A sewage sponge

Last Updated 24 February 2015, 04:09 IST

Guarding wetlands East Kolkata Wetlands, home to a wide range of biodiversity, is also a major source of livelihood for the urban poor. Bindu Gopal Rao stresses on the need to conserve this ecological haven.

On a recent visit to Kolkata I had an opportunity to visit  East Kolkata Wetlands(EKW) and was amazed to see the ecological diversity haven, situated right in the heart of the City. Spread over 125 sq km, these wetlands comprise of a large number of water bodies, that feed the world’s largest wastewater- fed aqua culture system.

When we think of wetlands, we picturise marshy, swampy and mucky areas. Wetlands are unique and beautiful ecosystems that host a wide range of biodiversity. In short, wetlands are not only areas with abundant water, but they also include seasonal wetlands, making them one of the most fragile ecosystems in nature.

In 2002, East Kolkata Wetlands was recognised as a Wetland of International Importance under the Ramsar Convention. Through the Conservation and Management Ordinance in November 2005, a green lobby led by a citizens group called PUBLIC (People United for Better Living in Calcutta) won an important battle to protect the fragile area from encroachments.

“As far as challenges are concerned, the biggest ones are encroachments aided and abetted by politicians and ‘land sharks’. Adding to this was the half-hearted approach of the government to demarcate East Kolkata Wetlands. No governmental organisations came forward to educate local communities on the importance of such wetlands. Moreover, inadequate release of sewage added to the woes,” says Bonani Kakkar, founder-member of PUBLIC.

The organisation also opposed the idea of a West Bengal Industrial Development Corporation-funded aqua park, which had shockingly obtained permissions from nine different departments of the state government.

“The problem is that in the government, very often, actions are uncoordinated. Also, wetlands are one of the three wards in Kolkata that don’t have a land use and development control plan. This makes it easy to alter the land use,” adds Bonani.

A part of the Ganges Delta, the wetlands must be preserved as a flood control
system and a living environment. Therefore, a regional planning strategy is needed. “Lately, a combination of nature, native intelligence and legal protection have given the wetlands a globally unique status as a natural resource recovery system. To demystify the enigma of EKW and their unique relationship to the adjacent metropolis, we need to first look at what wetlands are and why East Kolkata Wetlands have a special environmental, hydrological, ecological and social relevance,” says Bonani.

Natural spill basin

The gradient of the land in Kolkata slopes away from River Hooghly from west to east, towards the wetlands. The city’s sewage and drainage systems have been designed to take advantage of this.
Gravitational force takes the discharge eastward and EKW serves as a natural spill basin, a giant sponge of sorts.

“The vast 12,500 hectares of wetland on Kolkata’s eastern fringe acts as a vital receptacle for the city’s carbon emissions. The absorption capacity of the combination of water surface and vegetation
provides critical relief from the air pollution that hangs over Kolkata. It is estimated that one sq metre of water produces 23.75 gm of oxygen per minute, after meeting the requirements of aquatic animals,” says Bonani.

Moreover, Wetlands International-South Asia has estimated that the EKW provides a livelihood for 2,00,000 urban poor. The fishermen and vegetable growers whose farms, fed with organic waste from the city, provide a significant proportion of the city’s daily food requirements (about 15,000 tons of fish annually and 150 tons of vegetables per day) and also make a good living out of it.

Also, this place has been treating the raw sewage in a completely natural, eco-friendly manner: sewage is pumped through a series of canals into an area consisting of fish farms (bheris) and provides vital nutrients to the fish. A network of settling ponds, exposure to the Sun’s radiation and the work of algae and other natural agents, such as water hyacinth, treat the mix of sewage and storm water effectively.

These wetlands are also home to some of the major flora and fauna species. The High Court in Kolkata estimated that there are about 155 species of birds thriving in the water bodies of EKW, of which 64 species are resident and 91 are migratory. Additionally, 40 species of algae, 2 species of fern, 7 species of monocot and 21 species of dicots are also a part of the wetlands.

Several studies have identified the vulnerability of Kolkata to climate change. In 2012, a World Bank report predicted a rise of 1.2-1.8 degree Celsius in Kolkata by 2050, along with a fractional increase in rainfall. “A rise in sea level of 27 cm over the next four decades was predicted along with storm surge while calculating the climate-induced impact on the city. The EKW, as part of the Sunderbans system of mangrove forests and distributaries, increases the city’s resilience to withstand storm surges,” says Bonani.

With such significant ecological, social and hydrological functions performed by these wetlands, it is no wonder that they are a widely recognised ecosystem in dire need of protection.

(Published 24 February 2015, 04:09 IST)

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