The biggest mass coral destruction recorded could be underway, researchers have warned. The world’s coral reefs are losing their vibrancy in the third ever global bleaching of the underwater ecosystems. It’s expected to affect 38 percent of the world’s reefs and kill 2 percent by the end of this year.
“We’re in unchartered territory, we’re heating the ocean up at a very rapid rate and a lot of what we’re seeing at the moment is completely novel,” Ove Hoegh-Guldberg, lead researcher at the Global Change Institute at The University of Queensland, told WIRED.
Coral bleaching occurs when coral is exposed to high temperatures and excessive sunlight. Warm temperatures cause brown algae within the body tissues of coral to produce toxic compounds rather than energy. This causes the coral to expel the algae and turn white.
Bleaching is not necessarily fatal if the coral has time to recover. But rising ocean temperatures coupled with the current El Niño system means some reefs have experienced near-fatal temperatures for more than 12 months.
“If you have a bleaching event that’s not too hot for too long and the corals don’t die, then they can regain their symbiotic algae in the months after the bleaching event. But if they die then it could take 10 to 20 years to recover,” Hoegh-Guldberg continued.
Corals can start to die within weeks of warmer temperatures, according to Hoegh-Guldberg.
“We’ve had chronic stress in the Pacific that’s lasted for more than 12 months. In those areas we’ve seen a lot of mortality,” he said. “The corals are starving, they’re getting disease, it’s essentially taken away their food source — the symbiotic algae that gives photosynthetic products.”
Coral bleaching was first seen by researchers in 1979, but in a localised area. Then in 1998 the first global bleaching killed 16 percent of the world’s corals. The current global cycle could be as bad, if not worse.
“If we get the same sorts of temperatures, which appears to be on the cards we’ll have that scale of impact or more,” Hoegh-Guldberg warned. “With hundreds of millions of people relying on fisheries and reefs for sustenance, the repercussions of a global coral bleaching event could be potentially disastrous.”
Coral reefs account for less than 0.1 percent of the ocean floor, but are home to 25 percent of all marine species. The researchers estimate the livelihoods of 500 million people are dependent on healthy coral reefs.
Technology available to researchers today, which didn’t exist in 1998, could help researchers understand the bleaching phenomenon and raise awareness of the problem.
“With technology that helps us map where bleaching is occurring, we can facilitate the research necessary to understand this phenomenon and determine the impact climate change is having on reefs worldwide,” said Richard Vevers, executive director of XL Catlin Seaview Survey, which conducted the research. “As bleaching becomes more widespread, we can learn how to better understand and determine which areas will be most affected and how to better prepare for and respond to these dramatic changes.”
In 1999 Hoegh-Guldberg predicted the current global bleaching crisis would occur — and he thinks it could get worse still.
“It’s a very new phenomenon, and it’s been growing worse and worse. The time between global bleaching events is shortening […] We’re getting to the point that it doesn’t take an El Niño to get you beyond the threshold for coral,” said Hoegh-Guldberg. “That has most of us very worried.”
The current El Niño is one of the four strongest since 1950, and is responsible for rising air temperatures too. This year and next are set to be the warmest years on record due to El Niño, recently released Met Office figures revealed.