An urban biodiversity refuge
Just outside the dense urban center of Colombo, the Bellanwila-Attidiya Sanctuary protects a 372-hectare remnant of a once extensive marshland. Officially declared a sanctuary in 1990, this suburban wetland is a critical habitat within a metropolitan area that the Ramsar Convention recognizes as a "Wetland City". The sanctuary's shallow lakes, marshes, and seasonal floodplains help the surrounding city, including flood control during monsoon rains and local climate regulation.
The wetland's true scientific value is its surprising biodiversity. Studies have documented a variety of life, including dozens of species of fish, butterflies, and reptiles. The sanctuary is particularly important for its fish populations. It provides a habitat for several endemic and threatened freshwater fish, such as the Ornate paradisefish (Malpulutta kretseri), an endangered species native only to Sri Lanka's southwestern wet zone. This small, colorful gourami thrives in the shaded, slow-flowing streams with leaf-littered substrates found within the protected area. The presence of such specialized species in a fragmented urban wetland demonstrates the capacity of small, protected areas to are last-chance refuges.
Conservation in a concrete jungle
The Bellanwila-Attidiya wetland persists despite immense pressure from urbanization. The number of buildings within the protected area increased from 5,158 in 2004 to 7,524 in 2017. This encroachment leads to habitat loss and pollution, which threaten the delicate ecosystem. Between 1995 and 2024, the wetland's vegetation cover decreased by nearly 38%.
Invasive alien species present another significant threat. Plants like the Pond Apple (Annona glabra) and animals like the Tank Cleaner catfish (Hypostomus plecostomus) have established populations in the sanctuary, competing with native species. The sanctuary's fish population has shown a marked decline over recent decades; studies recorded 33 species between 1980 and 1988, a number that fell to just eight by 2012.
Conservation efforts are underway to combat these threats. The Department of Wildlife Conservation manages the site, and partnerships with organizations like the Wildlife and Nature Protection Society focus on restoration. These projects involve the systematic removal of invasive species and the planting of thousands of native trees to restore the natural flora and support the sanctuary's unique fauna. The survival of Bellanwila-Attidiya is a case study in the challenges and possibilities of preserving biodiversity within a rapidly growing urban landscape.