India is racing to restore Kariyachalli, a sinking coral island in the Gulf of Mannar that has lost over 80 percent of its landmass since 1969 due to rising sea levels, severe erosion, and historical coral mining. Backed by a 460 million rupee government-backed initiative, conservationists are deploying thousands of artificial reef modules and planting seagrass to protect local fishing communities from escalating climate threats before a projected 2036 submersion date.
The Shrinking Landmass of Kariyachalli Island
Kariyachalli’s acreage has plummeted from 20.85 hectares in 1969 down to a mere 3.14 hectares by 2025. If current environmental pressures remain unchecked, scientific models project the entire island could disappear beneath the Indian Ocean by 2036. The landmass sits within a chain of twenty-one uninhabited islands that once buffered the coastline against the catastrophic 2004 tsunami. K. Diraviya Raj, a professor at the Suganthi Devadason Marine Research Institute leading the preservation project, explained that these small islands, seagrass beds, and coral masses absorbed the shock of that disaster and act as natural barriers against extreme weather events.
Climate change and rising ocean temperatures have supercharged the erosion process, completely erasing two islands from the regional map already. The Gulf of Mannar Marine Biosphere Reserve stands as one of Asia’s most biologically rich marine zones, supporting diverse flora, vulnerable dugongs, and extensive coral reefs. However, Kariyachalli’s surrounding coral cover dropped steeply from 500 hectares in 2005 down to 197 hectares by 2021.
Engineering Solutions on the Seafloor
The Government of India granted the Agence France-Presse exceptional access to observe the active conservation work unfolding four kilometers by boat off the coast of Thoothukudi. Funded by a budget of 460 million rupees, equivalent to 4.2 million euros, the restoration scheme relies on heavy engineering and manual labor. Workers install 8,500 artificial reef modules, transplant resilient corals, and restore vast underwater meadows of seagrass.
Each artificial reef block weighs between two and three tons, providing a stable substrate where new coral can anchor and grow. Meanwhile, local residents working near the shoreline tie green shoots with jute string onto wooden structures. Divers then submerge these wooden frames and anchor them firmly to the seabed. The planted seagrass serves a dual purpose by anchoring loose marine sediments and establishing critical nursery habitats for local fish populations.
Community Involvement and the Human Stakes
Daily operations on the island involve roughly a dozen residents belonging to local communities that depend on fishing and salt marshes for their survival. Martina, a 29-year-old resident working on the restoration project since early 2026, explained how the revival of marine resources supports her family. Her father works as a fisherman, and she noted that the seagrass beds boost fish reproduction to preserve the ecosystem and improve local livelihoods.
Supriya Sahu, an official from the state of Tamil Nadu, stated that this intervention remains the sole viable solution to shield coastal inhabitants from compounding threats. Without these defenses, local populations remain dangerously exposed to intensifying storms, recurring cyclones, sea-level rise, and unyielding shoreline erosion. The project began in April 2025 and is scheduled to wrap up its current phase by late September 2026 before entering a long-term monitoring period overseen by researchers.
Previous Island Restorations and Climate Resilience
Conservation teams have already tested these techniques on two other islands in the Gulf of Mannar, yielding encouraging results. At Vaan Island, the placement of roughly 10,000 artificial reef modules successfully recovered a portion of the island’s lost surface area. On Shingle Island, transplanted corals demonstrated higher resilience against severe bleaching events than older, established reefs during ocean temperature spikes.
A United Nations report released in March highlighted that the world’s oceans absorb 91 percent of excess planetary heat, acting as a buffer against atmospheric warming. Professor Raj noted that his team is actively identifying specific coral species that naturally tolerate abnormal temperature fluctuations to integrate them into future restoration blueprints. These adaptive strategies aim to help the marine ecosystem survive heating waters and form the coastal breakwaters of tomorrow.
