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

In an effort to foster a more open, transparent and accessible scientific dialogue, we've started a new effort aimed at inspiring pioneering use of technology, new media and computational thinking in the communication of science to diverse audiences. Initially, we'll focus on communicating the science on climate change.

We're kicking off this effort by naming 21 Google Science Communications Fellows. These fellows were elected from a pool of applicants of early to mid-career Ph.D. scientists nominated by leaders in climate change research and science-based institutions across the U.S. It was hard to choose just 21 fellows from such an impressive pool of scientists; ultimately, we chose scientists who had the strongest potential to become excellent communicators. That meant previous training in science communication; research in topics related to understanding or managing climate change; and experience experimenting with innovative approaches or technology tools for science communication.

This year's fellows are an impressive bunch:

• Brendan Bohannan, Associate Professor of Environmental Studies and Biology, University of Oregon
• Edward Brook, Professor, Department of Geosciences, Oregon State University
• Julia Cole, Professor, Department of Geosciences, University of Arizona
• Eugene Cordero, Associate Professor, Meteorology and Climate Science, San Jose University
• Frank Davis, Professor, Landscape Ecology & Conservation Planning, University of California-Santa Barbara
• Andrew Dessler, Professor, Atmospheric Sciences, Texas A&M University
• Noah Diffenbaugh, Assistant Professor, Environmental Earth System Science, Stanford University
• Simon Donner, Assistant Professor, University of British Columbia
• Nicole Heller, Research Scientist, Climate Central
• Brian Helmuth, Professor, Biological Sciences, University South Carolina
• Paul Higgins, Associate Director, Policy Program, American Meteorological Society
• Jonathan Koomey, Consulting Professor, Civil and Environmental Engineering, Stanford University
• David Lea, Professor, Earth Science, University of California-Santa Barbara
• Kelly Levin, Senior Research Associate, World Resources Institute
• David Lobell, Assistant Professor, Environmental Earth System Science, Stanford University
• Edwin Maurer, Associate Professor, Civil Engineering, Santa Clara University
• Susanne Moser, Research Associate, Institute of Marine Sciences, University of California-Santa Cruz
• Matthew Nisbet, Associate Professor, School of Communication, American University
• Rebecca Shaw, Director of Conservation, The Nature Conservancy, CA Chapter
• Whendee Silver, Professor, Ecosystem Ecology and Biogeochemistry, University of California-Berkeley
• Alan Townsend, Professor, Ecology and Evolutionary Biology, University of Colorado

At our Mountain View, Calif. headquarters in June, the fellows will participate in a workshop, which will integrate hands-on training and facilitated brainstorming on topics of technology and science communication. Following the workshop, fellows will be given the opportunity to apply for grants to put their ideas into practice. Those with the most impactful projects will be given the opportunity to join a Lindblad Expeditions & National Geographic trip to the Arctic, the Galapagos or Antarctica as a science communicator.

Congratulations to all of the fellows! And we'll keep you posted on more ideas and tools emerging for science communication.

A team of researchers from Stanford University, the Carnegie Institution for Science, and Arizona State University has found that converting large swaths of land to bioenergy crops could have a wide range of effects on regional climate.

In an effort to help wean itself off fossil fuels, the U.S. has mandated significant increases in renewable fuels, with more than one-third of the domestic corn harvest to be used for conversion to ethanol by 2018. But concerns about effects of corn ethanol on food prices and deforestation had led to research suggesting that ethanol be derived from perennial crops, like the giant grasses Miscanthus and switchgrass. Nearly all of this research, though, has focused on the effects of ethanol on carbon dioxide emissions, which drive global warming.

"Almost all of the work performed to date has focused on the carbon effects," said Matei Georgescu, a climate modeler working in ASU's Center for Environmental Fluid Dynamics. "We've tried to expand our perspective to look at a more complete picture.  What we've shown is that it's not all about greenhouse gases, and that modifying the landscape can be just as important."

Georgescu and his colleagues report their findings in the current issue (Feb. 28, 2011) of the Proceedings of the National Academy of Sciences (see Direct Climate Effects of Perennial Bioenergy Crops in the United States). Co-authors are David Lobell of Stanford University's Program on Food Security and the Environment and Christopher B. Field of the Carnegie Institution for Science, also located in Stanford, California.

In their study, the researchers simulated an entire growing season with a state-of-the-art regional climate model. They ran two sets of experiments - one with an annual crop representation over the central U.S. and one with an extended growing season to represent perennial grasses. In the model, the perennial plants pumped more water from the soil to the atmosphere, leading to large local cooling. 

"We've shown that planting perennial bioenergy crops can lower surface temperatures by about a degree Celsius locally, averaged over the entire growing season. That's a pretty big effect, enough to dominate any effects of carbon savings on the regional climate." said Lobell.

The primary physical process at work is based on greater evapotranspiration (combination of evaporated water from the soil surface and plant canopy and transpired water from within the soil) for perennial crops compared to annual crops. 

"More study is needed to understand the long-term implication for regional water balance." Georgescu said. "This study focused on temperature, but the more general point is that simply assessing the impacts on carbon and greenhouse gases overlooks important features that we cannot ignore if we want a bioenergy path that is sustainable over the long haul."

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.

David Lobell will be giving two talks this week at the AGU fall meeting:

Towards accurate models of global crop-climate interactions

This talk will provide a brief overview of the major links between climate and crops that are most in need of representation in global models. The talk will then focus on one of the key links - the effect of climate variation on crop productivity across a range of cropping systems and regions. I will present some recent work to use historical datasets to build statistical models at the scale of individual countries. The effects of different datasets and modeling assumption will be explored, to identify areas where statistical models provide robust representation of crop responses to climate. A sample application of these models - estimating the net regional and global impacts of recent trends in climate - will be presented.

Assessing the future of crop yield variability in the United States with downscaled climate projections

One aspect of climate change of particular concern to farmers and food markets is the potential for increased year-to-year variability in crop yields. Recent episodes of food price increases following the Australian drought or Russian heat wave have heightened this concern. Downscaled climate projections that properly capture the magnitude of daily and interannual variability of weather can be useful for projecting future yield variability. Here we examine the potential magnitude and cause of changes in variability of corn yields in the United States up to 2050. Using downscaled climate projections from multiple models, we estimate a distribution of changes in mean and variability of growing season average temperature and precipitation. These projections are then fed into a model of maize yield that explicitly factors in the effect of extremely warm days. Changes in yield variability can result from a shift in mean temperatures coupled with a nonlinear crop response, a shift in climate variability, or a combination of the two. The results are decomposed into these different causes, with implications for future research to reduce uncertainties in projections of future yield variability.

In this paper, FSE visiting fellow Luiz Martinelli, along with FSE director Rosamond L. Naylor, Peter Vitousek, and Paulo Moutinho, contrasts the country's agricultural system with its oppressive record of income and land inequalities and environmental degradation. The authors discuss ways to reconcile economic, social, and environmental goals. Brazil faces this challenge and opportunity with other tropical developing countries--and with success, it could become a role model to other nations in Latin America, Asia, and Africa.