93% of Great Barrier Reef affected by mass bleaching

On the west coast of Queensland, Australia, rising temperature is wreaking havoc to the largest reef formation on Earth. By flying over 911 individual reefs scattered along the coast, scientists have mapped the severity of the event, said to be more devastating than two other previously mass bleaching which happened in 1998 and 2002. In the northern sector of the reef, 60% to 100% of corals are severely bleached. From these numbers, some regions are expected to see 90% mortality rate of affected corals, with the average number being 50%.

Corals, marine animals which live in compact colonies, experience bleaching when heightened temperatures force them to eject photosynthetic algae which live on them, known as zooxanthellae. Removal of the algae not only causes the corals to lose their vivid coloration—hence the term bleaching—but also the nutrients they provide. Bleaching pauses the coral’s growth, and unless the temperature drops back, allowing the algae to recolonize the coral, the host may die.

The reef, which spans across 2,300 km (1430 miles) across the east coast of the country, shelters countless other living creatures in the region. It also generates an annual income of AUD 5 billion and employs 70,000 people through the tourism sector.

While parts of the reefs especially near the southern end are still in good shape, recovery is expected to be slow. Some old, slower growing corals require decades to grow back, and some may not even return in this generation’s lifetime.