Scientists are making progress in helping millions of wheat farmers adapt to hotter conditions, but the gains have been uneven, reports a new study led by Stanford University. New approaches to breeding are needed to withstand increasingly common heat waves and keep pace with growing global food demand.

Wheat is the most widely grown crop in the world; unfortunately it is also one of the most sensitive to future global warming. Scientists around the world strive to develop new wheat varieties each year that incorporate improved features, much like car companies release new models each year. Different strategies are commonly used; some target fully irrigated conditions that favor very high yields, while others focus on dry and hot conditions where yield maintenance under stress is a priority.

The team, which includes scientists from Stanford and the International Maize and Wheat Improvement Center (known as CIMMYT), evaluated 25 years of data from historical trials around the globe and analyzed the outcome of different past breeding approaches to help prioritize future strategies. The fully irrigated nursery, known as the elite spring wheat yield trials, produces varieties that are released for the majority of wheat farmers in countries like India and Egypt each year. While cultivars selected under stressed conditions showed significant yield progress at higher temperatures, the elite trials did not.

“There has been very impressive progress in improving yields for the elite varieties at the cooler temperatures that wheat prefers,” explains lead author Sharon Gourdji, a post-doctoral scholar in Stanford’s department of Environmental Earth System Science and Center on Food Security and the Environment (FSE).

“However, to date, our analysis shows a lack of yield gains for these varieties in hot environments over the past 25 years. Along with the gains in cool conditions, this means that the yield difference between cool and hot conditions is getting larger.”

A CIMMYT researcher plants wheat seed in pots in the center's greenhouse facilities. Photo credit: X. Fonseca/CIMMYT

"I think we have learned that the current main approach to breeding won't quite cut it in terms of adapting wheat to climate change,” said co-author David Lobell, assistant professor in Environmental Earth System Science and FSE center fellow. “That is useful information as breeding centers try to raise their game to contend with long-term warming."

Lobell notes that there are good reasons why improved heat tolerance for the elite varieties has not happened naturally.

“Breeding is tough since scientists are aiming for so many traits at once – for example, disease resistance, high yields, and good quality for bread making. Adding heat tolerance is like telling a scout looking for a superstar athlete, ‘by the way, make sure he’s a straight A student’,” said Lobell.

One important lesson from the study is that sifting through historical data can help identify what works and what does not.

“It can often be a hard sell to have breeders take the time to send their data back once they have selected their varieties and moved on,” explains CIMMYT wheat physiologist and co-author Matthew Reynolds. “This study clearly demonstrates the advantage of having these data to assess progress. It shows the genetic potential of wheat to adapt to warmer-than-usual conditions, and reinforces the value of screening under stress as a strategy for adaptation to climate change.”

The progress in the nursery targeted towards stress conditions shows that it is possible to make sizable gains in improving heat tolerance. But whether this can be combined with continued high performance under cooler conditions remains to be seen.

“It is critically important for farmers that they not only survive the bad or hot years, but that they can take full advantage of the favorable years” says Gourdji. “What is needed is a breeding strategy that can successfully achieve both.”

This work was supported by a grant from the Rockefeller Foundation. Additional co-authors of the study include CIMMYT’s Ky Mathews and Jose Crossa.

FSE affiliated faculty member Pamela Matson was the keynote speaker at the Senator George J. Mitchell Center at the University of Maine. Her talk focuses on what is needed to transition to a sustainable world. She frames her lecture around FSE's agricultural sustainability research in the Yaqui Valley, Mexico.

Food security expert David Lobell talks with Stanford's Generation Anthropocene about the wide range of problems our changing climate will have on agriculture and the prospects for creating a sustainable food system in the future.

Wheat is a staple crop throughout much of India, but in many areas it is commonly sown past the optimum yield window. A study led by FSE associate director David Lobell uses satellite measurements to estimate a decade’s worth of sow dates in wheat-growing areas of India.

The study finds, among other developments, that wheat was sown one week earlier by 2010 than it was at the beginning of the decade, a change that explains 5% in country-wide yield gains. It also predicts that yield benefits from sow date shifts will likely diminish in the next decade.

"There's an important, one time boost farmers have gotten recently from moving into the optimum sowing window, but the data suggest this effect will run out of steam in the coming years," says Lobell.

Without coordinated global action on climate change, it will be increasingly hard to reduce poverty in the world's poorest countries, said UN Development Program Administrator Helen Clark. Clark's visit to campus comes a few weeks before global climate negotiations are set to begin in Doha, Qatar. 

She highlighted ways in which climate change will, and is already, impacting food security in the world's most vulnerable regions: 

Outside of China, the world now has more food insecure and nutrient deficient people than it had a decade ago, and the prevalence of obesity-related diabetes, high blood pressure and cardio-vascular diseases is increasing at very rapid rates. Expanded food production has done little to address the fact that between one-third and one-half of all deaths in children under five in developing countries are still related to malnutrition.

“With only three years away from the Millennium Development Goals deadline, this is a terrible track record,” said food and nutrition policy expert Per Pinstrup-Andersen at FSE's Global Food Policy and Food Security Symposium Series last week.  

Pinstrup-Andersen, the only economist to win the World Food Prize (the ultimate award in the food security field), has dedicated his career to understanding the linkages between food, nutrition, and agriculture. What is driving persistent food insecurity and malnutrition in a food abundant world?

Poor food supply management is part of the problem. According to the United Nations Food and Agricultural Organization (FAO), 20-30% of food produced globally is lost every year. That’s enough to feed an additional 3-3.5 billion people.

Jatropha in Africa. Photo credit: Ton Rulkens/flickr.

Biofuels production, such as jatropha in Africa, now competes with food for land, and climate change is already negatively impacting crop yields in regions straddling the equator—with major implications for food supply.

For low-income consumers in both the U.S. and developing countries increasing and more volatile food prices, such as those seen in 2007, are also driving food insecurity. Poor consumers respond by purchasing cheaper, less nutrient food, and less of it.

Nutritional value chain

Consensus is developing—at least rhetorically—among national policymakers and international organizations that investments in agricultural development must be accelerated. Members of the G8 and G20 have committed $20 billion in international economic support for such investments and some developing countries such as Ethiopia and Ghana are planning large new investments.

While most of these recent initiatives focus on expanded food supplies, there is an increasing understanding that merely making more food available will not assure better food security, nutrition, and health at the household and individual levels.

“It matters for health and nutrition how increasing food supplies are brought about and of what it consists,” said Pinstrup-Andersen. “We need to turn the food supply chain into a nutritional value chain.”

Diet diversity is incredibly important for good nutrition. Agricultural researchers and food production companies need to look at a number of different commodities, not just the major food staples, said Pinstrup-Andersen.

“The Green Revolution successfully increased the production of corn, rice, and wheat, increasing incomes for farmers, and lowering prices for consumers, but now it is time to invest in fruits, vegetables and biofortification to deal with micronutrient deficiency,” said Pintrup-Andersen.

Biofortification, the breeding of crops to increase their nutritional value, offers tremendous opportunity for dealing with malnutrition in the developing world, but is not widely available.

This is particularly important for areas in sub-Saharan Africa where between one and three and one and four people are short in calories, protein, and micronutrients. Obesity is actually going up in these countries with the introduction of cheap, processed, energy-dense foods (those high in sugar and fat) contributing to the diabetes epidemic.

Pathways to better health

Women hauling water to their gardens in Benin.

The path to better health and nutrition must look beyond the availability of food at affordable prices, clean water, and good sanitation, and consider behavioral factors such as time constraints for women in low-income households.

“Field studies have shown time and time again that one of the main factors preventing women from providing themselves and their families with good nutrition is time,” explained Pinstrup-Andersen.

He told the story of a woman in Bolivia too burdened with farm and household responsibilities to take the time to breastfeed her six-month old daughter. Enhancing productivity in activities traditionally undertaken by women could be a key intervention to improving good health and nutrition at the household level.

Access is another issue. A household may be considered food secure, in that sufficient food may be available, but food may not be equally allocated in the household.

“If we focus on the most limiting constraint we can be successful,” said Pinstrup-Anderen. “But we must tailor our response to each case.”

For sub-Saharan Africa, this includes investments in rural infrastructure, roads, irrigation systems, micronutrient fertilizer, climate adaptation strategies, and other barriers holding back small farmers.

Fortunately, there has been a renewed attention to the importance of guiding food system activities towards improved health and nutrition. The Global Agriculture and Food Security Program (GAFSP), which facilitates the distribution of some of the G8 and G20 $20 billion commitments, prescribes that country proposals for funding of agricultural development projects must show a clear pathway from the proposed agricultural change to human nutrition.

“But it’s not going to be easy to implement good policies,” warned Pinstrup-Andersen. “There are few incentives in government for multidisciplinary problem solving. The economy is set up around silos and people are loyal to their silos. Agricultural and health sectors are largely disconnected in their priorities, policy, and analysis."

Incentives must change to encourage working across ministries and disciplines to identify the most important health and nutrition-related drivers of food systems, impact pathways, and policy and program interventions to find win-wins for positive health and nutrition.