The die-off of warm-water coral reefs, the world's first climate tipping point, is being discussed at COP30 this week.
Scientists have warned for decades that countries must adhere to the thresholds in the Paris Agreement for 1.5C of average warming, in order to minimise loss of coral reefs, which support a quarter of all marine life.
Delegates will hear from the International Coral Reef Initiative, currently chaired by Saudi Arabia, that 84% of the world's coral reefs have already been impacted by a fourth global bleaching event, which is ongoing and the most widespread and severe on record.
According to the second Global Tipping Points report, which was released last month, based on the work of more than 160 scientists, the central estimate of the thermal tipping point for tropical corals of 1.2C global warming, has already been crossed.
"We've seen an unprecedented coral bleaching event hit 80% of the world's low latitude reefs. So that kind of confirmed our collective deduction that the tipping point, the sort of temperature tipping point for corals was probably below 1.5C," explained Tim Lenton, Director of the Global Systems Institute at the University of Exeter, England.
Among the solutions being examined at COP30 are expanding protected marine areas and supporting innovative restoration solutions. This includes new technology called assisted evolution and "super corals", which can involve the more controversial practice of changing coral genes in a lab, so they can be made more tolerant to heat stress.
Coral planting in the Maldives
The Maldives are made up of thousands of low-lying coral islands, its coral reef system being the seventh largest in the world. This means it has a lot to lose, as a result of coral bleaching and degradation.
It may just be a drop in the ocean, but visiting tourists there can now plant their own piece of coral which becomes part of a coral garden, or man-made reef.
Katelyn Hegarty-Kelly is originally from Co Kildare, and studied at the Atlantic Technological University in Galway. She is now the Managing Marine Biologist for Reefscapers in the Maldives.
Based at the Sheraton Full Moon Resort and Spa in the Maldives on the private island of Furanafushi in the North Male Atoll, the resort gives tourists a chance to sponsor and create their own piece of coral reef, which is grown on a frame. It is then added to a coral garden which is beginning to flourish. The guests can then be sent a photo of their developing coral every six months.
"It's quite a rewarding activity for our guests to get involved in. They feel like they can help and give back and that they're leaving a little piece of themselves here at the resort," she explained.
The economy of the Maldives is heavily dependent on tourism, yet air travel is a major contributory factor to the carbon emissions that are driving global warming and the rising sea temperatures which are threatening the islands' very existence.
Ms Hegarty-Kelly said those working in marine biology in the Maldives are very aware of the dangers coral reefs face and know that man-made reef gardens are just a small part of the solution.
Whilst the work is very rewarding, she said they faced a difficult year last year with rising sea temperatures.
"We had the huge mass coral bleaching event last year in 2024, which was a worldwide mass coral bleaching event."
She said corals across the Maldives as a whole and their project were impacted.
"It’s quite an emotional rollercoaster seeing that happen, when you're working on a project and then it slowly starts to be impacted by this mass environmental change that you as a singular person cannot control and do much about.
"Sometimes when you hear about the news for the tipping point for our coral reefs, it hit home especially for a lot of people here in the Maldives.
"We need a lot more action but not just from ourselves, but from the bigger people that are on top, but we're doing as much as we can," said Ms Hegarty-Kelly.
The man-made nature of the coral means they have the leeway to move it as it, as needed, as it grows.
Since last year some changes have been made to where they position their coral gardens: "We know specifically what sites are not going to do well in the future, when these changes do happen, because it's not a matter of if, unfortunately, it is a matter of when."
Around 40 corals are added to the cage-like structure of frame using fragmented pieces of coral from a larger donor colony.
"Hopefully in around five years from when that coral is planted, the entire metal structure that you have just put out in the ocean, you won't even be able to see the legs or the structure, because the coral has grown so big. It supports a huge range of marine life but also us as humans on land as well."
She said more is now being understood around the patterns of coral reproduction, which in the Maldives happens for around five months of the year. The fact that the coral is reproducing suggests these newly planted corals are healthy, and they are now conducting a series of night dives to try to capture the moment this happens.
"These corals will only reproduce as the sun is setting and at nighttime and we are witnessing corals spawning, releasing male and female eggs. We are seeing the reproduction of our corals and we're seeing little baby corals hopefully landing out into our natural reef."
Ireland’s cold-water corals - are they also under threat?
Coral reefs exist in over 100 countries and territories around the world. But around 5,100 species of coral on the planet, or about 50% of all corals exists in deep, dark waters, including off the southwest coast of Ireland in the Porcupine Bank Canyon at the edge of Ireland’s continental shelf in the Atlantic.
"Many people when they think the word coral, they think, Great Barrier Reef," said Dr Aaron Lim, Senior Lecturer at the Department of Geography at UCC.
"Offshore in Ireland, we have these cold-water coral mounds, or cold-water coral reefs that are formed from cold-water corals."
The canyon is about 300kms due west of An Daingean in Co Kerry, and about 900 metres deep into the water.
"These are some of the most well-studied coral reefs on the planet," said Dr Lim.
However, even though they have existed in Ireland for 2.6 million years, their depth means they have only been studied for the past two decades.
They cannot be reached by divers so instead a Remotely Operated Vehicle is used to photograph and monitor them.
"From using underwater robotics, we have imagery that shows pollutants in and around these reefs, and specifically plastic or rubbish and fishing gear, lines and nets deposited in and around the coral reefs.
"And in some cases, we see these nets actually essentially smothering the reefs. And when we take a closer look at the corals, then we find actually there's microplastics or microfibres adsorbed onto the surface of the corals, and in some cases, even ingested into the corals."
These cold-water corals are static and so they rely on the tides to bring them their food.
Unlike their warm-water cousins, they don’t have a symbiotic relationship with algae, which lives within healthy coral, providing it with essential nutrients. Instead, they eat small particles from the ocean, which is why they may be particularly vulnerable to ingesting microplastics from wastewater and washing machine run-off, which ends up in the ocean. Early research suggests that over time, this may inhibit or slow their growth.
Climate change may also be contributing to increasing current speeds, which means the corals are less able to trap food in the faster-moving water. They may also become eroded over time.
Dr Lim said that maintaining these corals is essential because they are hot spots of biodiversity in otherwise barren parts of the ocean. They are also essential for sustaining Ireland’s seafood economy which is currently valued at €1.3bn of GDP.
"They play an important part in fisheries, in that they sustain habitat as well as a healthy ocean and healthy ecosystem, which is important, then, for sustainable fisheries," added Dr Lim.
Additional reporting Reuters
