4 days ago
Lakshadweep's coral cover halved in 24 yrs
A 24-year-long study of corals in the Lakshadweep archipelago has found a 50% decline in coral cover compared to 1998 as a result of repeated marine heatwaves, exacerbated by climate change. The study published in the journal of Diversity and Distributions said this decline was explained by reduced recovery rates after each bleaching event, despite coral mortality decreasing with successive events. The paper concluded that the fate of corals in Lakshadweep will be determined by the return time of bleaching events. (HT photo)
The paper concluded that the fate of corals in Lakshadweep will be determined by the return time of bleaching events, underscoring that urgent climate action is critical to secure the ecological integrity of tropical reefs. The scientists leading the study, including Rohan Arthur and Mayukh Dey from the Oceans and Coasts Programme of Nature Conservation Foundation concluded that 'the one thing reefs need to recover is time'.
'Without a pause in the frequency of marine heatwaves, whatever resilience tropical reefs have is likely to be short lived. Our results show that fewer corals die simply because less is available to die in later years,' they added.
'In the long run, we must call the crisis by its name and acknowledge that the integrity of tropical reefs, like the rest of global biodiversity, cannot sustain the seemingly impervious logic of the prevailing economic order. Without scale-appropriate radical policies, laws, and actions to address these ultimate causes, anything we do locally for reefs will be symptomatic and palliative fixes,' the scientists said.
Lakshadweep Archipelago has 12 coral atolls in the northern Indian Ocean. The archipelago is among the most densely populated atoll systems globally with 10 populated islands, with more than 2000 people/sq km. Lakshadweep has experienced three marine heatwaves associated with the El Niño phase of the ENSO phenomena in 1998 (5.3 Degree Heating Weeks, DHW), 2010 (6.7 DHW) and 2016 (5.2 DHW), with 2010 being the most severe of the three.
Hindustan Times, in a series on Lakshadweep published last year reported how the islands experienced a severe bleaching event in 2024. The heat stress in Lakshadweep (Laccadive Sea) and in Southeast India was record-setting in 2024 according to Derek P Manzello, Coordinator, NOAA Coral Reef Watch.
The metric used to gauge heat stress on corals is called Degree Heating Weeks (DHW). DHW shows how much heat stress has accumulated in an area over the past 3 months. In 2024, Lakshadweep reached 9.2 DHWs, whereas SE India reached 9 DHWs. The prior record for Lakshadweep was 6.7 DHW in 2010, and it was 6.9 DHW for SE India in 2016, said Manzello.
Since 1998, researchers from the Nature Conservation Foundation have been tracking reef conditions at three atolls across the Lakshadweep Archipelago , Agatti, Kadmat and Kavaratti , to understand how reefs respond to climate change. This monitoring programme has monitored reefs as they declined and recovered from three major El Niño Southern Oscillation (ENSO) events — in 1998, 2010 and 2016. The data was analysed to explore if changes in the composition of coral could be explained by the number of heatwaves experienced and by more local factors, such as seasonally strong wave action and depth at which corals are found.
The team also found that these results challenge the simplistic narrative that all coral reefs respond in a similar fashion to climate change, and are universally doomed. Even within a small archipelago like Lakshadweep, there is a large variability in responses -- sometimes in reefs only a few kilometres apart.
'The Lakshadweep reefs have been home to me since I first dived here as a young researcher. To see these diverse ecosystems decline before my eyes is soul-destroying. Our findings are a bittersweet offering. On the one hand, it shows me that the reef is more complex and more resilient in its responses than I could ever have imagined it to be the first time I saw it bleaching in 1998. On the other hand, I realise that we have a limited window to change the narrative on tropical reefs. Without real and considered action on climate change, the reefs of Lakshadweep could well be functionally extinct in my lifetime -- and I cannot bear to think of what that would mean for my friends who call Lakshadweep their home,' said Rohan Arthur, Senior Scientist at the Nature Conservation Foundation who heads the Oceans and Coasts Programme.
'Many coral areas in our reefs are now dead. We have seen it first hand. The corals in the eastern end of Kavaratti are dead. This was seen after cyclone, Ockhi in 2017. We cannot express how we feel about this loss,' said Saheer Ali, diving instructor in Kavaratti.
The Indian Ocean basin, the fastest warming basin in the world, will see accelerated warming at a rate of 1.7 degree C-3.8°C per century during 2020-2100, a research paper published in Elsevier last year said. It also warned that this will lead to an increase in severe weather events, prolonged marine heatwaves and extreme Indian Ocean Dipole events that will influence the monsoon and cyclone development.
