Almost half the coral reef ecosystems in United States territory are in poor or fair condition, mostly because of rising ocean temperatures, according to a government report.
The reefs discussed in the National Oceanic and Atmospheric Administration report serve as breeding grounds for many of the world's seafood species and act as indicators of overall ocean health.
"They are a major indicator of something that could go wrong with the environment," said Timothy Keeney, NOAA's deputy assistant secretary for oceans and atmosphere.
Keeney said 25 percent of all marine species need coral reefs to live and grow, while 40 percent of the fish caught commercially use reefs to breed.
"If we lose the reefs, you lose a very significant and important habitat," Keeney said.
Since NOAA's last report in 2005, the Caribbean region has lost at least 50 percent of its corals, largely because sea temperatures have risen, Keeney said.
Elkhorn and staghorn corals have also been listed as threatened under the Endangered Species Act, the first corals ever to receive such protections based on rapid declines.
The 569-page report took 18 months to complete with input from 270 federal, state and university scientists. It documented 15 ecosystems in U.S. states and territories, including the U.S. Virgin Islands, Puerto Rico, Florida, Hawaii, American Samoa and Guam. It was released at the 11th International Coral Reef Symposium in Fort Lauderdale.
The report's authors noted it was the first detailed NOAA study to go beyond anecdotal evidence and patchy science to provide conclusive data that the nation's coral reefs are in trouble.
"We can actually document these declines now," said Jenny Waddell, coeditor of the study and a NOAA marine biologist.
The report found that coral bleaching caused largely by rising sea temperatures is a major factor. Carbon dioxide released by burning fossil fuels is absorbed by the oceans, making the waters more acidic and corrosive on corals.
Land-based pollution, such as sewage, beach erosion, coastal development and overfishing also are to blame.
The study does not make recommendations, but simply serves as what its authors deem a "call to action" for state governments and Caribbean countries.
Keeney sees corals as "a sentinel species of the planet," and calls them "the rain forests of the sea." Beyond their importance as breeding grounds for fish, reefs could hold cures for diseases.
He said there are also positive signs that people are beginning to understand "the value of coral reefs to our economy."
Kenney argues the report adds another layer of scientific certainty that man-made climate change is stressing the nation's oceans and could ultimately have huge economic and social impacts if its effects are not reversed.
"There's no question that ... man-made actions are the major cause for these losses and stresses on the reefs," Keeney said.
Dave Allison, a senior campaign director for the advocacy group Oceana, said the entire world's coral reefs "border on disaster."
"All the world's coral reefs are being stressed by both short-term and long-term human impacts," Allison said. "We've known about the human impact on corals for decades. It's just that the combination of problems confronting the corals have never come together in such a perfect storm."