El Niño Threatens Singapore's Coral Reefs in 2027

Singapore, Singapore Jul 27, 2026 ALN: If a super El Niño develops as predicted, it could turn Singapore’s reefs white again in 2027, just three years after the country’s coral reefs suffered widespread bleaching.

This is likely to take place between March and May 2027, during the expected tail end of the current El Niño event, as its impact on temperatures is highest when it weakens.

While this is not a certainty, El Niño conditions are already present and are likely to become strong during August and September, according to the Meteorological Service Singapore’s May 29 update.

The National Parks Board said that if El Niño proceeds as predicted, impacts on coral reefs may intensify in 2027, adding that it is monitoring the situation.

Marine biologist Huang Danwei, deputy head of NUS’ Lee Kong Chian Natural History Museum, said that if El Niño picks up rapidly and extends through the middle of 2027, there is a “good chance” that higher sea temperatures will cause severe coral bleaching.

Corals get their vibrant colours from microscopic algae that live in their tissues. When they are stressed by rising sea temperatures, the corals expel the algae and turn ashen white in a phenomenon known as coral bleaching.

These algae supply the corals with nutrients, so when bleaching occurs, the corals become vulnerable to disease and may eventually die.

Global coral bleaching events occurred in 1998, 2010, 2016 and 2024, with Singapore also experiencing mass bleaching during those years.

All four global bleaching events followed El Niño – a climate phenomenon that warms sea surface temperatures and lifts global temperatures.

Severe bleaching during strong El Niño events can cause extensive coral mortality, reduce their structural complexity and lead to long-term declines in reef fish diversity and abundance, said Karenne Tun, group director of NParks’ National Biodiversity Centre.

While recent studies show that repeated bleaching in Singapore has caused relatively low immediate coral death – usually under 10 per cent, and about 5 per cent in the 2024 bleaching event – the reefs are changing and have “flattened” over time, she said.

Studies also indicate that a combination of factors, including heat stress, chronic turbidity, sedimentation and coastal development, has, over recent decades, shifted reefs from branching, structurally complex corals to more stress-tolerant, massive and dome-shaped forms, said Tun.

Repeated bleaching and such shifts to simpler reefs may affect coral spawning and potentially reduce reproductive output, limiting coral reefs’ long-term resilience even if they appear to recover, she added.

“Even when coral mortality is relatively low and coral cover remains moderate, research indicates that the loss of structurally important coral species can reduce habitat availability, biodiversity, ecosystem resilience, carbonate production and coastal protection functions,” she said.

Huang noted that the increased frequency of coral bleaching events also means that coral reefs will have less time to recover between them.

When corals do not recover, the flora and fauna that depend on reef habitats also decline in abundance and diversity.

Declines in reef fish – which are critically important for the food security and livelihoods of millions in South-east Asia – could endanger the lives of the most vulnerable communities, he added.

This comes as coral reefs have been under siege.

The third World Ocean Assessment, published on June 8, found that global coral cover continues to decline due to increasing ocean temperatures associated with climate change, continued coastal development, pollution, sedimentation, diseases, and marine resource destruction and over-extraction.

The frequency and severity of disturbances caused by heatwaves, disease outbreaks and tropical storms have also increased, it wrote, curtailing the recovery time between such disturbances.

This pattern is projected to continue on its current trajectory or accelerate, it added.

Written by more than 650 experts from 86 countries, the assessment provides the latest insights into the health of the oceans, providing a vital evidence base to help make better decisions for a sustainable future.

It is also the only global integrated assessment of the state of the marine environment that explores the environmental, economic and social dimensions of the ocean.

Tun said the report, unlike most global reports, does not prescribe policy. Instead, it brings together hundreds of national and regional assessments into an authoritative “health check” of the ocean that is policy-neutral but policy-relevant.

Documenting how climate change, pollution and overfishing, among other factors, put ocean systems under severe strain, the report calls for stronger multilateral cooperation and is designed to help policymakers sustainably manage the ocean.

The paper also found that ocean acidification – which refers to rising carbon dioxide levels in seawater – adds further stress to corals.

Ocean acidification makes it harder for corals to build their structures and weakens the reef foundation, making it difficult for reefs to keep growing upwards, said marine biogeochemist Patrick Martin from NTU’s Asian School of the Environment.

While Martin – who contributed to the report – noted that studies have shown that excessive acidification can harm corals, he said corals also show tolerance to acidification to a certain extent, though more research is needed.

He added that while ocean acidification is currently not the most pressing threat to coral reefs and has not reached extreme levels, it is steadily increasing alongside other threats that damage coral reefs.

Tun, who also contributed to the report, said that ocean acidification is already contributing to reduced skeletal density, slower growth and greater erosion risk in South-east Asian reefs, although these effects are harder to detect than bleaching and are often masked by co-occurring local stressors.

She said that the report also highlights that South-east Asia as a hot spot where warming, ocean acidification, nutrient pollution and land run-off coalesce, with reefs also experiencing low carbonate levels, which worsen the effects of acidification.

Under high-emissions scenarios, modelling and observational work in South-east Asia suggest that many reefs will become “marginal” for net reef growth between 2020 and 2050, said Tun.

This means that the rate of coral growth could barely keep pace with physical and biological erosion, even if live coral cover persists, she added.