Global warming compounded by destructive fishing habits could be driving nearly a third of coral reefs across the world to destruction, according to a research paper in journal Science.
Coral reefs are also fondly called "the rain forests of the ocean" - they 25 percent of the world's marine species, including sponges, lobsters, turtles, shrimp, sharks and commercially important fish.
But such reefs like those are few and far between these days. In his paper, Kent Carpenter, a reef expert at Virginia's Old Dominion University, US, reports says a global coral crisis is now in full bloom.
A third of the world's coral species are now declining toward extinction, partly owing to increased outbreaks of coral diseases. "This is a whole ecosystem that we potentially could be losing," he said.
Corals that aren't killed off by these new diseases are recovering more slowly, he reports. Some are slowly overwhelmed by ugly gobs of algae.
Carpenter prepared the paper with the help of coral researchers affiliated with the International Union for Conservation of Nature, a nonprofit conservation group.
They pored through records kept at field stations near coral reefs found all over the tropics.
The paper warns ocean waters are becoming more acidic as they soak up carbon dioxide, the main global warming gas. And while there's evidence that coral reefs can find ways to adapt to waters warmed by global climate change, there's no proof that they can cope with more-acidic oceans.
"Obviously the overarching problem that has to be solved is the [buildup of man-made] carbon dioxide in the atmosphere," he said.
Carpenter's new paper drew support from a different report prepared by scientists with the National Oceanic and Atmospheric Administration at a recent conference. That paper concluded that a quarter of the coral reefs in U.S. waters were in poor condition.
There is some good news nevertheless. Reefs in some parts of the far Pacific are now thriving in the warming waters.
Besides research conducted near the Great Barrier Reef appeared to show that when a wounded coral reef is put off limits to commercial fishermen, large numbers of big fish fill the area in a few years, says Philip Munday, a reef expert at Australia's James Cook University. That is the crisis is reversible.
"That gives us enormous hope that these populations ... can rebound if they're given the chance to do so," he says.
All the same Munday stresses these programs won't protect coral reefs from problems caused by global warming. But they might help buy the reefs a little extra time.