Water for Food

A New Atlas to Shape How We Feed the World

November 5, 2014


By Ken Cassman, PhD, Faculty Fellow, Robert B. Daugherty Water for Food Institute at the University of Nebraska, Agronomy Professor

Participating in the 2014 World Food Prize Week in Des Moines, Iowa has me thinking about water and how we can best use this scarce resource to produce more food.

The world’s population is expected to reach 9 to 10 billion by 2050, causing a doubling in food demand. And not only is the population is growing, it’s also becoming more prosperous. As incomes rise, people have the means to eat more meat and dairy products, which require much more grain. At the same time, corn, soybeans and other crops are being diverted to biofuel production, which places additional pressure on food supply. Urban expansion often comes at the expense of prime agricultural land, with only drier, less fertile land to replace it. The result of these trends is an escalating need for agriculture to produce more food, feed, fiber and fuel on a limited supply of good farmland, and intense competition for water resources.

Agriculture now uses more than 70 percent of the world’s freshwater resources, the vast majority used for irrigating crops. Indeed, irrigated production uses only 18% of total farm land and yet contributes 40% of global food supply. Yet lack of water for irrigating crops is a constraint to producing food for hundreds of millions of people in the world. In some areas, water is scarce due to large population and/or too little rainfall, such as in the US southwest. In other regions, such as parts of sub-Saharan Africa, water may be available, but access to pumps, power, and appropriate technologies limits agricultural development. Or water may be unusable due to pollutants and toxic contaminants. In addition, free-flowing water in streams and rivers is needed to maintain wildlife and biodiversity.

Given this situation, the best way to meet global food demand is to double crop yields on existing farmland and achieving highest possible water use efficiency. While water conservation efforts and wasting less food can help, they can’t replace the need for massive yield increases. This increase in yield must come with a reduction in the environmental footprint of agriculture, which is something that has proven difficult to accomplish, even during the green revolution of the past 50 years.

But where can we increase yields the most? How do we know which land has reached its full production potential, and which has more to give? And among areas with large potential for higher yields, where is it possible to do so with the smallest requirements for energy and fertilizers or to consistently produce high yields in the face of variable and changing climate?

To help answer these questions at local-to-global scales, there is a new tool called the Global Yield Gap and Water Productivity Atlas. Using the best available science and data, the Atlas measures the difference in what existing farmlands are producing, and what these lands could be producing—a difference known as the yield gap. The Atlas also measures the efficiency with which water is converted to food, or water productivity.

Unlike previous efforts to estimate yield potential and yield gaps, the Atlas uses a “bottom-up” approach. For four years, Faculty Fellows of the Robert B. Daugherty Water for Food Institute at the University of Nebraska and their colleagues at Wageningen University in the Netherlands have partnered with agronomists worldwide to collect data about local conditions and farming methods that are required to provide realistic estimates of potential yields and yield gaps. These results are then scaled to national, regional and global levels based on “weighting” each local estimate for its contribution to total production.

The Atlas enables farmers and other stakeholders to identify regions with the greatest potential to produce more food in a sustainable manner by getting the most bang for the buck from prudent use of inputs such as better seed, fertilizer—and water.

The data show that Sub-Saharan Africa—primarily smallholder farmers practicing subsistence agriculture in Burkina Faso, Ethiopia, Kenya, Mali, Niger, Nigeria, Tanzania and Uganda—can potentially increase yields of existing farms by twofold or more. And when coupled with data on location of water resources that could sustainably be used for irrigation, it is possible to identify areas where investment in appropriate-scale irrigation infrastructure will have greatest benefits for African farmers.

For example, studies have shown that Ethiopia’s surface water and groundwater supplies could irrigate 10 times as much land than at present, and the Atlas can identify which of these areas have the largest exploitable yield gaps. Within each of these areas, a key issue is estimating the amount of water that can be used for irrigation based aquifer re-charge rates or the water flow in streams and rivers required to maintain ecological integrity of riparian habitat and limiting the scale of irrigated area accordingly.

Together, closing exploitable yield gaps in rainfed agriculture and strategic expansion of irrigation are the keys to reducing rural poverty and improving nutrition in rural areas of sub-Saharan Africa, South and Southeast Asia. The Global Yield Gap Atlas will help show the way.

Disclaimer: The Daugherty Water for Food Institute welcomes blog articles from guest contributors. Please note the comments shared by guests represent their own views and not necessarily those of DWFI, the University of Nebraska or any institutions with which DWFI may be affiliated.

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