Mark Carwardine

The broad­caster and cam­paigner looks at the im­pact of global warm­ing on our oceans and whales, and in­vites your thoughts on the sub­ject.

BBC Wildlife Magazine - - Contents -

The ef­fects of global warm­ing

There’s no deny­ing it – hu­man-in­duced cli­mate change is an ex­is­ten­tial threat to all life on Earth. A re­cent land­mark re­port by the UN In­ter­gov­ern­men­tal Panel on Cli­mate Change tells us that we have un­til about 2030 to get our act to­gether, if there is to be any hope of keep­ing it to man­age­able pro­por­tions. If we don’t, we’ll pass a tip­ping point and the con­se­quences will be noth­ing less than cat­a­strophic.

The ev­i­dence is all around us – shrink­ing glaciers, dis­ap­pear­ing sea-ice, wors­en­ing floods, more and more hur­ri­canes with es­ca­lat­ing power, and longer and more in­tense heat waves and droughts.

For wildlife, global warm­ing is plac­ing ad­di­tional pres­sures on ecosys­tems that are al­ready stressed by many other hu­man-in­duced threats. At worst, warm­ing tem­per­a­tures will lead to pop­u­la­tion or species ex­tinc­tions. At best, they are forc­ing an­i­mals to shift their breed­ing sea­sons or move to higher lat­i­tudes or el­e­va­tions (caus­ing fur­ther com­pli­ca­tions, as they en­ter re­gions oc­cu­pied by other species).

It may not be cat­a­clysmic – at least, not in the scheme of things – but there are sig­nif­i­cant changes afoot in the world of whales. And it’s be­cause oceans, which serve as nat­u­ral sponges, have ab­sorbed more than 90 per cent of the ex­cess heat and about 30 per cent of the car­bon diox­ide gen­er­ated by hu­man con­sump­tion of fos­sil fu­els. In 2017, ocean tem­per­a­tures were by far the hottest ever recorded. The Arc­tic Ocean, in par­tic­u­lar, is warm­ing more rapidly than any other re­gion on the planet

– ac­cord­ing to NASA, it is likely to be­come com­pletely ice-free in sum­mer be­fore the mid­dle of the cen­tury.

Con­se­quently, some whales are go­ing where they have never been be­fore. It was head­line news re­cently when a pair of sperm whales was spot­ted off the north­ern tip of Baf­fin Is­land, in Canada’s high Arc­tic, far from their nor­mal range. But that is just the tip of the ice­berg, so to speak.

Killer whales are tak­ing ad­van­tage of longer, ice-free sum­mers by ex­tend­ing their range fur­ther and fur­ther north into the Arc­tic – with some po­ten­tially se­ri­ous con­se­quences. For a start, they are hunt­ing nar­whal. These tusked whales are not used to be­ing threat­ened by any­thing other than peo­ple and oc­ca­sional po­lar bears, and are be­ing driven from some of their rich­est feed­ing grounds by this new cetacean peril.

Per­haps more im­por­tantly, the loss of Arc­tic sea-ice is open­ing up the North­west and North­east Pas­sages to all sorts of whales. Un­til quite re­cently, ice pre­vented them from swim­ming be­tween the North Pa­cific and North At­lantic – but now they can. In the past decade, for ex­am­ple, grey whales – which were hunted to ex­tinc­tion in the At­lantic – have been spot­ted again for the first time since the early 18th cen­tury (one off the coast of Is­rael and an­other off Namibia). As ice bar­ri­ers are re­duced, it is quite pos­si­ble that we will start to see a steady trickle of them ar­riv­ing in the At­lantic from the Pa­cific and, ul­ti­mately, they could re­colonise. There is ev­i­dence that other species are also mov­ing to the ocean next door or meet­ing in the mid­dle. How they will fare – or what im­pact they might have on their new homes – no one knows.

An ed­i­to­rial in The Guardian summed up our com­pla­cent at­ti­tude to cli­mate change per­fectly: ‘Even apoc­a­lyp­tic sci­ence fic­tion deals with bands of sur­vivors who have, by def­i­ni­tion, sur­vived. And we al­ways imag­ine our­selves as among the sur­vivors.’ Un­less we live up to the most am­bi­tious goals of the Paris Agree­ment – which, given cur­rent ev­i­dence, seems shock­ingly un­likely – ocean-hop­ping whales will be the least of our wor­ries.

MARK CARWARDINE is a frus­trated and frank con­ser­va­tion­ist.

WHAT DO YOU THINK? If you want to sup­port Mark in his views or shoot him down in flames, email wildlifele­t­[email protected]­me­di­

If we don’t act, we will pass a tip­ping point, with cat­a­strophic con­se­quences.

Loss of sea-ice leads to species, such as grey whales, mov­ing be­yond their usual range.

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