Thanks to the dire condition of the Earth's coral reefs, the planet has now reached its first tipping point due to human-caused climate change, according to a new report released Oct. 13 by scientists in Europe.

The second Global Tipping Points Report said that warm-water coral reefs - on which nearly a billion people and a quarter of all marine life depend - are "passing their tipping point."

According to the report, widespread coral dieback is taking place and - unless global warming is reversed - extensive reefs as we know them will be lost, although small refuges may survive and must be protected.

A "tipping point" occurs when a small change tips a system into a new state, causing significant and long-term transformation. With the climate, these points of no return are specific moments when the planet has warmed so much that certain effects become irreversible.

The debate about tipping points in the climate system has intensified over the past two decades, according to a study released earlier this year.

Professor Tim Lenton, from the Global Systems Institute at the UK's University of Exeter and lead author of the new report, said in a statement that "We are rapidly approaching multiple Earth system tipping points that could transform our world, with devastating consequences for people and nature."

He said this demands immediate, unprecedented action from leaders and policymakers worldwide.

Other tipping points include melting ice sheets, Amazon rainforest dieback and the collapse of vital ocean currents.

"Very serious," said Lenton in an e-mail to USA TODAY. "Coral reefs support the livelihoods of half a billion people, and they provide ecosystem services that have been valued at over $2 trillion per year. This includes supporting abundant fisheries and providing vital coastal protection from storm surges and rising sea levels for communities living behind them and their assets.

Overall, corals are vital to the health of the oceans. Although they cover only 0.2% of the ocean floor, they are home to at least a quarter of all marine species. They provide safety for juvenile fish and are home to small organisms and fish that provide food for larger fish.

A report released in 2022 showed that almost 15% of the planet's reefs have vanished since 2009.

More: Earth is headed toward several catastrophic climate 'tipping points,' study warns

"We assessed the coral reef tipping point to likely be around 1.2 degrees (Celsius; more than 2 degrees Fahrenheit) global warming and at a maximum of 1.5 degrees global warming," Lenton said in an e-mail to USA TODAY. "In the two years since our first global tipping points report, the world has spent most of the time at 1.5 degrees above the pre-industrial level.

"This has caused marine heatwaves that have led to severe bleaching impacts on 80% of the world's coral reefs," he said. "It has also become clear that the world will inevitably exceed 1.5 degrees average global warming (perhaps as soon as 2030). Therefore we conclude that coral reefs have passed a tipping point where a majority of them are suffering (or will suffer) widespread dieback."

Experts not involved in the report agree that coral reefs have indeed passed their tipping point: "I believe many reefs have passed their tipping point ‒ especially in Florida and the Caribbean," said William F. Precht, director of coral and marine sciences at Bio-Tech Consulting, in an e-mail to USA TODAY.

"Clearly, global climate change in all of its manifestations (bleaching, increased coral disease, increased storminess from tropical systems, and ocean acidification) are the existential threat to reef health. Without amelioration of the root cause ‒ reefs are headed in the wrong direction," he said.

Another expert, Terry Hughes of James Cook University in Australia, said in an e-mail to USA TODAY that "arguably, we passed the tipping point for coral reefs decades ago, and the transition from historical coral reefs to a different type of ecosystem is already well underway.

"The first global-scale coral bleaching event occurred in 1998, the hottest year (then) on record. Scientists predicted then that these mass mortality events would reoccur more and more frequently as temperatures continued to increase due to global heating."

They were right, he said: The Great Barrier Reef in Australia, for example, has experienced widespread and severe coral bleaching six times in the past decade (in 2002, 2016, 2017, 2020, 2022, 2024 and 2025). There are now almost no unbleached reefs left anywhere in the world, he said.

"The report is a wake-up call (again) for the world's governments to deal urgently with the coral reef crisis. Local protection isn't enough - and too often it's a smokescreen for inaction on climate change. For example, countries like the USA, Australia and Saudi Arabia claim to be world leaders in protecting reefs and restoring tiny patches of them, while they still refuse to curtail fossil fuels."

"We can all play a part in triggering positive tipping points that accelerate the transition to zero emissions - to limit the risk from further climate tipping points," Lenton said. "For example, by adopting clean technology (e.g. a rooftop solar panel or an EV) we stimulate the learning-by-doing and economies-of-scale that improve the quality and reduce the price of those technologies, making them more attractive for the next person to adopt - creating an amplifying feedback."

There has been some progress in the past couple of years: "In the two years since the first Global Tipping Points Report, there has been a radical global acceleration in some areas, including the uptake of solar power and electric vehicles," Lenton said in a statement.

"But we need to do more - and move faster - to seize positive tipping point opportunities. By doing so, we can drastically cut greenhouse gas emissions and tip the world away from catastrophic tipping points and towards a thriving, sustainable future."

Coral reef collapse drives world across first climate tipping point