Here is the power point presentation in French (Séminaire Œuvre Durable)
According to Stanford research U.S. corn yields are growing more sensitive to heat and drought. Farmers are faced with difficult tradeoffs in adapting to a changing climate in which unfavorable weather will become more common.
The study, which appears in the journal Science, was led by Stanford’s David Lobell, associate professor of environmental Earth system science and associate director of the Center on Food Security and the Environment. “The Corn Belt is phenomenally productive,” Lobell said, referring to the region of Midwestern states where much of the country’s corn is grown. “But in the past two decades we saw very small yield gains in non-irrigated corn under the hottest conditions. This suggests farmers may be pushing the limits of what’s possible under these conditions.”
He predicted that at current levels of temperature sensitivity, crops could lose 15 percent of their yield within 50 years, or as much as 30 percent if crops continue the trend of becoming more sensitive over time.
As Lobell explained, the quest to maximize crop yields has been a driving force behind agricultural research as the world’s population grows and climate change puts pressure on global food production. One big challenge for climate science is whether crops can adapt to climate change by becoming less sensitive to hotter and drier weather.
“The data clearly indicate that drought stress for corn and soy comes partly from low rain, but even more so from hot and dry air. Plants have to trade water to get carbon from the air to grow, and the terms of that trade become much less favorable when it’s hot,” said Lobell, also the lead author for a chapter in the U.N. Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report, which details a consensus view on the current state and fate of the world’s climate.
Rain, temperature, humidity
The United States produces 40 percent of the world’s corn, mostly in Iowa, Illinois, and Indiana. As more than 80 percent of U.S. agricultural land relies on natural rainfall rather than irrigation, corn farmers in these regions depend on precipitation, air temperature and humidity for optimal plant growth.
According to the research, over the last few decades, corn in the United States has been modified with new traits, like more effective roots that better access water and built-in pest resistance to protect against soil insects. These traits allow farmers to plant seeds closer together in a field, and have helped farmers steadily raise yields in typical years.
But in drought conditions, densely planted corn can suffer higher stress and produce lower yields. In contrast, soybeans have not been planted more densely in recent decades and show no signs of increased sensitivity to drought, the report noted.
Drought conditions are expected to become even more challenging as temperatures continue to rise throughout the 21st century, the researchers said.
Lobell said, “Recent yield progress is overall a good news story. But because farm yields are improving fastest in favorable weather, the stakes for having such weather are rising. In other words, the negative impacts of hot and dry weather are rising at the same time that climate change is expected to bring more such weather.”
Lobell’s team examined an unprecedented amount of detailed field data from more than 1 million USDA crop insurance records between 1995 and 2012.
“The idea was pretty simple,” he said. “We determined which conditions really matter for corn and soy yields, and then tracked how farmers were doing at different levels of these conditions over time. But to do that well, you really need a lot of data, and this dataset was a beauty.”
Lobell said he hopes that the research can help inform researchers and policymakers so they can make better decisions.
“I think it’s exciting that data like this now exist to see what’s actually happening in fields. By taking advantage of this data, we can learn a lot fairly quickly,” he said. “Of course, our hope is to improve the situation. But these results challenge the idea that U.S. agriculture will just easily adapt to climate changes because we invest a lot and are really high-tech.”
Lobell and colleagues are also looking at ways crops may perform better under increasingly hot conditions. “But I wouldn’t expect any miracles,” he said. “It will take targeted efforts, and even then gains could be modest. There’s only so much a plant can do when it is hot and dry.”
Laura Seaman is the communications and external relations manager for Stanford’s Center on Food Security and the Environment, a joint program of Stanford’s Freeman Spogli Institute for International Studies and the Stanford Woods Institute for the Environment.
WRI’s Aqueduct project recently evaluated, mapped, and scored water risks like these in 100 river basins, ranked by area and population, and 181 nations—the first such country-level water assessment of its kind. 37 countries face “extremely high” levels of baseline water stress (see list at bottom). This means that more than 80 percent of the water available to agricultural, domestic, and industrial users is withdrawn annually—leaving businesses, farms, and communities vulnerable to scarcity.
An adaptation plan to deal with the detrimental effects of climate change can be seen as a planning tool to be used to examine the issue of climate change in context and in all fields of activities of a municipal government, to identify and prioritize the key risks, and to adopt a vision as well as to provide steps for implementing short, medium and long-term adaptation measures to changing climatic conditions.
The Caribbean Climate Online Risk and Adaptation TooL (CCORAL), unveiled last month (12 July) in Saint Lucía, allows users to identify whether their activity is likely to be influenced by climate change and how to deal with this.
It helps project managers to understand climate influence on decisions, and to choose and apply risk management processes.
“The site is not set up to tell a manager what decision they should make, but rather to help them understand the factors involved and to explore and weigh options.”
Overcoming the threats to agriculture and food security in a changing climate requires a strong scientific evidence base to both help smallholder farmers choose resilient strategies and to guide development policy and investments.
Building on a Bioversity and CCAFS systematic review of the role of diversification in agricultural systems, the Platform for Agrobiodiversity Research is now hosting the ReFARM (the Resilience Framework for Agriculture and Risk Management) Database, to feature hundreds of reviewed case studies on these issues.
Case studies can be quickly screened according to a range of categories including region, scale, climate risks, diversification type and other management categories, along with other features of agricultural systems. Practitioners who would like to contribute their own work are invited to submit a case directly through the site.
So far the database has 37 case studies on diversification and livestock …
Follow the link to the web site ReFARM