76% of coral reefs in Indo-Pacific at risk of drowning from rising seas in coming decades: NTU study

A recent study by Nanyang Technological University (NTU) reveals that three-quarters of coral reefs in the Indo-Pacific region, which includes Singapore, are at risk of drowning due to rising sea levels. The study found that if sea level rise exceeds 5.3mm per year, most corals will not be able to keep pace, a threshold that could be surpassed by the 2060s if greenhouse gas emissions continue to increase rapidly.

As of 2023, global sea level rise has been around 4.5mm per year, according to NASA. Rising sea level is not the only threat; longer-term sea level rise exacerbates the challenges corals already face due to coastal construction and bleaching caused by marine heatwaves. Coral reefs, which are submerged, will increasingly sit under deeper water as sea levels rise faster than their growth, a process known as reef drowning.

In Singapore, corals already live in murky waters, and further reduction in light reaching them could be dangerous. The loss of complex reef structures could reduce habitats for fish and other marine animals, impacting fisheries, tourism, and communities that rely on reefs for food and income. The NTU study analyzed 288 ancient reef cores from 92 sites across the Indo-Pacific, including the Great Barrier Reef in Australia, Maldives, and the Coral Triangle.

By calculating the vertical growth rate of these reef cores over the past 11,700 years, scientists can reconstruct past coral growth and changes in coral types. The study projects that under high-emissions scenarios, the sea will rise faster than 76% of the studied reefs can grow, leading to inundation by 2100. Weedy species, which grow rapidly but lack structure, may accelerate reef drowning.

Conservation efforts must consider local conditions, such as water quality and sediment movement, to improve the chances of coral reef persistence.