Switch­ing to or­ganic farm­ing could cut green­house gas emis­sions, study shows

The Guardian Australia - - Environment - Fiona Har­vey En­vi­ron­ment cor­re­spon­dent

Con­vert­ing land from con­ven­tional agri­cul­ture to or­ganic pro­duc­tion could re­duce green­house gas emis­sions, the run-off of ex­cess ni­tro­gen from fer­tilis­ers, and cut pes­ti­cide use. It would also, ac­cord­ing to a new re­port, be fea­si­ble to con­vert large amounts of cur­rently con­ven­tion­ally farmed land with­out cat­a­strophic harm to crop yields and with­out need­ing huge amounts of new land.

The study, pub­lished in the jour­nal Na­ture Com­mu­ni­ca­tions, found that by com­bin­ing or­ganic pro­duc­tion with an in­creas­ingly veg­e­tar­ian diet, ways of cut­ting food waste, and a re­turn to tra­di­tional meth­ods of fix­ing ni­tro­gen in the soil in­stead of us­ing fer­tiliser, the world’s pro­jected 2050 pop­u­la­tion of more than 9 bil­lion could be fed with­out vastly in­creas­ing the cur­rent amount of land un­der agri­cul­tural pro­duc­tion.

This is im­por­tant, as con­vert­ing other land such as forests, cer­rado or peat­lands to agri­cul­tural use would in­crease green­house gas emis­sions from the land. The au­thors found that an in­crease in or­ganic farm­ing would re­quire big changes in farm­ing sys­tems, such as grow­ing legumes to re­plen­ish ni­tro­gen in the soil.

How­ever, other sci­en­tists were cau­tious over en­dors­ing the re­port’s find­ings, point­ing out that the size of the world’s agri­cul­tural sys­tems and their vari­abil­ity, as well as as­sump­tions about fu­ture nu­tri­tional needs, made gen­er­al­i­sa­tions about con­vert­ing to or­ganic farm­ing dif­fi­cult to make.

Sir Colin Berry, emer­i­tus pro­fes­sor of pathol­ogy at Queen Mary, Univer­sity of Lon­don, said: “As for all mod­els, as­sump­tions have to be made and what weight you at­tach to which item can greatly change out­comes. The as­sump­tion that grass­land ar­eas will re­main con­stant is a large one. The wastage is­sue is im­por­tant but so­lu­tions, not ad­dressed here, to post-har­vest- pre­mar­ket losses will be dif­fi­cult with­out fungi­cides for grains. Some pop­u­la­tions could do with more pro­tein to grow and de­velop nor­mally, de­spite the mod­els here re­quir­ing less an­i­mal pro­tein.”

Les Fir­bank, pro­fes­sor of sus­tain­able agri­cul­ture at Leeds Univer­sity, said: “One of the ques­tion marks about or­ganic farm­ing is that it can’t feed the world. [This pa­per] con­cludes or­ganic farm­ing does re­quire more land than con­ven­tional meth­ods, but if we man­age the de­mand for food by re­duc­ing waste and re­duc­ing the amount of crops grown

as an­i­mal feed, or­ganic farm­ing can feed the world.”

He warned: “[These] mod­els can only be viewed as a guide: there are many as­sump­tions that may not turn out to be true and all these sce­nario ex­er­cises are re­stricted by limited knowl­edge [and] are fairly sim­plis­tic com­pared to real life, but re­al­is­tic enough to help for­mu­late pol­icy. The core mes­sage is valu­able and timely: we need to se­ri­ously con­sider how we man­age the global de­mand for food.”

Even with­out con­vert­ing to or­ganic pro­duc­tion, how­ever, the US, In­dia, China and Rus­sia – four of the world’s big­gest green­house gas emit­ters – could turn into some of the big­gest ab­sorbers of car­bon, through bet­ter man­age­ment of their agri­cul­tural land.

A sep­a­rate new study shows that these coun­tries have the great­est po­ten­tial for the se­ques­tra­tion of car­bon diox­ide through chang­ing the way soils are pro­tected, through bet­ter farm­ing meth­ods that can also help to pre­serve de­clin­ing soil fer­til­ity.

Sci­en­tists said the po­ten­tial of us­ing soil as a car­bon sink was equiv­a­lent to tak­ing be­tween 215m and 400m cars off the road, even if only small changes are made, of a kind which should be achiev­able on all farms. The study, pub­lished on Tues­day in the Na­ture jour­nal Sci­en­tific Re­ports, and con­ducted by ex­perts from the Chi­nese Academy of Science, the Na­ture Con­ser­vancy NGO, and the In­ter­na­tional Cen­tre for Trop­i­cal Agri­cul­ture, found that farm­ing crops dif­fer­ently could make a big con­tri­bu­tion to achiev­ing the goals of the Paris agree­ment on cli­mate change.

To­day’s in­ten­sive agri­cul­tural meth­ods, in­volv­ing fre­quent till­ing of soils and the ex­ces­sive use of chem­i­cal fer­tilis­ers, could be re­placed with the re­vival of older meth­ods such as the in­creased use of ma­nure, cover crop­ping, mulching and grow­ing trees next to crop­land. How­ever, the role of land man­age­ment in pre­vent­ing dan­ger­ous lev­els of cli­mate change has of­ten been over­looked at the talks, where dis­cus­sions over the burn­ing of fos­sil fu­els have dom­i­nated. This is partly be­cause of the ur­gency of switch­ing away from fos­sil fu­els, and partly be­cause land man­age­ment is a dif­fuse and di­verse prob­lem spread across the globe from small farm­ers to agri-in­dus­tri­al­ists, whereas fos­sil fuel sources tend to be larger and more mono­lithic, such as coal-fired power plants.

The re­sults will be pre­sented to del­e­gates at the UN COP23 cli­mate talks in Bonn on Wed­nes­day. Na­tions at the talks are dis­cussing ways to in­crease the com­mit­ments on emis­sions re­duc­tions made along­side the Paris agree­ment, and which sci­en­tists say are cur­rently in­ad­e­quate to hold the world to no more than 2C of warm­ing, the bind­ing tar­get un­der the land­mark 2015 ac­cord.

Em­ploy­ees work on a salad field on an or­ganic farm in Brodowin, Ger­many. Pho­to­graph: Axel Sch­midt/Getty Images

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