I was the neoprene queen – Jacques Cousteau had nothing on me. Suckered into a tight black wetsuit, weight-belt on, the air-tank octopus grazing the back of my head, and my knees buckling under the burden of it all, I waited. Perspiration streamed down my face and prickled the back of my neck as I swayed heavily in the sweltering sun, eager to make my ungainly splash into the cool Coral Sea, off the north-east coast of Australia.
Having been there two years previously, I knew what glories lay ahead in the hidden water world, where fish shimmered like jewels among gardens of coral in fantastic colours.
“The coral’s not as good this year, because of El Nino,” the dive master had warned me while we loaded up the boat.
But nothing could prepare me for what I encountered on that dive.
The coral bed had been entirely drained of colour. I’d expected to see an underwater carpet of vivid pinks, yellows and purples, but the seabed looked as though it had been replaced by a polystyrene model, the colour of concrete. What remnants of life remained were fast being gobbled by a mass of crown-of-thorns starfish. It was profoundly shocking, and I swam anxiously back and forth trying to locate some evidence of the rich biodiversity from my visit two years previously. I ran out of air before I could find any.
Coral reefs are on track to be the first of the world's ecosystems to be entirely wiped out by humans. Some scientists estimate that reefs will have disappeared as soon as 2050 – many calculate atmospheric carbon dioxide concentration is already above the levels that will condemn corals to extinction.
If so, the Anthropocene – the Age of Man – will not only be far less colourful place, it will also be far poorer in terms of fish diversity, islands and coastlines will be more prone to erosion, and millions of livelihoods will be threatened. Coral reefs support a quarter of marine life on Earth – they contribute to half of the GDP in many Caribbean countries, from creating sandy beaches to harbouring the fish people eat. And as the sea levels rise, they provide vital protection against storm surges and inundation.
I had experienced the aftermath of the 1998 mass bleaching event caused by high sea temperatures from El Nino – globally, all coral reefs were effected, with 90% of the Indian Ocean’s colourful reefs killed, and 16% of reefs worldwide effectively destroyed. The effects caused by El Nino weren't related to human activity, but they give a chilling indication of our potential impact on marine life.
Before 1998, coral bleaching had been rare, localised and reefs recovered. Since then, there have been at least six major bleaching events, with the most recent and severe in 2010, when a vast area of Southeast Asia and the Indian Ocean was hit by warm waters, with Indonesian corals being particularly hard hit. When I dive now, I am shocked if I see healthy coral on a reef rather than the other way around.
Scientists estimate that over the past two decades at least 20% of Australia's Great Barrier Reef – the world's largest – has been destroyed, and up to 90% of coral has been lost in the Indian Ocean from East Africa to island states of Maldives and Seychelles.
Human-induced global warming has a double whammy effect on corals: higher ocean temperatures force the marine organisms to expel the colourful zooxanthallae algae that live inside its skeleton and that provide most of its nutrients; and oceans become more acidic as a result of absorbing higher levels of atmospheric carbon dioxide, slowing down the rate at which corals can build their calcium carbonate skeletons. During a coral bleaching event, reefs lose so much zooxanthallae that they become white and experience massive die-offs.