Wetlands are valuable ecosystems and urban wetlands provide numerous ecosystem services ranging from food, water, habitat for plants and animals, climate regulation and flood control, tourism and recreation, and supportive services like nutrient recycling. Wetlands also help in maintaining environmental quality and biodiversity and are considered as kidneys of the landscape as they absorb both water and waste induced from natural and anthropogenic activities.
However, wetlands in urban areas are disappearing fast and it has been found that since the beginning of the 20th century, 50 percent of the wetlands have been lost around the world while the remaining continue to undergo degradation due to agricultural expansion, urban growth, and expansion of infrastructure.
Urban wetlands, in crisis
Urban wetlands are highly sensitive to Land use and Land cover (LULC) changes that greatly affect the quality of ecosystem services and up-to-date information on LULC changes is essential to monitor the wetlands to prevent them from further degradation.
While rapidly urbanising Delhi has as high as 573 water bodies and wetlands in and around NCR area there is very little information on the impact of changing LULC patterns on wetlands in the region informs this paper titled 'Geospatial analysis of land use and land cover dynamics and its impact on urban wetland ecosystems in Delhi NCR region, India' published in Journal of Scientific & Industrial Research.
The paper discusses the findings of a study that examined the spatio-temporal LULC dynamics from 1998 to 2018 in and around the selected wetlands of Delhi NCR region of India. The study area included nine major wetlands namely Bhalswa Lake (BL), Pusa Hill Forest (PHF); Yamuna Biodiversity Park (YBP); Najafgarh Lake (NLW); Okhla Bird Sanctuary (OBS); Hauz Khas Wetland (HKW); Surajpur Wetland (SPW); Sanjay Lake Wetland (SLW) and (9) Asola Wildlife Sanctuary (AWS).
The study revealed that:
All wetlands were under threat to to aggressive infrastructural changes and expansion of built up areas.
In Bhalswa lake in the northwest part of Delhi NCT, the built-up area has increased while the plantations/forests have declined. The area under water has also shrunk by more than a half from 2.48 km2 to 0.95 km2.
Yamuna Biodiversity Park (YBP) is a protected man-made wetland situated on the bank of River Yamuna. The built-up area has been growing near the wetland while the cropland has remained the same. Barren land, area under plantations and water bodies show a huge decline.
The area around Pusa Hill Forest (PHF) is now being dominated by built-up land which shows an increasing trend while water bodies have reduced to half. The plantation/forest and water bodies have been converted to built-up areas and croplands.
The Sanjay Lake Wetland (SLW) is an artificial lake which was developed by Delhi Development Authority in east Delhi in 1970s. Built up land has declined whereas the cropland and plantations and water bodies have shown an increase near the wetlands.
The Hauz Khas Wetland (HKW) is situated in the highly urbanised area of south Delhi is the largest constructed wetland system in Delhi. Area under barren land shows an increase while area under cropland shows a decline. Area under plantations shows a positive change while area under water bodies has increased near the wetland.
Okhla Bird Sanctuary (OBS) Okhla Bird Sanctuary is situated on the Okhla barrage over Yamuna River in Noida, NCR Delhi. Barren land, built-up and water bodies have declined whereas the plantations and cropland have increased in the wetland.
Najafgarh Lake Wetland (NLW) lies in southwest Delhi and is an important wetland ecosystem. The built-up area around this wetland has dramatically increased while plantations and water bodies show a decline.
Asola Wildlife Sanctuary (AWS) Asola Wildlife Sanctuary is spread over Gurugram, Faridabad and Delhi. Built-up area has continuously increased while water bodies show a positive change.
Surajpur Wetland is an urban wetland in Yamuna basin situated in Greater Noida area of NCR Delhi. Built-up and cropland in the area around Surajpur wetland has shown an increasing trend while barren land, plantations and water bodies have decreased within the period of 1998 and 2018.
What do these patterns show
The built up areas and croplands have increased in Delhi NCR and areas where the nine wetlands are located due to high population growth and rapid urbanisation. The rural areas in and around Delhi have shrunk from 53.79 percent in 1991 to 24.9 percent in 2011 whereas the urban areas have increased from 46.21 percent to 75 percent during the same period. The population increased from 9.4 million in 1991 to 16.7 million in 2011. It is expected to rise to about 30 million in 2021 posing more threat to the sensitive ecosystems like wetlands.
The area under plantation has declined by more than half and about 40 km2 of area under water bodies have been lost during these twenty years while 700 km2 of area has been converted into cropland. Forested land of 658 km2 has been lost to either built-up area or agriculture.
Plantations, croplands and built-up areas seem to be connected. While plantations have decreased from 1998 to 2008 by 658 km2, croplands have increased during the same period by 868 km2. Majority of the barren land has been converted into cropland, while the remaining area has been developed as built-up area.
From 2008 to 2018 the area under cropland has decreased by 189 km2 and built-up increased by 356 km2 . Plantation and forest decreased by 35 km2 while barren land decreased by 110 km2 , showing that the plantations which were converted into agriculture were further converted into the built-up land. Water bodies have been converted into cropland.
The percent change in built-up around the wetlands is higher than NCR, which is matter of concern as more built-up area around the wetlands can lead to disposal of garbage, human waste and degradation that decline the ecosystem services provided by the wetlands. Land use modifications diminish the value of ecosystem services. Water bodies and vegetation are the two important elements of wetland ecosystems which are important for biodiversity and maintaining the health of ecosystems and provision of ecosystem services such as recreation etc in urban areas.
The study recommends an alternative, ecosystem based approach for city planning that is based on development that is sustainable and includes urban ecosystems such as urban water bodies, vegetation etc in the developmental planning and the importance of geospatial analysis to understand and evaluate the situation of wetlands in cities to devise appropriate sustainable solutions.
