Coral reefs aren't just pretty, they're also vital to marine species and island communities. But they're also facing threats from warming seas. NBC's Anne Thompson reports.

56 coral species face extinction danger from warming, acidic seas

More than half of 82 species of coral being evaluated for inclusion under the Endangered Species Act "more likely than not" would go extinct by 2100 if climate policies and technologies remain the same, federal scientists concluded.

The experts cited "anthropogenic," or manmade, releases of carbon dioxide as a key driver of warming seas and oceans absorbing more CO2, in turn making waters more acidic. "The combined direct and indirect effects of rising temperature, including increased incidence of disease and ocean acidification, both resulting primarily from anthropogenic increases in atmospheric CO2, are likely to represent the greatest risks of extinction to all or most of the candidate coral species over the next century," the experts concluded in a report released Friday by the National Marine Fisheries Service.

The report was part of a process to determine which species, if any, merit protection. The Center for Biological Diversity in 2009 had petitioned for the review of 82 species it considered in jeopardy.

Of the 82 species, all of which are in U.S. waters, 46 are "more likely than not" to face extinction by 2100, while 10 are "likely," the report stated. The authors did note that the limited science of corals meant that "the overall uncertainty was high." The fisheries service will next seek public comment as it considers the petition for listing.

The Center for Biological Diversity, which in 2006 petitioned and got protection for staghorn and elkhorn corals, said conditions have only worsened for corals.

"Coral reefs are home to 25 percent of marine life and play a vital function in ocean ecosystems," the center said in a statement. "Since the 1990s, coral growth has grown sluggish in some areas due to ocean acidification, and mass bleaching events are increasingly frequent."