A team led by FSE fellow David Lobell has found a valuable, untapped resource in historical data from crop yield trials conducted across sub-Saharan Africa. Combined with weather records, they show that yield losses would occur across 65 percent of maize-growing areas from a temperature rise of a single degree Celsius, even with sufficient water. Data from yield tests in other regions of the world could help predict changes in crop yields from climate change.

A hidden trove of historical crop yield data from Africa shows that corn - long believed to tolerate hot temperatures - is a likely victim of global warming.

Stanford agricultural scientist David Lobell and researchers at the International Maize and Wheat Improvement Center (CIMMYT) report in the inaugural issue of Nature Climate Change next week that a clear negative effect of warming on maize - or corn - production was evident in experimental crop trial data conducted in Africa by the organization and its partners from 1999 to 2007.

Led by Lobell, the researchers combined data from 20,000 trials in sub-Saharan Africa with weather data recorded at stations scattered across the region. They found that a temperature rise of a single degree Celsius would cause yield losses for 65 percent of the present maize-growing region in Africa - provided the crops received the optimal amount of rainfall. Under drought conditions, the entire maize-growing region would suffer yield losses, with more than 75 percent of areas predicted to decline by at least 20 percent for 1 degree Celsius of warming.

"The pronounced effect of heat on maize was surprising because we assumed maize to be among the more heat-tolerant crops," said Marianne Banziger, co-author of the study and deputy director general for research at CIMMYT."

"Essentially, the longer a maize crop is exposed to temperatures above 30 C, or 86 F, the more the yield declines," she said. "The effect is even larger if drought and heat come together, which is expected to happen more frequently with climate change in Africa, Asia or Central America, and will pose an added challenge to meeting the increasing demand for staple crops on our planet."

Similar sources of information elsewhere in the developing world could improve crop forecasting for other vast regions where data has been lacking, according to Lobell, who is lead author of the paper describing the study.

"Projections of climate change impacts on food production have been hampered by not knowing exactly how crops fair when it gets hot," Lobell said. "This study helps to clear that issue up, at least for one important crop."

While the crop trials have been run for many years throughout Africa, to identify promising varieties for release to farmers, nobody had previously examined the weather at the trial sites and studied the effect of weather on the yields, said Lobell, who is an assistant professor of environmental earth system science and fellow at Stanford's Program on Food Security and the Environment.

"These trials were organized for completely different purposes than studying the effect of climate change on the crops," he said. "They had a much shorter term goal, which was to get the overall best-performing strains into the hands of farmers growing maize under a broad range of conditions."

The data recorded at the yield testing sites did not include weather information. Instead, the researchers used data gathered from weather stations all over sub-Saharan Africa. Although the stations were operated by different organizations, all data collection was organized by the World Meteorological Organization, so the methods used were consistent.

Lobell then took the available weather data and interpolated between recording stations to infer what the weather would have been like at the test sites. By merging the weather and crop data, the researchers could examine climate impacts.

"It was like sending two friends on a blind date - we weren't sure how it would go, but they really hit it off," Lobell said.

Previously, most research on climate change impacts on agriculture has had to rely on crop data from studies in the temperate regions of North America and Europe, which has been a problem.

"When you take a model that has been developed with data from one kind of environment, such as a temperate climate, and apply it to the rest of the world, there are lots of things that can go wrong" Lobell said, noting that much of the developing world lies in tropical or subtropical climates.

But he said many of the larger countries in the developing world, such as India, China and Brazil, which encompass a wide range of climates, are running yield testing programs that could be a source of comparable data. Private agribusiness companies are also increasingly doing crop testing in the tropics.

"We're hoping that with this clear demonstration of the value of this kind of data for assessing climate impacts on crops that others will either share or take a closer look themselves at their data for various crops," Lobell said.

"I think we may just be scratching the surface of what can be achieved by combining existing knowledge and data from the climate and agriculture communities. Hopefully this will help catalyze some more effort in this area."

Lobell is a Center Fellow at the Program on Food Security and the Environment, a joint program of Stanford's Woods Institute for the Environment and Freeman Spogli Institute for International Studies.

The work was funded by the Rockefeller Foundation

An October 13 New York Times headline article warned that an increasing volatile market for grains could lead to a repeat of the 2008 food price run-up. That price spike left over 1 billion people in a state of food insecurity-a threshold symbolic in its extreme order of magnitude and in the challenges it presents for combating global hunger in the future. In a paper released December 20 in Population and Development Review FSE director Rosamond L. Naylor and deputy director Walter P. Falcon provide insight into the causes and consequences of these volatile events.

"Price variability, particularly spikes, has enormous impacts on the rural poor who spend a majority of their income on food and have minimal savings," said Naylor. "Impacts at the local level have not been well measured, yet are key to improving food security globally." 

Expectations--often faulty--have played a key role in price volatility over the past decade. Uncertain exchange rates and macro policies added to price misperceptions, as did flurries of speculative activity in organized futures markets, particularly as a result of the growing biofuels market.

"These events highlight new linkages between agriculture-energy and agriculture-finance markets that affect the world food economy today," explained Falcon. "More importantly, volatile markets compound problems of low crop productivity, increase reliance on food imports, and aggravate other internal causes of instability--conflict, weak institutions, and inadequate infrastructure--that typically plague the world's poorest countries."

To see how the rural poor were impacted on a local scale, Naylor and Falcon looked at Ghana, Uganda, Malawi, Guatemala, and India. Price changes at the local level during the 2008 price spike were frequently half that of international prices, primarily as a consequence of domestic food and trade policies.

"The price bubble was undeniably grim for poor consumers, particularly for households living under $1/day or $2/day, but not as debilitating as many commentators suggested," said Falcon. "Unfortunately, most price stabilization efforts aimed at the poor, however well intended, ended up helping larger net producers much more than those at the margin."

Additionally, domestic self-sufficiency polices tended to have long-term negative impacts on the international market when governments lacked the resources to defend a targeted price or were ‘large actors' with significant shares of global production or consumption.

For example, in the spring of 2008, the Indian government placed a ban on rice exports--a major staple in the country--when it feared significant increases in grain prices and a spread of Ug99 (wheat rust). This ban affected food prices from Asia to Africa, created mini-panics within food importing countries, and added to global grain price variability. It underscored the growing food-security and crop interdependencies among nations arising from pathogens, prices, and policies.

The extreme heat wave that hit Russia and Eastern Europe in the summer of 2010, coupled with floods in Pakistan, declining estimates of maize stocks in the U.S., and uncertainties about global GDP growth have captured the attention of many analysts and policymakers. What will happen to prices in terms of spikes, trends, and variations during 2011-2013 and beyond is uncertain.

What is known, said Naylor, is that the causes and consequences of food-price variability deserve much more attention if we are going to alleviate global food insecurity in the future.

Global agricultural expansion cut a wide swath through tropical forests during the 1980s and 1990s. More than half a million square miles of new farmland - an area roughly the size of Alaska - was created in the developing world between 1980 and 2000, of which over 80 percent was carved out of tropical forests, according to Stanford researcher Holly Gibbs.

"This has huge implications for global warming, if we continue to expand our farmland into tropical forests at that rate," said Gibbs, a postdoctoral researcher in the Department of Environmental Earth System Science and in the Program on Food Security and the Environment, who led the study.

Gibbs and colleagues at several other universities analyzed Landsat satellite data and images from the United Nations to reach their conclusions. Theirs is the first study to map and quantify what types of land have been replaced by the immense area of new farmland developed across the tropical forest belt during the 1980s and 1990s.

While this huge increase was happening within the tropics, agricultural land in the non-tropical countries actually decreased in area.

The study was published this week in the online Early Edition of the Proceedings of the National Academy of Sciences.

The United Nations Food and Agriculture Organization estimates that to keep pace with increasing demand, global agricultural production will have to keep increasing, possibly even doubling by 2050. That would likely lead to millions of additional acres of tropical forest being felled over the next 40 years.

Direct impact on carbon released into atmosphere

"Every million acres of forest that is cut releases the same amount of carbon into the atmosphere as 40 million cars do in a year," Gibbs said.

Most of the carbon released comes from burning the forests, but even if the trees are simply cast aside, the bulk of the carbon from the plants makes its way into the atmosphere during decomposition, she said.

Gibbs and her colleagues found that about 55 percent of the tropical forests that had been cut between 1980 and 2000 were intact forests and another 28 percent were forests that had experienced some degradation, such as some small-scale farming, logging or gathering of wood and brush for cooking or heating fuel.

"The tropical forests store more than 340 billion tons of carbon, which is 40 times the total current worldwide annual fossil fuel emissions," Gibbs said. "If we continue cutting down these forests, there is a huge potential to further contribute to climate change."

The increasing demand for agricultural production stems in part from the ever-growing number of people on the planet, who all want to eat. Additionally, members of the growing middle class in emerging economies such as China and India are showing interest in eating more meat, which further intensifies demand. And incentives to grow crops for biofuel production have increased.

But Gibbs and her colleagues also observed some encouraging signs. The patterns of change in the locations they analyzed made it clear that during the 1990s, less of the deforestation was done by small family farms than was the case in the 1980s and more was done by large, corporate-run farms. Big agribusiness tends to be more responsive to global economic signals as well as pressure campaigns from advocacy organizations and consumer groups than individual small farmers.

In Brazil, where a pattern had developed of expanding soy production by direct forest clearing and by pushing cattle ranching off pastureland and into forested areas, a campaign by Greenpeace and others resulted in agreements by key companies to rein in their expansion. Instead, they worked to increase production on land already in agricultural use.

'Seeing positive changes'

"These farmers effectively increased the yield of soy on existing lands and they have also increased the head of cattle per acre by a factor of five or six," Gibbs said. "It is exciting that we are starting to see how responsive industry can be to consumer demands. We really are seeing positive changes in this area."

Along with wiser use of land already cleared, Gibbs said, improvements in technology and advances in yield intensification also could slow the expansion of farming into the forests.

Other studies that analyzed land use changes between 2000 and 2007 have shown that the pace of cutting down the tropical forests has begun to slow in some regions.

But as long as the human population on the planet continues to grow, the pressure to put food on the table, feed in the barnyard and fuel in the gas tank will continue to grow, too.

"It is critical that we focus our efforts on reducing rates of deforestation while at the same time restoring degraded lands and improving land management across the tropics," Gibbs said. "The good news is that pressure from consumer groups and nongovernmental organizations combined with international climate agreements could provide a real opportunity to shift the tide in favor of forest conservation rather than farmland expansion."

In addition to her position at the Department of Environmental Earth System Science and the Program on Food Security and the Environment, Gibbs is affiliated with Stanford's Woods Institute for the Environment. Jon Foley, a professor of ecology, evolution and behavior, and director of the Institute on the Environment at the University of Minnesota, was Gibbs' PhD adviser when the research was begun. He is a coauthor of the paper.

Initial funding for the project was provided by NASA. Gibbs is currently funded by a David H. Smith Conservation Research Fellowship.

 

Starting winter 2011, FSE will bring the world's leading policy experts in the fields of food and agricultural development to Stanford University to participate in an integrated seminar series on pro-poor growth and food security policy. The series, funded by a grant from the Bill & Melinda Gates Foundation, will consist of twelve lectures delivered on the Stanford campus over the course of two years.

"Providing food security for a world that will be warmer, more populous, and continually developing requires the implementation of sound policies that enhance agricultural production, incomes, and resource stewardship," said FSE director Rosamond L. Naylor.

"New ideas and exchanges are needed to meet this challenge and this seminar series intends to facilitate that process."

Participants will address the major themes of hunger and rural poverty, agricultural productivity, resource and climate constraints on agriculture, and food and agriculture policy. The series will draw heavily from economics, and will embrace polices related to demand, supply, price formation, marketing, trade and development.

"We focus this series on policy because it has proven to be extremely difficult to develop successful projects for hunger and poverty alleviation without first ensuring that sound policies are in play," noted Walter P. Falcon, FSE deputy director and project director. "Even the best-designed programs and projects at the local scale often fail due to counter-productive national policies."

The specific challenges will be to supply sufficient food at reasonable prices, to provide economic access to that food by all segments of society, and to do so without destroying the environment in the process, said Naylor.

In addition to lecturing, participants will write a significant paper that brings together new, relevant thinking about a particular topic area. At the end of the series, a volume of edited papers on international food security and food policy issues will be published. The volume will be designed for M.A. programs and mid-career professionals-individuals who later in their careers will have policy responsibilities. All the materials, including the videotaped lectures, will be freely available on the FSE website.

"We see an important opportunity to complement other efforts that have been funded by the Gates Foundation," said Naylor. "For example, the lecture series and educational volume are expected to contribute to the curriculum of the new Collaborative Master of Science in Agricultural and Applied Economics (CMAAE) program of the African Economic Research Consortium, partially funded by the foundation."

The lecture series will also target audiences in South Asia, and in particular India where there are more malnourished people than in all of sub-Saharan Africa.

The grant also provides funding to produce a specialized educational unit on food policy and food security for high school students. FSE will work closely with Stanford Program on International and Cross-Cultural Education (SPICE) to complete this project.

With the renewed interest in food, agriculture, and food security, it is important that the next generation have access to thoughtful commentary about global food issues, said Falcon.

This grant is part of the foundation's Agricultural Development initiative, which is working with a wide range of partners to provide millions of small farmers in the developing world with tools and opportunities to boost their yields, increase their incomes, and build better lives for themselves and their families. The Foundation is working to strengthen the entire agricultural value chain-from seeds and soil to farm management and market access-so that progress against hunger and poverty is sustainable over the long term.

The Woods Institute for the Environment has awarded four new Environmental Venture Project grants for interdisciplinary projects promoting global sustainability. FSI faculty Jeremy Goldhaber-Fiebert, PI, Walter P. Falcon, Paul H. Wise, and David Lobell, won an award for a project on nutrition-related health policies in India, which examines the impact of climate change on agricultural production and food availability.