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Beyond the Great Barrier Reef: Bleaching Undoes India Coral Restoration

In India’s Gulf of Mannar, more than a decade of efforts have spurred a slow recovery of coral reefs that protect the coast and feed communities. But climate change has reversed that success.

Written by Karthikeyan Hemalatha Published on Read time Approx. 6 minutes
Bleached corals in the Gulf of Mannar.SDMRI

TAMIL NADU, India – From the pristine shores of Kurusadai, one of the 21 uninhabited islands off the eastern coast of India’s southern tip, patches of maroon are visible beneath the sea as waves crash far away from shore.

Both the color and distant breaks are a healthy sign of the Gulf of Mannar’s protective reef, one of India’s four major coral areas. But the surface is deceiving – these live corals were hit hard by the global bleaching event that affected reefs around the world, according to a recent research paper.

Over nearly 20 years, the Gulf of Mannar reef’s slow recovery has been a hopeful story for conservation. The ecosystem and its coral islands barely survived decades of coral mining that ended by 2005. That was around the same time that locals saw a powerful demonstration of the reef’s value, when they were spared the worst effects of the 2004 Indian Ocean tsunami that damaged other communities nearby. Since then, reefs have been recovering, but global bleaching events linked to climate change have dealt the coral ecosystem a significant setback.

Many developing nations have been working to protect their reefs. But lately it’s like running on a treadmill. Along many coastlines, including the Gulf of Mannar, warming oceans are undoing hard-fought conservation progress.

A traditional boat near the coast of Kurusadai, one of the 21 islands surrounded by coral reefs. (Karthikeyan Hemalatha)

“While a substantial effort was put in by the local administration in protecting these corals from local impacts, climate change is beyond their control,” said Edward J.K. Patterson, director of the Suganthi Devadason Marine Research Institute and author of the recent bleaching study.

Between 2014 and 2017, the world suffered unprecedented back-to-back bleaching events. As ocean temperatures remained abnormally warm during these years, mass bleaching of corals – when corals expel their symbiotic algae – was reported in the Caribbean, Indian and Pacific oceans. But while bleaching in places like Australia’s Great Barrier Reef made global headlines, areas like the Gulf of Mannar have suffered more quietly.

The new research paper found that at least a quarter of all live corals in the Gulf of Mannar region bleached between March and June 2016. During that time, water temperatures were warm, but not necessarily out of the normal high range, the study said. What was unusual was that warm temperatures started earlier and lasted longer. The result: By October 2016, live coral cover on the reef “drastically” dropped from 39 percent to 22 percent, the study found.

The Gulf of Mannar was hit hard by bleaching in 2016. (SDMRI)

Of the four major reef areas in India, the Gulf of Mannar corals are probably the most important to people – and have also faced the most stress.

Other coral areas, in the Bay of Bengal and Arabian Sea, are relatively remote, while corals in the Gulf of Kutch are near communities in which fewer people depend on the sea, according to Chowdula Satyanarayana, a coral reef scientist with the Zoological Survey of India. But in Tamil Nadu, the densely populated state bordering the Gulf area, many fishers depend on the sea for their livelihoods – and for their protection.

This hit home during the 2004 tsunami. “Nagapattinam in the north and Kanyakumari in the south were completely battered,” said Thavasiyanti Gunasekaran, the head of the fishers’ association in a village in the coastal district of Rameswaram. “Our villages saw minimal damage. It did not take too long for us to realize what protected us.”

In fact, overexploitation of these reefs, from both overfishing and mining, nearly killed off the ecosystem in the previous decades. In the 1990s, when mining corals was rampant, nearly 25,000 metric tons of coral material was removed annually.

This legacy is visible in the city of Thoothukudi, where corals were used in the construction of many buildings erected before 2000. A few dilapidated structures, with their paint peeling off, betray the natural coral patterns below. Unregulated mining got so bad that two islands sank into the sea due to erosion.

By 2005, more than 60 percent of the 110 square km (40 square miles) of reefs in the Gulf of Mannar were already destroyed. But coral mining was effectively halted in that year, just in time before irreversible losses could take place, said Patterson. That was the result of a 2001 national decision to classify corals as Schedule 1 under India’s Wildlife Protection Act. Overnight, taking corals out of the water became punishable by up to six years in prison, although it wasn’t until 2005 that the law was strictly enforced in the region. When the mining finally stopped, the corals began to recover.

Corals were used in the construction of buildings in coastal districts near the Gulf of Mannar. (Karthikeyan Hemalatha)

Around the same time that enforcement against poaching ramped up, the government also worked with fishing communities to tamp down on a destructive overfishing cycle. “With dropping fish catch, fishermen become more desperate and use more exploitative measures to catch more fish and sustain themselves,” said Ashok Kumar, wildlife warden for the coastal district Ramanathapuram.

In 2002 the state forest department and the United Nations Development Program together formed the Gulf of Mannar Biosphere Reserve Trust (GoMBRT) to provide fishers with alternative income sources. With a fund of more than $1.2 million, the group has given thousands of small, low-interest loans for groups to start businesses like making fish pickles and weaving baskets. It’s also offered young people vocational courses.

“This extra income steers the men to stay away from fishing,” said Kumar. “While this helps in conserving the marine ecology, it also gives the family a stable income without the need for destroying the oceans.”

The end of mining, combined with less fishing pressure, has helped spur a slow recovery. Between 2005 and 2009, the area of live corals on the reef increased from an estimated 37 percent to 43 percent.

This progress, however, was short-lived as a wave of global bleaching in 2010 struck the Gulf of Mannar. This time, the newly formed corals were hit hard and live coral coverage fell to 33 percent. Over the next six years, coral cover recovered to 40 percent by the time the most recent and intense bleaching event occurred. After the 2016 event, total coverage dropped to just 22 percent, the recent survey showed.

Across the coast, there is anecdotal evidence that with increasing temperatures, there is also decreasing catch for fishing communities.

“There is a drastic drop in the population of commercially important species like anchovies and sardines,” Deepak Samuel, a marine biologist and former project specialist at the Gulf of Mannar Biosphere Reserve Trust (GoMBRT), said. “While several factors play a role in this, increasing sea temperature has been key.”

Patterson said that the SDMRI has recently been working to transplant live corals – around 6 hectares (14 acres) so far – to speed up recovery. Divers take live corals from one part of a healthy reef and transplant them to a degraded area where the substrata are still healthy. Patterson said the scientists have observed increasing fish density around the live corals.

Fishing trawlers moored in Rameswaram, India. (Karthikeyan Hemalatha)

Yet this is not enough for fishers to make a living and when fish catch drops many still resort to more destructive methods, such as using small net sizes that scrape up eggs and small juvenile fish. The state has few resources to implement rules requiring larger mesh sizes, said Samuel.

But many local fishers do value the reef, especially since the 2004 storm. Gunasekaran, head of the local fishers’ association, said, “The corals were a natural barrier against killer waves – for which we are grateful. A lot of us are now more respectful and mindful to corals.”

Satyanarayana said global warming is now the biggest threat to corals in India, even though they will continue to take local action to improve the reef’s health.

“While it is difficult to have specific action plans to protect corals from global warming, protecting them from local pressures gives them the resilience they need to survive future bleaching events,” he said.

Satyanarayana added that trying to restore the coral ecosystem is still imperative to thousands of fishers along the coast. “However, any efforts in protection measures or transplantation will not matter if such bleaching events continue to occur,” he said.

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