A group of 22 ecologists and marine experts have written to Tamil Nadu Chief Minister M.K. Stalin, asking him to stop the proposed Mamallan Reservoir project. They warn this plan will badly harm the Kovalam-Nemmeli backwater wetlands, a crucial coastal ecosystem. The scientists wrote to the Chief Minister and Additional Chief Secretary for Environment, Climate Change and Forests. They said studies show brackish wetlands depend on tidal flows that bring in salty water. Changing this flow would alter the water’s salinity, temperature, and movement, hurting marine life. They explained that Kovalam-Nemmeli is a tidal-marsh ecotone connected to the Bay of Bengal by inlets, not just a freshwater area. The southern part near Mamallapuram remains healthy due to tidal water inflow. But the Nemmeli area is already breaking up because of roads and bunds. The wetlands have seagrass, mudflats used by migratory birds, and habitats for young fish and shrimp. Turning it into a freshwater reservoir would destroy these features. This would harm local fisheries, bird homes, and natural barriers against coastal storms. The experts also flagged flooding dangers. According to the Environmental Impact Assessment, flooding in nearby villages happens because of drainage blockages on key roads. The reservoir plan does not fix these problems. Building 4.5-meter-high walls in the tidal floodplain could remove natural flood protection and raise cyclone risk. The scientists urged the government to declare the site a protected lagoonal wetland. This would help conserve wildlife, sustain fisheries, and build climate resilience. The letter includes signatures from top names like Asad Rahmani (former Bombay Natural History Society Director), John Kurien (former CDS Professor), Romulus Whitaker (Madras Crocodile Bank), and other leading environmentalists and academics.