In a lecture to the Stanford community Tuesday night, Professor Sir Gordon Conway argued that sustainably intensifying agriculture, especially in Africa, is the only way to feed a growing global population without greatly expanding the amount of land used for farming. Sir Gordon is an agricultural ecologist and was an early pioneer of sustainable agriculture while working in Malaysia in the 1960s. He is now a professor of international development at Imperial College London and the director of Agriculture for Impact, a project funded by the Bill and Melinda Gates Foundation.

Sir Gordon's lecture, "Can Sustainable Intensification Feed the World?" was the second installment of the Food and Nutrition Policy Symposium Series sponsored by the Center on Food Security and the Environment.

Sir Gordon described three major challenges to ensuring future global food security: food prices are higher and more volatile, one billion people are malnourished (including 1 in 5 children), and rising demand means that 60 to 100 percent more food will be needed to feed the world by 2050. Solving the food security crisis will mean improving both the quantity and the nutrition of food, at stable and affordable prices, in the face of major challenges.

These challenges include factors on the demand side of the global food economy, such as population growth, changing diets, and the use of crops for biofuels. Supply side factors like high fertilizer prices, climate change, and scarcity of land and water put even more pressure on the food system. 

The solution, Sir Gordon said, is agricultural intensification, a set of practices that allow farmers to produce more food with existing land and water. Sustainability is a key component, so that intensification does not also raise greenhouse gas emissions, deplete soil quality, or damage the resilience of farming systems. Sustainable intensification will be especially important in Africa, said Sir Gordon, where population growth and dietary changes will be most dramatic, and where currently crop yields are far below most other areas of the world.

 Farmers, scientists and policymakers can take several approaches to sustainable intensification. An ecological approach includes practices that safeguard environmental resources and reduce farmers’ dependence on chemicals like herbicides and pesticides, such as through organic farming, integrated pest management, agroforestry or conservation agriculture. A genetic intensification approach includes developing better plant varieties, with traits that promote more sustainable agriculture by resisting pests and diseases, or that provide more nutrition. A third approach is socio-economic intensification of agriculture, through the development of farmers’ cooperatives, better links between farmers and markets, and improved access by farmers to insurance and credit.

The goal, Sir Gordon said, is to help farmers “build resilient livelihoods” that will withstand economic and environmental shocks in the coming decades. Good science is important, but strong political leadership, especially within Africa, will be just as crucial.

To predict how agriculture will be affected by future climate change, scientists often rely on a single crop model – a computer simulation of how a specific crop’s yield responds to temperature changes. By combining 30 such models into a single study, and comparing each model against data from existing experimental wheat fields around the world, a team of researchers including Stanford professor David Lobell have developed a more powerful and accurate way to predict future wheat yields.

In a new analysis published in Nature Climate Change, the team’s results support previous work suggesting that wheat yields around the world are sensitive to rising temperatures. Using the new method of analysis, the team estimates an average six percent future yield loss for every one degree Celsius rise in global mean temperature.

“Combining 30 models gives us a much greater ability to predict future impacts and understand past impacts,” said Lobell. “This is a clear step forward.”

Lobell is professor of environmental earth system science in the School of Earth Science at Stanford and the deputy director of the Center on Food Security and the Environment. He is a senior fellow at the Stanford Woods Institute for the Environment and at the Freeman Spogli Institute for International Studies.

The estimated six percent yield loss for every degree increase is equivalent to about a quarter of the current volume of wheat traded globally in 2013. Yields at some sites, notably those in Mexico, Brazil, India and Sudan, show simulated wheat yield losses of more than 20 percent - in Sudan’s case, more than 50 percent - under a scenario in which global mean temperature rises by two degrees Celsius.

With higher temperatures also comes an increase in the variability of wheat yields, both by location and between years. More fluctuation in wheat yields could mean greater global price volatility for the staple crop.

Approximately 70 percent of the wheat produced today is grown either on irrigated plots or in rainy regions. The research team accounted for this factor by focusing its simulations on multiple regional-specific varieties of wheat that are commonly grown under these conditions.

The new paper includes several suggestions for avoiding some of the predicted yield losses. For example, some varieties of wheat are more heat tolerant than others, and farmers in the places hardest hit by rising temperatures could switch varieties to capitalize on this heat resistance. The effects of rising temperatures could also be managed, in part, by adjusting sowing and harvesting dates, or changing the way fertilizers are applied to crops.

Contact: David Lobell, dlobell@stanford.edu