This generation will probably see the demise of the Great Barrier Reef unless humanity acts with far more urgency to rein in climate change, according to scientists in Australia who released new research on heat in the surrounding ocean.

The Great Barrier Reef is the largest coral reef system in the world and is often called the largest living structure on Earth. The study, published on Wednesday in the journal Nature, found that recent extreme temperatures in the Coral Sea are at their highest in at least 400 years, as far back as their analysis could reach.

It included modeling that showed what has been driving those extremes: Greenhouse gas emissions caused by humans burning fossil fuels and destroying natural places that store carbon, like forests.

“The heat extremes are occurring too often for those corals to effectively adapt and evolve,” said Ben Henley, a paleoclimatologist at the University of Melbourne and an author of the new study. “If we don’t divert from our current course, our generation will likely witness the demise of one of Earth’s great natural wonders, the Great Barrier Reef.”

The study’s scientific prose put it this way: “The existential threat to the Great Barrier Reef ecosystem from anthropogenic climate change is now realized.”

Tanya Plibersek, Australia’s environment minister, said in a statement that the government understood its responsibility to act on climate change and safeguard the reef. She pointed to a recent law that calls for a 43 percent reduction of emissions by 2030 and to $1.2 billion in measures to protect the reef.