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.

Synthetic fertilizers have dramatically increased food production worldwide. But the unintended costs to the environment and human health have been substantial. Nitrogen runoff from farms has contaminated surface and groundwater and helped create massive "dead zones" in coastal areas, such as the Gulf of Mexico. And ammonia from fertilized cropland has become a major source of air pollution, while emissions of nitrous oxide form a potent greenhouse gas.

These and other negative environmental impacts have led some researchers and policymakers to call for reductions in the use of synthetic fertilizers. But in a report published in the June 19 issue of the journal Science, an international team of ecologists and agricultural experts warns against a "one-size-fits-all" approach to managing global food production.

"Most agricultural systems follow a trajectory from too little in the way of added nutrients to too much, and both extremes have substantial human and environmental costs," said lead author Peter Vitousek, a professor of biology at Stanford University and senior fellow at Stanford's Woods Institute for the Environment.

"Some parts of the world, including much of China, use far too much fertilizer," Vitousek said. "But in sub-Saharan Africa, where 250 million people remain chronically malnourished, nitrogen, phosphorus and other nutrient inputs are inadequate to maintain soil fertility."

Other co-authors of the Science report include Woods Institute Senior Fellows Pamela Matson, dean of Stanford's School of Earth Sciences, and Rosamond L. Naylor, director of the Program on Food Security and the Environment.

China and Kenya

In the report, Vitousek and colleagues compared fertilizer use in three corn-growing regions of the world--north China, western Kenya and the upper Midwestern United States.

In China, where fertilizer manufacturing is government subsidized, the average grain yield per acre grew 98 percent between 1977 and 2005, while nitrogen fertilizer use increased a dramatic 271 percent, according to government statistics. "Nutrient additions to many fields [in China] far exceed those in the United States and northern Europe--and much of the excess fertilizer is lost to the environment, degrading both air and water quality," the authors wrote.

Co-author F.S. Zhang of China Agriculture University and colleagues recently conducted a study in two intensive agricultural regions of north China in which fertilizer use is excessive. Their results showed that farmers in north China use about 525 pounds of nitrogen fertilizer per acre (588 kilograms per hectare) annually--releasing about 200 pounds of excess nitrogen per acre (227 kilograms per hectare) into the environment. Zhang and his co-workers also demonstrated that nitrogen fertilizer use could be cut in half without loss of yield or grain quality, in the process reducing nitrogen losses by more than 50 percent.

At the other extreme are the poorer countries of sub-Saharan Africa, such as Kenya and Malawi. In a 2004 study in west Kenya, co-author Pedro Sanchez and colleagues found that farmers used only about 6 pounds of nitrogen fertilizer per acre (7 kilograms per hectare)--little more than 1 percent of the total used by Chinese farmers. And unlike China, cultivated soil in Kenya suffered an annual net loss of 46 pounds of nitrogen per acre (52 kilograms per hectare) removed from the field by harvests.

"Africa is a totally different situation than China," said Sanchez, director of tropical agriculture at the Earth Institute at Columbia University. "Unlike most regions of the world, crop yields have not increased substantially in sub-Saharan Africa. Nitrogen inputs are inadequate to maintain soil fertility and to feed people. So it's not a matter of nutrient pollution but nutrient depletion."

U.S. and Europe

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A comparison of 3 agricultural areas of the world found massive imbalances in fertilizer use, resulting in malnourishment in some regions and pollution in others. Photo: David Nance, USDA

The contrast between Kenya and China is dramatic and will require vastly different solutions, the authors said. However, large-scale change is possible, they said, noting that since the 1980s, increasingly stringent national and European Union regulations and policies have reduced nitrogen surpluses substantially in northern Europe.

In the Midwestern United States, over-fertilization was the norm from the 1970s until the mid-1990s. During that period, tons of excess nitrogen and phosphorus entered the Mississippi River Basin and drained into the Gulf of Mexico, where the large influx of nutrients has triggered huge algal blooms. The decaying algae use up vast quantities of dissolved oxygen, producing a seasonal low-oxygen dead zone in the Gulf that in some years is bigger than the state of Connecticut.

Since 1995, the imbalance of nutrients--particularly phosphorus--has decreased in the Midwestern United States, in part because better farming techniques have increased yields. Statistics show that from 2003 to 2005, annual corn yields in parts of the Midwestern United States and north China were almost the same, even though Chinese farmers used six times more nitrogen fertilizer than their American counterparts and generated nearly 23 times the amount of excess nitrogen.

"U.S. farmers are managing fertilizer more efficiently now," said co-author Rosamond Naylor, who is also a professor of environmental Earth system science and senior fellow at Stanford's Freeman Spogli Institute for International Studies. "The dead zone in the Gulf of Mexico persists due to continued fertilizer runoff and animal waste from increased livestock production."

Low nitrogen in Africa

In sub-Saharan Africa, the initial challenge is to increase productivity and improve soil fertility, the authors said. To meet that challenge, co-author Sanchez recommends that impoverished farmers be given subsidies to purchase fertilizer and good-quality seeds. "In 2005, Malawi was facing a serious food shortage," he recalled. "Then the government began subsidizing fertilizer and corn seeds. In just four years production tripled, and Malawi actually became an exporter of corn."

Food production is paramount, added co-author G. Philip Robertson, a professor of crop and soil sciences at Michigan State University. "Avoiding the misery of hunger is and should be a global human priority," Robertson said. "But we should also find ways to do this without sacrificing other key aspects of human welfare, among them a clean environment. It doesn't have to be an either/or choice."

For countries where over-fertilization is a problem, the authors cited a number of techniques to reduce environmental damage. "Some of these--such as better-targeted timing and placement of nutrient inputs, modifications to livestock diets and the preservation or restoration of riparian vegetation strips--can be implemented now," they wrote.

Designing sustainable solutions also will require a lot more scientific data, they added. "Our lack of effective policies can be attributed, in part, to a lack of good on-farm data about what's happening with nutrient input and loss over time," said co-author Alan Townsend, an associate professor of ecology and evolutionary biology at the University of Colorado-Boulder. "Both China and the European Union have supported agricultural research that yields policy-relevant information on nutrient balances. But the U.S. is particularly lacking in long-term data for a country with such a well-developed scientific enterprise."

Even in Europe, with its strong research programs on nutrient balances and stringent policies for reducing fertilizer runoff, nitrogen pollution remains substantial. "The problem of mitigation of excess nitrogen loss to waters is not easily resolved," said co-author Penny Johnes, director of the Aquatic Environments Research Centre at the University of Reading, U.K. "Society may have to face some difficult decisions about modifying food production practices if real and ecologically significant reductions in nitrogen loss to waters are to be achieved."

According to Vitousek, it is important in the long run to avoid following the same path to excess in sub-Saharan Africa that occurred in the United States, Europe and China. "The past can't be altered, but the future can be and should be," he said. "Agricultural systems are not fated to move from deficit to excess. More effort will be required to develop intensive systems that maintain their yields, while minimizing their environmental footprints."

Other co-authors of the Science report are Tim Crews, Prescott College; Mark David, University of Illinois at Urbana-Champaign; Laurie Drinkwater, Cornell University; Elisabeth Holland, National Center for Atmospheric Research; John Katzenberger, Aspen Global Change Institute; Luiz Martinelli, University of São Paulo, Brazil; Generose Nziguheba, Columbia University; Dennis Ojima, The H. John Heinz III Center for Science, Economics and the Environment; and Cheryl Palm, Columbia University.

This work is based on discussions at the Aspen Global Change Institute supported by NASA, the William and Flora Hewlett Foundation, and the David and Lucile Packard Foundation; and at a meeting of the International Nitrogen Initiative sponsored by the Scientific Committee on Problems of the Environment.