Author(s): Zinara Rathnayake

From wastelands to wetlands: The fight to save Sri Lanka's natural flood buffers

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Sri Lanka's capital is transforming floating garbage patches into biodiverse wetlands which are teeming with life.

Pay Drechsel is going for his daily morning walk around Thalangama Wetland, in Sri Lanka's capital Colombo. The Sun casts a warm glow over flowering pink water lilies as a farmer scrubs down his water buffalo. A kingfisher hovers nearby. Soon, photographers will arrive to capture curved-necked egrets, waders probing for crawling worms, and little cormorants diving for freshwater fish.

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The community came together to keep the massive wetland complex clean, forming the Thalangama Wetland Watch. Residents organise weekly collection runs, piling up sorted waste at a small collection unit which the municipality sends off for recycling. School kids volunteer, kayaking through the lake to dig up invasive water hyacinth.

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As Colombo is located in a river basin, the city is naturally prone to floods. Colombo's wetlands act as a flood buffer, with 40% of floodwaters draining into wetland areas. They also sink carbon, purify the air and control temperatures. As temperatures warm and rains become more erratic, "wetlands are important to the city to mitigate climate change impacts", says Chethika Gunasiri, an environmental scientist at the University of Tokyo who was part of Colombo's Ramsar application. "Wetlands help Colombo mitigate pollution and natural disasters. They help reduce human stress as more and more people are now living in high rise buildings," she adds.

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Although there's an attitude shift and residents are now aware of the value the wetlands add to the city, problems are far from over, Hettiarachchi says. After the civil war ended in 2009, Colombo's urban population expanded rapidly. Developments sprung up, leading to the draining of wetlands for housing, businesses and infrastructure. Since 2009, Colombo has lost 2.12 sq km (0.8 sq miles) of its wetlands. According to a 2024 study, wetlands absorb 62.1mm more floodwater than built up areas in Colombo. Despite collective efforts to clean and restore some of the city's wetlands, the overall loss of wetland area means that Colombo is becoming more vulnerable to floods, the 2024 study notes.

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Hazards Flood
Country and region Sri Lanka

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