South Korea’s Coral Gardens Are Collapsing Again as Scientists Warn Climate Change Could Worsen the Damage

JEJU, SOUTH KOREA — A dramatic decline in the soft coral gardens surrounding South Korea’s Jeju Island is raising alarm among divers and marine scientists, as unusually warm waters and increasingly severe weather put one of the region’s most distinctive underwater ecosystems under growing pressure.

The phenomenon is known as “slumping” — a process in which soft corals lose their upright form, droop and eventually break apart.

After a major slumping event in 2024, divers and researchers say signs of the phenomenon have appeared again in 2026, prompting concerns that continued warming and extreme weather could cause further damage to Jeju’s coral communities.

The warning comes as South Korea experiences another year of extreme heat and heavy rainfall, conditions researchers say can place additional stress on marine ecosystems.

‘I Was Afraid the Whole Sea Might Be Collapsing’

For local divers, the changes are deeply personal.

Ko Myeong-hyo, a third-generation haenyeo, or traditional Jeju sea woman, has spent years diving in the waters around the island.

She remembers the coral gardens as vibrant underwater landscapes filled with colour and marine life.

But in recent years, she has watched sections of the ecosystem deteriorate.

“Watching the coral garden collapse and turn white, it was so disorienting,” Ko said, describing her experience of seeing the damaged coral.

She said the changes made her fear that the wider marine environment could also be collapsing.

Her concerns extend beyond the appearance of the coral.

For generations, Jeju's haenyeo have depended on the surrounding waters for their livelihoods, harvesting seafood such as abalone, sea cucumbers and shellfish.

Ko's mother, 70-year-old Son Choon-sook, told Reuters that catches have declined significantly during her decades working in the sea.

The changing conditions have made traditional fishing increasingly difficult.

What Exactly Is ‘Coral Slumping’?

The term slumping describes a phenomenon that is different from the more familiar coral bleaching seen around tropical reefs.

Hard corals have rigid calcium-carbonate skeletons that provide structural support.

Soft corals, by contrast, depend partly on internal fluid pressure to maintain their upright shapes.

When environmental conditions disrupt that system, the corals can begin to sag.

Scientists studying Jeju's coral communities have described a progression that can involve inflation, drooping, dangling, deflation and eventually disintegration.

The result can be a dramatic transformation from an upright coral garden into damaged or fragmented colonies.

Researchers at the Korea Institute of Ocean Science and Technology, or KIOST, formally documented the phenomenon following the large-scale event observed around Jeju in 2024.

Their research was published in Scientific Reports in May 2026 and represents the first scientific description of widespread soft-coral slumping in Korean waters.

The 2024 Collapse Was a Major Warning

The first major documented event occurred during the summer of 2024.

According to researchers, sea temperatures around Jeju rose above 30°C, significantly higher than the area's typical summer temperatures.

At the same time, the region experienced unusually heavy rainfall and other environmental changes.

Researchers believe the combination of thermal stress, changes in salinity and water quality may have contributed to the coral collapse.

However, scientists have stressed that more research is needed to determine precisely how each factor contributed to the phenomenon.

The 2024 event was particularly significant because it affected coral communities across an approximately 80-kilometre stretch of Jeju's southern coastline, according to conservationists cited by Mongabay.

Scientists Are Watching 2026 Closely

The current situation has revived concerns that another major slumping episode could develop.

The Paran Ocean Citizen Science Center, a group of divers and local residents monitoring Jeju's underwater ecosystems, reported that roughly half of one coral cluster near Beomseom had been struggling in recent months.

Researchers say the 2026 conditions appear similar in some respects to those seen in 2024.

But they are cautious about predicting another widespread collapse.

Scientists told Mongabay earlier this year that widespread slumping had not occurred during 2025 and had not yet matched the scale of 2024 during the first part of 2026.

That means the coming weeks could be important.

If high water temperatures persist, the stress on the coral communities could intensify.

El Niño Could Make the Situation Worse

Another concern is the possibility of a strong El Niño later this year.

Researchers monitoring Jeju's coral communities have warned that El Niño could bring conditions capable of increasing temperatures and intensifying storms and heavy rainfall.

Such weather could add further stress to already vulnerable coral colonies.

Kim Taihun, a researcher involved in studying the phenomenon, has called for consistent and quantitative monitoring so scientists can determine the scale and progression of coral losses.

Without long-term measurements, researchers may struggle to distinguish temporary damage from a deeper ecological shift.

Climate Change Is Not the Only Pressure

While warming temperatures are a major concern, scientists say Jeju's soft corals face several environmental pressures at once.

Researchers have identified changes in salinity and water quality as potential contributors.

Other reported pressures include pollution, fishing, diving activity and submarine tourism.

There is also evidence that some tropical hard coral species are expanding northward into waters around Jeju, potentially creating additional competition for space with soft corals.

That makes the situation more complicated than a simple story of rising temperatures.

The coral communities are being exposed to multiple changes simultaneously, and scientists are still working to determine how those pressures interact.

Why Jeju’s Coral Gardens Matter

Jeju's soft coral communities are not merely an attraction for divers.

They form part of the foundation of the island's marine ecosystem.

The coral communities provide habitat and nursery areas for marine organisms, supporting a wider food web that ultimately affects fisheries and other coastal activities.

The coral gardens are also located within an area of significant ecological and cultural importance.

Jeju's surrounding marine environment is part of the Jeju Island Biosphere Reserve, while some coral communities are protected through national conservation designations.

Environmental experts warn that continued degradation could therefore have consequences far beyond the coral itself.

Yoon Sanghoon of Paran described the coral and surrounding marine vegetation as a foundational ecosystem for Jeju.

If that foundation deteriorates substantially, other parts of the marine ecosystem could also be affected.

A Warning From the People Who Know the Sea Best

For Jeju's traditional divers, the changes are already visible in their daily lives.

Son Choon-sook said she has worked in the sea for about 45 years, earning money and supporting her family through what the ocean provided.

But she now sees fewer marine resources than in the past.

Her working hours have also become shorter, partly because of health and partly because there is less to collect.

The experience of the haenyeo provides a human perspective on what scientists are measuring in the water: a changing ocean is not simply an environmental statistic.

It can directly affect people's livelihoods, traditions and connection to the sea.

Scientists Say More Monitoring Is Urgently Needed

South Korean authorities are monitoring the coral communities and have said they intend to conduct further investigations into the scale and causes of the changes.

The Korea Heritage Service said it would continue long-term research into the coral colonies, while the Ministry of Oceans and Fisheries said it planned a detailed investigation.

Scientists say consistent monitoring will be essential.

The goal is not simply to document dead or damaged coral after an event has already occurred, but to understand when the corals begin to experience stress, how quickly they deteriorate, whether they can recover and what environmental conditions trigger the process.

That information could become increasingly important as ocean temperatures continue to change.

Jeju’s Underwater Future Is Becoming a Climate Warning

The coral gardens south of Jeju once represented a remarkable example of marine life surviving near the northern edge of its natural range.

Now they are becoming a warning sign.

The 2024 slumping event showed how quickly a major environmental shock could transform the underwater landscape.

The signs being reported in 2026 suggest that the threat has not disappeared.

Scientists are not yet predicting the complete collapse of Jeju's coral ecosystem, and the full causes of slumping remain under investigation.

But the combination of warming seas, extreme weather, changing water conditions and other human pressures is making the coral communities increasingly vulnerable.

For the divers documenting the changes, the message is already clear.

The ocean around Jeju is changing — and its coral gardens may be among the first places showing just how dramatically that change is unfolding.

WWC ONE MEDIA J.M.D