In the last, wrenching episode of BBC’s Blue Planet 2, there’s a distressing moment when a young Australian diver, expert in his patch of the Great Barrier Reef, admits ‘I cried in my mask’ as he swam over an ossuary of recently bleached-out coral bones. Professor Callum Roberts’s memoir of a life devoted to the study of our oceans, and in particular their coral reefs, is a ravishing, alarming account of these underwater palaces of wonder, and the existential threat they face from humanity and our warming climate.
Reefs take up just 0.1 per cent of our planet’s surface, yet provide home and breeding grounds for more than a quarter of all sea life. They are also the canaries in the carbon dioxide coal mine. As ocean temperatures rise, corals bleach and die, the tiny organisms that feed them (zooxanthellae) expelled from their chalky hosts. Further, the acidification of the seas weakens the very structures the coral relies on for support and reduces the amount of calcium carbonate available in the seawater to make new coralline homes.
Roberts’s first student dives in 1982 were made off the Saudi coast of the Red Sea, counting reef fish with a waterproof whiteboard. He writes of the traditional Arab attitude towards the desert as an endless waste disposal and how one of his heroes, Jacques Cousteau, saw the sea the same way. Cousteau regretted this much later, writing: ‘Water and air, the two essential fluids on which all life depends, have become global garbage cans.’
The chief pleasure of this book is Roberts’s rich descriptive power. He was an adviser for Blue Planet 2, and his writing does more than justice to those stunning films. Nature’s throne rooms are thrown open by Roberts’s prose. Here he describes a dive in the Hol Chan Marine Reserve off Belize:
Coral outcrops rise through the canopy like Mayan temples above rainforest… A group of batfish swim past, their bodies like pewter plates. Passing into the channel, fish coalesce into shoals of hammered copper, slate and sulphur, liveried with royal blue.
Roberts visits some of the most idyllic places on earth, and finds them under threat from mining, tourism and war. Most human development seems to spell doom. He surveys reefs in Egypt and sets up a marine centre, before being shunted off for the massive Sharm-el-Sheikh resort. He inspects Arab reefs hit by Saddam’s deliberate release of oil in Kuwait in 1991 and finds that local fishing fleets have inflicted even more terrible damage.
Flying back to Kuwait City, he looks out of the window to see the aftermath of Saddam’s obscene tactic:
In the sun’s glare, the spills shine like pools of water on the dry earth. Thousands of migrating birds fell for the same illusion, alighting on the water’s surface only to find themselves mired in oil.
Shadows cast by burning wells cause the sea temperatures to fall and blot the sun so the coral struggles to photosynthesise.
One Saudi fertiliser plant flushes 5.8 million cubic metres of water poisoned with ammonia and heavy metals into the sea every year. The Saudi city of Al Khobar expels ten million cubic metres of raw sewage into the gulf annually. In Bonaire, a Caribbean island off the coast of Venezuela, Roberts finds a massive wipe-out of the coral, up to 99 per cent. The culprit: human gut bacteria ‘from sewage sloshed into the sea’. Fertilisers and spillage from land developments and the overfishing of grazing fish cause seaweed to explode, smothering reefs and boosting the numbers of Crown of Thorns starfish, who feast on coral’s corpses like looters after a massacre.
Extreme weather events like El Niño, their frequency and impact aggravated by the climate crisis, also play a part. By the end of 1998, roughly 70 to 95 per cent of all corals had perished across a vast swathe of the Indian Ocean from the Seychelles to Sri Lanka, Kenya to the Maldives. ‘This catastrophe had no historical precedent.’ One Australian professor Roberts quotes believes all is lost: reefs have become a ‘zombie ecosystem’ set to collapse by the century’s end.
Roberts and his colleagues rake through the ashes of a desolate future, looking for embers of hope. Some corals have been found that can live in acidified water, and perhaps natural selection will throw up heat-tolerant corals, although the adaptation might be slower than the oceans’ rate of warming. Perhaps there will be less diverse, but more resilient reefs, like the hardier corals Roberts encountered in the Arabian Gulf.
Maybe technology could use molecular or genetic engineering to make heat-proof corals. There’s also evidence in the Caribbean that the manageable stresses of pollution, overfishing and development are hurting coral more than the climate crisis, and the creation of marine parks could help mitigate this. Reducing fishing, fertilisers, pulling development back from the coasts — these would all be local actions not hamstrung by the inertia of global agreements on greenhouse gas reduction.
Roberts is wary of putting a capital value on reefs, despite the services reefs provide being worth billions of dollars worldwide: the risk of monetising nature is that ‘markets will assume that the loss of habitats is just a cost of doing business’. For Callum Roberts, it’s the moral argument that we have a duty of care to preserve as many species as we can: ‘What right do we have to rob future generations of their chance to revel as we do in the sheer joy of what is, arguably, the greatest show on Earth?’