Ocean’s End

How the world’s oceans and all ma­rine life are on the brink of to­tal col­lapse. by James Bradley

The Monthly (Australia) - - CONTENTS - by James Bradley

How the world’s oceans and all ma­rine life are on the brink of to­tal col­lapse

In June this year, sci­en­tists from the Univer­sity of Tas­ma­nia and the Univer­sity of Tech­nol­ogy Sydney pub­lished re­search show­ing that over the past decade the biomass of large fish in Aus­tralian wa­ters has de­clined by more than a third. The re­sults may have jarred with gov­ern­ment claims of Aus­tralian fish­eries be­ing among the most sus­tain­able in the world, but they closely matched of­fi­cial fig­ures show­ing a 32 per cent de­cline in Aus­tralian fish­ery catches in the same pe­riod. The de­clines were sharpest in species tar­geted for fish­ing and ar­eas in which fish­ing is per­mit­ted, but even pop­u­la­tions of species not ex­ploited by fish­ing de­clined across the same pe­riod. The no­tion that a third of large fish in Aus­tralian wa­ters dis­ap­peared in just 10 years should be of pro­found con­cern to all. The health of ma­rine food webs depends upon healthy pop­u­la­tions of the preda­tor species that reg­u­late pop­u­la­tions of smaller species; de­clines in their num­bers are likely to lead to has­ten­ing dis­rup­tion of ocean ecosys­tems. Even more dis­turbingly, th­ese falls mir­ror sim­i­lar de­clines in ma­rine life around the world. Ac­cord­ing to a 2015 re­port by the World Wildlife Fund for Nature, pop­u­la­tions of ma­rine ver­te­brates in­clud­ing fish, tur­tles, birds, whales, dol­phins and seals fell by half be­tween 1970 and 2010. And although the drops in num­bers were most ex­treme dur­ing the 1970s and early 1980s, in re­cent years they have ac­cel­er­ated again, sug­gest­ing a sim­i­lar study con­ducted to­day would find an even greater de­cline. And in a sep­a­rate study the United Na­tions found that, although de­mand for fish is still ris­ing, al­most 90 per cent of the world’s fish­eries are fully fished or over­fished. There is no ques­tion th­ese head­line fig­ures dis­guise con­sid­er­able vari­a­tion be­tween species and re­gions. (The study of Aus­tralian fish­eries found the biomass of ex­ploited species ac­tu­ally in­creased in ar­eas where they were pro­tected from fish­ing.) But that should not di­vert our at­ten­tion from the fact that de­clines were worst in those species hu­mans rely upon for food: the WWF study found pop­u­la­tions of tuna, mack­erel and bonito dropped by 74 per cent in the same pe­riod. Or that other stud­ies es­ti­mate the pop­u­la­tions of large species such as whales, dol­phins, sharks, seals, rays and tur­tles have de­clined by more than 75 per cent on av­er­age, with some species, such as right whales, leatherback tur­tles and blue whales, de­clin­ing by 90 per cent or more. Half of all ma­rine ver­te­brates gone in 40 years. A third of large fish in Aus­tralian wa­ters gone in the past decade. Ninety per cent of the world’s fish­eries al­ready at their lim­its or be­yond. Th­ese fig­ures speak to a re­al­ity few want to ac­knowl­edge, and the de­cline is made even more shock­ing by the fact that it has taken place so rapidly. As Eelco Rohling, pro­fes­sor of ocean and cli­mate change at the Aus­tralian Na­tional Univer­sity, points out, although there is ev­i­dence that ho­minids were trav­el­ling by boat more than 50,000 years ago, and mid­dens and other ar­chae­o­log­i­cal ev­i­dence make it clear we have re­lied upon the ocean for even longer, ma­rine en­vi­ron­ments re­mained largely pris­tine un­til fewer than 500 years ago. In fact, they only re­ally be­gan chang­ing in the early 1800s. “While we were still sail­ing around in wooden ships pow­ered by the wind, hu­mans didn’t re­ally have much of an in­flu­ence. The real change comes with in­dus­tri­al­i­sa­tion, and the power to move our­selves around with steam and other tech­nolo­gies. Once that hap­pens, you be­gin to see mass whal­ing and fish­ing on scales that were unimag­in­able be­fore­hand.” It is dif­fi­cult for us to imag­ine the oceans be­fore hu­mans trans­formed them, and how they teemed with life. In Anna Clark’s his­tory of fish­ing in Aus­tralia, The Catch, she de­scribes the “fish­ing Eden” that greeted early Eu­ro­peans: “the sea floor off the west coast of Tas­ma­nia car­peted red with cray­fish; fish so thick that nets could be set at any time of the day; an ‘as­ton­ish­ing mag­ni­tude’ of Aus­tralian salmon; and moun­tains of mul­let that mi­grated an­nu­ally up the east coast”. This ac­cords with James Cook’s and Joseph Banks’ de­scrip­tions of the den­sity of ma­rine life they found in Botany Bay, where the crew speared stingrays weigh­ing as much as 152 kilo­grams and re­ported catch­ing “about 300 pounds weight of fish” in just “3 or 4 hauls” of the net. In Tas­ma­nia, whales con­gre­gated in the Der­went River in such num­bers they were a haz­ard to ship­ping, while on the other side of the globe, off the coast of Corn­wall, a shoal of sar­dines was spot­ted in 1836 that stretched for well over 100 kilo­me­tres. To­day there are ap­prox­i­mately 90,000 nest­ing fe­male green tur­tles left world­wide, but stud­ies sug­gest that when Eu­ro­peans ar­rived in the Amer­i­cas there were more than 50 mil­lion in the Caribbean alone. Re­ports de­scribe them fill­ing the ocean from hori­zon to hori­zon as they grazed upon the sea­grass that sur­rounded the Cay­man Is­lands; as late as the 18th cen­tury, ships en route to the Cay­mans could nav­i­gate through dark­ness by the sound of the tur­tles’ shells knock­ing to­gether as they fed. Fur­ther back again the Ro­man writer Op­pian de­scribes a Mediter­ranean so full of fish it was pos­si­ble to catch tuna by sim­ply drop­ping a log with a spike on it into the wa­ter. More of­ten than not, th­ese de­scrip­tions of as­ton­ish­ing abun­dance were merely the pre­lude to their de­struc­tion. De­spite Indige­nous Aus­tralians hav­ing fished along coast­lines for tens of thou­sands of years with­out ad­verse ef­fect, Aus­tralian fish­eries be­gan to col­lapse within a few gen­er­a­tions of Euro­pean coloni­sa­tion. The bays around Sydney were de­nuded of oys­ters by the 1860s; by 1880 Sydney Harbour, once brim­ming with fish, was de­scribed as “scarcely … a source of sup­ply at all”; and by the 1920s stocks of Sydney’s tiger flat­head had col­lapsed due to the in­tro­duc­tion of ocean trawl­ing. The de­cline in num­bers also brought re­duc­tions in size, as fish were caught and killed be­fore they could reach adult­hood: where once stur­geon up to 5 me­tres long were com­mon in the bays and es­tu­ar­ies of North Amer­ica, now they are gone, while the im­mense rays that glided across the sandy bot­tom of Botany Bay in Cook and Banks’ time would be ex­cep­tional to­day. Even Op­pian’s teem­ing Mediter­ranean is now so de­void of fish that many ma­rine bi­ol­o­gists call it the Dea­diter­ranean.

Con­cern about oil spills has been over­taken by grow­ing alarm about the im­pact of plas­tic upon ma­rine en­vi­ron­ments.

Yet for sheer fo­cused fe­roc­ity, lit­tle com­pares to the car­nage wrought upon ma­rine mam­mals by whalers and seal­ers. Sci­en­tists es­ti­mate at least three mil­lion whales were wiped out in the 20th cen­tury alone, a mas­sacre that peaked in the 1960s and killed more than two thirds of the global pop­u­la­tion of sperm whales and 90 per cent of blue whales, as well as bring­ing north­ern right whales (so known be­cause their placid nature and ten­dency to float af­ter death made them the “right” whale to kill) to the brink of ex­tinc­tion. Seals were also killed in the mil­lions: in his clas­sic book, Sea of Slaugh­ter, Cana­dian writer Far­ley Mowat cal­cu­lates at least 13 mil­lion seals were killed be­tween 1830 and 1860 in New­found­land alone, while in the early years of the 19th cen­tury pop­u­la­tions of south­ern fur seals on sub­antarc­tic is­lands were re­duced from be­tween one and two mil­lion to a mere few hun­dred in just a few decades. It is dif­fi­cult not to re­coil from th­ese sorts of sta­tis­tics. The vi­o­lence and cru­elty they speak to hor­ri­fied even ob­servers of the era, and in a time when we are in­creas­ingly aware that other an­i­mals think and feel and even grieve, the idea of this sort of slaugh­ter is al­most un­bear­able. Yet such ex­ploita­tion is also only one symp­tom of a much larger cri­sis over­tak­ing ma­rine en­vi­ron­ments, a per­fect storm of pres­sures that is al­ter­ing the oceans in pro­found and of­ten ir­re­versible ways. The mag­ni­tude of this trans­for­ma­tion is dif­fi­cult to com­pre­hend. Mak­ing sense of it de­mands we grap­ple with its ter­ri­fy­ing scale and ra­pid­ity in ge­o­log­i­cal terms. But, more deeply, it de­mands that we recog­nise not just the com­plex­ity and in­ter­con­nect­ed­ness of the forces that shape life on Earth but also the de­gree to which we are all im­pli­cated in what is tak­ing place. Two hun­dred kilo­me­tres to the east of the Philip­pines, the ocean floor drops ver­tig­i­nously into the Mar­i­ana Trench, a vast cres­cent-shaped scar in the Earth’s sur­face. More than 2500 kilo­me­tres long, and av­er­ag­ing some 70 kilo­me­tres in width, its deep­est point, the Chal­lenger Deep – a small, slot-shaped val­ley at its south­ern end – lies 11 kilo­me­tres be­neath the sur­face. Tes­ta­ment to the vi­o­lence of the forces that drive the Earth’s drift­ing con­ti­nen­tal plates, it was once be­lieved to be ev­i­dence for the now-dis­cred­ited the­ory that the Pa­cific basin is the wound left when the Moon’s mat­ter was ripped free of the Earth by cen­trifu­gal force. The depth of the Mar­i­ana Trench makes it im­pos­si­bly hos­tile to sur­face-dwelling life. Wa­ter pres­sure is more than 1000 times that at sea level, and tem­per­a­tures rarely rise above 4 de­grees Cel­sius. Hu­mans have been there only four times, yet in May of this year re­searchers from Ja­pan’s Global Oceano­graphic Data Cen­ter found a plas­tic bag at its bot­tom. This bag has the du­bi­ous dis­tinc­tion of be­ing the deep­est known piece of plas­tic waste. Yet it is only one of the thou­sands of pieces of rub­bish cat­a­logued in the cen­tre’s Deep Sea De­bris Data­base, which also in­cludes fish­ing nets, tyres, wash­ing ma­chines, bot­tles, tins, sneak­ers … even a gym bag. Of th­ese items, more than 33 per cent are plas­tic, and 89 per cent of those are sin­gle-use prod­ucts such as plas­tic bot­tles and uten­sils, ra­tios that in­crease to 52 per cent and 92 per cent at depths of more than 6 kilo­me­tres. Un­til re­cently, pub­lic con­cern about ma­rine pol­lu­tion was pri­mar­ily fo­cused on oil spills and their cat­a­strophic ef­fects on seabirds and coastal en­vi­ron­ments. Th­ese mostly used to come from tankers – 1989’s Exxon Valdez dis­as­ter re­leased more than 40 mil­lion litres of crude oil across 28,000 square kilo­me­tres of ocean and 2100 kilo­me­tres of coast­line. But as de­mand has pushed global oil pro­duc­tion ever higher and tech­nol­ogy has al­lowed fos­sil-fuel com­pa­nies to drill in wa­ters that only a few decades ago would have been re­garded as im­pos­si­bly deep, the num­ber of spills from pipe­lines and drilling has in­creased four­fold. This con­ver­gence of grow­ing tech­no­log­i­cal ca­pa­bil­ity and in­creased risk un­der­pins pub­lic re­sis­tance to re­cent at­tempts to open the rel­a­tively pris­tine wa­ters of the Great Aus­tralian Bight to ex­plo­ration and drilling. As is of­ten the case, though, this is only part of the story. While the short-term ef­fects of oil spills are of­ten cat­a­strophic – the Exxon Valdez dis­as­ter killed hun­dreds of thou­sands of seabirds, thou­sands of ot­ters, large num­bers of seals, dol­phins and or­cas, and count­less fish and in­ver­te­brates, as well as caus­ing long-term dam­age to the area’s ecosys­tems – the amount of oil re­leased by spills is barely a third of the amount that en­ters ma­rine en­vi­ron­ments as run-off from hu­man ac­tiv­i­ties on land, ship­ping dis­charges, and use of fos­sil fu­els. In re­cent years, how­ever, con­cern about oil spills has been over­taken by grow­ing alarm about the im­pact of plas­tic upon ma­rine en­vi­ron­ments. Hu­mans have pro­duced 8.3 bil­lion tonnes of plas­tic since mass pro­duc­tion of it be­gan in the early 1950s, a fig­ure that con­tin­ues to rise ver­tig­i­nously year by year: a stag­ger­ing 335 mil­lion met­ric tonnes is es­ti­mated to have been cre­ated in 2016 alone. Able to be pro­duced so cheaply that re­cy­cling is rarely eco­nomic, most plas­tic ends up in in­cin­er­a­tors and land­fill. The rest leaks out into the

en­vi­ron­ment, with at least 8 mil­lion tonnes a year wash­ing into the oceans. Jen­nifer Lavers, a ma­rine bi­ol­o­gist at the Univer­sity of Tas­ma­nia, re­cently made the scale of the prob­lem graph­i­cally clear. In 2015, Lavers and six oth­ers trav­elled to Hen­der­son Is­land in the South Pa­cific to con­duct pre­lim­i­nary work on a pro­gram to erad­i­cate rats in­tro­duced by Poly­ne­sians al­most a thou­sand years ago. Hen­der­son Is­land is roughly mid­way be­tween New Zealand and South Amer­ica. Save for the 50 peo­ple liv­ing on Pit­cairn Is­land some 200 kilo­me­tres to the south­west, one must travel al­most 700 kilo­me­tres west to the Gam­bier Is­lands be­fore en­coun­ter­ing hu­man habi­ta­tion. To the east there is nothing but Easter Is­land, al­most 2000 kilo­me­tres away. Prior to this year Hen­der­son was prin­ci­pally fa­mous as a foot­note to lit­er­ary his­tory: in 1820 Cap­tain Ge­orge Pol­lard and what was left of his crew made land­fall on the is­land af­ter their ship, the Es­sex, was rammed and sunk by a sperm whale; 30 years later their story would help in­spire Moby Dick. Lavers has been study­ing plas­tic pol­lu­tion for much of her ca­reer. Yet what she saw when she ar­rived on Hen­der­son Is­land shocked even her. “I know plas­tic is ubiq­ui­tous. It’s found from the Arc­tic to the Antarc­tic and ev­ery­where in be­tween, so I don’t go any­where with­out ex­pect­ing to find it. Yet ev­ery now and then I ar­rive some­where I’m caught off guard. Hen­der­son is one of the most re­mote is­lands in the world, it’s one of only a hand­ful of raised coral atolls in the world, it’s World Heritage listed, it’s sur­rounded by one of the largest ma­rine pro­tected ar­eas in the world. And yet there laid out in front of me was a con­cen­tra­tion of plas­tic un­like any­thing I’d ever seen.” Lavers and her team cal­cu­lated there were 17.6 tonnes of plas­tic lit­ter­ing Hen­der­son’s beaches with an av­er­age of more than 670 in­di­vid­ual pieces per square me­tre. Of this, most was ly­ing on the sur­face or buried in the first 10 cen­time­tres of sand. And th­ese amounts were in­creas­ing all the time: a survey of a 10-me­tre stretch of the is­land’s north beach found new pieces of plas­tic wash­ing up ev­ery day. Yet as Lavers points out, the 17.6 tonnes of plas­tic she and her team found on Hen­der­son con­sti­tutes less than two sec­onds of the an­nual global pro­duc­tion of plas­tic, and only a tiny pro­por­tion

of the es­ti­mated five tril­lion pieces of plas­tic be­lieved to be float­ing in the ocean. One does not have to look far for ex­am­ples of the toll plas­tic ex­acts upon ocean wildlife: birds, fish, whales and other ma­rine an­i­mals are all vul­ner­a­ble to en­tan­gle­ment. Like­wise, stud­ies of tur­tles, seals, dol­phins and birds sug­gest tens of thou­sands per­ish ev­ery year from swal­low­ing plas­tics. On Mid­way Atoll, in the North Pa­cific, up to a third of al­ba­tross chicks die ev­ery year, many of them starv­ing to death af­ter be­ing fed plas­tic refuse that their par­ents have mis­taken for food. Amer­i­can pho­tog­ra­pher Chris Jor­dan’s im­ages of their bedrag­gled corpses, rot­ting bel­lies dis­tended with plas­tic caps and other refuse, pro­vide a mutely elo­quent tes­ta­ment to the ef­fects of this process. But plas­tics also pose a more in­sid­i­ous threat. Once adrift in the ocean they be­gin to break down, dis­solv­ing into what is known as mi­croplas­tics, tiny frag­ments rang­ing in size from mil­lime­tres to nanome­tres. The high­est con­cen­tra­tions of th­ese mi­croplas­tics are found in the oceans’ gyres: vast cir­cu­lat­ing cur­rents cre­ated by the Earth’s ro­ta­tion that act like huge vor­tices, draw­ing wa­ter­borne ob­jects to­ward their cen­tres. The best known of th­ese gyres is in the North Pa­cific, and at its cen­tre lies the now-in­fa­mous Great Pa­cific Garbage Patch. Lo­cated mid­way be­tween Hawaii and North Amer­ica, the patch cov­ers ap­prox­i­mately 1.6 mil­lion square kilo­me­tres (or twice the size of New South Wales), with con­cen­tra­tions of plas­tic pol­lu­tion reach­ing 100 kilo­grams per square kilo­me­tre at its cen­tre. But while the Great Pa­cific Garbage Patch has re­ceived the most at­ten­tion, it is not alone. As Lavers’ ex­pe­ri­ence on Hen­der­son demon­strates, high con­cen­tra­tions of plas­tic pol­lu­tion are also to be found at the cen­tre of the South Pa­cific gyre, as well as those in the North and South Atlantic, while new re­search by Lavers and oth­ers sug­gests the In­dian Ocean gyre may ac­tu­ally be more pol­luted than the Pa­cific’s. Along with the tiny beads of plas­tic de­lib­er­ately added to prod­ucts such as face scrubs and tooth­paste, and the bil­lions of tiny fil­a­ments pro­duced by ar­ti­fi­cial fi­bres, th­ese mi­croplas­tics have in­vaded the ocean’s food chain, gath­er­ing in higher and higher con­cen­tra­tions as one moves up­ward through the lay­ers of pre­da­tion. In the east­ern Pa­cific, mi­croplas­tics are now ubiq­ui­tous in the host of species of tiny free-swim­ming or float­ing an­i­mals known as zoo­plank­ton. Th­ese crea­tures fill the oceans’ wa­ters and act as a foun­da­tion of the oceans’ ecosys­tems. In some parts of the ocean there is now more plank­ton-sized plas­tic than plank­ton, mean­ing or­gan­isms that rely on plank­ton for food, such as whales, are con­sum­ing it in ex­tremely large quan­ti­ties. The long-term ef­fects of this are not yet well un­der­stood, but there is no doubt ocean mi­croplas­tics are also be­ing con­sumed by hu­mans: stud­ies have de­tected them in fresh and tinned fish, while a study pub­lished ear­lier this year found that mus­sels in Bri­tain con­tained up to 700 pieces of mi­croplas­tic per kilo­gram, and other stud­ies have found them in both fish and sea salt, while a study in Cal­i­for­nia found a fifth of fish in lo­cal mar­kets con­tained fi­bres from ar­ti­fi­cial fab­rics (one study found a sin­gle load of polyester or acrylic cloth­ing can re­lease more than half a mil­lion mi­crofi­bres). Their preva­lence is made even more dis­turb­ing by the grow­ing ev­i­dence that mi­croplas­tics ab­sorb pol­lu­tants such as DDT from sea­wa­ter, as well as organic mol­e­cules such as oestra­diol, which is used for birth con­trol. Other stud­ies have found that mi­croplas­tics con­tain high lev­els of chem­i­cals that are known to dis­rupt the en­docrine sys­tem and af­fect re­pro­duc­tion in many species. Plas­tic pol­lu­tion is far from the only form of oceanic pol­lu­tion. Eelco Rohling from ANU, for in­stance, points to the largely un­re­ported threat of poly­chlo­ri­nated biphenyls, or PCBs. Orig­i­nally used in the 1920s for cooling and in­su­la­tion, PCBs were quickly in­cor­po­rated into paints, ad­he­sives, the PVC coat­ings on elec­tri­cal wires and many other prod­ucts. While their wide­spread use meant large quan­ti­ties were re­leased into the en­vi­ron­ment, it was not un­til the mid 1960s that Sören Jensen, a Dan­ish sci­en­tist look­ing for ev­i­dence of DDT in fish, found traces of PCBs in pike caught in Swe­den. Over the next two years he found traces of them ev­ery­where: in fish, in birds, even in the hair of his wife and daugh­ter. In the years since Jensen’s dis­cov­ery, PCBs have been banned or reg­u­lated in many coun­tries. But PCBs have not gone away. Quite the op­po­site: stud­ies show PCBs have per­me­ated ma­rine en­vi­ron­ments around the world, so much so that one re­cent study found high con­cen­tra­tions of them in the bod­ies of shrimp-like crus­taceans called am­phipods liv­ing al­most 10 kilo­me­tres be­neath the ocean’s sur­face. The pres­ence of PCBs in the ocean is ex­tremely con­cern­ing. Highly toxic in even small doses, they cause can­cer, liver dam­age, re­pro­duc­tive prob­lems and de­for­mi­ties in many species, in­clud­ing hu­mans, as well as dis­turb hor­monal bal­ances in fish, birds and mam­mals, and cause neu­ro­log­i­cal dis­or­ders in birds. Be­cause they col­lect in fatty tis­sues they also be­come more con­cen­trated as they move up the food chain, mean­ing they ac­cu­mu­late in the bod­ies of long-lived high-level preda­tors such as sharks, seals and cetaceans. The long-term ef­fects of this are not yet fully un­der­stood, but they may well be sig­nif­i­cant: PCBs have al­ready been im­pli­cated in mass die-offs of cer­tain pop­u­la­tions of dol­phins, and are known to re­sult in in­creased in­fant mor­tal­ity in whales and dol­phins, who trans­fer high con­cen­tra­tions of them to their young in their milk. Worse yet, PCBs break down ex­tremely slowly when kept out of sun­light, mean­ing they can linger in the deep ocean and in the bod­ies of an­i­mals and fish for decades or even longer, their con­tin­ued pres­ence a re­minder of the way the ef­fects of our ac­tions per­sist. The threat posed by plas­tics, PCBs and other forms of ma­rine pol­lu­tion may be im­mense, but it pales into

in­signif­i­cance against that of cli­mate change, some­thing that was made heart­break­ingly clear in 2016 and 2017, when the Great Bar­rier Reef suf­fered dev­as­tat­ing backto-back bleach­ing events that killed al­most half of its coral. Coral bleach­ing oc­curs when ris­ing wa­ter tem­per­a­tures cause coral polyps to ex­pel the colour­ful al­gae they se­crete in their bod­ies. Be­cause the polyps – tiny an­i­mals that ex­ist in a sym­bi­otic re­la­tion­ship with the al­gae – rely upon the al­gae for food, bleached corals quickly starve or suc­cumb to dis­ease. With the coral gone, reef ecosys­tems col­lapse, the teem­ing com­mu­ni­ties of fish and other or­gan­isms giv­ing way to the al­gae-coated skele­tons of dead coral. Only 40 years ago, coral bleach­ing was al­most un­known. But in the 1980s re­searchers be­gan to ob­serve bleach­ing events on reefs in the Pa­cific and the Caribbean. At first th­ese events were ge­o­graph­i­cally con­fined and, in the Pa­cific at least, as­so­ci­ated with the el­e­vated sea tem­per­a­tures pro­duced by El Niño events. Then, in 1998, un­usu­ally warm wa­ters trig­gered mass bleach­ing events on reefs around the globe, killing 16 per cent of the world’s coral. The pat­tern was re­peated when mass bleach­ing struck the Great Bar­rier Reef in 2002, but this time with a fright­en­ing new twist. Whereas the el­e­vated sea tem­per­a­tures of 1998 had been pro­duced by the in­tense El Niño of 1997–98 com­pound­ing the back­ground warm­ing as­so­ci­ated with cli­mate change, in 2002 there was no El Niño: the wa­ter was just hot. In the decade and a half since 2002, ris­ing ocean tem­per­a­tures have led to more fre­quent bleach­ing on reefs around the world. Yet the events of 2016 and 2017 were ex­cep­tional in both scale and sever­ity, and sug­gested we have en­tered a new and crit­i­cal phase in the trans­for­ma­tion of ma­rine en­vi­ron­ments. In pre­vi­ous bleach­ing events there tended to be what James Kerry, a re­searcher at the Aus­tralian Re­search Coun­cil Cen­tre of Ex­cel­lence for Coral Reef Stud­ies at James Cook Univer­sity and co­or­di­na­tor of the Na­tional Coral Bleach­ing Task­force, calls “a spec­trum of win­ners and losers”, mean­ing some corals – mostly the less struc­turally com­plex va­ri­eties – fared bet­ter than oth­ers. But, in 2016 es­pe­cially, tem­per­a­tures were so high that even the re­ally hardy corals be­came losers. Kerry ex­plains that “we have cat­e­gories we use to as­sess the level of bleach­ing, the high­est of which is cat­e­gory four, which means 60 per cent or more of the coral is bleached. But af­ter 2016 we re­ally need a cat­e­gory five, for reefs that are 80 or 100 per cent bleached.” For Kerry and many other sci­en­tists who work on the Great Bar­rier Reef, the events of 2016 and 2017 were deeply up­set­ting. De­scrib­ing his first sight of the dam­age, he hes­i­tates. “We had one day in a he­li­copter when we flew for eight hours, and of the 500 reefs we sur­veyed only three weren’t bleached, which meant you were fly­ing for hun­dreds of kilo­me­tres and ev­ery reef you saw was white. That was re­ally dif­fi­cult.” This sit­u­a­tion is be­ing re­peated around the world. In the Mal­dives, up to 90 per cent of reefs bleached in 2016 and 2017. Else­where in the In­dian Ocean, reefs in Kenya, Sri Lanka and along Aus­tralia’s west coast all suf­fered ex­ten­sive dam­age, with up to 90 per cent of shal­low-wa­ter corals af­fected. Reefs in the Caribbean have been badly dam­aged, los­ing up to 80 per cent of hard coral cover since the 1970s, while in Florida one survey found up to two thirds of coral had died. For Ove Hoegh-Guld­berg, pro­fes­sor of ma­rine science at the Univer­sity of Queens­land and co­or­di­nat­ing lead au­thor on the oceans chap­ter of the In­ter­gov­ern­men­tal Panel on Cli­mate Change’s Fifth As­sess­ment Re­port, the events of 2016 and 2017 were not a sur­prise. In 1999 Hoegh-Guld­berg pub­lished a pa­per pre­dict­ing the dis­ap­pear­ance of most warm-wa­ter corals and the reefs they build by the mid­dle of the cen­tury. At the time his pre­dic­tions were dis­missed as alarmist; to­day they look con­ser­va­tive. “We un­der­es­ti­mated how quickly the changes would oc­cur. Two decades ago we pre­dicted back-to-back bleach­ing events by mid cen­tury. They’re hap­pen­ing right now.” Given time, reefs can re­cover, re­colonised from other reefs or deeper, cooler wa­ter. But this process is slow: even fast-grow­ing corals re­quire 10 to 15 years to re­grow, while oth­ers can take decades. In a warm­ing world, that is not time they are likely to get, as Kerry makes clear. “Year on year, there’s a 30 per cent chance that each year will be hot­ter than the year be­fore, so the chances of get­ting another bleach­ing event are very high. The chances that those corals will reach adult­hood with­out ex­pe­ri­enc­ing a se­ri­ous bleach­ing event is very low. That means the prob­lem isn’t that the reef doesn’t have the ca­pac­ity to re­gen­er­ate, but that it will keep get­ting knocked down by th­ese big events. Look­ing ahead, that’s the most likely sce­nario.” Hoegh-Guld­berg’s as­sess­ment is even starker. With­out de­ci­sive ac­tion on cli­mate change he fore­sees bleach­ing events be­com­ing an an­nual oc­cur­rence within a decade or two. “If we don’t rapidly put the brakes on emis­sions, coral reefs as we know them will dis­ap­pear by 2025 or 2030.”

“If we don’t rapidly put the brakes on emis­sions, coral reefs as we know them will dis­ap­pear by 2025 or 2030.”

The coral reef might be the first ma­rine ecosys­tem to suf­fer ir­re­versible dam­age or col­lapse due to cli­mate change, but it will not be the last. In many parts of the world, kelp beds, which un­der­pin a range of tem­per­ate ma­rine ecosys­tems, are re­treat­ing, driven to­wards the poles by the ef­fects of warm­ing wa­ters. In Aus­tralia this process is al­ready vis­i­ble along the east coast: in north­ern New South Wales the range and health of kelp forests are al­ready sig­nif­i­cantly di­min­ished, while kelp beds off the Soli­tary Is­lands near Coffs Harbour have en­tirely dis­ap­peared. Sim­i­larly on the west coast, 100 kilo­me­tres of kelp beds dis­ap­peared in the af­ter­math of a ma­rine heat­wave in 2011. Yet nowhere have the ef­fects of this process been felt more acutely than in Tas­ma­nia. Beds of gi­ant kelp that were once so thick they had to be marked on ship­ping maps have all but dis­ap­peared, largely as a re­sult of the ar­rival of the long-spined sea urchin, borne south from the main­land by warm­ing wa­ters. Like­wise in Antarc­tica, where upper ocean wa­ter tem­per­a­tures have risen by more than 1 oC since 1950, new species such as the king crab (a fe­ro­cious preda­tor pre­vi­ously con­fined to the deep ocean) are in­vad­ing the ecosys­tems of the con­ti­nen­tal shelf. Nor are warm­ing wa­ters the only threat as­so­ci­ated with cli­mate change. In 2013 the In­ter­gov­ern­men­tal Panel on Cli­mate Change pre­dicted sea-level rises of be­tween 26 and 82 cen­time­tres by the end of this cen­tury, but those fig­ures look in­creas­ingly op­ti­mistic. In 2015 NASA re­search pre­dicted sea-level rises of a me­tre or more over the next cen­tury or so, while a 2017 re­port from the US Na­tional Oceanic and At­mo­spheric Ad­min­is­tra­tion found that rises of 2 to 2.7 me­tres were plau­si­ble, par­tic­u­larly in light of the in­creas­ing in­sta­bil­ity of Antarc­tic ice sheets. To say we are un­pre­pared for this is an un­der­state­ment. Sea-level rises of up to a me­tre or more within decades are now in­evitable. And while th­ese will sig­nif­i­cantly af­fect cities and com­mu­ni­ties in low-ly­ing ar­eas, they will also threaten the vi­a­bil­ity of a wide range of coastal and es­tu­ar­ine en­vi­ron­ments, in par­tic­u­lar vi­tally im­por­tant man­groves and sea­grass beds, and place even greater pres­sure upon coral reefs. Th­ese ef­fects will be am­pli­fied by the like­li­hood of more vi­o­lent storms and larger waves. Yet the most in­sid­i­ous and dan­ger­ous ef­fect of cli­mate change may lie else­where, in what Eelco Rohling

Even more dis­turbingly, re­search shows reefs ex­posed to more acidic wa­ter will ac­tu­ally be­gin to dis­solve.

calls the “silent killer” of ocean acid­i­fi­ca­tion. To ap­pre­ci­ate the prob­lem of ocean acid­i­fi­ca­tion it is nec­es­sary to un­der­stand that ocean chem­istry and at­mo­spheric chem­istry are linked, and that the lev­els of gases in each are in equilib­rium. As the con­cen­tra­tion of car­bon diox­ide in the atmosphere rises, so too does the con­cen­tra­tion of car­bon diox­ide dis­solved in sea­wa­ter. Dis­solv­ing car­bon diox­ide in sea­wa­ter causes a chem­i­cal re­ac­tion that pro­duces car­bonic acid and lib­er­ates hy­dro­gen ions. This in­creases the acid­ity of the wa­ter (the “H” in the term pH refers to hy­dro­gen) and, be­cause some of th­ese hy­dro­gen ions also bind with car­bon­ate and arag­o­nite, also re­duces the amount of th­ese chem­i­cals present in sea­wa­ter. This re­ac­tion is part of what is known as the ma­rine car­bon cy­cle. Inor­ganic car­bon trans­ferred from the atmosphere into the warmer sur­face lay­ers of the oceans is ab­sorbed by the ac­tions of al­gae that pho­to­syn­the­sise it into organic car­bon, and or­gan­isms such as shell­fish, coral and plank­ton that com­bine it with car­bon­ate and arag­o­nite to cre­ate cal­cium-car­bon­ate shells and skele­tons. Upon the death of th­ese or­gan­isms, much of the organic car­bon and cal­cium car­bon­ate they cre­ated is trans­ferred to the colder deep ocean, where it ei­ther set­tles into sed­i­ment or is re­turned to the upper lev­els of the ocean through the pro­cesses of ther­mo­ha­line ex­change that drive the world’s cur­rents. Over the long timescales of nat­u­ral vari­abil­ity, th­ese cy­cles reg­u­late the pH of the ocean’s wa­ters, pre­vent­ing sig­nif­i­cant change. But very rapid in­creases in car­bon diox­ide, such as those of re­cent decades, can­not be ac­com­mo­dated by th­ese nat­u­ral cy­cles, re­sult­ing in ris­ing acid­ity. Although the bulk of car­bon diox­ide has been pro­duced since the 1960s, hu­mans have been adding it to the atmosphere since the start of the in­dus­trial rev­o­lu­tion. This has oc­curred ei­ther through the use of fos­sil fu­els or by in­ter­fer­ing with the planet’s ca­pac­ity to ab­sorb the gas by clear­ing forests or drain­ing nat­u­ral car­bon sinks like swamps and peat bogs. Of that ex­tra car­bon diox­ide, some­where around 30 per cent has been ab­sorbed by the oceans, in­creas­ing their acid­ity and de­creas­ing their av­er­age pH from 8.2 in pre-in­dus­trial times to 8.1 to­day. (Some­what con­fus­ingly, an in­crease in acid­ity cor­re­sponds to a de­crease in pH.) This might seem an in­signif­i­cant amount, but pH is a log­a­rith­mic scale, where one unit equals a ten­fold change, which means this drop of 0.1 cor­re­sponds to a 30 per cent change. And this process is ex­pected to ac­cel­er­ate as the amount of car­bon diox­ide in the atmosphere con­tin­ues to in­crease, re­duc­ing the pH of the oceans to 7.8 or 7.7 by the end of the cen­tury. Sea­wa­ter is nat­u­rally slightly al­ka­line, so this sort of in­crease won’t trans­form it into bat­tery acid. None­the­less this rate of change is ter­ri­fy­ingly fast in ge­o­log­i­cal terms: a sim­i­lar rate of change has not been recorded since the mass ex­tinc­tions that ac­com­pa­nied the dis­ap­pear­ance of the di­nosaurs. Rapid acid­i­fi­ca­tion of the oceans was also at least partly re­spon­si­ble for the Per­mian-Tri­as­sic Ex­tinc­tion event that took place just over 250 mil­lion years ago. This was the sin­gle largest mass ex­tinc­tion in our planet’s his­tory, wip­ing out 90 per cent of all life on Earth and 95 per cent of life in the oceans. Ocean acid­i­fi­ca­tion is likely to af­fect some ma­rine an­i­mals di­rectly. Re­search shows fish ex­posed to more acidic wa­ter de­velop a con­di­tion known as aci­do­sis, af­fect­ing their growth, res­pi­ra­tion and abil­ity to re­pro­duce. Other stud­ies sug­gest more acidic wa­ters in­ter­fere with a neu­ro­trans­mit­ter that plays a cru­cial role in reg­u­lat­ing a range of be­hav­iours in a wide va­ri­ety of or­gan­isms. Snails and crabs af­fected in this way be­come less able to make survival de­ci­sions or be­come con­fused when evad­ing preda­tors, while clown­fish ex­hibit be­hav­iours that sug­gest their sense of smell – cru­cial for their abil­ity to avoid preda­tors – is sig­nif­i­cantly im­paired, mak­ing them prime can­di­dates for ex­tinc­tion. The in­creased en­ergy re­quired to ab­sorb car­bon­ate from more acidic wa­ter will also have se­ri­ous con­se­quences for mol­luscs, corals, crus­taceans, and other ma­rine or­gan­isms that use cal­cium car­bon­ate to con­struct shells and other skele­tal struc­tures. As Eelco Rohling ex­plains, “If an or­gan­ism has to ex­pend too much en­ergy be­cause the wa­ter is too acidic then the or­gan­ism’s shell will be in­com­plete or mal­formed or won’t form at all, mean­ing the or­gan­ism isn’t vi­able. Lar­vae that have to pro­duce car­bon­ate to grow will find that par­tic­u­larly dif­fi­cult, and many sim­ply will not sur­vive.” Stud­ies sim­u­lat­ing the ef­fects of lev­els of acid­ity ex­pected by the end of the cen­tury show many mol­luscs and crus­taceans will de­crease in size and be­come more vul­ner­a­ble to preda­tors and dis­ease. Th­ese ef­fects are al­ready vis­i­ble in some parts of the world, with acid­i­fy­ing wa­ters linked to the de­cline in oys­ter num­bers along the west coast of the United States, and to re­duced sizes in crabs and other crus­taceans in Alaska. Acid­i­fi­ca­tion will also place fur­ther pres­sure on coral reefs al­ready dev­as­tated by ris­ing wa­ter tem­per­a­tures. Re­search shows in­creased acid­ity is af­fect­ing the abil­ity of polyps to lay down the cal­cium-car­bon­ate skele­tons that sup­port the branches and folds of bony corals, weak­en­ing their struc­ture and slow­ing their growth.

Even more dis­turbingly, re­search shows reefs ex­posed to more acidic wa­ter will ac­tu­ally be­gin to dis­solve, a process that is al­ready tak­ing place in Florida and Hawaii, and is likely to over­take reefs world­wide by 2050 if cur­rent rates of acid­i­fi­ca­tion are main­tained. Ocean acid­i­fi­ca­tion has a mas­sive im­pact on some of the ocean’s small­est in­hab­i­tants, in par­tic­u­lar upon the tiny mol­luscs known as pteropods. Th­ese zoo­plank­ton, sel­dom larger than a cen­time­tre in length, are ac­tu­ally sea snails in which the foot has di­vided to be­come wing-like ap­pendages that they use to pro­pel them­selves through the wa­ter. Seen through a mi­cro­scope pteropods are crea­tures of ex­tra­or­di­nary, oth­er­worldly beauty, their al­most trans­par­ent wings emerg­ing from translu­cent shells whose cones and whorls re­sem­ble im­pos­si­bly del­i­cate ice sculp­tures. The in­tri­cate struc­tures of th­ese shells are in­cred­i­bly thin, rang­ing from 6 to 100 thou­sandths of a mil­lime­tre in thick­ness, and as a re­sult, are par­tic­u­larly vul­ner­a­ble to acid­i­fy­ing wa­ters: placed in wa­ter for six weeks with the sorts of acid­ity lev­els ex­pected by the end of the cen­tury, pteropods’ shells sim­ply dis­solve. In the Arc­tic, where melt­ing sea ice is caus­ing rapid changes to ocean chem­istry, changes in ptero­pod shells have al­ready been ob­served, while Antarc­tic wa­ters are ex­pected to reach sim­i­lar lev­els of acid­ity within a decade or two. Krill are also likely to be se­ri­ously af­fected by acid­i­fi­ca­tion. Usu­ally no more than a cen­time­tre or two in length, th­ese shrim­p­like crus­taceans gather in vast schools that can spread across hun­dreds of square kilo­me­tres. Although the pop­u­la­tions of most krill species are im­mense, none comes close to that of the Antarc­tic krill. Even al­low­ing for re­cent re­duc­tions caused by changes in sea ice, Antarc­tic krill is the most abun­dant species on Earth, with a pop­u­la­tion of 300 to 400 tril­lion and a com­bined biomass that ex­ceeds that of ev­ery hu­man on the planet. Yet even the Antarc­tic krill’s as­ton­ish­ing abun­dance may not be enough to save it from the ef­fects of acid­i­fi­ca­tion: in 2013 a study by Aus­tralian Antarc­tic Di­vi­sion sci­en­tists found acid­i­fy­ing wa­ters in­ter­fere with the com­plex life cy­cle of the krill, and could push them to­wards a tip­ping point be­yond which their num­bers might col­lapse. Fish, whales and many bird species rely on krill for survival; crabeater seals alone con­sume more than 100 mil­lion tonnes of krill ev­ery year. As the Aus­tralian Antarc­tic Di­vi­sion study noted, in a de­par­ture from the care­fully an­o­dyne lan­guage that char­ac­terises most sci­en­tific re­ports, any col­lapse in krill pop­u­la­tions would have “cat­a­strophic con­se­quences” for ma­rine mam­mals and birds of the South­ern Ocean. It is not re­ally a sur­prise that we find it dif­fi­cult to as­sim­i­late this sort of in­for­ma­tion. Our abil­ity to con­cep­tu­alise fun­da­men­tal changes to the world we in­habit is ex­tremely lim­ited, as is our ca­pac­ity to think mean­ing­fully about prob­lems that are years or even decades away. To ex­ist in a mo­ment in which ge­o­log­i­cal time and hu­man time are col­laps­ing into each other is to be brought up against the bounds of our imag­i­na­tions. This prob­lem is am­pli­fied when it comes to the ocean: although we may know one part of the coast­line in­ti­mately, the ocean’s im­men­sity means that for most of us the rest of the ocean re­mains es­sen­tially un­known, a track­less non-place. Nowhere is this clearer than in the way con­tem­po­rary travel re­duces the ocean to a blue empti­ness glimpsed in pass­ing through a win­dow or, just as of­ten, a blue space on a screen. An aware­ness of this is one of the things that drives Jen­nifer Lavers. “Peo­ple can’t care about what they don’t know about. You can’t in­spire peo­ple to fight for things they don’t even know ex­ist. Ninety-nine point nine per cent of the world’s pop­u­la­tion will never go to Hen­der­son, it’s com­pletely off lim­its. So, for me, it wasn’t just about col­lect­ing data and crunch­ing num­bers; it was about telling a story that helped peo­ple feel a con­nec­tion with th­ese places. I have to show peo­ple how beau­ti­ful th­ese is­lands are, how spe­cial th­ese species are, how im­por­tant their ecosys­tems are, then they can un­der­stand the tragedy of what’s hap­pen­ing.” Yet there is no ques­tion we are on the brink of a mo­ment unimag­in­able even a gen­er­a­tion ago. “We’re at a point of com­plete trans­for­ma­tion,” says Pro­fes­sor Jes­sica Meeuwig, direc­tor of the Cen­tre for Ma­rine Fu­tures at the Univer­sity of Western Aus­tralia. “A few

But change is pos­si­ble. In Hoegh-Guld­berg’s words, “We have to re­ally con­front those peo­ple who sup­port fos­sil fu­els.”

years ago the French ma­rine bi­ol­o­gist Daniel Pauly said that at the rate we’re fish­ing down the food web it won’t be long be­fore we’ll all be eat­ing jel­ly­fish. A few weeks ago I was in Beijing and I went to the fish mar­kets and where once they would have been full of fish, I was over­whelmed by the amount of jel­ly­fish and other in­ver­te­brates that were be­ing sold.” For Meeuwig the sit­u­a­tion is dou­bly frus­trat­ing be­cause, when it comes to fish stocks, the real prob­lem is not sci­en­tific but po­lit­i­cal. Like many ma­rine sci­en­tists she points to years of stud­ies show­ing that cre­at­ing ma­rine re­serves cov­er­ing 30 to 40 per cent of the world’s oceans is the only ef­fec­tive way to pro­tect de­clin­ing fish stocks, but em­pha­sises this strat­egy is a win-win for fish­eries. “The data is re­ally clear. Pro­tect­ing ar­eas from fish­ing doesn’t just pro­tect fish in the re­serves, it in­creases the eco­nomic value of fish­eries as­so­ci­ated with those re­serves.” She cites work by Pro­fes­sor Rashid Su­maila of the Univer­sity of Bri­tish Columbia, Canada, demon­strat­ing that clos­ing the high seas to fish­ing would not only in­crease the num­ber of fish we could catch, as the ris­ing num­ber of fish in the pro­tected ar­eas spilled out into neigh­bour­ing wa­ters, but also lay the ground­work for a far more just dis­tri­bu­tion of the wealth gen­er­ated by fish­eries. “In­stead of all the eco­nomic ben­e­fit flow­ing to Span­ish, Tai­wanese and Korean dis­tant-wa­ter fish­ing fleets,” Meeuwig says, “coun­tries like In­done­sia and na­tions in west and east Africa would be able to take ad­van­tage of their do­mes­tic fish­eries.” The so­cial-jus­tice di­men­sion of fish­ery man­age­ment is sel­dom dis­cussed, but for Meeuwig it is a vi­tal part of any con­ver­sa­tion about fish stocks. “A lot of the pirates in So­ma­lia were for­mer fish­er­men who could no longer catch fish be­cause for­eign fish­ing fleets had swooped in and trashed the place.” Like­wise, de­clin­ing fish stocks con­trib­ute to slav­ery and other forms of labour abuse that per­sist in the fish­ing sec­tors of many coun­tries. Re­cent re­ports show Ro­hingya refugees and Cam­bo­di­ans have been used as slaves on Thai fish­ing ves­sels, and In­done­sians have been kept in slave-like con­di­tions on South Korean ves­sels in New Zealand wa­ters. Meeuwig says that “catches are now so low the only way many dis­tant-wa­ter fish­ing in­dus­tries can make a buck is through gov­ern­ment sub­si­dies or by not pay­ing their labour”. She also ar­gues that cre­at­ing ef­fec­tive ma­rine re­serve sys­tems is a key strat­egy for build­ing re­silience to pres­sures such as pol­lu­tion and cli­mate change, point­ing to stud­ies of the im­pact of warm­ing wa­ters on kelp forests in Tas­ma­nia. “In ar­eas where there was no fish­ing the kelp didn’t col­lapse be­cause it was more re­sis­tant to cli­mate in­vaders. In the same way re­search shows that af­ter the flood­ing in 2011 the ar­eas around Bris­bane that were closed to fish­ing re­cov­ered faster, and that ar­eas of the Great Bar­rier Reef that were closed to fish­ing have been more re­silient to bleach­ing and crownof-thorns starfish.” None­the­less, in March of this year the Turn­bull gov­ern­ment wound back pro­tec­tions for Aus­tralia’s ma­rine parks. The move, which more than 1200 sci­en­tists had de­scribed as “deeply flawed” and “ret­ro­grade”, opened al­most half the area pre­vi­ously clas­si­fied as pro­tected to com­mer­cial fish­ing. Most con­tentious was the open­ing of large ar­eas of the Coral Sea, a re­gion al­ready un­der as­sault from cli­mate change, to both recre­ational and com­mer­cial ex­ploita­tion. En­vi­ron­ment Min­is­ter Josh Fry­den­berg hailed the de­ci­sion as a win for both fish­eries and the en­vi­ron­ment. Meeuwig doesn’t mince her words: “The idea we’d ac­tively un­der­mine re­silience by al­low­ing fish­ing in re­serves is just in­cred­i­bly stupid.” Meeuwig is equally direct about where th­ese choices are tak­ing us. “For a long time, sci­en­tists have ar­gued that you don’t see ex­tinc­tions in the ocean be­cause broad­cast [or mass] spawn­ing makes it dif­fi­cult to wipe out an en­tire species. But the only rea­son it looks dif­fer­ent is that we only started in­dus­tri­al­is­ing the oceans in the 1960s, whereas we’ve been in­dus­tri­al­is­ing ter­res­trial en­vi­ron­ments for thou­sands of years. So we’re just catch­ing up, and that means that we’re go­ing to be­gin see­ing ex­tinc­tion rates in the ocean that are un­par­al­leled.” For those work­ing in ar­eas where cli­mate change is the driving force, the sit­u­a­tion is even grim­mer. “We’re at break­ing point,” says Eelco Rohling. “Some­time in the [next] decade we’re go­ing to have to make a choice. Do we keep do­ing what we’re do­ing or do we go all out and re­ally de­crease emis­sions, not just by some neg­li­gi­ble per­cent­age a year, but rapidly and to­wards zero? Be­cause if we don’t do that, we’re go­ing to make the planet un­live­able.” Jen­nifer Lavers con­curs. “Min­ers used to take ca­naries down into the coalmines with them to warn them if the air be­came poi­sonous. As long as the birds kept singing they knew it was okay. In the same way, seabirds and other ma­rine species are re­li­able sen­tinels of ocean health. And seabirds are de­clin­ing faster than any other bird group. The birds tell us the tip­ping point is near.” For coral reefs, that tip­ping point is al­ready here. Yet those who work on them are wary of al­low­ing de­spair to colour their work, in­sist­ing there is still time to save reefs. As James Kerry ar­gues, “If we say the Great Bar­rier Reef is writ­ten off, then the politi­cians will write it off.”

De­spite his pre­dic­tion that most of the world’s coral reefs will be gone within a decade or two, Ove Hoegh-Guld­berg also re­fuses to give up. “The fact we might lose 70 to 90 per cent of corals over the next decade or two shouldn’t be our focus. Our focus has to be on the 10 to 30 per cent we can save, and on sta­bil­is­ing global cli­mate as close to 1.5 de­grees above prein­dus­trial tem­per­a­tures as we can. That’s still pos­si­ble if we make a very rapid shift away from fos­sil fu­els. And that’s the dou­ble punch we need. We have to get to the low­est lev­els of CO2 and other green­house gases as fast as pos­si­ble, while pro­tect­ing more for­tu­nate re­gions where the cli­mate may be chang­ing less rapidly. It’s in­cred­i­bly im­por­tant we pro­tect th­ese more for­tu­nate sites from lo­cal im­pacts such as pol­lu­tion, over­fish­ing and un­sus­tain­able coastal de­vel­op­ment that is so dam­ag­ing to reefs. Be­cause they’re the places from which re­gen­er­a­tion will be pos­si­ble if we sta­bilise Earth’s atmosphere and cli­mate.” The forces ranged against ef­fec­tive ac­tion on cli­mate change and the other pres­sures trans­form­ing the oceans are pow­er­ful. But change is pos­si­ble. In HoeghGuld­berg’s words, “We have to re­ally con­front those peo­ple who sup­port fos­sil fu­els, and out­line the mas­sive en­vi­ron­men­tal and hu­man costs of the path we’re on rel­a­tive to the cost of shift­ing to low-car­bon re­new­ables. The ar­gu­ment we can’t switch be­cause it’s too ex­pen­sive is sim­ply baloney. And, quite frankly, reck­less. It doesn’t cost that much rel­a­tive to the dam­age, and we re­ally need to com­pel our po­lit­i­cal lead­ers to stop treat­ing cli­mate change like a sec­ond-tier ir­ri­ta­tion and start treat­ing it as a global emer­gency.” Achiev­ing that re­quires peo­ple to do more than merely hope. It re­quires us to take ac­tion, not just as in­di­vid­u­als but also col­lec­tively. As Lavers says, “Hope is an in­cred­i­bly dan­ger­ous thing be­cause it’s what we do when we feel we don’t have any con­trol any­more. That’s why I ask peo­ple, I plead with peo­ple: don’t hope, do. Do some­thing. Do any­thing. Do what­ever you can. At an in­di­vid­ual level, at a com­mu­nity level. Don’t give up. Don’t wave the white flag. Just do some­thing.” The ocean is part of us, part of ev­ery liv­ing thing. We bear the mem­ory of it in our cells, en­coded into our DNA. It af­fects al­most ev­ery as­pect of life on Earth: in­flu­enc­ing the weather, reg­u­lat­ing the atmosphere and the tem­per­a­ture, shap­ing our his­tory and cul­ture. It even suf­fuses our imag­i­na­tive lives – its im­men­sity and great cy­cles of tide and wind and wave speak­ing to our sense of the in­fi­nite, its mys­tery to our ap­pre­hen­sion of time’s depth. Yet while we are ac­cus­tomed to think­ing of the ocean as lim­it­less, it is not. We have pushed many of its in­hab­i­tants to the brink of ex­tinc­tion and be­yond. We have choked its wa­ters with plas­tics and other pol­lu­tants, leach­ing poi­sons into the bod­ies of fish and other an­i­mals as well as our­selves. We have al­ready ir­re­versibly al­tered its ecol­ogy, its bi­ol­ogy, even its very chem­istry. Many of the ef­fects of our ac­tions will be felt for mil­len­nia. But, de­spite the scale of the changes we have un­leashed, there still re­mains an ever-nar­row­ing win­dow of op­por­tu­nity to stave off the worst ef­fects of the dis­as­ter that is un­fold­ing around us. As I write this, the Bu­reau of Me­te­o­rol­ogy is re­port­ing that a new El Niño may be build­ing in the Pa­cific, po­ten­tially bring­ing another round of cat­a­strophic bleach­ing to the Great Bar­rier Reef. Per­haps it will be spared this year, but even if it is, the up­ward trend in wa­ter tem­per­a­tures en­sures that in the ab­sence of con­certed ac­tion to re­duce emis­sions any re­prieve will be tem­po­rary at best. Whether that hap­pens is up to us. We need to recog­nise that by fail­ing to act we are mak­ing a choice, the ef­fects of which will soon be out of our hands.

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