry, vegetation and other factors, including human disturbance. Indeed, wetlands are found from the tundra to the tropics and on every continent except Antarctica. Two general categories of wetlands are recognized: coastal or tidal wetlands and inland or non-tidal wetlands.

Coastal/Tidal Wetlands

Coastal/tidal wetlands in the United States, as their name suggests, are found along the Atlantic, Pacific, Alaskan and Gulf coasts. They are closely linked to our nation's estuaries where sea water mixes with fresh water to form an environment of varying salinities. The salt water and the fluctuating water levels (due to tidal action) combine to create a rather difficult environment for most plants. Consequently, many shallow coastal areas are un-vegetated mud flats or sand flats. Some plants, however, have successfully adapted to this environment. Certain grasses and grasslike plants that adapt to the saline conditions form the tidal salt marshes that are found along the Atlantic, Gulf, and Pacific coasts. Mangrove swamps, with salt-loving shrubs or trees, are common in tropical climates, such as in southern Florida and Puerto

Rico. Some tidal freshwater wetlands form beyond the upper edges of tidal salt marshes where the influence of salt water ends.

Inland/Non-tidal Wetlands

Inland/non-tidal wetlands are most common on floodplains along rivers and streams (riparian wetlands), in isolated depressions surrounded by dry land (for example, playas, basins and "potholes"), along the margins of lakes and ponds, and in other low-lying areas where the groundwater intercepts the soil surface or where precipitation sufficiently saturates the soil (vernal pools and bogs). Inland wetlands include marshes and wet meadows dominated by herbaceous plants, swamps dominated by shrubs, and wooded swamps dominated by trees. Certain types of inland wetlands are common to particular regions of the country.

Many of these wetlands are seasonal (they are dry one or more seasons every year), and, particularly in the arid and semiarid West, may be wet only periodically. The quantity of water present and the timing of its presence in part determine the functions of a wetland and its role in the environment. Even wetlands that appear dry at times for significant parts of the year -- such as vernal pools-- often provide critical habitat for wildlife adapted to breeding exclusively in these areas.

Significance of Wetlands

Wetlands are considered to have unique ecological features which provide numerous products and services to humanity.  Ecosystem goods provided by the wetlands mainly include - water for irrigation, fisheries, non-timber forest products, water supply and recreation.

The major services include carbon sequestration, flood control, groundwater recharge, nutrient removal, and toxics retention and biodiversity maintenance.

  • Agriculture and allied sectors: Wetlands such as tanks, ponds, lakes, and reservoirs have long been providing multiple-use water services which include water for irrigation, domestic needs, ground-water recharge, etc.
  • In terms of growth in fish production in India, wetlands play a significant role. Around 61 percent of fish production in the country is from inland water bodies and it is also the second largest aquaculture farmed fish producer in the world.
  • Carbon Sequestration: Swamps, mangroves, peat lands, mires and marshes play an important role in carbon cycle. Wetland soils may contain as much as 200 times more carbon than its vegetation.
  • In India, coastal wetlands are playing a major role in carbon sequestration. The total extent of coastal ecosystems (including mangroves) in India is around 43000 km.
  • Overall, mangroves are able to sequester about 1.5 metric tonne of carbon per hectare per year and the upper layers of mangrove sediments have high carbon content, with conservative estimates indicating the levels of 10 percent.
  • Pollution Abatement: Wetlands act as a sink for contaminants in many agricultural and urban landscapes. In India too, wetlands are polluted through agricultural runoff and discharge of untreated sewage and other waste from urban areas.
  • Flood Control: Wetlands play an important role in flood control. Wetlands help to lessen the impacts of flooding by absorbing water and reducing the speed at which flood water flows. Further, during periods of flooding, they trap suspended solids and nutrient load.
  • A large network of lakes and ponds in major cities like Srinagar, Bhopal, Bengaluru, Chennai and Hyderabad were constructed with the objective of flood control
  • Besides, the mangroves along the sea shores, especially on the western coast in West Bengal and Odisha have been playing a major role in protecting the coastal environment from the destruction of cyclones that frequently emanate in the Bay of Bengal.
  • Biodiversity Hotspots: Wetlands are important in supporting species diversity. Because wetlands provide an environment where photosynthesis can occur and where the recycling of nutrients can take place, they play a significant role in the support of food chains.
  • In India lakes, rivers and other freshwater bodies support a large diversity of biota representing almost all taxonomic groups. For example, freshwater ecosystems of Western Ghats alone have 290 species of fish. Similarly, Loktak Lake is famous for being the only refuge of the endangered Sangai (Manipur brow-antlered deer).
  • Wetlands are also important breeding areas for domestic and migrating bird species. In many such wetland areas of India, like Bharatpur wild life sanctuary in Rajasthan, and little Rann of Kutch and coastal areas of Saurashtra in Gujarat, many migratory species of birds, including siberian crane, from western and European countries come during winter.
  • Sarus cranes, black necked cranes, Gangetic river dolphins, the Indian mud turtle and numerous threatened species of birds and fauna, feed (off) and live in and around wetlands
  • As per an estimate, the approximate number of species of migratory birds recorded from India is between 1200 and 1300, which is about 24 percent of India's total bird species.
  • Tourism: Wet-lands such as coral reefs, beaches, reservoirs, lakes and rivers are considered to be a significant part of the tourism experience in the country.
  • As per an estimate, every year, around seven million tourist visit Kerala's backwaters, beaches and wildlife sanctuaries, 3 million visit Uttarakhand's lakes and other natural wetlands and one million visit Dal lake in Jammu and Kashmir.
  • Cultural Significance: Wetlands especially lakes and ponds (e.g. Pushkar lake in Rajasthan and Ramappa lake in Telangana) are intrinsically linked to the local culture. They are revered by the masses in recognition of the fact that they are the means of sustenance of their livelihood.

Conservation of Wetland

Since the advent of industrialization and urbanization the wetlands came under severe threat due to increased anthropogenic-pressures. As per an estimate, India has lost 38 percent of its wetlands between 1991 and 2001 alone.

  • Urbanization and Land Use Changes: During the 90 year period from 1901 to 1991, the number of urban centers doubled while urban population has increased eightfold. This magnitude of growth exerted tremendous pressure on wetlands and flood plain areas for meeting water and food demand of growing population.
  • For example, the Kanwar Lake in Bihar, Asia's largest freshwater oxbow lake, has shrunk to one-third of its size due to encroachment, much like Jammu and Kashmir's Dal Lake. And, about 34000 hectares of the water spread area of the Kolleru Lake (Andhra Pradesh) have been reclaimed for agriculture in recent years.
  • Agricultural residues: As a result of intensification of agricultural activities over the past four decades, fertilizer consumption in India has increased from about 2.8 million tons in 1973-1974 to 28.3 million tons in 2010-2011.
  • As per estimates, 10-15 percent of the nutrients added to the soils through fertilizers eventually find their way to the surface water system. High nutrient contents stimulate algal growth, leading to eutrophication of surface water bodies.
  • Municipal and Industrial pollution: Less than 31 percent of the domestic wastewater from Indian urban centers is treated, compared to 80 percent in the developed world, which is largely discharged in the natural water bodies such as streams and rivers.
  • For example, River Yamuna, which passes through 6 Indian States, receives about 1789 MLD of untreated waste water from the capital city of Delhi alone. This is about 78 percent of the total pollution load that flows in to the river every day.
  • Similarly, untreated industrial effluents have become a major threat to the survival of wetlands. For instance, the Bellandur Lake in Bengaluru city was 'on fire' in May 2015 due to the discharge of effluents (especially nutrient rich foams) by the surrounding industries.
  • Climate Change: In 2007, the UNESCO estimated that Global climate change is expected to become an important driver of loss and change in wet-land ecosystem. These findings are important for India which has been experiencing the flood-drought-flood cycle for the last 2 decades.
  • As per a study, wetlands located in high altitude as well as coastal areas, like mangroves and coral reefs, are some of the most sensitive classes that will be affected by climate change.
  • For example, climate change caused rise in level of Tsomoriri Lake in Ladakh, a glacial fed high altitude lake, thereby causing submerged important breeding islands in the lake where endangered migratory birds like the Black-necked Crane and Bar-headed Goose would breed.
  • As per an estimate, India will lose about 84 percent of coastal wetlands and 13 percent of saline wetlands with climate change induced sea water rise of 1 meter.

Apart from the above major threats, immersion of ritual waste, introduction of exotic species, encroachments and unregulated aquaculture (e.g. Kolleru lake) backed by Bureaucrats- Politicians-Businessmen nexus, dredging, un planned urbanization and development projects  are some of the other dangers threatening the existence of wetlands across the country.

Wetlands (Conservation and Management) Rules, 2017

The new rules, notified by the environment ministry, decentralize wetlands management by giving states powers to not only identify and notify wetlands within their jurisdictions but also keep a watch on prohibited activities.

Seeking to protect over 2 lakh wetlands across the country, the Centre has come out with rules to identify and manage these ecologically fragile areas which play an important role in flood control, groundwater recharge, preserving plant varieties, supporting migratory birds and protecting coastlines. The new rules, notified by the environment ministry, decentralize wetlands manage-ment by giving states powers to not only identify and notify wetlands within their jurisdictions but also keep a watch on prohibited activities. It also indirectly widens the ambit of permitted activities by inserting the 'wise use' principle, giving powers to state-level wetland authorities to decide what can be allowed in larger interest. The notification says, "The wetlands shall be conserved and managed in accordance with the principle of 'wise use' as determined by the Wetlands Authority." The Centre's role under the Wetlands (Conserv-ation and Management) Rules, 2017, will be restricted to monitoring its implementation by states/UTs, recommending trans-boundary wetlands for notification and reviewing integrated management of selected wetlands under the Ramsar Convention - an international arrangement to preserve identified wetlands.

(The author is Associate Professor, Department of Environmental Science, Shree Guru Gobind Singh Tricentenary University (SGT) University, Gurugram. e-mail id: abhishek swami1@gmail.com)

Views expressed are personal.

Image Courtesy: Google