Concrete reefs come to the rescue of sinking islands off south Indian coast

"The project will have the long-term benefit of making the entire ecosystem resilient to climate change impacts."

By Rina Chandran

MUMBAI - Deploying artificial reefs made of concrete to protect and restore a sinking island off India's southeast coast has proved so successful that national funds will be used to pay for other similar reefs, a state environment director said on Wednesday.

Tamil Nadu's H. Malleshappa said the reefs, installed in 2015, helped save Vaan Island and regenerate biodiversity in the Gulf of Mannar as warmer temperatures prompt rising sea waters that threaten ecologies and livelihoods.

Vaan Island is one of 21 uninhabited islands in the Gulf of Mannar between India and Sri Lanka which was declared Asia's first marine biosphere reserve in 1989.

Malleshappa said the project had proved so successful that more such reefs will now be placed in other degraded areas to also boost fish stocks and help fishermen.

"The primary aim was to protect Vaan Island from further erosion and submergence," Malleshappa told the Thomson Reuters Foundation.

"The other objectives were restoration of the island, conservation of biodiversity including the coral reefs, and enhancement of fishery production, thereby ensuring a sustained livelihood for fisherfolk," he said.

More than 150,000 fishermen depended on the marine national park and its buffer zone of 10,500 sq km (4,000 sq miles) for their livelihoods.

But coral mining and over-fishing led to the erosion and submergence of two of the 21 islands, Poovarasanpatti and Vilanguchalli. Vaan had shrunk to a tenth of its original size, to less than 2 hectares (5 acres), Malleshappa said.

The environment department discussed artificial reefs as a solution and worked with the Indian Institute of Technology in Chennai and a marine research centre to design and build them.

The triangular modules they developed are made of ferro-cement with holes of varying sizes.

The reefs helped prevent further erosion and led to an increase in Vaan's surface area, Malleshappa said. Several types of coral have regenerated and more fish are now seen, he said.

This is not the first experiment with artificial reefs but these reefs in the Gulf of Mannar are the first in India to be recognised for their ability to minimise climate-change impact.

New York City has, for years, been dumping retired subway cars - after stripping them of motors, wheels, seats and toxic materials - into the Atlantic Ocean to create artificial reefs.

In India, a 110-metre long artificial reef was placed in the waters off the coast of Kerala state to break the waves hitting the popular tourist beach Kovalam.

Following the success with Vaan Island, money from the national climate change adaptation fund has been allocated for more such reefs, Malleshappa said.

"The project will have the long-term benefit of making the entire ecosystem resilient to climate change impacts," he said.