Scientists pinpointed bleaching as the main cause of death of about a third of giant corals at the Great Barrier Reef. Main affected areas are the northern and central parts.

The 2,300-kilometer Australian reef holds 35 percent of dying or dead coral reefs. According to Terry Hughes, Australian Research Council's Center of Excellence for Coral Reef Studies director, the damage has serious implications.

Terry Hughes said that corals that have died would be gone for good. This would affect the sea creatures that are depending on corals for shelter and food. Older corals would have difficulty to rejuvenate, but younger ones can recover once the water temperature drops.

UNESCO did not put the Great Barrier Reef under "in-danger" listing yet, but issues a warning for Australia to do changes for damage prevention. It has recognized the conservation efforts of Australia to heal the affected regions. However, it has given the country five years to show significant progress.

UNESCO on Wednesday praised the country's efforts but asked them to watch out for climate change, water pollution caused by the coal industry, and industrial port development. Environmental organizations GreenPeace and World Wide Fund For Nature are the ones who brought the concerns upfront. Germany and Portugal are among the countries that have criticized Australia's treatment of its reefs for the past 30 years.

Australia responded to the incident by limiting erection of new ports on Queenland, prohibiting dumping of scouring soil in the nearby waters, and minimize pollution runoff to 80 percent in 10 years.

"Continuing to invest in reef science is critical for ongoing management of our iconic natural wonder," Greg Hunt, minister of the Australian environment said. "This is particularly important, with the current coral bleaching event now reaching level three."

The Great Barrier Reef is the largest coral reef system, and is a tourism spot in Australia.