Written by PPL Newsroom• October 6, 2026• 11:44 am• Nature & Wildlife

Tamil Nadu rebuilds reefs and seagrass to save shrinking Kariyachalli island

A $4.79 million state programme is placing about 8,500 artificial reef modules off Thoothukudi, with four years of monitoring planned after installation.

Tamil Nadu is rebuilding the natural sea defences around Kariyachalli, a shrinking island in the Gulf of Mannar off Thoothukudi. The work uses artificial reefs, transplanted corals and seagrass meadows. It aims to slow erosion and protect the mainland coast from storm surges and rising seas, according to an AFP report published at the end of September 2026.

An island losing ground

Kariyachalli is one of a chain of 21 islands in southern Tamil Nadu. Government estimates cited by AFP show it shrank from 20.85 hectares in 1969 to 3.14 hectares last year, a loss of more than 80 per cent. The report says it could vanish by 2036 if erosion continues unchecked.

The reefs around it have also thinned. Coral mining in the 1960s and 1970s did severe damage. Pollution, overfishing and bleaching in warming seas added to the pressure. Reef cover near Kariyachalli fell from roughly 500 hectares in 2005 to 197 hectares in 2021, so less than 40 per cent of the earlier area remained.

What is being built

The restoration is part of a $4.79 million state conservation programme. It includes about 8,500 artificial reef modules. Each weighs several tonnes and is placed using data on seabed conditions, currents and waves. The modules are meant to break incoming waves and give corals new surfaces to settle on.

Experts are also transplanting corals. Workers are restoring seagrass by tying shoots to wooden frames and anchoring them on the seabed. Seagrass helps hold sediment in place and provides nursery grounds for marine life. Deployment was expected to finish by the end of September. The site will then be monitored for at least four years.

Early signs from nearby islands

The team is building on earlier work in the Gulf of Mannar. On Vaan Island, about 10,000 artificial reef modules helped recover part of the lost landmass. On Shingle Island, transplanted corals came through a 2024 bleaching event better than older colonies. Wildlife warden Akhil Thampi said “Vaan island restoration results were very promising”, and that this led officials to take up Kariyachalli.

Scientists acknowledge that marine heatwaves make reef restoration harder. They are searching for coral species that naturally tolerate heat.

What this means for India

The project is an example of nature-based coastal protection in Tamil Nadu. A 2025 paper in Frontiers in Marine Science describes India’s response to sea-level rise as having three parts: coastal zoning, hard structures such as seawalls, and conservation of mangroves, seagrass and reefs. Research on coastal protection finds that corals, seagrass and mangroves together protect more than any single habitat. Kariyachalli’s four-year monitoring will show whether this approach works on Indian shores. Local saltpan workers are also being paid for seagrass work.

The Gulf of Mannar’s reefs and seagrass beds have protected the coast before. During the 2004 tsunami, which killed more than 8,000 people in Tamil Nadu, marine scientists say these ecosystems acted as a natural barrier and prevented a much larger disaster.

The project also brings income to nearby communities. Devkani, a 47-year-old saltpan worker who prepares seagrass frames, told AFP she no longer had to borrow at high interest during the lean months this year because of the sea-based work.