Study says warm­ing may re­duce sea life by 17%

If the world re­duces car­bon pol­lu­tion, losses may be lim­ited to only 5 per­cent


WASHINGTON — The world’s oceans will likely lose about one­sixth of their fish and other marine life by the end of the cen­tury if cli­mate change con­tin­ues on its cur­rent path, a new study says.

Ev­ery 1.8 de­grees Fahren­heit that the world’s oceans warm, the to­tal mass of sea an­i­mals is pro­jected to drop by 5 per­cent, ac­cord­ing to a com­pre­hen­sive com­puter-based study by an in­ter­na­tional team of marine bi­ol­o­gists. And that does not in­clude ef­fects of fish­ing.

If the world’s green­house gas emis­sions stay at the present rate, that means a 17 per­cent loss of biomass — the to­tal weight of all the marine animal life — by the year 2100, ac­cord­ing to Tues­day’s study in the Pro­ceed­ings of the Na­tional Academy of Sciences. But if the world re­duces car­bon pol­lu­tion, losses can be lim­ited to only about 5 per­cent, the study said.

“We will see a large de­crease in the biomass of the oceans,” if the world doesn’t slow cli­mate change, said study co-au­thor Wil­liam Che­ung, a marine ecologist at the Uni­ver­sity of Bri­tish Columbia. “There are al­ready changes that have been ob­served.”

While warmer wa­ter is the big­gest fac­tor, cli­mate change also pro­duces oceans that are more acidic and have less oxy­gen, which also harms sea life, Che­ung said.

Much of the world re­lies on the oceans for food or liveli­hood, sci­en­tists say.

“The po­ten­tial ramificati­ons of these pre­dicted losses are huge, not just for ocean bio­di­ver­sity, but be­cause peo­ple around the world rely on ocean re­sources,” said Uni­ver­sity of Vic­to­ria bi­ol­ogy pro­fes­sor Ju­lia

Baum, who wasn’t part of the study but says it makes sense. “Cli­mate change has the po­ten­tial to cause se­ri­ous new con­flicts over ocean re­source use and global food se­cu­rity, par­tic­u­larly as hu­man pop­u­la­tion con­tin­ues to grow this cen­tury.”

The big­gest an­i­mals in the oceans are go­ing to be hit hard­est, said study co-au­thor Derek Tit­ten­sor, a marine ecologist at the United Na­tions World Con­ser­va­tion Mon­i­tor­ing Cen­ter in Eng­land.

“The good news here is that the main build­ing blocks of marine life, plank­ton and bac­te­ria may de­cline less heav­ily, the bad news is that those marine

an­i­mals that we use di­rectly, and care about most deeply, are pre­dicted to suf­fer the most as cli­mate change is work­ing its way up the food chain,” coau­thor Boris Worm, a marine bi­ol­o­gist at Dal­housie Uni­ver­sity in Canada, said in an email.

Trop­i­cal ar­eas, al­ready warm, will also see the big­gest losses, Che­ung said.

Sci­en­tists had al­ready thought that cli­mate change will likely re­duce fu­ture ocean life, but past com­puter sim­u­la­tions looked at only part of the pic­ture or used only one model. This study uses six dif­fer­ent state-of-the-art com­puter mod­els that give the best big pic­ture look yet, Che­ung said.

It is hard to sep­a­rate past cli­mate change im­pacts from

those of fish­ing, but past stud­ies have shown places where ob­served fish loss can be at­trib­uted to hu­man-caused cli­mate change, Chung added.

Tit­ten­sor pointed to lob­sters off Maine and North At­lantic right whales as ex­am­ples of crea­tures al­ready be­ing hurt by global warm­ing hit­ting the ocean.

Uni­ver­sity of Ge­or­gia marine bi­ol­o­gist Samantha Joye, who wasn’t part of the re­search, praised the study as metic­u­lous and said it is also “an ur­gent call for ac­tion.”

“Healthy oceans are re­quired for planetary sta­bil­ity,” Joye said in an email. “Ag­gres­sive global ac­tion to slow cli­mate change is a moral im­per­a­tive.”

AP file photo

as it moves to hide be­low aquatic plants off the coast of Bid­de­ford, Maine. A study pub­lished Tues­day finds a warmer world may lose a bil­lion tons of fish and other marine life by the end of the cen­tury. The in­ter­na­tional study used com­puter mod­els to project that for ev­ery de­gree Cel­sius the world warms, the to­tal weight of life in the oceans drops by 5 per­cent.

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