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Climate-induced food crisis seen by 2100

Jan. 10, 2009
Courtesy University of Washington
and World Science staff

Glob­al warm­ing will probably se­ri­ously ham­per crop yields in the world’s hot­ter zones by 2100, and could leave half of all peo­ple short on food un­less they adapt, a study has found.

Com­pounding mat­ters, the researchers said, the most at-risk areas, the tro­pics and sub­tro­pics, in­clude many of the poor­est and fast­est-grow­ing po­pu­la­tions.

“You’re talk­ing about hun­dreds of mil­lions of ad­di­tion­al peo­ple look­ing for food be­cause they won’t be able to find it where they find it now,” said Da­vid Bat­tisti, a Uni­ver­s­ity of Wash­ing­ton at­mos­pher­ic sci­ent­ist. He is lead au­thor of the study in the Jan. 9 edi­tion of the res­earch journal Sci­ence.

“The stresses on glob­al food pro­duc­tion from tem­per­a­ture alone are go­ing to be huge, and that does­n’t take in­to ac­count wa­ter sup­plies stressed by the high­er tem­per­a­tures.” 

To cope, peo­ple will have to “take dec­ades to de­vel­op new food crop va­ri­eties that can bet­ter with­stand a warm­er cli­mate,” said col­la­bo­ra­tor Ro­sa­mond Nay­lor, di­rec­tor of the Pro­gram on Food Se­cur­ity and the En­vi­ron­ment at Stan­ford Uni­ver­s­ity in Cal­i­for­nia.

The study com­bined di­rect ob­serva­t­ions with da­ta from 23 glob­al cli­mate mod­els that con­tri­but­ed to No­bel prize-winning re­search in 2007 by the In­ter­gov­ern­ment­al Pan­el on Cli­mate Change.

Bat­tisti and Nay­lor con­clud­ed there is more than a 90 per­cent chance that by 2100 the low­est grow­ing-season tem­per­a­tures in the trop­ics and subtrop­ics will be high­er than any tem­per­a­tures rec­orded there to date.

They used the da­ta to re-assess his­tor­ic in­stances of se­vere food in­se­cur­ity, and con­clud­ed such cases are likely to hap­pen more of­ten. Those in­clude se­vere episodes in France in 2003 and the Ukraine in 1972. In the case of the Ukraine, a near-rec­ord heat wave re­duced wheat yields and con­tri­but­ed to dis­rup­tions in the glob­al ce­real mar­ket that lasted two years.

Back then, “peo­ple could al­ways turn some­where else to find food,” Nay­lor said. “But in the fu­ture there’s not go­ing to be any place to turn un­less we re­think our food sup­plies.”

The se­ri­ous cli­mate prob­lems won’t be lim­it­ed to the trop­ics, the sci­en­tists con­clude. As an ex­am­ple, they cite rec­ord tem­per­a­tures that struck West­ern Eu­rope in June, July and Au­gust of 2003, kill­ing an es­ti­mat­ed 52,000 peo­ple. The summer-long heat wave in France and Italy cut wheat yields and fod­der pro­duc­tion by one-third. In France alone, tem­per­a­tures were nearly 6.5 de­grees Fahr­en­heit above the long-term mean, and the sci­en­tists say such tem­per­a­tures could be nor­mal for France by 2100.

In the trop­ics, the high­er tem­per­a­tures can be ex­pected to cut yields of the pri­ma­ry food crops, maize and rice, by 20 to 40 per­cent, the re­search­ers said. But ris­ing tem­per­a­tures al­so are likely to play hav­oc with soil mois­ture, cut­ting yields even fur­ther.

“We have to be re­think­ing ag­ri­cul­ture sys­tems as a whole, not only think­ing about new va­ri­eties but al­so rec­og­niz­ing that many peo­ple will just move out of ag­ri­cul­ture, and even move from the lands where they live now,” Nay­lor said.

Three bil­lion peo­ple now live in the trop­ics and subtrop­ics, and their num­ber is ex­pected to nearly dou­ble by the cen­tu­ry’s end. The ar­ea stretches from the south­ern Un­ited States to north­ern Ar­gen­ti­na and south­ern Bra­zil, from north­ern In­dia and south­ern Chi­na to south­ern Aus­tral­ia and all of Af­ri­ca. The sci­en­tists said that many who now live in these ar­e­as sub­sist on less than $2 a day and de­pend largely on ag­ri­cul­ture to get by. 


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Global warming will probably seriously alter crop yields in the tropics and subtropics by 2100, and could leave half the world’s population hungry unless people adapt, a study suggests. To compound matters, the population of this equatorial belt – from about 35 degrees north latitude to 35 degrees south latitude – is among the poorest on Earth and is growing faster than anywhere else. “The stresses on global food production from temperature alone are going to be huge, and that doesn’t take into account water supplies stressed by the higher temperatures,” said David Battisti, a University of Washington atmospheric sciences professor. He is lead author of the study in the Jan. 9 edition of Science. To cope, people will have to “take decades to develop new food crop varieties that can better withstand a warmer climate,” said collaborator Rosamond Naylor, director of the Program on Food Security and the Environment at Stanford University in California. The study combined direct observations with data from 23 global climate models that contributed to Nobel prize-winning research in 2007 by the Intergovernmental Panel on Climate Change. Battisti and Naylor concluded there is greater than a 90 percent probability that by 2100 the lowest growing-season temperatures in the tropics and subtropics will be higher than any temperatures recorded there to date. They used the data as a filter to view historic instances of severe food insecurity, and concluded such cases are likely to happen more often. Those include severe episodes in France in 2003 and the Ukraine in 1972. In the case of the Ukraine, a near-record heat wave reduced wheat yields and contributed to disruptions in the global cereal market that lasted two years. “I think what startled me the most is that when we looked at our historic examples there were ways to address the problem within a given year. People could always turn somewhere else to find food,” Naylor said. “But in the future there’s not going to be any place to turn unless we rethink our food supplies.” The serious climate problems won’t be limited to the tropics, the scientists conclude. As an example, they cite record temperatures that struck Western Europe in June, July and August of 2003, killing an estimated 52,000 people. The summer-long heat wave in France and Italy cut wheat yields and fodder production by one-third. In France alone, temperatures were nearly 6.5 degrees Fahrenheit above the long-term mean, and the scientists say such temperatures could be normal for France by 2100. In the tropics, the higher temperatures can be expected to cut yields of the primary food crops, maize and rice, by 20 to 40 percent, the researchers said. But rising temperatures also are likely to play havoc with soil moisture, cutting yields even further. “We have to be rethinking agriculture systems as a whole, not only thinking about new varieties but also recognizing that many people will just move out of agriculture, and even move from the lands where they live now,” Naylor said. Three billion people now live in the tropics and subtropics, and their number is expected to nearly double by the century’s end. The area stretches from the southern United States to northern Argentina and southern Brazil, from northern India and southern China to southern Australia and all of Africa. The scientists said that many who now live in these areas subsist on less than $2 a day and depend largely on agriculture for their livelihoods. “You are talking about hundreds of millions of additional people looking for food because they won’t be able to find it where they find it now,” Battisti said.