More than 2,600 of the world's top marine scientists Monday warned coral reefs around the world were in rapid decline and urged immediate global action on climate change to save what remains.

The consensus statement at the International Coral Reef Symposium, being held in the northeastern Australian city of Cairns, stressed that the livelihoods of millions of people were at risk.

Coral reefs provide food and work for countless coastal inhabitants globally, generate significant revenues through tourism and function as a natural breakwater for waves and storms, they said.

The statement, endorsed by the forum attendees and other marine scientists, called for measures to head off escalating damage caused by rising sea temperatures, ocean acidification, overfishing and pollution from the land.

"There is a window of opportunity for the world to act on climate change, but it is closing rapidly," said Terry Hughes, convener of the symposium, held every four years, which attracted some 2,000 scientists from 80 countries.

Jeremy Jackson, senior scientist at the Smithsonian Institution in the United States, said reefs around the world have seen severe declines in coral cover over the last several decades.

In the Caribbean, for example, 75-85 percent of the coral cover has been lost in the last 35 years.

Even the Great Barrier Reef in Australia, the best-protected reef ecosystem on the planet, has witnessed a 50 percent decline in the last 50 years.

Jackson said while climate change was exacerbating the problem, it was also causing increased droughts, agricultural failure and sea level rises at increasingly faster rates, which implied huge problems for society.

"That means what's good for reefs is also critically important for people and we should wake up to that fact," he said.

"The future of coral reefs isn't a marine version of tree-hugging but a central problem for humanity."

Stephen Palumbi, director of Stanford University's Hopkins Marine Station, said addressing local threats, such as poor land development and unsustainable fishing practices, was also critical.

More than 85 percent of reefs in Asia's "Coral Triangle" are directly threatened by human activities such as coastal development, pollution, and overfishing, according to a report launched at the forum earlier Monday.

The Coral Triangle covers Indonesia, Malaysia, Papua New Guinea, the Philippines, The Solomon Islands, and East Timor and contains nearly 30 percent of the world's reefs and more than 3,000 species of fish.

International Society for Reef Studies president Robert Richmond stressed that the consensus statement was not just another effort at documenting the mounting problems.

Instead he said it was also about making the best available science available to leaders worldwide.

"The scientific community has an enormous amount of research showing we have a problem. But right now, we are like doctors diagnosing a patient's disease, but not prescribing any effective cures," he said.

"We have to start more actively engaging the process and supporting public officials with real-world prescriptions for success."