In Aqaba, Jordan's only coastal town, a man walks further and further out into the Red Sea. It's not long before he's no longer visible from the shore. But if you follow him under the surface, you will see a reef that is considered one of the world's last arks for corals and their inhabitants. Some giant corals look like bony trees, others like brains or lettuce heads. Lionfish, clownfish and schools of sardines buzz around in the pristine water as if they have been waiting to make an appearance.

With a few strokes of his fins, the diver reaches his destination. Here, at a depth of six metres, a coral observation station has been set up. About a dozen small tables stand on the seabed like forgotten pieces of furniture. Corals of all shapes and colours grow on them. There are two such observation stations in the world, one here off Aqaba, the other a few kilometres away off Eilat in Israel. The staff at the Marine Science Station in Aqaba check their side of the shore every day to make sure the high-tech equipment is recording every detail. The collected data and images are transmitted in real time to scientists and policy makers. In both countries, the corals are asked the same question every day: How are you doing? So far, the answer has always been: surprisingly well - despite climate change.

Maoz Fine runs the observatory on the Israeli side. He was also the one who noticed that the corals in the Red Sea were more resilient than their counterparts in other parts of the world. The marine scientist had spent three years in Australia watching the Pacific reefs bleach at a rapid rate. Diving off the coast of Eilat on his return, it was as if someone had swapped a black and white film for an HD blockbuster: the corals in the Gulf of Aqaba were bursting with life and colour. Fine then put their resilience to the test in a simulator. He placed the corals in more than 80 aquariums and gradually increased the temperature from 26 to 34 degrees Celsius, with the result that the Aqaba corals are exceptionally resilient.

"Normally, corals bleach at one to two degrees above the summer maximum of their environment," says Fine. "Our corals, on the other hand, can tolerate an extra five to six degrees." In other words, corals in the Gulf of Aqaba could survive for another century despite rising temperatures. "This resilience is unique in the world," says Fine. "Crazy!"

From South Africa to Japan, from Hawaii to Australia, coral reefs are getting worse. The ecosystems are made up of tiny cnidarians that form huge colonies and live in symbiosis with algae that produce oxygen and sugar through photosynthesis.

In return, they find a protected habitat in the coral's calcareous skeleton. What has worked as a partnership for centuries is now beginning to unravel as the oceans warm. Under heat stress, algae produce toxins that cause corals to reject their fellow inhabitants. They become sick and bleach. This is their ultimatum: only if the temperatures drop in time can the vital energy suppliers return. If this does not happen within a few weeks, the reef will die.

In 2018, the Intergovernmental Panel on Climate Change (IPCC) warned that global warming of 1.5 degrees would cause between 70 and 90 per cent of coral reefs to die. In February this year, an international team of researchers published an even bleaker prediction: they expect 99 per cent of coral reefs to be lost by 2030, as studies show that heatwaves in the world's oceans are becoming more frequent.

The reefs have less time to recover from the heat. If the predictions materialise, the world will lose a large part of its most diverse ecosystem. This would also be an economic disaster. More than 450 million people live from and with the reefs. The question remains: what has already been lost and what can still be saved? The search for an answer leads to the reefs in the Gulf of Aqaba. According to Fine's hypothesis, anyone who wants to unravel the secret of their resilience needs to take a look at the world map - and at the past. The Gulf of Aqaba is less than half the size of Lake Constance. It measures 24 kilometres at its widest point and 160 kilometres at its longest. Four countries curve around the bay, which looks like an out-of-shape I on the map: Saudi Arabia and Jordan lie to the east, followed by Israel and Egypt to the west after a sudden bend.

During the last ice age, the Red Sea sank and was almost completely cut off from the ocean, the salinity rose dramatically and the native corals died. Later, when larvae from the Gulf of Aden made their way back into the Red Sea, the waters of the hot south became an evolutionary barrier. Only the most heat-resistant coral larvae survived. Some settled in the much cooler northern tip. The maximum monthly average surface temperature there is currently around 27 degrees Celsius, while in the south of the Red Sea it is more than four degrees higher. The corals have retained their resistance to the heat over the centuries. "All this gives us great hope: we have the opportunity to preserve the reefs for future generations," says Fine.

His findings have put the Red Sea in the scientific spotlight. For one crucial question remains unanswered: What genes make the region's corals so resilient? On a Saturday morning in late October, two scientists from Switzerland sit in a hotel lobby in Aqaba. One of them is Anders Meibom, director of the Transnational Red Sea Centre (TRSC), who, together with other researchers, published a study in 2017 confirming Fine's findings. "If we want to protect the corals in the Red Sea from possible local sources of destruction, then all the surrounding countries need to pull together," he says. But the geopolitical situation could hardly be more delicate. To the south, hot spots such as the Horn of Africa and Yemen surround the Red Sea. Egypt and Saudi Arabia follow further north. Then there is the Middle East conflict, which has been simmering for years. This gave Meibom the idea of combining science and diplomacy, and he was able to convince the Swiss Foreign Ministry to support his project and the TRSC was founded in 2019.

Since then, Meibom and his team have been on a mission in the Red Sea. Their first coup was to set up observation stations off Aqaba and Eilat. The idea came from Israeli researcher Fine. As soon as the reefs show signs of stress, research teams on both sides of the coast are alerted. The monitoring stations bring Jordan and Israel closer together. Previously, each country conducted its own research, but now, for the first time, there is comparable data, and if Meibom and his team have their way, all Red Sea countries will soon have such a station. "The reef is a unifying element," he says. "There is nobody who is not interested in the survival of these corals." Off the coast of the two countries, the Swiss, together with local experts, collected DNA samples from the corals and their environment and used new technologies to create a 3D map. "Until now, we have only had tiny, fragmented glimpses of the whole system," says Guilhem Banc-Prandi, Meibom's companion and scientific coordinator of the TRSC. "Our approach is to look at the reef as a whole. In a biological sense, but also in terms of scale. After all, the ecosystem knows no political boundaries.

Over the past few weeks, they have been collecting samples in Djibouti. They want to use the new material to study how healthy and resilient the reefs are. And what species they are made up of. To do this, they are sending the samples halfway around the world: first, the researchers extract the DNA at the Marine Science Station in Aqaba. In the next step, scientists from the Swiss Federal Institute of Technology in Lausanne and the University of Constance take over. In their laboratories, they will sequence the corals' DNA, i.e. decipher the exact sequence of its building blocks, and characterise the genomes. Since Fine discovered the resilience of coral reefs, another question has arisen: can we use them to revive destroyed reefs, for example by transferring corals from the Red Sea to other reefs? Jordanian scientist Ehab Eid of the International Union for Conservation of Nature (IUCN) says by phone: "We hope that we can preserve the genetic resources of the coral reefs in Aqaba, because they could be the last refuges for corals in the world".

Examples from Jordan and other regions have shown that corals generally tolerate transplants well. How the survival rate for transplants from one region to another from one region to another is still uncertain, says Eid: "We need more research and studies on this." The TRSC researchers also stress how complex such transplants are: Are we talking about individual species - or entire coral ecosystems in all their diversity? Are the characteristics of the donor and recipient regions compatible, for example in terms of salinity? Last but not least, the size of the areas is also crucial. The Great Barrier Reef off Australia alone covers an area the size of Italy. "We need a better understanding of the whole biome: the coral itself and all the symbionts," says Banc-Prandi of the Transnational Red Sea Centre. And his colleague Meibom adds that only by understanding the ecosystem in all its complexity will it be possible to draw conclusions for other regions. "There are many projects underway to accelerate or support evolution. We could select resistant corals with a certain genotype and breed them locally. For now, however, their main concern is to preserve the reefs in the Red Sea.

Israeli researcher Fine also warns against relying on scientific innovation alone. There is an easier and much cheaper way to protect reefs. "If we reduced our emissions and were more careful, many corals would recover on their own," he says. "We just have to let them." But he also says: "The heat waves are increasing so fast that we probably won't make it in time.

Fine's plea echoes concerns about the reefs of his home country. Corals can withstand higher temperatures, but not necessarily other stressors - especially man-made ones. In recent years, the population and infrastructure of the coastal region around the Gulf of Aqaba has grown rapidly, and with it the pressure on the underwater world. "The area is fiercely contested: tourism, industry, fishing - everyone wants a piece of the action," says Abdullah Al-Momany, a slim man with a friendly smile. His diving school is one of the oldest in Aqaba; he took it over from his father 25 years ago. Al-Momany has been diving in the Red Sea since he was a boy, and now he steers his boat out of the marina, past huge cruise ships and small fishing boats, where tourists sit close together in glass-bottomed boats, gazing at the underwater world beneath their feet.

"Our coral reefs are unique. There is no other place in the world with such a diversity in such a small area," says Al-Momany, adding that more than 150 species of coral and 500 species of fish live off the Jordanian coast alone. Al-Momany stops his boat and looks out over a public beach. Families are relaxing on the shore, plastic rubbish piles up beside them. It won't be long before it ends up in the sea. Jordan has no recycling system. Al-Momanys regularly picks up rubbish on his dives and frees the corals from the fishing lines that are wrapped around them like deadly ropes. More often, however, the foreign objects are slowly killing the reefs: studies show that plastic waste in the ocean can carry a wide range of bacteria, including pathogens that can make corals sick. The effects can range from stunted growth to necrosis and the death of individual limbs. Plastic debris can also damage the coral's delicate tissue and cause infections.

This morning, Al-Momany pulls a mobile phone screen out of the water. Other divers from the area do the same. Project Sea, founded by two young Jordanians, organises regular clean-ups off Aqaba, and in the past year and a half the volunteers have removed five tonnes of rubbish from the Red Sea. "We can only pick up a fraction of the rubbish, and a little later the next load ends up in the water. There's nothing we can do about that. He gets angry when talking about the small plastic cups with lids that have become particularly popular since the coronavirus pandemic. Water in 200 millilitre portions, drunk in seconds, lasts up to half a century in the sea, so what should be done? "The rules and laws on environmental protection are not enforced strictly enough," says Al-Momany. This is partly for financial reasons - not enough money, not enough manpower - but also for cultural reasons.

"First of all, we need to raise awareness, educate and inform." Researchers like Fine also believe that politicians have a duty. "We know how it is in this region: when heads of state make decisions, things move very quickly," he says. "This is about saving coral reefs and ultimately human lives. This is beyond any conflict, they just have to prioritise it."

Meibom's team at the TRSC are now making their way further into the Red Sea, knowing that the mission will continue to take a lot of time and dedication. Despite the results so far, not all neighbouring countries are on board. Egypt, for example, which hosted the recent climate summit, is still missing. With 1,500 kilometres of coastline on the Red Sea, the country has a key role to play. "The time will come," says Meibom. The next expedition will take the researchers to Sudan. "The great thing about our mission is that there is still real hope here." Fine, too, is optimistic about the future. In late 2022, a fire ravaged his research institute on the coast of Eilat. Asked how his corals are doing, he says: Well, as always. "That was the first thing we took care of."