The bold plan to save the world's coral
Bleaching has devastated reefs around the world, raising fears of an irreversible shift. Yet new interventions have revealed that corals can be remarkably resilient if we can give them enough help to recover
June 9, 2026
in Australia’s Great Barrier Reef, was once so bountiful that an of it is now hurtling on a spacecraft beyond the outer reaches of our solar system – one of a handful of pictures stored on the Voyager Golden Records, a selection of the very best examples of life on Earth.
When marine ecologist began studying how corals are entangled with other creatures on the reef, he was also drawn to the site’s beauty. Then, just as he was finishing up his project in the mid-2010s, everything changed.
The colour had drained from the corals, bleached by a prolonged increase in water temperatures. “I just remember fields of white corals as far as you could see underwater. It was ethereal,” says Nitschke. The grief of such rapid, widespread bleaching catalysed him, along with many other reef researchers, into action: “I felt that shift. It was like: what are the technologies we can develop?”
They began developing new ways to restore reefs, from larvae-spawning machines to coral probiotics. A decade later, these researchers find themselves racing against an escalating onslaught of marine heatwaves that last year pushed corals past the first-ever climate tipping point – an abrupt and potentially irreversible shift. “There's only so much time that we can buy,” says marine biologist at the University of Technology Sydney.
Today, reef researchers are somewhat split on which path can preserve coral reefs for future generations. Can these innovations be scaled up to bring corals back from the brink? Or are simpler solutions that rely on corals’ natural ability to regenerate a surer route to rescue?
Major coral bleaching events
Corals can’t flourish by themselves. Each coral polyp lives in a mutually beneficial – or symbiotic – partnership with algae, which capture sunlight and turn the energy into sugars that the coral uses to build the reef. “The symbiont is like an endless food particle. It's the snack that keeps on giving,” says Nitschke who is at the Australian Institute of Marine Science (AIMS).
But like all relationships, challenging circumstances can cause break-ups. Oceans have that has accumulated on Earth because of climate change, escalating the frequency and intensity of marine heatwaves, which alter how coral and algae share nutrients. “Neither of them are meeting their end of the bargain, but the coral seems to have the final say and ejects the symbiont,” says Nitschke. Once coral kicks out its algal partner, it begins to starve and is likely to die.
In 1998, the first global coral-bleaching event, 21 per cent of reefs experienced bleaching-level heat stress. Then in 2010, during the second global events, 37 per cent of reefs experienced this level of heat stress.
Reefs can be remarkably resilient, and many corals returned over the following years. But when back-to-back bleaching events strike, . From 2014 to 2017, marine heatwaves bleached 68 per cent of reefs around the world; then, from 2023 to 2025, record ocean heat drove the most widespread bleaching event yet, affecting 84 per cent of reefs.
By 2025, the project announced that the first-ever climate tipping point had been breached. “We saw carnage across the majority of coral reefs,” says at the University of Exeter, UK, who leads the project.
Tipping points are self-propelling feedback loops that are abrupt and tough to come back from. This can occur for corals when bleached reefs become swamped by macroalgae, such as seaweed, a process that is supercharged by excessive nutrients washed from the land and the loss of fish that naturally keep seaweed in check. Other human disturbances, such as blast fishing and trawling, directly dismantle reefs, as do tropical storms, which are intensifying with climate change.
Meanwhile, the spread of disease and acidifying waters that are starved of oxygen compound the problem. “It's not just one stress,” says Camp. “It's like you've gone through a cold and you've gone through covid, and now you've got cancer, now you've broken your leg.”
Lenton offers an optimistic view, emphasising that tipping points can be , when virtuous cycles pull ecosystems out of the harmful ruts they have landed in. “It is about what you do afterwards,” he says. “Like many parts of the biosphere, coral reefs have shown an impressive ability, in some contexts, to bounce back.”
Major coral bleaching events
Corals can’t flourish by themselves. Each coral polyp lives in a mutually beneficial – or symbiotic – partnership with algae, which capture sunlight and turn the energy into sugars that the coral uses to build the reef. “The symbiont is like an endless food particle. It's the snack that keeps on giving,” says Nitschke, who is at the Australian Institute of Marine Science (AIMS).
But like all relationships, challenging circumstances can cause break-ups. Oceans have that has accumulated on Earth because of climate change, escalating the frequency and intensity of marine heatwaves, which alter how coral and algae share nutrients. “Neither of them are meeting their end of the bargain, but the coral seems to have the final say and ejects the symbiont,” says Nitschke. Once coral kicks out its algal partner, it begins to starve and is likely to die.
In 1998, the first global coral-bleaching event, 21 per cent of reefs experienced bleaching-level heat stress. Then in 2010, during the second global event, 37 per cent of reefs experienced this level of heat stress.
Reefs can be remarkably resilient, and many corals returned over the following years. But when back-to-back bleaching events strike . From 2014 to 2017, marine heatwaves bleached 68 per cent of reefs around the world; then, from 2023 to 2025, record ocean heat drove the most widespread bleaching event yet, affecting 84 per cent of reefs.
By 2025, the project announced that the first-ever climate tipping point had been breached. “We saw carnage across the majority of coral reefs,” says at the University of Exeter, UK, who leads the project.
Tipping points are self-propelling feedback loops that are abrupt and tough to come back from. This can occur for corals when bleached reefs become swamped by macroalgae, such as seaweed, a process that is supercharged by excessive nutrients washed from the land and the loss of fish that naturally keep seaweed in check. Other human disturbances, such as blast fishing and trawling, directly dismantle reefs, as do tropical storms, which are intensifying with climate change.
Meanwhile, the spread of disease and acidifying waters that are starved of oxygen compound the problem. “It's not just one stress,” says Camp. “It's like you've gone through a cold and you've gone through covid, and now you've got cancer, now you've broken your leg.”
Lenton offers an optimistic view, emphasising that tipping points can be when virtuous cycles pull ecosystems out of the harmful ruts they have landed in. “It is about what you do afterwards,” he says. “Like many parts of the biosphere, coral reefs have shown an impressive ability, in some contexts, to bounce back.”
Innovating to save coral
In this vein, technology might help bring corals back from the brink. Coral restoration is an umbrella term for a that have been around in one form or another for decades. Traditionally, this largely involved growing coral fragments in nurseries and then planting them out in the wild – known as coral gardening. “You multiply the same colonies, like a photocopier, over and over again,” says , a biologist at AIMS.
Most coral restoration still happens this way, but it is a slow process and if corals planted on the reef are genetically similar, they may all suffer the same fate in disease-ridden or heat-stressed environments. The 2014-17 mass bleaching made it clear to some researchers that coral gardening wasn’t enough. “That was a wake-up call. So much coral was lost,” says ecological geneticist at AIMS. In 2017, a group of 18 leading researchers – including van Oppen and Bay – .
As well as cloning corals, researchers began sexually reproducing them to increase genetic diversity. Each year, seas around reefs become a blizzard of white and pink as eggs and sperm are released in spectacular spawning events. Some restoration methods , collecting eggs and sperm and then fertilising them on a mass scale in sea simulators that .
More ambitious still are restoration methods that try to create corals and algae with traits that make them more tolerant to heat stress and bleaching. For millennia, humans have selected valuable traits in livestock and crops. Over the past decade, van Oppen has pioneered doing much the same with corals, but in an accelerated process called . “Even when there's a really bad thermal-bleaching event, you will find some weird and wonderful corals that have somehow managed to survive that. So, you try to understand how they are different,” says Camp.
Often, this comes down to the algae that co-exist with the coral. After heat-tolerant algae have been identified in the wild, they are subjected to even warmer temperatures in the lab. Each generation, many of the algae die, but the few that survive are selected and the process is repeated. Van Oppen and Nitschke have done this almost non-stop for over a decade to evolve algae that can survive at 31°C (87.8°F) – the peak temperature of recent marine heatwaves on the Great Barrier Reef. Heat-tolerant algae are then given back to corals in the hope that they keep living in harmony, despite the harsh conditions. Pilot studies in the wild, which are currently under review, “look very promising”, says van Oppen.
Meanwhile, other researchers are trying to harness the microbes associated with healthy reefs, which help them feed themselves, ward off diseases and buffer stressful environments. “They act as the coral’s first line of defence and adaptation,” says marine biologist at the King Abdullah University of Science and Technology (KAUST) in Saudi Arabia, who has developed a range of and that have shown .
Yet van Oppen cautions that the promise of these approaches might not be replicated everywhere. Reefs are complex ecosystems that respond differently to the restoration tools on offer, which must be . For instance, simple methods that have worked in the Coral Triangle in South-East Asia – such as stabilising rubble or sinking structures for coral to grow on – aren’t effective in the Caribbean, where there are fewer free-swimming coral larvae, says , executive director of the Coral Restoration Consortium.
Industrial coral farming
Saudi Arabia, meanwhile, is throwing everything it can at the problem. The KAUST Coral Restoration Initiative, in partnership with NEOM, a mega-city and economic zone on the Red Sea coast, is advertised as part of its drive to shift away from fossil fuels towards a “blue economy” – although its climb.
Marine biologist , who leads the initiative, began collaborating with tourism operators on the Great Barrier Reef following the 2014-17 mass bleaching to try to scale up restoration. “Saudi Arabia came knocking on the door, saying that we've seen the model that you use”, and asked how the country could go further, he says.
KAUST’s field site covers about 1 square kilometre, while typical restoration projects are a small fraction of that size. In May, the initiative’s coral nursery, which is 12 times bigger than any other in the world, opened and began its first restoration campaign, timed with the coral’s annual spawning.
Innovating to save coral
In this vein, technology might help bring corals back from the brink. Coral restoration is an umbrella term for a that have been around in one form or another for decades. Traditionally, this largely involved growing coral fragments in nurseries and then planting them out in the wild – known as coral gardening. “You multiply the same colonies, like a photocopier, over and over again,” says , a biologist at AIMS.
Most coral restoration still happens this way, but it is a slow process, and if corals planted on the reef are genetically similar, they may all suffer the same fate in disease-ridden or heat-stressed environments. The 2014-17 mass bleaching made it clear to some researchers that coral gardening wasn’t enough. “That was a wake-up call. So much coral was lost,” says ecological geneticist at AIMS. In 2017, a group of 18 leading researchers – including van Oppen and Bay – .
As well as cloning corals, researchers began sexually reproducing them to increase genetic diversity. Each year, seas around reefs become a blizzard of white and pink as eggs and sperm are released in spectacular spawning events. Some restoration methods , collecting eggs and sperm and then fertilising them on a mass scale in sea simulators that .
More ambitious still are restoration methods that try to create corals and algae with traits that make them more tolerant to heat stress and bleaching. For millennia, humans have selected valuable traits in livestock and crops. Over the past decade, van Oppen has pioneered doing much the same with corals, but in an accelerated process called . “Even when there's a really bad thermal-bleaching event, you will find some weird and wonderful corals that have somehow managed to survive that. So, you try to understand how they are different,” says Camp.
Often, this comes down to the algae that co-exist with the coral. After heat-tolerant algae have been identified in the wild, they are subjected to even warmer temperatures in the lab. Each generation, many of the algae die, but the few that survive are selected and the process is repeated. Van Oppen and Nitschke have done this almost non-stop for over a decade to evolve algae that can survive at 31°C (87.8°F) – the peak temperature of recent marine heatwaves on the Great Barrier Reef. Heat-tolerant algae are then given back to corals in the hope that they keep living in harmony, despite the harsh conditions. Pilot studies in the wild, which are currently under review, “look very promising”, says van Oppen.
Meanwhile, other researchers are trying to harness the microbes associated with healthy reefs, which help them feed themselves, ward off diseases and buffer stressful environments. “They act as the coral’s first line of defence and adaptation,” says marine biologist at the King Abdullah University of Science and Technology (KAUST) in Saudi Arabia, who has developed a range of and that have shown .
Yet van Oppen cautions that the promise of these approaches might not be replicated everywhere. Reefs are complex ecosystems that respond differently to the restoration tools on offer, which must be . For instance, simple methods that have worked in the Coral Triangle in South-East Asia – such as stabilising rubble or sinking structures for coral to grow on – aren’t effective in the Caribbean, where there are fewer free-swimming coral larvae, says , executive director of the Coral Restoration Consortium.
Industrial coral farming
Saudi Arabia, meanwhile, is throwing everything it can at the problem. The KAUST Coral Restoration Initiative, in partnership with NEOM, a mega-city and economic zone on the Red Sea coast, is advertised as part of its drive to shift away from fossil fuels towards a “blue economy” – although its climb.
Marine biologist , who leads the initiative, began collaborating with tourism operators on the Great Barrier Reef following the 2014-17 mass bleaching to try to scale up restoration. “Saudi Arabia came knocking on the door, saying that we've seen the model that you use”, and asked how the country could go further, he says.
KAUST’s field site covers about 1 square kilometre, while typical restoration projects are a small fraction of that size. In May, the initiative’s coral nursery, which is 12 times bigger than any other in the world, opened and began its first restoration campaign, timed with the coral’s annual spawning.
To monitor the site and decide where and how to restore coral, the team has built a 3D “digital twin” that is updated every six months using data collected by autonomous underwater vehicles, plus an army of boats and divers wielding high-resolution cameras. The digital twin is detailed and expansive: at around 22 petabytes, it is roughly 24 times the size of Wikipedia’s entire contents at the time of publication.
No doubt this initiative is impressive, but most countries supporting reefs can’t tap into fossil-fuel revenues to build sophisticated systems like these. Suggett acknowledges it is “a bit of a white elephant globally”, but sees value in the Red Sea site in demonstrating what is possible with enough backing.
Still, unless there is a clear road map to make high-tech solutions available to local communities, showstopping efforts can be “disempowering”, says Vardi. “We're human beings. We're always going to shoot for the moon,” she says. “But if you don't think about how that will be translated from the very beginning, you're just creating a new engineering problem.”
Instead of building reef-monitoring systems with state-of-the-art cameras, you could do a . And instead of building a warehouse-sized aquaculture centre, you could build miniature, that can be shipped anywhere.
There is psychological evidence that humans are biased towards active interventions, says ocean governance expert at the University of Melbourne. He and his co-authors argue in a recent paper that before throwing resources behind “heroic interventions”, we need to pause and think widely about what kinds of conservation can lead to healthy reefs in the long term. Streit isn’t opposed to innovations, such as assisted evolution, but cautions that we shouldn’t overpromise or lose sight of the bigger picture.
If we continue on the path that we're on, we're going to be asking too much of corals, even with the technologies that we have available.
Reefs covered with corals are a boon for snorkelling and scuba-diving tourists, but don’t necessarily reflect a healthy reef – or one that meet the needs of local communities. Hundreds of millions of people to feed their families. Reefs can also hold cultural significance that can be overlooked when research is , says Streit. What’s more, less-interventionist approaches, which protect the whole ecosystem, such as creating and enforcing marine parks or improving water quality, could be more impactful. “Let’s put a buffer around things and have as as we can,” he says.
Scaling coral restoration
Intervening also necessarily comes at a cost. notes that between 2009 and 2018, around 11,700 square kilometres of reef were degraded and calculates that to rehabilitate a tenth of this would cost somewhere between $1 billion and $17 trillion – depending on the restoration methods used. “Even to restore a tiny portion of what we are losing, the costs are astronomical,” says lead author at the European Commission’s Joint Research Centre. “The main issue is: how much can you scale?”
Camp, Suggett and Vardi, among other researchers, argue it is still early days for coral restoration and wrong to make doom-and-gloom assessments based on the higher costs of experimental projects. There is also no need to pit technology and hands-off regeneration against each other, says Vardi. “There's a lot of this either-or mentality that is just plain idiotic,” she says. “We manage all the ecosystems on Earth, as much as we don't want to face that.”
Nonetheless, the success of restoration, and the ability to activate positive tipping points, often comes down to social factors as much as technological prowess, says Lenton. “If you give autonomy to the people of the reefs, then that seems to be a recipe for success. You have to build a relationship of trust.” For instance, artificial reef structures can be constructed from local materials, such as pottery and natural fibres, and fishing communities can be given control over the marine park zones instead of national governments.
No doubt this initiative is impressive, but most countries supporting reefs can’t tap into fossil-fuel revenues to build sophisticated systems like these. Suggett acknowledges it is “a bit of a white elephant globally”, but sees value in the Red Sea site in demonstrating what is possible with enough backing.
Still, unless there is a clear road map to make high-tech solutions available to local communities, showstopping efforts can be “disempowering”, says Vardi. “We're human beings. We're always going to shoot for the moon,” she says. “But if you don't think about how that will be translated from the very beginning, you're just creating a new engineering problem.”
Instead of building reef-monitoring systems with state-of-the-art cameras, you could do a . And instead of building a warehouse-sized aquaculture centre, you could build miniature, that can be shipped anywhere.
There is psychological evidence that humans are biased towards active interventions, says ocean governance expert at the University of Melbourne. He and his co-authors argue in a recent paper that before throwing resources behind “heroic interventions”, we need to pause and think widely about what kinds of conservation can lead to healthy reefs in the long term. Streit isn’t opposed to innovations, such as assisted evolution, but cautions that we shouldn’t overpromise or lose sight of the bigger picture.
If we continue on the path that we're on, we're going to be asking too much of corals, even with the technologies that we have available.
Reefs covered with corals are a boon for snorkelling and scuba-diving tourists, but don’t necessarily reflect a healthy reef – or one that meets the needs of local communities. Hundreds of millions of people to feed their families. Reefs can also hold cultural significance that can be overlooked when research is , says Streit. What’s more, less-interventionist approaches, which protect the whole ecosystem, such as creating and enforcing marine parks or improving water quality, could be more impactful. “Let’s put a buffer around things and have as as we can,” he says.
Scaling coral restoration
Intervening also necessarily comes at a cost. notes that between 2009 and 2018, around 11,700 square kilometres of reef were degraded and calculates that to rehabilitate a tenth of this would cost somewhere between $1 billion and $17 trillion – depending on the restoration methods used. “Even to restore a tiny portion of what we are losing, the costs are astronomical,” says lead author at the European Commission’s Joint Research Centre. “The main issue is: how much can you scale?”
Camp, Suggett and Vardi, among other researchers, argue it is still early days for coral restoration and wrong to make doom-and-gloom assessments based on the higher costs of experimental projects. There is also no need to pit technology and hands-off regeneration against each other, says Vardi. “There's a lot of this either-or mentality that is just plain idiotic,” she says. “We manage all the ecosystems on Earth, as much as we don't want to face that.”
Nonetheless, the success of restoration, and the ability to activate positive tipping points, often comes down to social factors as much as technological prowess, says Lenton. “If you give autonomy to the people of the reefs, then that seems to be a recipe for success. You have to build a relationship of trust.” For instance, artificial reef structures can be constructed from local materials, such as pottery and natural fibres, and fishing communities can be given control over the marine park zones instead of national governments.
An astronaut aboard the International Space Station used a powerful lens to photograph these three reefs in Australia's Great Barrier Reef. CREDIT: NASA Earth Observatory
An astronaut aboard the International Space Station used a powerful lens to photograph these three reefs in Australia's Great Barrier Reef. CREDIT: NASA Earth Observatory
Over the past decade, researchers have learned vital lessons about how novel restoration techniques could feed virtuous cycles within reef ecosystems. But as restoration efforts begin to be scaled up, the speed with which marine temperatures have spiralled during the current global bleaching event has taken everyone by surprise. “In some places, the coral tissue didn't even have time to bleach,” says Vardi. “It just dissolved.”
Bleaching events now happen almost every year, making it hard for coral restoration to keep pace. Strona calculates that the outlook for reefs restored so far is grim: 99.6 per cent of them are estimated to experience at least one bleaching event by the end of the century, with many of them experiencing dozens of bleaching events in this period. This has led some researchers to place hope in restoring reefs in “refugia”, such as the Red Sea, which are buffered from climate stresses, while cryo-banks are being built around the world to preserve coral species until a time when, hopefully, ocean temperatures stabilise.
Most everyone agrees on one thing: the only real way to create a future for coral reefs is to drastically cut carbon emissions. “This isn't a replacement for action in the climate space,” says Camp. “If we continue on the path that we're on, we're going to be asking too much of corals, even with the technologies that we have available.”
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Video (3D digital twin): KAUST Coral Restoration Initiative
Video (coral spawning): CSIRO
Restoration Initiative
Edited by Abby Beall and Jacklin Kwan