Within just a 17-kilometre radius in one Indonesian archipelago, there is an explosion almost every hour as locals practise “bomb fishing”, destroying coral reefs and decimating marine life.

Over 483 days between May 2023 and September 2024, at University College London and his colleagues deployed an acoustic monitoring system at Spermonde Archipelago, south-west of Sulawesi, Indonesia.

As well as being a global coral reef biodiversity hotspot, it is a location where fishers detonate explosives underwater, stunning and killing fish that can then be easily harvested.

“The sound of bomb fishing is so loud that if you’re on a dive it can shake you out of your skin,” says Williams. “You feel it more than you hear it. But if you put your head up on the surface, you likely won’t even see the boat responsible because the sound of bomb fishing travels such a huge distance underwater.”

The recording equipment sat at a depth of 17 metres and was able to detect explosions inside a radius of almost 17 kilometres. The team used AI to analyse their 3650 hours of raw audio. They recorded 3567 explosions, or just over 23 per day while the device was underwater.

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“We have shown the true extent of this practice in a known hotspot for the first time ever, which we hope will drive action to curb this destruction,” says Williams.

One of the biggest issues is that there is an illegal supply chain underpinning the bomb fishing, usually involving the sourcing of fertilisers and fuses or detonators, he says. “In other regions these may be stolen mining explosives or even military explosives.”

Once the fishers have the explosives, enforcement at sea is sparse. “It’s like Whac-A-Mole targeting the bomb fishers. The best approaches should tackle the illegal supply chain that gets the materials needed to make explosives to bomb fishers or sellers of these,” says Williams.

Bomb fishing is a problem across the tropics, and part of the solution is retraining locals in sustainable tourism and reef restoration, he says. “It’s been documented in 34 countries, from South America to the Mediterranean to the East Coast of Africa and South-East Asia.”

, who wasn’t part of the work, is currently studying at the University of Queensland, Australia, and has worked extensively with Indonesian non-governmental organisations in reefs targeted by bomb fishing. He says he wasn’t surprised at the scale of the problem.

“I expected the frequency to be high, but studies regarding bomb fishing are relatively scarce because it is notoriously difficult to quantify,” Gotama says.

He says the new method employed by the researchers might help combat the practice. “If this acoustic method could be replicated elsewhere, it could help with detecting and quantifying blast fishing and help identify hotspots of activity,” says Gotama.

“That could be valuable not only for ecological monitoring, but also for targeting enforcement and evaluating whether management interventions are actually reducing blast fishing.”

Coral reefs on a chain of islands off Western Australia were almost untouched by a prolonged heatwave that devastated corals in other regions in early 2025. Researchers hope that learning the secret of extreme heat tolerance in these corals will help to protect reefs across the globe, which are in danger of being wiped out by global warming.

 at the University of Western Australia in Perth and her colleagues dived at 11 sites across the Houtman Abrolhos archipelago in July 2025.

Further north at the Ningaloo Reef, up to 60 per cent of corals died during the same heatwave. This was a story repeated at reefs around the world, with marine heatwaves in 2025 killing vast swathes of coral globally.

But at Houtman Abrolhos, apart from a few tiny patches, there weren’t even any signs of stress, such as fluorescing coral. “We expected to see mass bleaching with lots of white colonies, and likely mortality of reefs, given we did surveys after many months of marine heatwave. We did not see this,” says Quigley.

Prolonged heat stress generally leads to coral bleaching, when corals expel the symbiotic algae that live in their tissues, which provide most of their food.

Researchers measure the heat stress faced by corals in (DHW), which accounts for how long a heatwave endures and how high temperatures reach.

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Over 4 °C-weeks, scientists expect to see significant bleaching and above 8 °C-weeks, the situation becomes dire. “Values of around 8 °C-weeks are generally considered catastrophic and are often associated with widespread bleaching and mortality,” says Quigley.

The waters around the Houtman Abrolhos Islands hit 4 °C-weeks in early February 2025 and 8 °C-weeks by early March, but the temperatures kept rising and by mid-April the corals had experienced 22 °C-weeks of heat stress.

Quigley and her colleagues were most surprised to find that the full array of coral species at the reef all seemed immune to what had proved disastrous elsewhere.

To try to determine just how heat-tolerant the coral at the Houtman Abrolhos Islands actually are, the scientists brought colonies from several species back to the lab and subjected them to prolonged high temperatures.

At 8 °C-weeks, compared with currently accepted thresholds, survival rates at the Houtman Abrolhos islands were twice as high and bleaching resistance was nearly four times higher. There was still nearly 100 per cent survival at around 16 °C-weeks.

While the upper limit of the tolerance of corals there is still unclear, it is “clearly substantial and higher than what has been documented at other reef locations studied so far around the world”, says Quigley.

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The next step for the researchers is to work out exactly how the corals are achieving this survival feat.

Because resistance was across many species, Quigley says it is possibly the algal symbionts that are giving the Houtman Abrolhos island corals their superpower.

“I think this location has a particular set of environmental factors that has driven the evolution of heat tolerance generally for the species that live there,” she says. Because of this, such reefs should be given the highest level of protection, and other similar high-tolerance sites should also be identified, she says.

at the Great Barrier Reef Foundation says such reefs serve as “natural laboratories for understanding heat tolerance”.

“They may also hold the key to advancing selective breeding and other interventions aimed at enhancing thermal resilience in conservation aquaculture and coral restoration,” says Lundgren.

While focusing on curbing global carbon emissions remains the most critical action to save these precious ecosystems, “providing adaptive assistance by, for example, seeding reefs with more heat-tolerant corals will give coral reefs their best chance at adapting to future heat stress events,” she says.

The extent of coral reefs worldwide has played a key role in Earth’s climate in the past 250 million years – but not in the way you might expect.

Coral reefs are net producers of carbon dioxide because the greenhouse gas is a by-product of the formation of calcium carbonate, which makes up corals’ skeletons.

Some types of plankton also build shells out of calcium carbonate, and when they die, this mineral is buried in the seabed. When large areas of shallow marine environments are covered in coral, calcium and carbonate ions that would normally be taken up by deep-sea plankton is no longer available.

 at the University of Sydney, Australia, and his colleagues modelled the interplay between shallow-water corals and deep oceanic plankton over the past 250 million years by integrating reconstructions of plate tectonics, climate simulations and changes in sediment flowing into the sea.

They found that the balance between corals and plankton has been disrupted when plate tectonics and geomorphology lead to periods when there are extensive areas of shallow continental shelf, which is the ideal habitat for reef-building corals.

When coral reefs are less extensive, calcium and alkalinity build up in the ocean, plankton become more productive and more carbonate is buried in the deep sea, which helps to lower CO2 levels and bring temperatures down.

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There were three major periods when the carbon cycle was severely disrupted in the past 250 million years, the researchers found. These events, in the mid-Triassic, the mid-Jurassic and the late Cretaceous, involved extensive coral reefs using huge amounts of calcium carbonate, leading to big rises in sea temperatures.

When the balance between shallow-water coral reefs and deep-sea plankton breaks down, says Salles, it can take hundreds of thousands to millions of years to re-establish equilibrium.

“So, even if the system manages to recover from a huge crisis, the rebalancing is going to happen over a really long time period that is much longer than human timescales,” says Salles.

On the positive side, says Salles, if planktonic nutrient blooms are ever out of control, corals are great at taking up excess nutrients to build coral reefs.

Now, human CO2 emissions are causing global warming and ocean acidification at an unprecedented rate, which is killing both corals and plankton, says Salles. The consequences are unknown, but are likely to be ecologically catastrophic, he says.

“The deep-time feedbacks we modelled do not apply today – the pace of modern change is far too rapid for carbonate-platform feedbacks to matter in any comparable way.”

at the Australian National University in Canberra says the study shows there is a “deeply intertwined feedback cycle between life and climate”.

He says people often think that species evolve and adapt in response to Earth’s climate, which is governed by “immutable physical and chemical processes”.

“However, more and more often we are seeing examples where biological species directly influence the climate itself, creating a co-evolving feedback loop,” says Skeels. “Not just corals, but also more ancient microbial colonies like stromatolites have played a key role in modulating atmospheric carbon.

“We know that carbon warms our climate, as it is doing so rapidly today, and reefs may have contributed to this process over very deep timescales, explaining oscillating warm and cold intervals.”

A recent surge in ocean temperatures has caused the widespread bleaching and death of warm-water corals around the world, officially triggering the first climate tipping point for one of Earth’s ecosystems, scientists have declared.

The collapse of one of the world’s most diverse and fragile ecosystems poses a “human health and security hazard” that governments are unprepared for, warns at 91ɫ��Ƭy Reefs for 91ɫ��Ƭy People, a conservation programme operating in Central America.

Warm-water coral reefs support up to and provide food, coastal protection and a source of income for up to a billion people around the world. Reef services .

Yet corals are highly sensitive to changes in water temperature. Record-breaking global temperatures documented since 2023 have pushed ocean heat levels to new highs, triggering a mass bleaching event that has affected more than 80 per cent of all the world’s corals. Bleaching is when corals expel the algae living in their tissues in response to high water temperatures, which turns them white. This leaves corals vulnerable to disease, and prolonged bleaching can kill them off altogether by depriving them of their primary food source.

The latest bleaching event has been a “different order of magnitude” to anything scientists have previously witnessed, says McField. “We’re in the tipping point,” she confirms. This is generally defined as a critical threshold that, if passed, could cause dramatic and probably irreversible changes in the climate system.

McField was one of the authors of the chapter on corals in the , released today. The report, the first update since 2023, is compiled by 160 scientists from around the world and co-ordinated by the University of Exeter in the UK and campaign group WWF. It warns that warm-water corals are the first Earth system to cross over into their tipping point and are now in the throes of an “unprecedented crisis”.

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Central academic estimates suggest that the thermal limit of warm-water corals is reached when global atmospheric temperatures hit 1.2°C above pre-industrial levels, with an upper threshold of 1.5°C. In 2024, global average temperatures exceeded 1.5°C above pre-industrial levels for the first time in recorded human history, an event that has pushed the world’s coral reefs beyond the limits of their endurance, according to at the University of Exeter, who led the report.

“We’ve taken a sample of the 1.5°C world, and we have seen the consequences,” he told reporters at a press briefing ahead of the report’s launch. “A majority of coral reefs are under risk of extensive dieback [or bleaching] and tipping into the alternative seaweed-dominated, algal-covered state.”

The best hope of saving the world’s warm water corals from almost complete extinction now lies in bringing global average temperatures down to 1.2°C above pre-industrial levels as soon as possible, he says. Whether or not such an ambitious goal – which goes well beyond the demands of even the 1.5°C temperature target – is feasible to achieve is a separate question, says Lenton.

at James Cook University in Australia warns there are now “almost no unbleached reefs left anywhere in the world”. But the situation can still be mitigated. “Where coral reefs end up in the next few decades is under our control, if global greenhouse gas emissions are rapidly curtailed,” he says.

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With temperature records tumbling, it is only natural to worry about cascading tipping points, but the reality is far more nuanced

Often the point at which climate tipping points could be triggered is highly uncertain, but researchers warn the widespread decline of the Amazon rainforest, the melting of polar ice sheets and the collapse of the crucial AMOC ocean current could all happen at warming levels below 2°C.

But people can also trigger “positive tipping points” to mitigate the risk, Lenton stresses, highlighting the exponential growth of renewable energy over the past decade and the rapid take-up of electric vehicles. Rapid adoption of cleaner technologies has the potential to deliver emissions cuts at the scale needed to keep warming below 2°C, the report notes.

In a statement, Lenton said urgent action is needed from world leaders at the upcoming COP30 summit in Brazil to accelerate emissions cuts across the global economy and minimise the amount of time global temperatures spend above 1.5°C. “We are rapidly approaching multiple Earth system tipping points that could transform our world, with devastating consequences for people and nature. This demands immediate, unprecedented action from leaders at COP30 and policy-makers worldwide,” he said.

There might be an upside to the loss of coral reefs. Their decline would mean oceans can absorb up to 5 per cent more carbon dioxide by 2100, researchers estimate, slowing the build up of this greenhouse gas in Earth’s atmosphere.

“It is a beneficial effect if you only care about the concentration of CO2 in the atmosphere,” says at Sorbonne University in Paris, France. But the decline of corals will also reduce biodiversity, harm fisheries and leave many coasts more exposed to rising seas, he says.

How much the world will warm depends mainly on the level of CO2 in the atmosphere. So far the land and oceans have been soaking up around half of the extra CO2 we have emitted. Any factors that increase or decrease these so-called land or ocean carbon sinks could therefore have a significant impact on future warming.

It is often assumed that corals remove CO2 from seawater as they grow their calcium carbonate skeletons. In fact, the process, also known as calcification, is a net source of CO2.

“You’re taking inorganic carbon in the ocean, generally in the form of carbonate and bicarbonate ions, turning it into calcium carbonate and that process releases CO2 into the seawater, some of which will be lost to the atmosphere,” says Kwiatkowski.

This means that if reef formation around the world slows or even reverses, less CO2 will be released by reefs and the oceans will be able to absorb more of this greenhouse gas from the atmosphere – a factor not currently included in climate models.

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Observations suggest coral reef calcification is already declining as rising seawater temperatures cause mass coral bleaching and die-offs. The higher level of CO2 is also making oceans more acidic, which can make it harder to build carbonate skeletons and even lead to their dissolution.

Kwiatkowski and his team took published estimates of how corals will be affected by warming and ocean acidification and used a computer model to work out how this might change the ocean sink in various emission scenarios. They conclude that the oceans could take up between 1 and 5 per cent more carbon by 2100, and up to 13 per cent more by 2300.

This doesn’t take account of other factors that can cause reef decline such as overfishing and the spread of coral diseases, says Kwiatkowski, so might even be an underestimate.

On the other hand, the work assumes that corals aren’t able to adapt or acclimatise, says at the University of Hawai’i at Manoa, who wasn’t involved in the study.

“If the worst-case or even medium-case scenario in this study comes to pass, it means the near-total destruction of coral reefs globally,” says Jury. “I think that with consideration of realistic levels of adaptation and acclimatisation by corals and other reef organisms, the authors might come to different conclusions under a low to moderate level of climate change.”

If Kwiatkowski’s team is correct, it means that the amount of emitted CO2 that will lead to a given level of warming – the so-called carbon budget – is a little larger than currently thought.

“I think we would like our budgets to be as accurate as possible, even if we’re blowing through them,” says Kwiatkowski.

Ocean acidification is sinking into marine regions as deep as 1500 metres, posing new threats to organisms like sea butterflies, sea snails and cold-water corals.

The ocean is the largest natural sink of carbon dioxide, absorbing about a quarter of our annual emissions. That uptake of CO2 makes the ocean’s surface more acidic, with consequences for sensitive ecosystems like coral reefs. But until now, researchers did not know the extent to which acidification was reaching deeper waters.

at the Federal Institute of Technology Zurich in Switzerland and his colleagues developed a 3D reconstruction of how CO2 moves through the ocean, based on global measurements of currents and other circulation patterns. They used this model to estimate how the carbon dioxide the oceans have absorbed since 1800, around the start of the industrial revolution, has affected deep-water acidity.

They found a clear acidification signal down to 1000 metres in most of the ocean. Some areas, such as the North Atlantic – where the powerful Atlantic meridional overturning current (AMOC) carries carbon from the surface to deeper waters – saw acidification down to 1500 metres. Some pockets of deeper water that are naturally more acidic saw even more acidification than the surface. Their higher original acidity reduces their capacity to absorb any added CO2, says Müller.

This is more or less what researchers expected would happen as the ocean takes up more CO2, says at the University of Rhode Island. “But it’s a different thing to really see the data coming in to affirm this.”

Notably, about half of all the acidification since 1800 occurred after 1994, as our emissions of CO2 have risen exponentially. “We see this rather rapid progression,” says Müller.

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The magnitude of the acidification is enough to threaten the survival of organisms in large areas of the ocean. Pteropods like sea snails and sea butterflies are at particular risk because they build their shells out of calcium, which dissolves if the water gets too acidic. The rise in acidification has also doubled the areas where cold-water corals will have trouble surviving.

And ocean acidification is set to continue as the water absorbs more CO2. “Even if we were able to stop CO2 emissions immediately, we would still – for a couple of hundred of years or so – see a process of ocean acidification in the interior,” says Müller.