Vital marine ecosystems are on the verge of collapse

A new global episode of coral bleaching, spanning more than two years, is wreaking havoc in the world's oceans, affecting approximately 84% of coral reefs - an absolute record in the history of documentation of these phenomena, according to the National Oceanic and Atmospheric Administration (NOAA) in the United States. This massive wave of bleaching, associated with unprecedented sea temperatures, endangers the survival of marine ecosystems essential for biodiversity, for the food security of millions of people and for the stability of the coastline in the face of extreme phenomena, informs AFP.

• Corals, direct victims of the climate crisis

Corals are organisms extremely sensitive to temperature variations. A mere 1-2°C increase in water temperature can cause the expulsion of symbiotic algae called zooxanthellae, responsible for the color and nutrition of corals. This process, known as coral bleaching, weakens the organisms and, in extreme cases, causes their death. "Between January 1, 2023 and April 20, 2025, heat stress associated with bleaching affected 83.7% of the world's reefs," NOAA announced in its report. The phenomenon is not isolated, but has a global reach: it is occurring in the Atlantic, Pacific and Indian Oceans, making it the fourth major global bleaching event recorded by the scientific community, after those in 1998, 2010 and 2016, according to the UN.

• A silent storm that leaves behind an underwater desert

"The scale and magnitude of the heat stress is shocking," warns Melanie McField, a marine biologist and founder of the Healthy Reefs for Healthy People initiative. She describes coral bleaching as a "silent snowstorm" that is hitting reefs, turning vibrant ecosystems into lifeless, faded landscapes. Satellite imagery and field observations confirm this description: vibrant colors have disappeared, fish populations have shrunk considerably, and coral death has already been recorded in several regions of the Caribbean and South Pacific.

• A billion people depend on reef health

Coral reefs are not just beautiful underwater sights - they are essential pillars of marine and human life. Approximately a billion people live within 100 km of a coral reef, benefiting from: food sources (subsistence and industrial fishing), protection from storms (by reducing the force of waves), tourism revenue, and biodiversity essential to the balance of ecosystems. The disappearance of these natural structures would mean huge losses at economic, ecological and social levels.

• What chance do corals have of survival?

There is hope: reefs can recover if temperatures cool and local stressors-such as pollution, overfishing, and uncontrolled tourism-are limited. But, as researchers warn, marine heat waves are becoming more frequent and intense. "It's hard to imagine how recovery could happen if this rate of warming continues," says McField. According to the IPCC, the UN's intergovernmental panel on climate change, the oceans have absorbed more than 90 percent of the excess heat generated by human activity since 1970. And the rate of warming has almost doubled since 2005.

• Climate scenarios are grim

With global warming of +1.5°C compared to the pre-industrial era (a level considered the safe threshold), it is estimated that between 70 percent and 90 percent of reefs could disappear. At +2°C, the maximum threshold set by the Paris Agreement, the losses could reach 99%. Currently, national commitments to reduce emissions are leading the planet to a warming of +3.1°C by the end of the century, according to the UN - which would mean the near total disappearance of corals. "We must urgently end the era of fossil fuels," said Surangel Whipps Jr., president of the Pacific island nation of Palau. He stressed the need for a rapid transition to clean energy sources and fair climate policies. At the same time, experts say that local measures should not be neglected. Alex Sen Gupta, a researcher at the University of New South Wales, proposes: reducing local pollution and nutrient leakage into the ocean; sustainably managing tourism; combating marine pests; protecting reefs through marine protected areas and banning destructive fishing.

As global average temperatures rise and reefs disappear, an entire underwater world is being lost, with tens of thousands of species that depend directly on these superorganisms. The alarm raised by the scientific community is clear: without coral, life in the ocean will not be the same - nor will life on land, which depends directly on the balance of the seas.