The oceans have long buffered the effects of climate change by absorbing a substantial portion of the greenhouse gas carbon dioxide. But this benefit has a catch: as the gas dissolves, it makes seawater more acidic. Now an international panel of marine scientists says this acidity is accelerating so fast it threatens the survival of coral reefs, shellfish and the marine food web generally.

The panel, comprising 155 scientists from 26 countries and other international groups, is not the first to point to growing ocean acidity as an environmental threat. For example, a group of eminent scientists convened by The Nature Conservancy issued a similar assessment in August. But the new report’s blunt language and international backing give its assessment unusual force. It called for “urgent action” to sharply reduce emissions of carbon dioxide.

“Severe damages are imminent,” the group said Friday in a statement summing up its deliberations at a symposium in Monaco last October. The statement, called the Monaco Declaration, said increasing acidity was interfering with the growth and health of shellfish and eating away at coral reefs, processes that would eventually affect marine food webs generally.

Already, the group said, there have been detectable decreases in shellfish and shell weights, and interference with the growth of coral skeletons.