Earth’s oceans cover over 70 percent of the planet and support billions of people, yet they are changing fast due to human-driven climate change. Long seen as vast buffers against rising heat and emissions, these waters are sending clear distress signals.
From coral graveyards in the Gulf of Thailand to souring seas along the Andaman coast, the signs are hard to ignore. New assessments, including the IPCC Sixth Report and live satellite data, show a sharp decline in ocean health.
With global temperatures about 1.1°C above pre-industrial levels, the seas absorb most of the extra energy, about 90 percent, and roughly 30 percent of the added carbon. This is not an abstract trend; it is a direct hit to marine ecosystems, fisheries, and coastal towns in Thailand and across the globe. Here are the most urgent impacts, supported by expert voices and field observations.
Warming Waters: Heat on the Ocean’s Front Lines
Ocean temperatures are rising at record speed. Since the late 1800s, average sea surface temperatures have increased by about 0.88°C, and the last decade was the hottest observed. Marine heatwaves are now common in the Pacific, home to some of the largest coral systems. In 2023, the Similan Islands in Thailand saw a severe bleaching event, and more than 80 percent of corals turned white from heat stress.
Dr. Somchai Boonstra of Chulalongkorn University explains the trigger. Corals eject the algae that feed them when water stays above 30°C for too long, which can lead to starvation and death if relief does not come. This pattern appears worldwide. The Great Barrier Reef has lost about half its corals over the last 30 years.
Warm waters also push fish to cooler zones. Tuna and mackerel, common in Thai markets, are moving toward higher latitudes, leaving fishers in the Gulf of Thailand with smaller catches. A 2024 study in Nature Climate Change projects tropical fish stocks could drop by 20 to 30 percent by 2050 if emissions stay high.
Heat buildup is not only at the surface. Stronger stratification traps warm water above cooler layers, which blocks nutrient upwelling. Plankton, the base of the food chain, then declines. Parts of the Indian Ocean have seen expanding low-nutrient zones, sometimes labeled dead zones. In coastal Thailand, including Rayong Province, warmer and stagnant waters have fueled more disease outbreaks in shrimp farms, costing the sector billions of baht each year.
Acidification: A Slow, Corrosive Shift
Rising carbon dioxide levels not only warm the air and water, but they also make seawater more acidic. Since the start of the industrial era, average ocean pH has fallen from about 8.2 to 8.1, equal to about a 30 percent increase in acidity. More acidic water eats away at calcium carbonate, which shellfish and corals need to build their shells and skeletons.
In the Andaman Sea, Thai coral reefs show warning signs. Juvenile corals are struggling to form skeletons, according to Dr. Nareerat Phongsuwan at the Phuket Marine Biological Center. An APEC assessment in 2025 flagged major risks for Thailand’s shellfish farms, with oyster larvae dying at far higher rates in acidified test conditions. The IPCC warns that the global economic hit could reach $1 trillion by 2100, putting pressure on food security for billions.
Acidification and warming feed into each other. As Arctic sea ice shrinks, more open water absorbs CO2, speeding up the shift. NASA’s Ocean Color Instrument has recorded falling phytoplankton activity in high-acid stress zones, which may cut oxygen production, and the oceans supply about half of the planet’s oxygen.
Rising Seas and Stronger Storm Surges: Coastlines Under Pressure
Global sea level has risen about 25 centimeters since 1880 and is now rising at about 4.5 millimeters a year. Heat expansion and melting land ice both contribute, while ice loss from Greenland and Antarctica adds big uncertainty.
Thailand faces tough odds. Bangkok sits only about 1.5 meters above sea level, and land subsidence from groundwater use makes it worse. A one-meter rise by 2100 could put about a tenth of the country’s land at risk of flooding.
The 2024 monsoon floods in southern Thailand offered a preview. Higher baseline seas amplified storm surges that ripped out mangroves in Krabi, which act as natural shields. Local activist Piyawat Srisuk notes that Thailand has lost about 35 percent of its mangroves since 1960. These forests lock away carbon faster than many land forests, so their loss also releases stored CO2 and speeds warming.
Worldwide, about 680 million people in low-lying zones are exposed to rising waters. The Maldives is already losing land, forcing climate displacement. Thailand’s travel hubs, including Phuket, face worsening beach erosion. A 2025 World Bank analysis projects annual losses near $10 billion linked to coastal damage and tourism impacts.
Deoxygenation: A Slow Suffocation
Oceans have lost roughly 2 percent of their oxygen since 1960. Hypoxic zones, where oxygen drops too low for most marine life, now number over 400 areas globally. Warmer water holds less oxygen, and farm runoff drives algal blooms that consume oxygen as they decay.
The Gulf of Thailand hosts one of these low-oxygen zones, expanded by nutrient-rich discharge from rivers such as the Chao Phraya. In 2024, mass fish kills washed ashore near Pattaya. Dr. Boonstra warns that squid and octopus, which are sensitive to oxygen loss, are moving away or dying. That threatens biodiversity in a sea that may hold millions of species, many still unknown.
In the open Pacific, oxygen minimum zones are expanding and sinking, squeezing the depth range for many species. An October 2025 paper in Science links these changes to jellyfish blooms, since jellyfish can handle low-oxygen conditions better than many fish.
Biodiversity Under Strain: From Microscopic Life to Apex Predators
The combined stresses are breaking down marine food webs. Coral reefs shelter about a quarter of ocean species, yet many reefs could lose function by mid-century if warming passes 1.5°C. Thailand’s Mu Ko Ang Thong National Park reports steep losses in seagrass meadows, key nurseries for dugongs, due to heat and murky runoff.
Charismatic species are also at risk. Sea turtles consume plastic that looks like jellyfish in warmer, polluted waters. Shark populations are falling from overfishing and shifting prey. The IUCN lists about one-third of marine mammals as threatened.
Feedbacks make the damage worse. Declining kelp forests release carbon, which adds to heating. In the Southern Ocean, shrinking krill stocks stress whales and penguins that depend on them.
Human Costs: Food, Jobs, and Health
For Thailand’s 26 million coastal residents, this crisis hits home. Fisheries contribute about 1.5 percent of GDP and employ around 2 million people. Shrinking catches push fishers into debt or out of the industry. In Ban Phe, Rayong, fisherman Somchai Thongdee recalls overflowing nets two decades ago, compared to near-empty nets today.
Public health risks are growing, too. Warmer, nutrient-rich waters drive toxic algal blooms that produce domoic acid, which can cause amnesic shellfish poisoning. In 2025, events along the California coast linked to Pacific patterns showed how connected these systems are.
Tourism feels the strain. Bleached reefs discourage divers in the Similans, and repeated shocks take a toll on mental health in coastal communities. Many young people report eco-anxiety tied to uncertainty and loss.
What Can Change: Mitigation and Adaptation
There is a path forward if action ramps up quickly. Meeting the Paris Agreement’s 1.5°C limit requires global net-zero emissions by 2050. Thailand’s Nationally Determined Contributions target 30 percent renewable energy by 2030, but coal use still drags on progress.
Marine Protected Areas help rebuild sea life when well managed. Expanding protection to 30 percent of the ocean by 2030, the UN’s 30×30 goal, could boost stocks and resilience. Thailand’s new Andaman MPA shows early gains, with fish biomass tripling in five years.
Researchers are testing options like ocean alkalinity enhancement, where minerals are added to reduce acidity. Local projects are delivering benefits now. Mangrove restoration in Satun Province stores carbon, supports fisheries, and buffers coasts from storms.
People can drive change through daily choices and civic action. Cut single-use plastics, choose seafood with MSC certification, and speak up for strong climate policy. As Dr. Phongsuwan says, every ton of CO2 avoided gives the ocean room to breathe.
The ocean is the planet’s blue heart, and it is under strain. From Thailand’s bright shores to the deepest trenches, the warning lights are on. Turning away risks lasting damage to sea life and human life. The real question is simple. Will society act in time to keep the oceans alive for future generations?
