KARIYACHALLI — Under a blazing sun, workers crouch on a shrinking island off India’s southern coast, threading bright green seagrass shoots onto wooden frames before anchoring them onto the ocean floor.

Restoration work on Kariyachalli island hopes to rebuild its natural defences with artificial reefs, transplanted corals and seagrass meadows, in a bid to slow erosion and protect the mainland from surging seas.

“If you are not able to provide that resilience, you are absolutely at the mercy of vulnerabilities of storm surges, cyclonic storms or sea-level rise and also erosion,” senior state official Supriya Sahu told AFP.

AFP travelled by boat to the protected island after being granted exclusive access by the foreign ministry.

Kariyachalli, which is part of a chain of 21 islands in southern Tamil Nadu state, has lost more than 80 per cent of its landmass over the past half century and could disappear entirely by 2036 if erosion is left unchecked.

Government estimates show Kariyachalli shrank from 20.85 hectares in 1969 to just 3.14 hectares last year.

The coral reefs in the Gulf of Mannar, where Kariyachalli and other islands are located, also play a vital role in softening the impact of natural disasters, such as the 2004 Indian Ocean tsunami.

More than 8,000 people were killed in Tamil Nadu during the tsunami, but marine scientists say these ecosystems acted as a crucial natural barrier and prevented a much larger disaster from happening.