Households depend upon food prices, incomes, and disease burdens that impact the ability to use consumed food. Climate change and extreme temperatures impact all of these factors. In this talk, David Lobell focuses on the impact of heat in growing regions that are important for food prices. He reviews recent research on heat impacts and discusses whether crop yields are becoming more or less sensitive to heat.

According to a new study by FSE's David Lobell, satellite data can play a critical role in understanding yield gaps and meeting future crop demand. Lobell's review appeared in a special issue in Field Crops Research dedicated to crop yield gap analysis.

To date, satellite data have played a relatively small role in understanding the magnitude and causes of yield gaps in most regions. However, the few examples that exist indicate that remote sensing can help to overcome some of the inherent spatial and temporal scaling issues associated with field-based approaches.

"Yield gap profiles, based on multiple years of satellite data, provide a useful measure of how persistent yield-controlling factors are through time," writes Lobell in his review. "Although the cost or availability of satellite data with sufficient spatial resolution to discriminate agricultural fields was an obstacle in the past, this barrier is rapidly diminishing."

Improved algorithms to pre-process remote sensing data and estimate yields, and the increased availability of new, large geospatial datasets on soils, management, and weather should also benefit future efforts in this area.

"Improved knowledge of yield gaps will play a critical role in meeting future crop demands at affordable prices and with minimal environmental impacts," concludes Lobell. "The use of satellite data can accelerate the pace of discovery, and as such it represents an important area for future work."

All papers in this special issue can be accessed free of charge.

We have read the headline a number of times now warning us that increasing temperatures are threatening global crop production. One need only to recall the drought and heat wave that hit the mid-western United States last summer, damaging corn and soybean production. Higher temperatures are certainly part of the problem, but a new study led by FSE associate director David Lobell finds its impacts in the U.S. are more indirect. Water stress may be the main culprit.

To validate this hypothesis and to help differentiate the different mechanisms impacting crop yields at higher temperatures, the research team used a model known as an Agricultural Production Systems Simulator (APSIM). High temperatures had a strong negative effect on corn yield response in the United States, in agreement with the data, but the predominate effect of heat in the model was via increased water stress.

As temperatures increase, plants transpire more water into the atmosphere, just as people sweat more on hotter days. With more hot days, the corn plant finds it harder to maintain growth rates, and at the same time loses more water, which sets up the risk of even more drought stress later in the season.

“APSIM computes daily water stress as the ratio of water supply to demand, and during the critical month of July this ratio is three times more responsive to 2 ºC warming than to a 20 percent precipitation reduction,” writes Lobell and co-authors in a new paper published in Nature Climate Change. “Water stress during July is particularly important for overall biomass growth and final yield, with July being the month with the most total biomass growth.”

Direct heat stress on the plant, such as happens on extremely hot days, played a more minor role in determining final yield. The study suggests that increased CO₂ may reduce crop sensitivity to extreme heat by increasing water use efficiency, but gains are likely to be no more than 25 percent.

“The APSIM model has been valuable in its ability to discriminate the importance of these factors,” said Lobell. “Models like these are useful for guiding efforts to develop crops with greater tolerance to increased temperatures, an important component of most adaptation strategies in agriculture, and helping to identify which processes are critical for modeling efforts to consider when projecting climate change impacts.”

The researchers project sensitivity to extreme heat will remain a severe constraint to crop production in the foreseeable future, especially as the region warms. They are now using the models to evaluate different strategies for developing new varieties of corn that can better handle the heat.

Many Stanford computer science majors hope to land coveted jobs in Silicon Valley upon graduation. Parth Bhakta or Ben Rudolph aren't so sure. They first want to take their skills far afield of the storied technology hub. 

Bhakta and Rudolph joined two other Stanford students earlier this month to travel to Ethiopia, making their way to remote refugee camps along the Sudanese border. They are researching ways in which technology and design innovation can help improve conditions for refugees and their surrounding communities.

“As a computer science student, I feel that a lot of Silicon Valley is focused on solving trivial problems,” said Bhakta, a senior from Palm Desert, Calif., who graduates this year with an undergraduate degree in symbolic systems and a master’s in computer science. “I hope to apply my skills toward something that has a meaningful impact. I want this experience to help me better understand how to tackle big, tangible problems.”

The students worked with the UNHCR and International Rescue Committee in the Bambasi and Sherkole refugee camps in western Ethiopia to test out ideas they’ve been working on with the goal of improving camp communications; food security and economic self-sufficiency; host community relations; and the often difficult process of setting up camps to house arriving refugees.

The idea for the trip emerged from a dialogue and collaboration between Stanford’s Center for International Security and Cooperation (CISAC) and the United Nations High Commissioner for Refugees (UNHCR). An official from the UN agency approached CISAC Co-Director Tino Cuéllar last spring, and encouraged CISAC to explore ideas to better protect and support the care of more than 42 million refugees, internally displaced and stateless people worldwide.

These early discussions led to a multidisciplinary partnership involving CISAC, students from across the Stanford campus and at the Hassno-Platner Institute of Design – better known as the d.school – as well as professors, NGOs, physicians, officials with experience in humanitarian settings, architects and other professionals eager to volunteer their time and expertise.

Among those professionals is Jeffrey Geisinger, an architect with Ennead Architects in New York. The firm, which designed the new Stanford Law School wing and the recently inaugurated Bing Concert Hall, is doing pro bono work on the project through its advocacy lab.

Geisinger hopes to start designing modules that might be used in shared spaces. To do this, he said, he must see what construction materials are available, what deficiencies typically exist out in the field and which social networks and local skills might be tapped to help the UN build more innovative structures shared by both communities.

“From an architect’s perspective, we’re interested in some kind of design solution,” said Geisinger. “But before we can even begin to put pencil to paper, it’s important to really define the problem.”

For CISAC, the project represents a further effort to bridge the gap between scholarship and practice.

“This is an extraordinary manifestation of CISAC’s mission to help shape public policy,” said Liz Gardner, CISAC’s associate director for programs. “This project marries up scholarship, teaching and close interaction with policymakers – with the ultimate goal of improving the lives of refugees.”

The project also led to dozens of students from a variety of majors to enroll in the Law School class, “Rethinking Refugee Communities,” co-taught by Cuéllar and Leslie Witt of the global design consultancy, IDEO. The students have been brainstorming and investigating, then hammering out concepts and prototypes they hope might one day be implemented by the United Nations.

Now, they want to put those ideas to the test.

Rudolph, a senior from Chicago, is working with his team to build a software platform that would enable early camp registration and provide two-way communication between the UNHCR and refugees, using mobile technology. RescueSMS is software designed to better profile each refugee and alert them to upcoming events or emergencies in the camp, as well as give them a voice to express concerns or ask questions of the UN.

“I’m excited about applying my computer science knowledge to humanitarian efforts, where I think software is underused,” said Rudolph, who has had a string of internships at Silicon Valley startups. “I wanted a change of pace from the corporate world; I was tired of working for traditional software startup companies.”

So he’s taking an untraditional route. Rudolph’s interest in the project has led to an internship with the UNHCR’s innovation lab in Geneva after he graduates this summer.

One of Cuéllar’s goals is to build long-term relationships with organizations such as the UNHCR so that the work by Stanford students becomes embedded in the innovation process of public organizations. 

Devorah West’s team is looking at infrastructure in the space that is shared by refugees and the indigenous people from the surrounding community. When thousands of refugees stream into border communities in neighboring countries, resources become scarce and tensions run high. West is representing the team looking at ways to build schools, medical facilities and marketplaces that could be shared by both communities.

“My team will use this trip to get a better understanding of realities on the ground,” said West, a second-year master’s student in international policy studies from Santa Fe, N.M., who graduates this summer. “We hope to find ways to defuse tensions over scarce resources and allow both communities to satisfy social and physical needs.”

West said she was drawn to the project by the interdisciplinary nature of the teams.

“Having worked in the policy world, I was really interested in using design thinking to fuse together academic research and policy development in order to have a concrete impact on refugee communities,” she said.

Jessica Miranda is representing the team focused on food security and economic self-sufficiency. They are working on understanding how to encourage small-scale mobile farming. During her visits to the camps, she will investigate the challenges that affect small-scale gardening and learn more about the terrain, the nutritional status of vulnerable households and what the cultural views are on agriculture.  

“I know how it feels to leave your country behind,” said Miranda, a second-year master’s student in international policy studies from Toluca, Mexico. “And I want to help. But it’s difficult to think about refugee camps from the comfort of my couch. It’s time to go and see how these ideas might work on the ground."

Beth Duff-Brown, CISAC’s communications manager, traveled with the students and will be reporting from the field.