84% of Coral Reefs at Risk in Record Bleaching Event

Scientists warned Wednesday that an unprecedented coral bleaching event, driven by human activity, is affecting 84% of the world’s reefs and could wipe out large portions of these vital ecosystems.

Since early 2023, the global coral bleaching crisis has escalated into the largest and most severe ever recorded, impacting reefs across the Pacific, Indian, and Atlantic Oceans.

Corals bleach and turn white under heat stress, and over the past two years, ocean temperatures have reached record highs due to human-driven greenhouse gas emissions.

While reefs can sometimes recover, scientists told AFP that prolonged ocean warming is shortening their recovery window.

In some areas, conditions have become so extreme that they could cause widespread or near-total coral death, according to the US National Oceanic and Atmospheric Administration (NOAA).

“Melanie McField of the Caribbean-based Healthy Reefs for Healthy People initiative said that even typically resilient coral species are now being affected.”

“If heatwaves keep coming one after another, it’s difficult to imagine how reefs can recover,” the veteran reef scientist told AFP from Florida.

Bleaching happens when corals expel the algae that not only give them their vibrant colors but also supply essential nutrients, leaving them vulnerable to disease and death.

According to the International Coral Reef Initiative, live coral cover has declined by 50% since the 1950s due to climate change and environmental degradation.

Scientists warn that with 1.5°C of global warming, up to 70–90% of coral reefs could vanish—a devastating outcome for ecosystems and the communities that depend on them.

Coral reefs benefit not only marine life but also hundreds of millions of people in coastal communities globally, offering food, storm protection, and economic opportunities through fishing and tourism.

A Result of Rising Ocean Temperatures Since the 1980s

Coral bleaching was first noted in the early 1980s and has become one of the most well-known and visible effects of the ongoing increase in ocean temperatures due to global warming.

The most recent coral bleaching event is the largest and fourth in total, marking the second occurrence within a decade and surpassing the extent of the area impacted during the previous 2014-2017 event.

“NOAA’s latest update on Monday reported that from January 1, 2023, to April 20, 2025, 83.7 percent of the world’s coral reefs have experienced bleaching-level heat stress.”

The oceans absorb 90 percent of the excess heat from human-caused fossil fuel emissions, leading to warmer sea temperatures, which are the primary cause of coral bleaching.

“The connection between fossil fuel emissions and coral death is both direct and undeniable,” stated Alex Sen Gupta, a climate scientist at the University of New South Wales in Australia.

To better reflect the increased threat of widespread coral mortality from this event, NOAA had to add three additional levels to the commonly used bleaching alert scale.

“It’s like adding Category 6 and 7 to the tropical cyclone scale for coral reefs,” Sen Gupta remarked.

Honduras Reef Shows Signs of Bleaching but Retains 46% Live Coral

McField stated that in September 2023, a renowned reef off the coast of Honduras was experiencing bleaching but still maintained 46 percent of its coral alive.

“By February 2024, everything had died, and the living coral coverage dropped to just five percent… We’ve never witnessed such mass die-offs before,” McField commented.

According to the EU’s climate monitor, Copernicus, global temperatures have already risen by at least 1.36°C compared to pre-industrial levels.

Scientists are warning that the 1.5°C threshold could be surpassed early in the next decade.

At 2°C of warming, nearly all coral reefs would vanish.

If all governments fully enforce current climate policies, the planet could warm by up to 3.1°C by 2100.

Read the original article on: Sciencealert

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