KAILUA, KONA, Hawai'i — By absorbing increasing amounts of the greenhouse gas carbon dioxide, the oceans are becoming increasingly acidic, weakening the world's coral reefs and threatening to unsettle the balance of entire ecosystems, experts say.

Marine scientists and The Nature Conservancy offered a plan to combat ocean acidification that includes limits on fossil fuel emissions, reduction of stress on reefs and the creation of protected areas to build the resilience of tropical marine ecosystems.

"It's happening much faster than we realized," said C. Mark Eakin, National Oceanic and Atmospheric Administration coral reef watch coordinator. "Sometime this century, coral reefs are no longer going to be able to keep with the rate of erosion. Five years ago I wasn't scared, but now I am."

Eakin said the combination of increased acidity and warmer water temperatures could have devastating, potentially irreversible effects on the world's oceans and marine life, which in turn would have effects on land.

"It all adds up," he said. "It goes far beyond just corals. It affects the entire balance. But there are things we can do."

The plan is contained in the Honolulu Declaration on Ocean Acidification and Reef Management, which the scientists presented Wednesday to the U.S. Coral Reef Task Force gathered on the Big Island.

The declaration grew from a workshop this month that included climate and marine scientists and coral reef managers from the United States and Australia — two countries with some of the world's largest stretches of coral reefs.

"Hawai'i's isolated reefs are especially vulnerable to stresses of any kind, particularly to the rapidly emerging stress brought on by climate change," said Rod Salm, director of tropical marine conservation for The Nature Conservancy's Asia-Pacific program.

Some scientists believe Hawai'i reefs will succumb faster to the impacts of ocean acidification because they exist in isolation and at a higher latitude in cooler waters. Research shows that carbon dioxide is absorbed more readily in cooler ocean waters, raising acidification levels and dropping the amount of carbonate available for calcifying organisms such as corals to build their skeletons.

In July, scientists at the International Coral Reef Symposium in Florida declared acidification the largest and most significant threat faced by oceans today. Current estimates show all coral reefs could be gone by the end of the century or, in the worst case scenario, possibly decades sooner, Salm said.

"Coral reefs are the lifeblood of our oceans and we depend on them for survival," said Suzanne Case, executive director of The Nature Conservancy of Hawai'i. "Without urgent action to limit carbon dioxide emissions and improve management of marine protected areas, even vast treasured reefs like the Great Barrier Reef (off Australia) and Northwestern Hawaiian Islands will become wastelands of dead coral."

The declaration identifies two major strategies, including limiting fossil fuel emissions to stabilize atmospheric carbon dioxide and building the resilience of tropical marine ecosystems to maximize their ability to resist and recover from climate change, including ocean acidification.

"While the consequences of inaction are too depressing to contemplate, there is good news," Salm said. "Our workshop showed that there are some practical steps we can take to buy time for coral reefs" while carbon dioxide levels are stabilized.

"There is hope for coral reefs if we act now."