How cli­mate afects the nutri­tion of rice

The East African - - OUTLOOK - By CHRIS MOONEY The Wash­ing­ton Post

HU­MAN-CAUSED green­house gas emis­sions threaten to make rice less nu­tri­tious, sci­en­tists said in a study re­leased mid-may, rais­ing a wor­ry­ing pos­si­bil­ity about the sta­ple food item of bil­lions of peo­ple.

Rice, the sci­en­tists found, con­tains lower lev­els of key vi­ta­mins when grown amid high con­cen­tra­tions of car­bon diox­ide, the most com­mon of the green­house gases driv­ing cli­mate change.

“If we do noth­ing, there are po­ten­tially pro­found neg­a­tive im­pacts on hu­man health,” said Kristie Ebi, a pub­lic health re­searcher at the Uni­ver­sity of Wash­ing­ton in Seat­tle and one of the au­thors of the study, which also in­volved re­searchers at in­sti­tu­tions in China, Ja­pan, Aus­tralia and the US Agri­cul­ture Depart­ment.

The study, con­ducted in Ja­pan and China, ex­am­ined 18 rice va­ri­eties in which the plants were sub­jected to at­mo­spheric car­bon diox­ide con­cen­tra­tions of 568 to 590 parts per mil­lion.

Cur­rent con­cen­tra­tions are about 410 parts per mil­lion, but they are grow­ing at about 2 parts per mil­lion ev­ery year — and could reach the study’s lev­els later this cen­tury.

Rice ac­counts for “ap­prox­i­mately 25 per cent of all global calo­ries,” ac­cord­ing to the study, which was pub­lished in the jour­nal Science Ad­vances. It was led by Chunwu Zhu of the Chi­nese Academy of Sciences.

The study found that at the high con­cen­tra­tions, the crop’s con­tent of the vi­ta­mins B1, B2, B5 and B9 all de­clined, by as much as 30 per cent for B9 (fo­late). The re­search also con­firmed pre­vi­ously dis­cov­ered de­clines in pro­tein, iron and zinc.

“There have been stud­ies over the past hun­dred years on the im­por­tance of these B vi­ta­mins,” Ebi said.

“One that de­clines with higher CO2 con­cen­tra­tions is fo­late, whose de­fi­ciency in preg­nant women can re­sult in chil­dren with var­i­ous birth anom­alies. So they are crit­i­cally important, for our health.”

The study re­search also sug­gest­ing that an­other ma­jor global sta­ple crop, wheat, could see lower yields as the planet warms.

The con­se­quences for wheat are tied to ris­ing tem­per­a­tures, but with rice, the im­me­di­ate is­sue ap­pears to be the grow­ing con­cen­tra­tions of car­bon diox­ide in the at­mos­phere.

Plants pull car­bon from the air and grow, and they will pull more of it as con­cen­tra­tions rise. The prob­lem is that other as­pects of their me­tab­o­lism may not keep pace, mean­ing that they would draw in less nu­tri­ents from soils as they grow, and pro­por­tion­ately more car­bon.

It is the change in this makeup of the plant it­self that could, in turn, trans­late into changes in its nu­tri­tional con­tent for those who con­sume it.

“CO2 is plant food in the sense that it makes plants grow more,” said Lewis Ziska, an­other study au­thor with the Depart­ment of Agri­cul­ture.

“But of­ten when plants grow more, it does not nec­es­sar­ily mean you get the same qual­ity of plant.”

The study also fits an in­creas­ingly com­mon theme in cli­mate find­ings, that the poor and dis­ad­van­taged glob­ally would be hit hard­est by these changes, and would be least able to ad­just or di­ver­sify their di­ets in or­der to ob­tain nu­tri­ents in other ways.

Pic­ture: AFP

Har­vest­ing rice af­ter dev­as­tat­ing floods and land­slides sub­merged pad­dies across Viet­nam last year.

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