The Earth has reached a critical tipping point the widespread bleaching and death of warm-water coral reefs. According to the Global Tipping Points Report 2025 prepared by 160 scientists from 23 countries, these vital ecosystems are undergoing irreversible decline due to surging ocean temperatures. The collapse threatens nearly one billion people who depend on coral reefs for food, income, and coastal protection. The report was released ahead of the COP30 climate summit in Brazil, where nations will discuss emission targets for the next decade.
Warm-water coral reefs shallow, tropical ecosystems built on the partnership between corals and photosynthetic algae called zooxanthellae are among the most biologically diverse habitats on Earth. When ocean temperatures rise, corals expel these algae, losing both their vibrant colours and their main source of nutrients. This process, known as bleaching, leaves corals weak and vulnerable to disease and death.
While bleaching has occurred naturally in the past, scientists warn that the frequency and intensity of recent marine heatwaves have left reefs with no recovery time. The current global bleaching event, ongoing since January 2023, is the fourth and most severe on record, affecting nearly 85 percent of coral reefs across more than 80 countries. It follows major bleaching events in 1997-98, 2010, and 2014-17.
In the Caribbean, recurrent heat stress linked to shifting ocean circulation patterns is causing bleaching even in years without El Niño conditions. Similarly, Australia’s Great Barrier Reef (GBR) has recorded unprecedented ocean warming, leading to massive coral mortality and disease outbreaks. Some regions have lost over 70 percent of their hard coral cover. Even previously resilient coral species are now collapsing under record heat the highest in 400 years.
The report describes a “reef to rubble” phenomenon, where coral colonies fragment and turn into rubble, marking a permanent shift to less complex ecosystems. Bleaching events on the GBR, once rare, are now occurring almost every two years, placing the world’s largest coral system under existential threat.
Beyond rising sea temperatures, additional pressures such as overfishing, water pollution, nutrient runoff, and microplastic contamination are accelerating coral decline. Over 80 percent of coral reefs globally are overfished or degraded. Microplastics are also reducing coral productivity, worsening the crisis.
Experts warn that while cutting-edge technologies from coral spawning preservation to breeding heat-resistant species offer hope, such measures may not be enough unless global temperature rise is limited to below 1.5°C. “We’re in a new climate reality,” says Tim Lenton of the University of Exeter, who led the report. “We have crossed a tipping point in the climate system.”
As COP30 approaches, the collapse of coral reefs stands as the first major ecosystem breakdown in the age of global warming a stark warning that the planet’s delicate systems are unraveling faster than predicted.