LONDON (Reuters) - A growing human population is pushing coral reefs in the Caribbean to breaking point and saving them will require a new, larger-scale approach, researchers said on Tuesday.

Coral reefs have long been under threat but pinpointing whether overfishing, climate change or development is the main culprit has proved both contentious and difficult, said Camilo Mora, a marine biologist at Dalhousie University in Canada.

In their study, researchers monitored coral reefs in 322 sites across 13 countries throughout the Caribbean and analyzed databases on fishing, sedimentation and population growth.

The team, which also looked at agricultural land use, temperature, hurricanes, coral disease and richness of the reefs, determined that coastal development was most harmful.

"The study showed clearly that the number of people living in close proximity to coral reefs is the main driver of mortality of corals," the researchers said in the study, which was published in the Proceedings of the Royal Society.

More people means more of everything that damages coral reefs, including fishing, sewage, coastal construction and human activities that contribute to warming oceans.

Coral reefs, delicate undersea structures resembling rocky gardens that are made by tiny animals called coral polyps, are important nurseries and shelters for fish and other sea life.

They are also considered valuable protection for coastlines from high seas, a critical source of food for millions of people, important for tourism and a potential storehouse of medicines for cancer and other diseases.

But researchers and environmental groups have warned that coral reefs worldwide could be destroyed unless governments urgently change how they manage the marine ecosystem.

"This new study moves from the traditional localized study of threats to a region-wide scale," Mora and colleagues wrote.

The coral reef is critical to the Caribbean economy, generating $4 billion each year in trade for the fishing and tourism industries, as well as jobs for government workers responsible for monitoring the reefs, Mora said.