Coral grief

A climatologist who is trying to explain why even the most immediate and drastic steps to reduce carbon dioxide emissions may not save the coral reefs, has embarked on a metaphor for climate change.

"The climate is like this big ship, right? We are all on this big ship and the problem is once you hit the brakes it takes a long time for the ship to actually slow down and stop," says Simon Donner of the University of British Columbia. "In our case the ship is the Titanic and we are going to hit the iceberg. It is going to be almost impossible for us not to hit the iceberg at this point. What we need to do is everything we can to put the brakes on, to slow the ship down and – to hope for the corals to help us – move the iceberg a little bit. The time for emission reductions isn't so much now, it was 20 years ago."

Modern marine biology is roughly 50 years old and comfortable with the language of the media, perhaps because it flowered from a happy mix of adventure and show business. Before about 1950, marine biology was prosecuted by men in laboratories who studied the damaged and incomplete contents of deepwater trawls or made guesses about the migrations of pelagic fish or paddled around rock pools between the tides. Then a French naval officer called Jacques Yves-Cousteau designed the aqualung, hired a ship called the Calypso and recruited a young cinematographer called Louis Malle to help him make a 1956 documentary called The Silent World, and marine biology began looking up, in the metaphorical sense.

For the first time, ichthyologists could swim with the fishes; they could go with the flow, they could mingle with the millions of other creatures that colonise the huge high-rise submarine apartment blocks of coral reef, they could follow the tides and go with the turtles and sharks into tropical estuaries and mangrove forests, they could stay put with the crustaceans or spout with the cetaceans. The world was their oyster, and they could have a whale of a time.

Because of Cousteau and his contemporaries – among them the best-selling US writer Rachel Carson, for instance, and the television film-maker Hans Hass – ocean science underwent (to exploit another yet irresistible cliché) a sea change. For the first time ever, researchers could take a sustained look at a fraction of the intricate ecology of the blue planet.

More than 70 per cent of the surface area of the Earth is covered by saltwater. Terrestrial animals occupy only the first few metres above and below the topsoil. They may colonise forest canopies, soar in thermal currents, or burrow deep into the mud, but most, like the biologists that study them, are essentially flatlanders. Sea creatures conversely have the run of one huge open-plan living space, from the sunlit surface of the Sargasso Sea to the abyssal plains of the Atlantic or the 11,000 metre depths of the Marianas Trench in the Pacific, spanning the planet from the North Pole to the Antarctic coastline. Marine biologists had a new world to explore, new stories to tell.

Earlier this month, about 3,000 of them gathered in Fort Lauderdale, Florida for the 11th international coral reef symposium. They included Australians at ease in Perpignan, Germans at home in Queensland, Americans who knocked around eastern coasts of Africa. They were all ages, but more than half were young and many of them were women. They spoke matter-of-factly of faraway places – of Pago Pago and Palau and the Flower Garden, of the Marianas and Chagos and Key Biscayne, of the Great Barrier and Okinawa and Mozambique. They were at home in the world's oldest environment, but theirs was in effect the youngest science. And many of them understood two things very clearly: that there was no point amassing their knowledge unless they could share it, and that there was no point in having something important to say unless they said it in words that everybody could understand.

One of the great messages of the conference was that as sea temperatures warm, corals bleach. That is, the little polyps eject the algae with which they live in an intricate and mutually helpful partnership. It isn't the same as death – bleaching is a survival mechanism – but it weakens the corals. The fear is that such events will happen more and more often in future. Douglas Fenner, a biologist working at the department of marine and wildlife resources in American Samoa told the conference that the future had already arrived. For the past five years, he had been watching corals bleach every summer in the fringing reefs off Pago Pago.

"There is a little bit of a caveat: this is happening in restricted pools where the water gets hotter than the open ocean. It is not happening on the open ocean reefs. But it is happening, and it is a window into the future. And it is not a particularly good view that I see. There are corals – not all, but some of them – that every summer are very close to death. There is essentially no step between where they are at, and dying. In one section of the pool, they spend almost the entire year bleaching. There is a very short period when they recover, just before the next summer's bleaching," he says. "A very slight increase in temperature, and death will start overwhelming the growth."

One of the other great messages of the conference was that as carbon dioxide levels rose, the seas would become increasingly acidic, and under such circumstances, corals would find it harder and harder to make the skeletons that become, quite literally, the backbone of all reefs. All marine biologists can do is warn everybody, and try to persuade governments to protect reefs from other human exploitation, to give them a better chance of survival. Reefs are the habitat for around one quarter of all marine species. One third of all reef building corals could be at some risk of extinction already. Five studies had already reported a slowing in the growth rate of massive corals, said Joan Kleypas of the US National Centre for Atmospheric Research. She faces a prospect that Cousteau and Hans Hass could never have imagined: a day when the corals have died, and the fish that depend on them have gone.

She calls it a "there-goes-the-neighbourhood situation," and "osteoporosis of the reef". She is addressing her fellow scientists, but they understand the peculiar irony of this kind of research, that you can discover something astounding, fashioned over millions of years only a few metres below the enigmatic surface of the ocean, and discover at the same time that in a few decades it could all be gone; that Cousteau's silent world may indeed soon become silent forever. It's a moment for straight talking, in terse, uncompromising language, to as many people as possible.