NOAA: 5 Percent of The World’s Coral Will Die This Year
MIAMI – The world’s coral reefs are in the midst of a mass die off – a “white death” spanning the globe.
That’s the stark message from reports about the impact of a monster El Niño that is warming the world’s oceans.
With hundreds of millions of people relying on coral reefs for their livelihood, as well as their safety, since reefs provide protection from storm surges, exactly what is going to happen and how it will affect them is more than an idle question. Here’s our guide.
What’s causing the coral bleaching?
Warming seas. The situation isn’t helped by a monster El Niño that is raging across the Pacific Ocean – some models predict it could be the strongest El Niño ever seen, beating the last record set in 1998.
El Niño happens roughly once every four years, warming waters in the tropics and heating up the globe. Many of the big impacts of El Niño are due to the way it redistributes rainfall around the world, but it is also felt in the ocean.
When coral is exposed to a temperature above what it can stand for more than a month, it can expel the algae that live inside it and provide it with food. This leaves the coral a ghostly white and with no source of energy. A percentage of coral won’t re-acquire their algae and die. Over a period of time, many reefs that have experienced this coral bleaching will recover, as new corals grow, but some will be permanently lost.
Which regions have been affected already?
So far coral bleaching has been seen around the Solomon Islands in the South Pacific, around Hawaii in the North Pacific and around the Maldives in the Indian Ocean. This distribution was the trigger for the announcement by the U.S. National Oceanic and Atmospheric Administration (NOAA) that we are seeing the third ever global coral bleaching event. These observations confirmed predictions made by NOAA, giving the agency confidence in its forecast of a much bigger global bleaching event brought about by El Niño.
Which reefs are under threat next?
According to NOAA’s four-month projection, coral bleaching will affect 38 per cent of the world’s coral reefs by the end of the year. That includes everywhere from the Great Barrier Reef in Australia to reefs in the Caribbean and the Indian Ocean.
NOAA makes these projections based on measurements of the surface temperatures of the world’s oceans using satellites, predicting how those temperatures will change. It then plugs the numbers into models to predict how much bleaching coral will experience. To confirm the predictions, groups like the XL Catlin Seaview Survey examine the coral up close, and report on whether it has actually been bleached or not.
Researchers are particularly concerned about Hawaii, which experienced bleaching last year, when an El Niño started to develop, but died off. In July, Mark Eakin, head of NOAA’s Coral Reef Watch in College Park, Maryland, said: “The bleaching that started in June 2014 has been really bad for corals in the western Pacific… We are worried that bleaching will spread to the western Atlantic and again into Hawaii.” That has now happened, and is expected to intensify over the coming month.
How bad will it be?
Based on temperature projections, NOAA predicts that 38 per cent of coral reefs will experience bleaching this year. Assuming most of those recover – which they normally do – NOAA reckons that will mean 12,000 square kilometres of coral will be permanently lost. That’s about 5 per cent of the world’s coral gone forever.
Are we certain this will happen?
No. There will certainly be substantial bleaching but how much is an open question. Weirdly, the fact that coral reefs have been hit with a lot of bleaching over the past two decades might mean they cope with it better than history would suggest, Eakin said.
Corals have been surprising scientists with their ability to evolve to withstand more stressful conditions. That can happen in one of two ways, says Eakin. Firstly, living coral can adapt – it might be able to respond to the increased heat stress and cope with it better over time. Or alternatively, the most sensitive coral species might have been killed off over time, leaving a more resilient – if less diverse – community. “The remaining corals may be tougher to bleach and/or kill-off this time around,” he said.
John Pandolfi at the University of Queensland in Brisbane, Australia, points out that the models that predict coral bleaching aren’t particularly good. “There’s other things besides just warming – there’s cloud cover and rain that can ameliorate the effects of the warming. Even things like flood events and nutrients can actually ameliorate the effects of temperature on corals – weird stuff.”
Is climate change to blame?
At first it might seem strange to blame climate change when El Niño is the cause, and El Niño is a natural phenomenon. But global coral bleaching doesn’t happen during all El Niños – it takes an extreme one. And extreme El Niños are going to be twice as frequent as a result of climate change, and already seem to be happening much more often. Looking back as far as 1870, it seems the three strongest El Niños have happened in the past 33 years: 1982, 1997 and this year.
What can we learn from this year’s bleaching event?
Eakin says that by watching the temperature of the water and looking at how much coral actually dies off – and which species are most affected – researchers will get a sense of whether or not corals are adapting to the increased frequency of bleaching.
Pandolfi says that while bleaching is devastating, the science that will come out of it is exciting. Researchers will be looking at different time scales to see how quickly the coral recovers and what the differences are between reefs that recover and those that don’t, he says.
Will corals survive in the future if bleaching is going to happen more often?
Some say they will be gone by the middle of the century. Others say they will survive much longer.
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