Historical effects of CO2 and climate trends on global crop water demand
A critical question for agricultural production and food security is how water demand for staple crops will respond to climate and carbon dioxide (CO2) changes1, especially in light of the expected increases in extreme heat exposure2. To quantify the trade-offs between the effects of climate and CO2 on water demand, we use a ‘sink-strength’ model of demand3,4 which relies on the vapour-pressure deficit (VPD), incident radiation and the efficiencies of canopy-radiation use and canopy transpiration; the latter two are both dependent on CO2. This model is applied to a global data set of gridded monthly weather data over the cropping regions of maize, soybean, wheat and rice during the years 1948–2013. We find that this approach agrees well with Penman–Monteith potential evapotranspiration (PM) for the C3 crops of soybean, wheat and rice, where the competing CO2 effects largely cancel each other out, but that water demand in maize is significantly overstated by a demand measure that does not include CO2, such as the PM. We find the largest changes in wheat, for which water demand has increased since 1981 over 86% of the global cropping area and by 2.3–3.6 percentage points per decade in different regions.
Everything that Can Go Wrong in a Field Experiment (round 2)
The Global Development and Poverty Initiative (GDP) seminar series returns with a reprise of its most popular seminar last year. Join us for a stimulating discussion on the opportunities, obstacles, and unforeseen events encountered while conducting field research in the developing world.
The panelists will share stories of challenges and successes from their own experiences and will offer insights on conducting effective research in the field.
Read more about last year's seminar here.

This seminar is located in the Knight Management Center's Class of 1968 Building. Click Here for a map.
Eran Bendavid
Encina Commons, Room 102,
615 Crothers Way,
Stanford, CA 94305-6019
My academic focus is on global health, health policy, infectious diseases, environmental changes, and population health. Our research primarily addresses how health policies and environmental changes affect health outcomes worldwide, with a special emphasis on population living in impoverished conditions.
Our recent publications in journals like Nature, Lancet, and JAMA Pediatrics include studies on the impact of tropical cyclones on population health and the dynamics of SARS-CoV-2 infectivity in children. These works are part of my broader effort to understand the health consequences of environmental and policy changes.
Collaborating with trainees and leading academics in global health, our group's research interests also involve analyzing the relationship between health aid policies and their effects on child health and family planning in sub-Saharan Africa. My research typically aims to inform policy decisions and deepen the understanding of complex health dynamics.
Current projects focus on the health and social effects of pollution and natural hazards, as well as the extended implications of war on health, particularly among children and women.
Specific projects we have ongoing include:
What do global warming and demographic shifts imply for the population exposure to extreme heat and extreme cold events?
What are the implications of tropical cyclones (hurricanes) on delivery of basic health services such as vaccinations in low-income contexts?
What effect do malaria control programs have on child mortality?
What is the evidence that foreign aid for health is good diplomacy?
How can we compare health inequalities across countries? Is health in the U.S. uniquely unequal?
Scott Rozelle
Encina Hall East, E404
Stanford, CA 94305-6055
Scott Rozelle is the Helen F. Farnsworth Senior Fellow and the co-director of Stanford Center on China's Economy and Institutions in the Freeman Spogli Institute for International Studies and Stanford Institute for Economic Policy Research at Stanford University. He received his BS from the University of California, Berkeley, and his MS and PhD from Cornell University. Previously, Rozelle was a professor at the University of California, Davis and an assistant professor in Stanford’s Food Research Institute and department of economics. He currently is a member of several organizations, including the American Economics Association, the International Association for Agricultural Economists, and the Association for Asian Studies. Rozelle also serves on the editorial boards of Economic Development and Cultural Change, Agricultural Economics, the Australian Journal of Agricultural and Resource Economics, and the China Economic Review.
His research focuses almost exclusively on China and is concerned with: agricultural policy, including the supply, demand, and trade in agricultural projects; the emergence and evolution of markets and other economic institutions in the transition process and their implications for equity and efficiency; and the economics of poverty and inequality, with an emphasis on rural education, health and nutrition.
Rozelle's papers have been published in top academic journals, including Science, Nature, American Economic Review, and the Journal of Economic Literature. He is fluent in Chinese and has established a research program in which he has close working ties with several Chinese collaborators and policymakers. For the past 20 years, Rozelle has been the chair of the International Advisory Board of the Center for Chinese Agricultural Policy; a co-director of the University of California's Agricultural Issues Center; and a member of Stanford's Walter H. Shorenstein Asia-Pacific Research Center and the Center on Food Security and the Environment.
In recognition of his outstanding achievements, Rozelle has received numerous honors and awards, including the Friendship Award in 2008, the highest award given to a non-Chinese by the Premier; and the National Science and Technology Collaboration Award in 2009 for scientific achievement in collaborative research.
Stanford Center on China’s Economy and Institutions
Learn more
Doomsday Vaults, Genebanks and Plant Breeding in the Age of Climate Change
Read a full event summary here.
Agricultural crops are on the front lines of climate change. Can we expect increased food production in the context of global warming? Do our crops come pre-adapted to a climate not seen since the dawn of agriculture, or must we take bold measures to prepare agriculture for climate change? This talk will focus on the role that crop diversity must necessarily play in facilitating the adaptation of agricultural crops to new climates and environments. Genebanks, the “Doomsday Vault” near the North Pole, and possible new roles for plant breeders and farmers will be explored.

Dr. Cary Fowler is perhaps best known as the “father” of the Svalbard Global Seed Vault, which UN Secretary General Ban Ki-Moon has described as an “inspirational symbol of peace and food security for the entire humanity.” Dr. Fowler proposed creation of this Arctic facility to Norway and headed the international committee that developed the plan for its establishment by Norway. The Seed Vault provides ultimate security for more than 850,000 unique crop varieties, the raw material for all future plant breeding and crop improvement efforts. He currently chairs the International Council that oversees its operations.
In 2005 Dr. Fowler was chosen to lead the new Global Crop Diversity Trust, an international organization cosponsored by Food and Agriculture Organization of the UN (FAO) and the Consultative Group on International Agricultural Research (CGIAR). This position carried international diplomatic status. During his tenure, he built an endowment of $130 million and raised an additional $100 million (including the first major grant given for agriculture by the Gates Foundation) for programs to conserve crop diversity and make it available for plant breeding. The Trust organized a huge global project to rescue 90,000 threatened crop varieties in developing countries – the largest such effort in history - and is now engaged in an effort Dr. Fowler initiated with the Royal Botanic Gardens (Kew) to collect, conserve and pre-breed the wild relatives of 26 major crops. He oversaw development of a global information system to aid plant breeders and researchers find appropriate genetic materials from genebanks around the world. These initiatives at the Crop Trust, positioned the organization as a major path-breaking player in the global effort to adapt crops to climate change.
Prior to leading the Global Crop Diversity Trust, Dr. Fowler was Professor at the Norwegian University of Life Sciences in Ås Norway. He headed research and the Ph.D. program at the Department of International Environment and Development Studies and was a member of the university committee that allocated research funding to the different departments.
The U.N.’s FAO recruited him in the 1990s to lead the team to produce the UN’s first global assessment of the State of the World’s Plant Genetic Resources. He was personally responsible for drafting and negotiating the first FAO Global Plan of Action on the Conservation and Sustainable Utilization of Plant Genetic Resources, formally adopted by 150 countries in 1996. Following this, Dr. Fowler served as Special Assistant to the Secretary General of the World Food Summit (twice) and represented the Consultative Group on International Agricultural Research (CGIAR/World Bank) in negotiations on the International Treaty on Plant Genetic Resources. He chaired a series of Nordic government sponsored informal meetings of 15 countries to facilitate negotiations for this treaty. And, he represented Norway on the Panel of Experts of the Convention on Biological Diversity.
Cary Fowler was born in 1949 and grew up in in Memphis, Tennessee, the son of a judge and a dietician. He studied at Simon Fraser University in Canada where he received a B.A. (honors – first class) degree. He earned his Ph.D. at Uppsala University in Sweden with a thesis on agricultural biodiversity and intellectual property rights. Dr. Fowler has lectured widely, been a visiting scholar at Stanford University and a visiting professor at the University of California – Davis. He is the author or co-author of more than 100 articles and several books including the classic Shattering: Food, Politics and the Loss of Genetic Diversity (University of Arizona Press), Unnatural Selection, Technology, Politics and Plant Evolution (Gordon & Breach Science Publishers) and The State of the World’s Plant Genetic Resources (UN-FAO).
Dr. Fowler currently serves on the boards of Rhodes College, the NY Botanical Garden Corporation, the Lillian Goldman Charitable Trust and Amy Goldman Charitable Trust. He remains associated with the Global Crop Diversity Trust as Special Advisor. He is a former member of the U.S. National Plant Genetic Resources Board (appointed by the Secretary of Agriculture) and former board and executive committee member of the International Maize and Wheat Improvement Center in Mexico. He has served as chair of the national Livestock Conservancy. He is the recipient of several awards: Right Livelihood Award, Vavilov Medal, the Heinz Award, Bette Midler’s Wind Beneath My Wings Award, the William Brown Award of the Missouri Botanical Garden and two honorary doctorates. He is one of two foreign elected members of the Russian Academy of Agricultural Sciences and is a member of the Russian Academy of Sciences.
A global perspective on food systems
European grain yield stagnation related to climate change
The European Union led the world in wheat production and exports in 2014-15. Yet Europe is also the region where productivity has slowed the most. Yields of major crops have not increased as much as would be expected over the past 20 years, based on past productivity increases and innovations in agriculture.
Finding the causes of that stagnation is key to understanding the trajectory of the global food supply.
Logically, it would seem that climate change would affect crops. But in the overall picture of agriculture, it's hard to figure out how much. European farming is a complex venture, and other possible stagnating factors include changes in government policy. For example, farm subsidies are no longer based on productivity and the use of fertilizer is now controlled to reduce runoff into water supplies. Ongoing positive factors include improvements in farm management practices and advances in crop genetics.
Historically, scientists relied on models to estimate the effects of climate change. Now Stanford's Frances C. Moore has for the first time statistically quantified the relative importance of climate in the stagnation of European crops. She found that warming and precipitation trends are affecting European grain harvests. Moore is a PhD candidate in the Emmett Interdisciplinary Program in Environment and Resources.
"This study is sobering in that it shows climate drags on some of the crops in this region," said David Lobell, co-author of the paper. "Yet this new approach to looking at the problem will help us understand more quickly what impacts require more attention, and that can only be positive in the long term." Lobell is an associate professor of environmental Earth system science and the deputy director of the Center on Food Security and the Environment at Stanford. He is also a senior fellow in the Freeman Spogli Institute for International Studies and the Stanford Woods Institute for the Environment. He studies ways to improve crop yields in major agricultural regions, with emphasis on adaptation to climate change.
"This is a major step in using quantitative analysis to disentangle the effect of climate change in a complicated system," said Dáithí Stone, a pioneer in comparing actual seasonal weather forecasts with what those forecasts would have been if human activities had not emitted greenhouse gases. "It demonstrates that the signal has become large enough that we may see the effect of climate change in a complicated system like agriculture." Stone is a research scientist in the Computational Chemistry, Materials and Climate Group of Berkeley Lab.
How wheat and corn and barley grow
Moore considered two factors in the study: actual crop yields and expected crop yields given historic temperature and precipitation trends. She applied statistical analyses to look for patterns in regional maps of actual European yields of wheat, maize (known in the United States as corn), barley and sugar beets, from 1989 to 2009.
The study found that climate trends can explain 10 percent of the slowdown in wheat and barley yields, with changes in government policy and agriculture likely responsible for the remainder of the stagnation. Moore found evidence that long-term temperature and precipitation trends since 1989 reduced overall European yields of wheat by 2.5 percent and barley by 3.8 percent, while slightly increasing maize and sugar beet yields.
Moore also wanted to find out to what extent farmers had adapted their practices to accommodate changing conditions. She applied power analysis, a statistical tool to test the effect of adaptation. But she discovered the test was not effective in the context of this study.
"We think farmers have been hurt already by warming and drying trends in Italy," Moore said. Undaunted by the limits of statistical analysis to measure farmer adaptation, she is planning another way to find out. "I have been doing this work in front of a computer – in the future I would like to go to Italy," she said. "It would be interesting to talk to the farmers."
Leslie Willoughby is an intern at Stanford News Service.
Media Contact
Frances C. Moore, Emmett Interdisciplinary Program in Environment and Resources: (617) 233-3380, fcmoore@stanford.edu
Dan Stober, Stanford News Service: (650) 721-6965, dstober@stanford.edu
The fingerprint of climate trends on European crop yields
The Tropical Oil Crop Revolution: Food, Feed, Fuel, and Forests
Over the last two decades global production of soybean and palm oil seeds have increased enormously. Because these tropically rainfed crops are used for food, cooking, animal feed, and biofuels, they have entered the agriculture, food, and energy chains of most nations despite their actual growth being increasingly concentrated in Southeast Asia and South America. The planting of these crops is controversial because they are sown on formerly forested lands, rely on large farmers and agribusiness rather than smallholders for their development, and supply export markets. The contrasts with the famed Green Revolution in rice and wheat of the 1960s through the 1980s are stark, as those irrigated crops were primarily grown by smallholders, depended upon public subsidies for cultivation, and served largely domestic sectors.
The overall aim of the book is to provide a broad synthesis of the major supply and demand drivers of the rapid expansion of oil crops in the tropics; its economic, social, and environmental impacts; and the future outlook to 2050. After introducing the dramatic surge in oil crops, chapters provide a comparative perspective from different producing regions for two of the world's most important crops, oil palm and soybeans in the tropics. The following chapters examine the drivers of demand of vegetable oils for food, animal feed, and biodiesel and introduce the reader to price formation in vegetable oil markets and the role of trade in linking consumers across the world to distant producers in a handful of exporting countries. The remaining chapters review evidence on the economic, social, and environmental impacts of the oil crop revolution in the tropics. While both economic benefits and social and environmental costs have been huge, the outlook is for reduced trade-offs and more sustainable outcomes as the oil crop revolution slows and the global, national, and local communities converge on ways to better managed land use changes and land rights.
by Derek Byerlee, Walter P. Falcon, and Rosamond L. Naylor
will be published by Oxford University Press on November 10, 2016
$74.00 | 304 Pages | 9780190222987