Warm­ing cli­mate to threaten sea life, fish­eries, study says

The Prince George Citizen - - News - Bob WE­BER

An­i­mal life in the world’s oceans will drop steadily and con­sis­tently as the cli­mate warms, a Cana­dian-led study sug­gests.

“What we see is pretty con­sis­tent,” said Derek Tit­ten­sor, a bi­ol­o­gist at Dal­housie Univer­sity in Hal­i­fax.

“For ev­ery de­gree of warm­ing, we project a five per cent de­cline in the abun­dance of an­i­mals. The warmer it gets, the more the de­cline.”

That means that the world’s oceans are on track to lose about 17 per cent of their pro­duc­tiv­ity by 2100 if there are no sig­nif­i­cant re­duc­tions in green­house gases.

The study found the im­pact of cli­mate change is so strong it al­most doesn’t mat­ter if com­mer­cial fish­eries are in­cluded in the calculatio­n. The re­sults are nearly the same.

The re­search, pub­lished Tues­day in the Pro­ceed­ings of the Na­tional Academy of Sciences, com­bined six marine ecosys­tem mod­els with global ecosys­tem mod­els and emis­sions pro­jec­tions. Tit­ten­sor said that pro­duced a com­pre­hen­sive pro­jec­tion for the oceans sim­i­lar to what al­ready ex­ists for the con­ti­nents.

“There are win­ners and losers,” he said.

Arc­tic seas are ex­pected to be­come more pro­duc­tive in a warmer world. Wa­ters north­east of Green­land could have 50 per cent more an­i­mals by 2100, the study sug­gests.

But the great ma­jor­ity of the world’s oceans will be less abun­dant. If greater ef­forts aren’t made to rein in emis­sions, al­most all mid-lat­i­tude and trop­i­cal seas will pro­duce be­tween 25 and 50 per cent less.

The re­port’s con­clu­sions have been tested against ac­tual data on fish stocks. The pre­dicted re­sults and the mea­sured trends agreed.

Warmer wa­ters re­duce an­i­mal growth in sev­eral ways, Tit­ten­sor said.

For ex­am­ple, they in­crease metabolism, which forces fish to burn more en­ergy just stay­ing alive and leaves them less for growth.

As well, warmer ocean wa­ter mixes less, which slows the cy­cling of sea floor nu­tri­ents needed by the tiny plants at the root of the ocean’s food web.

The de­cline in sea life will be con­cen­trated in larger fish, which tend to be the ones hu­mans rely on for food.

“The species that we have a real in­ter­est in are likely to be those that are more sus­cep­ti­ble,” said Tit­ten­sor.

United Na­tions fig­ures sug­gest 10 per cent of the world’s peo­ple de­pend on fish­eries for their liveli­hoods. They say 4.3 bil­lion peo­ple rely on fish for at least 15 per cent of their an­i­mal pro­tein.

“Five per cent might not seem like much of a de­cline,” Tit­ten­sor said.

“But we’re in a world that’s head­ing to­wards 10 bil­lion peo­ple and the oceans are hugely im­por­tant in terms like food se­cu­rity and mak­ing sure we can feed peo­ple.

“Any kind of cli­mate im­pact is another stress upon the oceans over and above the other stresses they’re ex­pe­ri­enc­ing.”

Some of the changes are in­evitable. Green­house gas lev­els in the at­mos­phere al­ready guar­an­tee a cer­tain level of warm­ing.

Tit­ten­sor said stud­ies such as his will help man­agers plan for the changes.

“We can try and adapt to this ef­fect.”

And, he added, we can al­ways try to re­duce it as much as pos­si­ble by cut­ting car­bon emis­sions.

“The fu­ture’s not fixed,” Tit­ten­sor said.

“We know the cli­mate’s chang­ing and we know that is go­ing to have con­se­quences. We can move to­ward re­duc­ing our green­house emis­sions.

“We have things we can do. We can tackle this.”

AP FILE PHOTO

Tuna are lined up at the Honolulu Fish Auc­tion at Pier 38 in Honolulu. A new Cana­dian-led study sug­gests that for ev­ery de­gree of global warm­ing, the abun­dance of ocean an­i­mals will de­cline by five per cent.

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