SYDNEY — Scientists are warning that vast swathes of Australia’s Great Barrier Reef may never recover from repeated coral bleaching.

A group of researchers led by Terry Hughes of James Cook University reports that rising ocean temperatures caused by global warming are responsible for the destruction of hundreds of miles of reef. Their findings are reported in the journal Nature.

Corals are marine animals that live in compact colonies of tiny, identical, individual polyps.

Most corals get their food from the microscopic algae that live inside their tissue. The algae convert energy from the sun into food. It is the algae that provide coral reefs with their vibrant color.

Coral bleaching mainly occurs when a rise in sea temperatures causes the algae to produce toxins. In self-defense, the corals then expel the algae, which exposes their limestone skeleton.

Corals can recover if there is a subsequent drop in water temperatures, but without the algae they risk starving to death.

Scientists have warned for decades that burning fossil fuels releases greenhouse gases that warm the oceans and put coral at risk. In turn, that jeopardizes the marine ecosystem, including fish that rely on the reefs to protect them from predators.

This could in turn spark a food shortage, because hundreds of millions of people worldwide rely on reef fish as their primary source of protein.