A new study out of Stanford University finds extreme temperatures are cutting wheat yields by 20 to as much as 50 percent, a finding worse than previously estimated. FSE center fellow David Lobell and his colleagues used nine years of satellite measurements of wheat growth in northern India's breadbasket, the Indo-Gangetic Plains, to analyze rates of wheat ageing after exposure to temperatures higher than 34 degrees Celsius. 

Extreme heat beyond the plant's tolerance zone damages photosynthetic cells. This causes wheat to age faster, reducing the length of the growing season and the amount and size of the wheat grains. The team's crop models found that a two degree increase in temperatures would reduce the growing season by nine days, yielding 20 percent less wheat.

As the world's second-biggest crop, lost wheat yields may become a major threat to global food security. Especially given the projection that global yields need to rise 50 percent by 2050 to feed a growing, more affluent population. The results imply that warming presents an even greater challenge to wheat than previous studies estimated, and that the effectiveness of adaptations will depend on how well they reduce crop sensitivity to very hot days, particularly in areas of the world such as India already experiencing warming conditions.

In Kenya, 11 million people suffer from malnourishment. Twenty percent of children younger than five are underweight, and nearly one in three are below normal height. In a typical day, the average Kenyan consumes barely half as many calories as the average American.

But Kenya – and other underfed countries throughout Sub-Saharan Africa – have more than enough land to grow the food needed for their hungry populations.

The juxtaposition of food deprivation and land abundance boils down to a failure of national agriculture policies, says Thom Jayne, professor of international development at Michigan State University. Governments haven’t helped small farmers acquire rights to uncultivated land or use the land they own more productively, he said.

Speaking earlier this month at a symposium organized by the Center on Food Security and the Environment, Jayne said lifting African farmers out of poverty will require a new development approach.

The focus, he said, should be on increasing smallholder output and putting idle land to work in the hands of the rural poor.

Much of Sub-Saharan Africa’s fertile land, Jayne explained, falls under the ownership of state governments or wealthy investors who leave large tracts of land unplanted.

Meanwhile, population density in many rural areas exceeds the estimated carrying capacity for rainfed agriculture – approximately 500 persons per square kilometer, according to the U.N. Food and Agriculture Organization. Above this density threshold, farm sizes become so small, farming becomes economically unsustainable.

“As farm size shrinks, it’s increasingly difficult to produce a surplus,” Jayne said. “As it’s difficult to produce a surplus, it becomes difficult to finance investments in fertilizer and other inputs that could help you intensify.”

Agricultural development policies, Jayne said, have exacerbated these problems. One Zambian fertilizer subsidy program, for example, delivered support payments to over 50 percent of farms greater than five hectares in size – but only reached 14 percent of farmers whose holdings measured one hectare or smaller.

“This was a poverty reduction program that was targeted to large farms,” Jayne said. “Where’re the allocations to R&D appropriate to one hectare farms, tsetse fly control, vet services, all the things that are going to make that one hectare farm more productive?”

He stressed that investments in small farms could reduce poverty.

“Fifty to seventy percent of the population in these countries is engaged in agriculture,” he said. “There aren’t very many levers to reduce poverty and get growth processes going except to focus on the activities that that fifty to seventy percent are primarily engaged in.”

Smallholder-based growth strategies delivered stunning results in Green Revolution-era India – while large-farm strategies in Latin American countries have largely failed to alleviate rural poverty, he said.

Symposium commentator Byerlee, a rural policy expert and former lead economist for the World Bank, agreed with Jayne. In particular, Byerlee expressed skepticism about the benefit of large land investments by foreign agricultural interests.

“The social impacts aren’t going to be very much,” he said of the large-scale mechanized farming operations favored by foreign investors.

“They don’t create many jobs,” he said. “That’s really what we should be focusing on in terms of poverty reduction – job creation.”

Byerlee also stressed the need to formalize Sub-Saharan Africa’s land tenure systems. Currently, he said, about eighty percent of Africa’s land is titled informally under “customary” rights.

“When you have this population pressure, and on top of that you have commercial pressures coming in from investors, this system is just not going to stand up,” he said. “If you had better functioning land markets, it could reduce the transaction costs for investors, allow smallholders to access land, and provide an exit strategy for people at the bottom end.”

Jayne suggested reforms and new policies should include mechanisms to help small farmers gain access to unused fertile land. He called for comprehensive audits of land resources in Sub-Saharan African nations, a tax on uncultivated arable acreage, and a transparent public auction to distribute idle state lands to small farmers.

Additionally, he said, governments can help by improving infrastructure in remote rural areas and clearing fertile land of pests – such as tsetse flies – that threaten crops and human health.

But whatever particular policies they choose to pursue, Jayne said, African governments cannot afford to ignore the problems associated with inequitable land distribution and low smallholder agricultural productivity and. Failure to implement broad-based, smallholder-focused growth strategies will result in “major missed opportunities to reduce poverty in Sub-Saharan Africa,” he said.

This was the seventh talk in FSE's Global Food Policy and Food Security Symposium Series.

Fourteen visionary, young trailblazers from around the world — including an astrobiologist, a Middle East peace worker and cultural educator, an Asian elephant specialist, a wastewater engineer, a filmmaker and a science entrepreneur — have been named to the 2011 class of National Geographic Emerging Explorers. Jennifer Burney, a Scripps postdoctoral researcher and FSE fellow helping to understand how changes in cooking habits could have complementary effects on climate change and public health, was named one of them.

The award provides financial support to the research efforts of scientists who are in their early careers. Burney is a University of California President’s Postdoctoral Fellow at Scripps Institution of Oceanography, UC San Diego and is an affiliate of Stanford University's Program on Food Security and the Environment. At Scripps, she is part of a team headed by Professor of Climate and Atmospheric Science Veerabhadran Ramanathan studying the effects of replacing homemade cookstoves in rural India with cleaner-burning alternatives in an effort called Project Surya.

“I love the puzzle of figuring out how to measure something be it with data or instrumentation and Surya by its nature is just a giant web of measurement problems. It’s a really great synergy,” said Burney, who received her doctorate in physics from Stanford University in 2007.

Among Burney’s objectives is to study the links between energy poverty and food and nutrition security and the environmental impacts of food production and consumption. In the case of Project Surya, this will mean helping Ramanathan assess what happens when emissions of soot and other black carbon are substantially reduced in a given area. Ramanathan expects that the experiment will show immediate reduction in the contribution of greenhouse agents from that area. On a large scale, the reduction of such pollution created by use of wood and dung as cooking fuel could have a major mitigative impact on climate change. It could also improve the respiratory health of local residents, who frequently must inhale the smoke from their stoves as they cook in poorly ventilated kitchens.

The Project Surya team is hoping to launch a phase later this year in which cookers are replaced with cleaner stoves in a 10-square-kilometer (four-square-mile) area in India. They will then measure emissions of black carbon via satellite and at ground level with help from local residents.

Burney will separately study the agricultural effects associated with temperature and precipitation changes that could be triggered by the cookstove switch.

“I am really delighted, but not surprised, that Jen got this well deserved honor,” said Ramanathan. “She brings lots of talent and experience to the Surya research. She is an asset.”

Burney said that the award will also support another project she is conducting in West Africa in which she is assessing the feasibility of using solar power to improve irrigation capabilities there.

The Emerging Explorers each receive a $10,000 award to assist with research and to aid further exploration. Burney and the other new Emerging Explorers are introduced in the June 2011 issue of National Geographic magazine, and comprehensive profiles can be found at http://www.nationalgeographic.com/emerging.

Policy brief: Climate trend and global crop production since 1980

Global warming is likely already taking a toll on world wheat and corn production, according to a new study led by Stanford University researchers. But the United States, Canada and northern Mexico have largely escaped the trend.

"It appears as if farmers in North America got a pass on the first round of global warming," said David Lobell, an assistant professor of environmental Earth system science and center fellow at the Program on Food Security and the Environment at Stanford University. "That was surprising, given how fast we see weather has been changing in agricultural areas around the world as a whole."

Lobell and his colleagues examined temperature and precipitation records since 1980 for major crop-growing countries in the places and times of year when crops are grown. They then used crop models to estimate what worldwide crop yields would have been had temperature and precipitation had typical fluctuations around 1980 levels.

The researchers found that global wheat production was 5.5 percent lower than it would have been had the climate remained stable, and global corn production was lower by almost 4 percent. Global rice and soybean production were not significantly affected.

The United States, which is the world's largest producer of soybeans and corn, accounting for roughly 40 percent of global production, experienced a very slight cooling trend and no significant production impacts.

Outside of North America, most major producing countries were found to have experienced some decline in wheat and corn (or maize) yields related to the rise in global temperature. "Yields in most countries are still going up, but not as fast as we estimate they would be without climate trends," Lobell said.

Lobell is the lead author of the paper, Climate Trends and Global Crop Production Since 1980, published May 5 online in Science Express.

Russia, India and France suffered the greatest drops in wheat production relative to what might have been with no global warming. The largest comparative losses in corn production were seen in China and Brazil.

Total worldwide relative losses of the two crops equal the annual production of corn in Mexico and wheat in France. Together, the four crops in the study constitute approximately 75 percent of the calories that humans worldwide consume, directly or indirectly through livestock, according to research cited in the study.

"Given the relatively small temperature trends in the U.S. Corn Belt, it shouldn't be surprising if complacency or even skepticism about global warming has set in, but this study suggests that would be misguided," Lobell said.

Since 1950, the average global temperature has increased at a rate of roughly 0.13 degrees Celsius per decade. But over the next two to three decades average global temperature is expected to rise approximately 50 percent faster than that, according to the report of the Intergovernmental Panel on Climate Change. With that rate of temperature change, it is unlikely that the crop-growing regions of the United States will continue to escape the rising temperatures, Lobell said.

"The climate science is still unclear about why summers in the Corn Belt haven't been warming. But most explanations suggest that warming in the future is just as likely there as elsewhere in the world," Lobell said.

"In other words, farmers in the Corn Belt seem to have been lucky so far."

This is the first study to come up with a global estimate for the past 30 years of what has been happening, Lobell said.

To develop their estimates, the researchers used publicly available global data sets from the United Nations Food and Agriculture Organization and from the University of Delaware, University of Wisconsin, and McGill University.

The researchers also estimated the economic effects of the changes in crop yield using models of commodity markets.

"We found that since 1980, the effects of climate change on crop yields have caused an increase of approximately 20 percent in global market prices," said Wolfram Schlenker, an economist at Columbia University and a coauthor of the paper in Science.

He said if the beneficial effects of higher carbon dioxide levels on crop growth are factored into the calculation, the increase drops down to 5 percent.

"Five percent sounds small until you realize that at current prices world production of these four crops are together worth nearly $1 trillion per year," Schlenker said. "So a price increase of 5 percent implies roughly $50 billion per year more spent on food."

Rising commodity prices have so far benefited American farmers, Lobell and Schlenker said, because they haven't suffered the relative declines in crop yield that the rest of the world has been experiencing.

"It will be interesting to see what happens over the next decade in North America," Lobell said. "But to me the key message is not necessarily the specifics of each country. I think the real take-home message is that climate change is not just about the future, but that it is affecting agriculture now. Accordingly, efforts to adapt agriculture such as by developing more heat- and drought-tolerant crops will have big payoffs, even today. "

Justin Costa-Roberts, an undergraduate student at Stanford, is also a coauthor of the Science paper. David Lobell is a researcher in Stanford's 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. Schlenker is an assistant professor at the School of International and Public Affairs and at the Department of Economics at Columbia.

The work was supported by a grant from the Rockefeller Foundation.