What are wetlands
Wetland is a place where water covers the soil or is near the soil surface for varying periods of time during the year. Wetlands include a wide variety of habitats ranging from lakes, marshes, swamps, estuaries, tidal flats, river flood plains, mangroves and even rice fields.
The Ramsar Convention defines wetlands as "areas of marsh, fen, peatlands or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt, including areas of marine water, the depth of which at low tide does not exceed six metres"
Read everything you want to know about wetlands here
Wetlands, under threat
Wetlands are one of the world’s most important natural resources and provide a range of benefits right from serving as a habitat for wildlife to helping in groundwater recharge, carbon storage, water regulation and providing a range of other ecosystem services (ESS) that benefit people, such as flood control, fish production, irrigation water, and recreation.
Wetlands today are under threat due to increasing pressure from human demands, as well as the changes in environmental and climatic conditions.
A recent study conducted in the context of the Ramsar Convention on Wetlands has found that 64 percent of the world’s wetlands have been lost since 1900!
A study titled 'Spatial and temporal dynamics of urban wetlands in an Indian megacity over the past 50 years' published in the journal Remote Sensing informs that the important role of urban wetlands in maintaining the ecology and environment was formally recognised only by 2008 as part of the Ramsar discourse.
Wetlands in fast growing cities such as Bengaluru
Urbanisation and industrialisation have been leading to rapid destruction of natural habitats, vegetated areas, and wetlands in urban areas in India.
Read here to know about threats to wetlands in India
The city of Bengaluru in Karnataka State, India is one of the fastest growing megacities in Asia with more than 10 million inhabitants. The growth of the IT sector has led to massive population growth along with drastic land cover changes in the city. Changes in agricultural use patterns and encroachment and pollution of water bodies has been leading to rapid loss of natural habitats in the city. However, there is limited knowledge on the impacts of these changes on small urban wetlands and (lake) water bodies in urban Bengaluru.
The study evaluates the long term changes in wetlands in Bengaluru city in terms of changes in land cover and dynamics of lake wetlands and their transformation along a rural–urban gradient by using remote sensing data.
Bengaluru, the city of lakes
Bengaluru city has historically been known as the “Garden City” or “City of Lakes”. The lake and tank systems in Bengaluru date back to the Vijayanagara empire when the then King Kempegowda established the first tanks to meet drinking water needs. The increasingly interconnected tank and lake system was further enlarged throughout the kingdom of the Wodeyars and the Maharajas of Mysore during the 17th and 18th century. The water demand of the growing town kept increasing and thus had to be met through the Cauvery-Arkavathi river system, which ended up becoming almost dry in drought years.
Since the colonial period, borewells as water sources were added to the water supply from Bengaluru’s tank-lake system to satisfy increasing demands for irrigated agriculture, sanitation and drinking water, which continue to put pressure on the already strained groundwater resources of the city in recent years.
The urban areas in the city have expanded more than ten times since 1949 transforming the rural landscape into an urban metropolis. Altogether, more than 200 lakes were present within Greater Bengaluru in 2010 with the rural having even larger number of lakes and wetlands. The remaining green space within Bengaluru is diverse and comprises home gardens, forest patches, wooded streets, wetlands, and parks.
The study finds that:
Bengaluru’s wetlands are shrinking
The most marked change in the city since 1965 has been the rapid expansion of built-up areas that have been at the cost of natural resources in the city such as the crop–shrub mosaic, wetlands and woodlands. This increase has been ten fold from 7.3 percent in 1965 to 52.4 percent in 2009 with the highest growth rate being from 2014 to 2018, whereas there has been a decrease in total area of water bodies from 3 percent to 2 percent.
The total wetland area was twice high in 1965 as compared to 2018 and the water bodies and flooded areas have shrunk from 64 km2 in 1965 to 55 km2 in 2018.
The total extent of cropland has shrunk due to massive urbanisation since 1965 and that in the city centre has been abandoned or transformed into commercial, industrial or residential areas.
Exotic plant species have replaced native plants and habitats drying up the lakes
There has been an increase in woodland from 2009 to 2014, which is mainly due to large scale conversion of cropland and wetlands to plantations of fast-growing trees and patches of parks. The high presence of exotic plant species, which dominate the park flora, limits the provision of ESS of and can negatively affect native plants and habitat.
The conversion of bodies of water to built-up areas has mainly occurred in the urban and transitional zone, where new residential and commercial areas, as well as industrial parks, have been established.
In rural areas, open water bodies have been converted into green spaces and woodlands in the south eastern and northern region, and the lakes have dried due to conversion of hydrophytic vegetation to shrub and tree habitats.
Many water bodies and wetland areas have dried out due to disruptions in the connected hydrological drainage network. The remaining wetlands within the city areas are threatened by pollution due to domestic and industrial waste, siltation, and the expansion of invasive weed species.
Community involvement in maintaining lakes has decreased
The decrease in the involvement of local communities in maintaining the lakes has also been one of the reasons for the rapid decline in lakes in the city.
Lakes and tanks in Bengaluru and their surroundings were used for fishing, irrigation of cropland, fodder production for cattle, drinking water, and domestic uses and, thus, played a key role in people’s livelihoods and were managed and maintained by local village communities.
The lakes and tanks soon fell into disuse due to the introduction of piped water from the Cauvery River in the 1970s and rapidly growing water extraction from borewells. Many lakes were thus converted for urban land usage and the extensive lake network was destroyed with a few isolated and disconnected lakes leading to an increasing risk of flooding in the monsoon season. The people too began to be less dependent on the lakes for irrigation and drinking water needs and preferred them for cultural and recreational services.
Currently, many lakes continue to be heavily polluted and degraded and/or encroached upon by invasive species, and used to dump large amounts of garbage, inspite of efforts being made to restore them. This continued loss of green space and water bodies poses a great challenge for the future availability of water thus affecting city development.
Better planning and management of urban areas needed
The study argues that failure is wetland governance has led to this dire situation in Bengaluru where wetlands are disappearing at a rapid pace not only threatening the water security of the city, but also the environmental sustainability of the region.
- There is a need for better planning, management and monitoring of current and past practices in urban areas of Bengaluru and focus on restoration activities that govern the past, present, and future of each lake.
- There is also an urgent need for research on the resilience of wetland ecosystems under different ecological, socio-economic, cultural, and institutional components of the complex urban social–ecological systems governing them.
The study can be accessed here