Changes in temperature due to climate change over the next few decades will put considerable pressure on crop production in already vulnerable areas of sub-Saharan Africa, states a new study from Stanford University's Program on Food Security and the Environment published this week in Environmental Research Letters. The study found that average yields for five staple crops - maize, sorghum, millet, groundnuts, and cassava -will likely be harmed by warming without successful adaptation

"In all cases except cassava, we estimate a very high (95%) probability that damages would exceed 7%, and a low (5%) probability that they exceed 27%," said co-author David Lobell, an assistant professor of Environmental Earth System Science and center fellow at the Program on Food Security and the Environment, a joint program of the Freeman Spogli Institute for International Studies and Woods Institute for the Environment at Stanford.

The findings present a surprisingly robust picture of how weather affects yields in sub-Saharan Africa (SSA) and suggest there is a real threat of large near-term impacts in this food-insecure part of the world. SSA has the highest proportion of malnourished populations in the world, with one in three people chronically hungry.

"These are very resource scarce countries," noted lead author Wolfram Schlenker, assistant professor of economics at Columbia University, "and a reliable picture of what climate change will mean for crop yields can be very useful in allocating investments."

Panel dataset approach

Up to this point, the scientific basis for estimating production risks and prioritizing investments has been quite limited. "Many approaches have been limited by a lack of reliable data on such things as soil properties, historical agricultural data, and management practices," said Lobell. "This has not inspired a lot of confidence in the estimates, and has caused many to question some high-level statements about risks of climate change to Africa. The results presented in this study are not as disastrous as some have claimed, but they are big enough to suggest that major adaptations are needed in this region."

Schlenker and Lobell utilized a different approach than had been tried, by matching country-level yields (ton/ha) with various weather measurements for 1961-2002. By combining all the countries into a panel dataset, they were able to see a much clearer signal of weather than would be possible looking at data from individual countries.

"The observational approach enabled us to measure how farmers react to weather shocks given various, shared constraints such as credit markets and lack of required inputs," said Schlenker. "This is very difficult to do with a field trial approach."

Future research and investments

The authors emphasize that the results are not predictions of what will happen, but of what the potential stakes are if we don't take the threat seriously. Varieties with greater drought and heat tolerance, improved and expanded irrigation systems, rainwater harvesting technologies, disaster relief efforts, and insurance programs will likely all be needed to foster agricultural development and adaptation to warming.

"There is arguably little scope for substantial poverty reductions in SSA without large improvements in agricultural productivity," conclude the authors. "The findings presented here suggest that this challenge will get even more difficult in a warming climate. Rather than a cause for despair, we view this as an added incentive for serious, immediate, and sustained investments in agricultural productivity in SSA."

This work was supported by a grant from the Rockefeller Foundation. The Program on Food Security and the Environment is jointly run by the Woods Institute for the Environment and the Freeman Spogli Institute for International Studies at Stanford.

Roughly a billion people around the world continue to live in state of chronic hunger and food insecurity. Unfortunately, efforts to improve their livelihoods must now unfold in the context of a rapidly changing climate, in which warming temperatures and changing rainfall regimes could threaten the basic productivity of the agricultural systems on which most of the world's poor directly depend. But whether climate change represents a minor impediment or an existential threat to development is an area of substantial controversy, with different conclusions wrought from different methodologies and based on different data.

This book aims to resolve some of the controversy by exploring and comparing the different methodologies and data that scientists use to understand climate's effects on food security. It explains the nature of the climate threat, the ways in which crops and farmers might respond, and the potential role for public and private investment to help agriculture adapt to a warmer world. This broader understanding should prove useful to both scientists charged with quantifying climate threats, and policy-makers responsible for crucial decisions about how to respond.

Solar-powered drip irrigation systems significantly enhance household incomes and nutritional intake of villagers in arid sub-Saharan Africa, according to a new study from Stanford's Program on Food Security and the Environment published in the January 14 issue of the Proceedings of the National Academy of Sciences (PNAS). The study found that solar-powered pumps installed in remote villages in the West African nation of Benin provide a cost-effective way of delivering much-needed irrigation water, particularly during the long dry season.

"Our case study on women's farming groups in rural Benin revealed solar-powered drip irrigation – a clean, cost-competitive technology – significantly improved nutrition and food security as well as household incomes in one year," said lead author Jennifer Burney, a postdoctoral scholar with the Program on Food Security and the Environment at Stanford.

"Solar-powered drip irrigation systems break seasonal rainfall dependence, which typically limits farmers to a three- to six-month growing season, and support the production of diversified, high-value crops in rural Africa," Burney added.

She and her co-authors noted that much of sub-Saharan Africa's rural population is considered "food insecure," surviving on less than $1 per person per day. "And whereas most are engaged in agricultural production as their main livelihood, they still spend 50 to 80 percent of their income on food, and are often net consumers of food," they wrote.

Benin pilot project

In 2007, with support from Stanford's Woods Institute for the Environment, Burney and her colleagues partnered with the nonprofit Solar Electric Light Fund (SELF) on a pilot irrigation project in rural Benin. SELF financed and led the installation of three solar-powered drip irrigation systems in two villages in Benin's Kalalé district. Each system is used by a local women's agricultural group, which typically consists of 30 to 35 women who share the maintenance costs of the new irrigation technology.

"In Kalalé, 80 percent of the villagers live on less than $1.25 per day, which is representative of a number of poor, rural communities in Africa," said study co-author Rosamond L. Naylor, director of the Program on Food Security and the Environment and a professor of environmental Earth system science at Stanford.

In rural Benin, women and girls traditionally are responsible for hauling water by hand, often from very long distances. The solar-powered irrigation systems were designed to free them from hauling water to grow vegetable crops, particularly during the dry season.

To measure the impact of the solar-powered drip irrigation technology, the researchers monitored the agricultural groups using the new irrigation systems, as well as two "control" villages where women continued growing vegetables in traditional hand-watered gardens. Household surveys were conducted at the start of the project in November 2007 and again in November 2008.

Nutrition and income

The results were striking. "In just one year, we saw that photovoltaic drip irrigation systems had important implications for food and nutrition security, as well as household income," Burney said.

The three solar-powered irrigation systems supplied on average 1.9 metric tons of produce per month, including such high-valued crops as tomatoes, okra, peppers, eggplants and carrots. In villages irrigated with solar-powered systems, vegetable intake increased to three to five servings per day – the U.S. Department of Agriculture's Recommended Daily Allowance for vegetables – with most of the improvement taking place during the long dry season. In a world where 20 to 25 percent of global disease burden for children is due to malnutrition, such improvements could have a large impact over time, Burney said.

"Seventeen percent of project beneficiaries reported feeling less food insecure, demonstrating a remarkable effect on both year-round and seasonal food access," Naylor added.

As for household income, the authors found that women who used solar-powered irrigation became strong net producers of vegetables and earned extra income from sales, allowing them to significantly increase their purchases of high-protein food and other staples during the dry season.

Project benefits quickly spread to other community members, Burney said. For example, an elementary school curriculum was developed to help village children learn about the benefits of solar drip technology. "There was an overwhelming sense of pride in the new system by teachers, children and women participating in the farmer groups," she added.

Sustainability

Each solar-powered drip irrigation system is about 1.24 acres (0.5 hectare) in size, costs approximately $18,000 to install and requires about $5,750 a year to maintain, the authors said. Based on the projected earnings of the farmers, the system should pay for itself in about 2.3 years, they concluded. And despite higher up-front costs, the durable solar systems should be more economical in the long run than less expensive irrigation systems that use gasoline, diesel or kerosene pumps, with the added benefit of being emissions free, they added.

Focusing on novel irrigation technologies for farmers could be the needed tool for escaping poverty in sub-Saharan Africa, according to Burney. "The photovoltaic irrigation drip system could potentially become a 'game changer' for agricultural development over time," she added.

"Solar-powered irrigation provides a cleaner source of energy that is less susceptible to global price fluctuations," Naylor said. "Improved agricultural productivity in the developing world can play a critical role in global poverty alleviation, and productivity-enhancing technologies provide a sense of hope for persistently poor households."

Other co-authors of the PNAS study are Lennart Woltering and Dov Pasternak of the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) in Niger and Marshall Burke of the Department of Agricultural and Resource Economics at the University of California-Berkeley.

The research was supported by an Environmental Ventures Projects grant from the Woods Institute for the Environment at Stanford. The Program on Food Security and the Environment is jointly run by the Woods Institute and the Freeman Spogli Institute for International Studies at Stanford.

Berkeley and Stanford - Climate change could increase the likelihood of civil war in sub-Saharan Africa by over 50 percent within the next two decades, according to a new study led by a team of researchers at University of California, Berkeley, Stanford University, New York University and Harvard University, and published in today's (Monday, Nov. 23) online issue of the journal Proceedings of the National Academy of Sciences (PNAS).

The study provides the first quantitative evidence linking climate change and the risk of civil conflict. It concludes by urging accelerated support by African governments and foreign aid donors for new and/or expanded policies to assist with African adaptation to climate change.

"Despite recent high-level statements suggesting that climate change could worsen the risk of civil conflict, until now we had little quantitative evidence linking the two," said Marshall Burke, the study's lead author,  a graduate student at UC Berkeley's Department of Agricultural and Resource Economics, and research associate at the Program on Food Security and the Environment. "Unfortunately, our study finds that climate change could increase the risk of African civil war by over 50 percent in 2030 relative to 1990, with huge potential costs to human livelihoods."

"We were definitely surprised that the linkages between temperature and recent conflict were so strong," said Edward Miguel, professor of economics at UC Berkeley and faculty director of UC Berkeley's Center for Evaluation for Global Action. "But the result makes sense. The large majority of the poor in most African countries depend on agriculture for their livelihoods, and their crops are quite sensitive to small changes in temperature.  So when temperatures rise, the livelihoods of many in Africa suffer greatly, and the disadvantaged become more likely to take up arms."

Understanding the causes and consequences of civil strife in much of the African continent has been a major focus of the social sciences for decades, said Miguel, given the monumental suffering has resulted from it.

In the study, the researchers first combined historical data on civil wars in sub-Saharan Africa with rainfall and temperature records across the continent. They found that between 1980 and 2002, civil wars were significantly more likely in warmer-than-average years, with a 1 degree Celsius increase in temperature in a given year raising the incidence of conflict across the continent by nearly 50 percent.

Building on this historical relationship between temperature and conflict, the researchers then used projections of future temperature and precipitation change to quantify future changes in the likelihood of African civil war. Based on climate projections from 20 global climate models, the researchers found that the incidence of African civil war could increase 55 percent by 2030, resulting in an additional 390,000 battle deaths if future wars are as deadly as recent wars.

All climate models project rising temperatures in coming decades, said David Lobell, study co-author and an assistant professor of environmental earth system science at Stanford and center fellow at Stanford's Program on Food Security and the Environment, a joint program of the Freeman Spogli Institute for International Studies and the Woods Institute for the Environment.

"On average, the models suggest that temperatures over the African continent will increase by a little over 1 degree Celsius by 2030," he added. "Given the strong historical relationship between temperature rise and conflict, this expected future rise in temperature is enough to cause big increases in the likelihood of conflict."

To confirm that this projection was not the result of large effects in just a few countries or due to overreliance on a particular climate model, the researchers recalculated future conflict projections using alternate data.  "No matter what we tried - different historical climate data, different climate model projections, different subsets of the conflict data - we still found the same basic result," said Lobell.

It's easy to think of climate change as a long way off, said the researchers, but their study shows how sensitive many human systems are to small increases in temperature, and how fast the negative impacts of climate change could be felt.

"Our findings provide strong impetus to ramp up investments in African adaptation to climate change, for instance by developing crop varieties less sensitive to extreme heat and promoting insurance plans to help protect farmers from adverse effects of the hotter climate," said Burke.

Applying findings from this study could prove useful to policy makers at the upcoming Copenhagen negotiations in December in determining both the speed and magnitude of response to climate change, the authors said.

"If the sub-Saharan climate continues to warm and little is done to help its countries better adapt to high temperatures, the human costs are likely to be staggering," said Burke.