New research by a Stanford team shows that climate change is expanding the amount of U.S. agricultural land that is suitable for harvesting two crops per growing season, a system known as double cropping. The practice offers higher productivity and more income for American farmers, but future yield losses from climate change may still outstrip the gains from double cropping. 

In a new study in the journal Environmental Research Letters, Stanford PhD student Christopher Seifert and professor David Lobell find that between 1988 and 2012, the area of farmland in the United States on which farmers were able to harvest two crops per year on the same plot of land grew by as much as 28 percent as a result of warmer temperatures and later fall freezes. Applying their model to two future climate change scenarios, the team projects that the amount of land suitable for double cropping in the United States – in this case, winter wheat followed by soybeans – may double or even triple by the end of the century.

Seifert and Lobell’s analysis includes 22 U.S. states east of the continental divide. They define the area suitable for double cropping as having at least 750 mm per year of rainfall and a 75 percent likelihood that both crops will survive to harvest.

The team built a first-of-its-kind model for a double cropping combination of winter wheat and soybeans, to measure the expansion of farmland that has become theoretically suitable to double cropping since 1988. Combining the model with existing U.S. government data, they find that their estimate of 28 percent growth closely mirrors the actual observed expansion of double cropping in the United States over this time period.

Seifert and Lobell then applied their model to two future climate change scenarios and found that as average temperatures rise, the area suitable for double cropping will likely grow steadily until 2060, then spike sharply between 2060 and 2080. Expansion is projected to slow between 2080-2100, as parts of the South become unsuitable due to a lack of the cold winter temperatures that winter wheat requires.

An expansion of double cropping area could be an important tool for U.S. farmers to protect against the negative effects of climate change on agriculture productivity. Yields of major staple crops like corn, soybeans and wheat are already showing increasing vulnerability to extreme heat, especially for plants that go through critical growth stages such as pollination during the hot summer months. Double cropping can help protect against these risks, and provide other benefits such as year-round ground cover that reduces soil erosion.

The new study does not incorporate data about yields, potential yields, or the changing moisture requirements of each crop as temperatures rise. Adding these factors to future analysis will improve scientists’ understanding of the value of double cropping, said lead author Seifert, a PhD student in environmental earth system science at Stanford.

The study also suggests that the negative impacts that climate change is expected to have on crops like corn and soybeans will likely be larger than the boost that double cropping can offer.

“Double cropping can be an important tool, but it’s important not to overstate its potential to ‘save’ American agriculture from climate change,” said co-author David Lobell, a professor of environmental earth system science and the deputy director of the Center on Food Security and the Environment at Stanford (FSE). FSE is a joint effort of the Freeman Spogli Institute for International Studies and the Stanford Woods Institute for the Environment.

“In the United States, double cropping can potentially make agriculture more resilient to climate change by improving overall productivity and by increasing farmers’ annual incomes,” said Seifert. “But the gains from double cropping will probably not be able to make up for the overall drop in crop yields that we expect to see with future climate change.”

CONTACT:

Christopher Seifert, Ph.D. student, Environmental Earth System Science, Stanford: cseifert@stanford.edu

David Lobell, Professor, Environmental Earth System Science, Stanford: dlobell@stanford.edu

Laura Seaman, Communications Manager, Center on Food Security and the Environment: lseaman@stanford.edu, 650-723-4920

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When we consider national security, we typically think of protecting our borders, securing data and preventing disease and conflict. Winning wars.

The U.S. military is increasingly thinking about the final frontier as the last stand for strategic defense.

“Space is no longer the sanctuary it was 30 years ago; it is becoming increasingly congested, contested and competitive,” said Air Force Lt. Gen. John “Jay” Raymond, commander of the 14th Air Force and the Joint Functional Component Command for Space, within the U.S. Strategic Command.

“Our ultimate goal is to promote the safe and responsible use of space while we execute our mission of supporting the war-fighter through delivering space capabilities,” said Raymond, who recently invited a dozen scholars from CISAC and the Freeman Spogli Institute for International Studies to Vandenberg Air Force Base.

Raymond visited CISAC last year to open a dialogue on policy and strategy among Stanford scholars and the U.S. Strategic Command, one of nine unified commands in the Department of Defense. Raymond’s mandate includes space surveillance and control.

CISAC has had a long partnership with USSTRATCOM headquarters in Omaha, Neb., with fellows visiting officers there each year. Raymond is now looking to Stanford for a policy partnership with his commanders at the Air Force base on the California coast between San Francisco and Los Angeles.

“To continue to be the best in this business we have to constantly assess our current policies and operations while always keeping an eye toward future challenges,” Raymond said. “This is where a relationship with CISAC is invaluable. I saw this as a phenomenal opportunity to provide the fellows insight into the real-world challenges we are facing in the space domain – and to help support, stimulate and develop their academic pursuits.”

CISAC Co-Directors Amy Zegart and David Relman are taking the general up on the proposal. Zegart led the delegation that toured the Joint Space Operations Center and then held senior-level policy and strategy talks with two dozen officers and NASA officials.

The off-the-record talks were lively and frank. The sessions focused on foreign counter-space threats, space policy efforts with China and Russia, the growing problem of space debris and the policy debate over the use of cube satellites.

“We naturally think about national security challenges on land, under water, in the air, and even in cyberspace,” said Zegart, who is also a senior fellow at the Hoover Institution. “But space is playing an increasingly vital role in international security, whether it's the 23,000 pieces of debris the U.S. tracks every day that could hit vital satellites, or deliberate moves by some nations to develop counter-space capabilities. In many ways, space really is the final frontier in the international security landscape.”

Space Debris

The Joint Space Operations Center currently tracks 23,000 objects in orbit; only 1,400 of which are active payloads. Another estimated 500,000 pieces of orbital debris are too small to track. Events such as the Chinese anti-satellite missile test in 2007 and the Iridium-Cosmos collision in 2009 produced thousands of pieces of debris at already congested altitudes.

 

European Space Agency

 

“Debris in space, particularly at lower orbits, travels upwards of 17,000 mph and presents a significant danger to space assets,” Raymond said. “Last year alone, satellites operators around the world executed 121 collision-avoidance maneuvers to avoid hitting debris.”

The participants also discussed the fine balance of militarily protecting space systems against disruption, while allowing the open use of space in a globally connected economy.

U.S. Strategic Commander Admiral Cecil B. Haney spent a day at CISAC and Hoover last year and touched on the importance of space in the nation's 21st century deterrence program. He recently told a House Armed Services subcommittee that China space capabilities are now threatening U.S. strategic satellite systems. He noted Beijing conducted a test of a missile-fire, anti-satellite kill vehicle as recently as last summer.

As more countries develop space capabilities, the problem will grow, the admiral said, according to a Department of Defense news release on Feb. 6.

North Korea has been busy upgrading launch facilities, Haney said, and Iran just successfully launched a satellite into orbit after a string of failures.

Countries also are working to take away America’s strategic advantage in space, Haney said, with China and Russia warranting the most attention.

“Both countries have advanced directed-energy capabilities that could be used to track or blind satellites, disrupting key operations, and both have demonstrated the ability to perform complex maneuvers in space,” he said. Multiple countries already are frequently using military jamming capabilities designed to interfere with satellite communications and global positioning systems.

Rod Ewing, a senior FSI fellow and Frank Stanton Professor in Nuclear Security at CISAC, said after the meeting at Vandenberg that it was important to keep dialogue open with other nations about joint space operations and agreements.

“Of particular interest to me was the intersection of space command issues with those of the space programs of other countries,” Ewing said, “particularly the effort to keep track of space debris.”

U.S. Strategic Command currently has more than 50 Space Situational Awareness data-sharing agreements with partner nations, intergovernmental organizations and commercial entities worldwide. The most recent one was signed with the European Space Agency to provide the ESA with more timely and better data about satellite positions and radio-frequency details for planned orbit maneuvers.

Stephen Krasner, a senior fellow at FSI and a professor of international relations, is working on a paper about governance in space for the European Space Policy Institute and traveled with the Stanford group. He said few Americans realize how much the United States contributes to making the benefits of space available to all.

“The work of the space operations center and U.S. Strategic Command – in particular its tracking of all objects in space above 10cm and its commitment to notify all states of potential collisions – is one more example of the exceptional capacity of the American military and the contributions that the United States makes to providing global public goods.”

CubeSats: The democratization of space and proliferation of debris

Another space conundrum is the rapid growth of 3-pound satellites called CubeSats. Cal Poly and Stanford University developed specifications for the cube-shaped satellites to help graduate students perform space experiments and exploration.

There currently are some 160 CubeSats in space; another 2,000 to 2,750 are expected to launch by 2020. They are built to remain in orbit for more than 25 year, before falling back to Earth. Since 2005, the nanosatellites have been involved in more than 360,000 close approaches of less than 5 kilometers with other orbiting objects, according to a study by the University of Southampton.

“Last year alone over 100 cubesats were launched into orbit,” Raymond said. “This trend is stressing our ability to have domain awareness.”

 

 

Climate Satellite Launch

Raymond had invited the Stanford group to observe the launch of a NASA satellite that is collecting data to provide the most accurate high-resolution maps of soil moisture ever obtained. The three-year Soil Moisture Active Passive mission will map soil moisture around the world.

Though the launch was scrubbed the day the Stanford group visited, due to high winds, it went off two days later and the climate satellite is currently in orbit.

NASA is running a smart Twitter campaign @NASASMAP, which follows the work of the first Earth-observing satellite designed to collect data on saturated ground for climate scientists, weather forecasters, agricultural and water resource managers, disease and prevention experts, as well as emergency planners and policymakers.

“High-resolution, space-based measurements of soil moisture will give scientists a new capability to observe and predict natural hazards of extreme weather, climate change, floods and droughts, and will help reduce uncertainties in our understanding of Earth’s water, energy and carbon cycles,” Raymond said.

Matthew Daniels was a predoctoral fellow at CISAC last year and is now an engineer at NASA’s Ames Research Center who studies new mission concept for Earth-orbit satellites. He contributed greatly to the closed-door talks.

“I think it’s really important for engineers outside the U.S. government to talk to military and national security leaders about space projects," said Daniels, who helped create NASA-DARPA partnerships on new space projects.

“National security space projects are facing some big decisions in the years ahead,” Daniels said, such as whether to keep building the large, consolidated satellites or move some capabilities toward smaller distributed systems.

“These are decisions that involve a combination of physics, engineering, military choices and national policy," he said. “So I think it’s really important for groups like CISAC to come and have conversations with the military leadership."

To predict how agriculture will be affected by future climate change, scientists often rely on a single crop model – a computer simulation of how a specific crop’s yield responds to temperature changes. By combining 30 such models into a single study, and comparing each model against data from existing experimental wheat fields around the world, a team of researchers including Stanford professor David Lobell have developed a more powerful and accurate way to predict future wheat yields.

In a new analysis published in Nature Climate Change, the team’s results support previous work suggesting that wheat yields around the world are sensitive to rising temperatures. Using the new method of analysis, the team estimates an average six percent future yield loss for every one degree Celsius rise in global mean temperature.

“Combining 30 models gives us a much greater ability to predict future impacts and understand past impacts,” said Lobell. “This is a clear step forward.”

Lobell is professor of environmental earth system science in the School of Earth Science at Stanford and the deputy director of the Center on Food Security and the Environment. He is a senior fellow at the Stanford Woods Institute for the Environment and at the Freeman Spogli Institute for International Studies.

The estimated six percent yield loss for every degree increase is equivalent to about a quarter of the current volume of wheat traded globally in 2013. Yields at some sites, notably those in Mexico, Brazil, India and Sudan, show simulated wheat yield losses of more than 20 percent - in Sudan’s case, more than 50 percent - under a scenario in which global mean temperature rises by two degrees Celsius.

With higher temperatures also comes an increase in the variability of wheat yields, both by location and between years. More fluctuation in wheat yields could mean greater global price volatility for the staple crop.

Approximately 70 percent of the wheat produced today is grown either on irrigated plots or in rainy regions. The research team accounted for this factor by focusing its simulations on multiple regional-specific varieties of wheat that are commonly grown under these conditions.

The new paper includes several suggestions for avoiding some of the predicted yield losses. For example, some varieties of wheat are more heat tolerant than others, and farmers in the places hardest hit by rising temperatures could switch varieties to capitalize on this heat resistance. The effects of rising temperatures could also be managed, in part, by adjusting sowing and harvesting dates, or changing the way fertilizers are applied to crops.

Contact: David Lobell, dlobell@stanford.edu

Rosamond (Roz) Naylor has been named the first holder of the new William Wrigley Professorship in the School of Earth Sciences. Since 2006 Naylor has directed the Center on Food Security and the Environment, within the Freeman Spogli Institute for International Studies and the Stanford Woods Institute for the Environment. She is also associate professor, by courtesy, of Economics at Stanford.

"Professorships are the best way to recognize faculty for their superior leadership and commitment to research, teaching, service to the university and service to humanity," said Pamela Matson, dean of the School of Earth Sciences at Stanford. "Roz epitomizes these qualities - she is incredibly fitting as the inaugural holder of the William Wrigley Professorship."

Walter Falcon, professor (emeritus) of economics at Stanford and a longtime research collaborator of Naylor's, added: “All of Roz’s colleagues are delighted at her selection. She has long been a thought leader on food security issues, she has limitless energy, and she has an extraordinary capacity for bringing scholars together at Stanford and beyond.”

The new William Wrigley Professorship is supported by Mrs. Julie Ann Wrigley, AB '71 (Anthropology) and Ms. Alison Wrigley Rusack, AB '80 (Communication).

Naylor's research focuses on economic and biophysical dimensions of food security, and the environmental impacts of crop and animal production.  She has been involved in many field-level research projects around the world and has published widely on issues related to intensive crop production, aquaculture and livestock systems, biofuels, climate change, food price volatility, and food policy analysis. At Stanford, Naylor teaches courses on the World Food Economy, Human-Environment Interactions, and Sustainable Agriculture. 

Naylor currently serves on the Scientific Advisory Board for the Beijer Institute in Stockholm, is a Science Advisor for United Nation’s Secretary General Ban Ki-Moon’s initiative on Sustainable Development (Sustainable Agriculture section), and trustee of The Nature Conservancy California Chapter. Additionally, she serves on the editorial board of the journals Global Food Security and Journal on Food Security. Naylor received her B.A. in Economics and Environmental Studies from the University of Colorado, her M.Sc. in Economics from the London School of Economics, and her Ph.D. in applied economics from Stanford University.