BANGKOK, Thailand — Nearly half of the world's coral reefs may be lost in the next 40 years unless urgent measures are taken to protect them against the threat of climate change, according to a new report released Tuesday by the World Conservation Union.

The Swiss-based organization called for the establishment of additional marine protected areas to prevent further degradation by making corals more robust and helping them resist bleaching.

"Twenty percent of the earth's coral reefs, arguably the richest of all marine ecosystems, have been effectively destroyed today," said Carl Gustaf Lundin, head of the agency's marine environment program who helped write the report "Coral Reef Resilience and Resistance to Bleaching."

"Another 30 percent will become seriously depleted if no action is taken within the next 20-40 years, with climate change being a major factor for their loss," he said in a statement.

Coral bleaching is caused by increased surface temperatures in the high seas and higher levels of sunlight caused by climate change. As temperatures rise, the algae on which corals depend for food and color die out, causing the coral to whiten, or "bleach."

Prolonged bleaching conditions over ten weeks can eventually lead to the death of the coral.

"Current predictions are that massive coral bleaching will become a regular event over the next 50 years," Lundin said.

In its report, the organization said that marine parks reduce the stress on coral reef ecosystems by reducing the impact of pollution and overfishing.

The report also recommends a strategy for the establishment of a global marine park network in the face of climate change, covering all important marine ecosystems including coral reefs.

Other key strategies to enable coral reefs to be more resilient to bleaching are sustainable fisheries management and integrated coastal management, the report found.

"Destructive fishing practices such as blast or poison fishing can make coral reef more vulnerable to bleaching," said The Nature Conservancy's Rod Salm in a statement. "It can decrease coral cover or deplete fish populations that are important for the coral reef ecosystem."

Source: Associated Press