Wetlands losing ground


By Sajitha Prematunge

It’s difficult to fathom that a new fish species could be discovered from an artificial wetland. One such discovery was recently made by a group of scientists conducting research at the Diyasaru Park, managed by the Sri Lanka Land Reclamation and Development Corporation (SLLRDC). As the species is still not published it’s all a bit hush hush. So no names!

This is just one example of the true value of an artificial wetland. Beddagna, Thalawathugoda (Diyasaru Park), Kimbulawela, Madiwela, Kolonnawa, Crow Island, Talangama Tank, and Beira Lake make up the Colombo wetlands complex with an estimated extent of 4,700 acres. This network of wetlands harbour extensive biodiversity, providing a habitat for more than 250 species of plants and 280 of animals. A significant number of these species are critically endangered.

However, as much as 60 percent of the wetland area in the Colombo Metropolitan Region has been lost since the 1980s. The current rate of loss due to infilling and solid waste disposal is estimated at 1.2 percent per year. If the trend continues the extent of wetlands is at risk of declining by one-third over the next two decades. The Colombo wetland area is now reduced to 20 square kilometres. The situation has become critical in the last five years, threatening the ecological health of wetlands, a situation made worse by routine dredging. Invasive plant species, choke waterways, threatening native biodiversity.

Diyasaru Park

Just imagine if Diyasaru Park was not converted into a wetland we would not have today our newly discovered John Doe the fish! Sprawled over 60 acres Diyasaru Park was formerly known as the Thalawathugoda wetlands. What used to be a paddy field is now converted into a wetland, after it was used to dump Diyawanna Oya dredging material. Together with Parliament Lake, the Park has been designated as a wildlife sanctuary, Sri Jayawardanepura Sanctuary, by the Department of Wildlife Conservation (DWLC) under the Fauna and Flora Protection Ordinance of 1937.

From toilets to an ecological laboratory Diyasaru Park provides every modern facility. Complete with a study centre, bird watching tower, bird hide, resting hut, organic agricultural area and boat jetty, the Park is home to more than 28 species of dragonflies, 28 species of reptiles, seven species of mammals, including the fishing cat and otter, and more than 80 species of birds, with a dedicated zone for butterfly species numbering in the 40s.

Talangama Tank

Talangama Tank is a prime example for an urban wetland that serves more than one purpose. Not only does the Tank provide water for paddy farming, it provides a host of ecosystem services such as water retention, groundwater recharge, drainage and purification, and is a breeding and roosting ground for wildlife. In fact, it’s used by many bird watchers and university research students for the diversity it affords.

The Talangama Tank is home to 70 species of birds and 30 species of other animals, including dragonflies, the fishing cat, purple-faced leaf monkey and mouse-dear, among others. The Tank and its associated wetlands, with an extent of about 35 acres, have been designated as an ‘environmental protection area’ (EPA) by the Central Environmental Authority (CEA) under the National Environment Act of 1980.

World Bank funded Metro Colombo Urban Development Project was aimed at reducing the flooding in Colombo City. Environmental specialist and World Bank consultant Nadeera Rajapakse Rubaroe explained that with the development of the Colombo city much of the natural drainage system was hampered, and with it the increased risk of flooding.

The Madiwela East Diversion Scheme was implemented in 1991 to prevent water from draining into the city by reducing the height of the Talangama Tank bund by putting in a weir through which the water was directed to the Averihena tank via a canal. Siltation and alien invasive plants such as the Pond Apple, locally known as Wel Atha, further reduced the Tanks capacity. The eventual capacity loss reduced water supply to paddy fields. The Tank provides water to 200 acres of paddy fields sustaining the livelihoods of 175 farmers.

Senior Researcher, Human and Environmental Health, International Water Management Institute (IWMI), Dr. Priyanie Amerasinghe explained that change is inevitable in natural ecosystems. Siltation is a result of ecological succession, a natural phenomenon in which an ecosystem is subject to change. A wetland, left to it’s own devises silt over time, turns into a march and ultimately dry ground.

The only solution was to dredge the Talangama Tank, "Dredging the initially recommended eight and half acres would have been environmentally unsound," said Rubaroe. "Because the system has already got naturalised." She pointed out that sweeping changes in a natural system is not without consequences.

Dredging would mean taking the Pond Apple out of the equation. "The Pond Apple is not just a plant species any more. It’s a habitat. If we progressively remove Wel Atha the birds may find alternate habitat but we don’t understand the ecology of the fishing cat well enough to know how it would react to the change," said Researcher – Natural Resources Governance, Sanjiv de Silva. He informed that the fishing cat is one of the wild cats of Sri Lanka. To be actually able to see it in an urban area, let alone the capital city of a country is actually a big deal. Ultimately 50 percent of the area was earmarked for dredging which added 18 more acre feet to the Tank’s capacity.

However, there is clearly a conflict of interest between the stakeholder groups such as the farming community, newly settled residents, conservation organizations and environmentalists and nature lovers. The new residents are vehemently opposed to dredging as are some environmental organizations. While the farmer community represented by Parakum Farmers Association, President, KD Padmalal claim that the new residents dispose waste water into the Tank and are encroaching into the Tank by infilling. Padmalal informed that even factories divert their waste water into waterways which ultimately wind up in the Tank.

"Wetlands perform such vital ecosystem functions that we can’t afford to lose another inch of them," reiterated Rubaroe. She informed that a detailed valuation on the Talangama Tank came up with ecosystems services that added up to millions of rupees. If these services were to be provided artificially, it would cost millions to the supplier, she emphasised.

Pics courtesy: Sanjiv de Silva and Madeline Dahm/IWMI


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