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

It is August again, and my wife and I are back on our farm. We have a medium-sized operation in east-central Iowa that produces soybeans, alfalfa, and corn, and that also supports an Angus cow-calf herd. These summers are supposed to be quiet, relaxing times away from the bustle of Stanford University. However, the days here seem anything but tranquil.  Two years ago my almanac report dealt with one of the worst droughts in Iowa’s history; last year the focus was on flooding and the wettest planting season on record.  I suppose it is only fair that wind should be the main topic this year. For our rural neighborhood, only problems, not answers, seemed to have been blowin’ in it.

Two evenings after our arrival from California, we were sent scurrying to our doubly reinforced “safe” room in the basement. Warning sirens blared, all television stations went on emergency broadcasting, and the spontaneous neighborhood phone line magically got activated.  Everything was for real, and all hell broke loose.  Eighty-five m.p.h. flat-line winds, grape-sized hail, and buckets of rain.  The power went out, and our safe-room conversation centered on whether or not to start our small generator—not for lights, but to assure that the sump pump continued working!

For a swath three miles wide and 15 miles long the tornado danced—jumping here and skipping there. Some farms were spared; others were pretty much demolished.  We were moderately lucky.  We lost an infinite number of branches and our largest oak tree—a four-foot diameter, 70-foot tall specimen. Entire trees were twisted off like toothpicks. Shingles from roofs went missing, as did white fencing. But we were among the lucky ones—no major buildings were lost and no people or animals were injured.

Two farms over, the five-bin corn storage unit took a direct hit. Two 120-foot tall elevators that lift grain to the top (called legs, although the anatomy analogy makes no sense) lay in a crumpled mess.  These bins hold some 240,000 bushels of corn and there are massive amounts of steel involved. The broken legs looked, at 120X scale, like an angry third-grader had deliberately slammed his Lego creations onto the ground. The difference is that the repairs, labor costs, and replacement parts for the bins and legs total $750,000. Farmers soon began re-reading their insurance policies about acts of God, depreciation allowances, and the rules for full versus partial replacement.

The morning following the storm, an eerie calm was soon replaced by a different form of energy.  Other work seemed to stop in a region larger than the storm-hit area.  No one arranged it, but neighbors suddenly appeared at each other’s farmsteads with tractors, loaders, pickups, and chainsaws. Small mountains of brush, trees, and building parts began to emerge, to be burned at a later date—no doubt with generous burn permits being granted by the county.

Morning coffee conversations at the old limestone café have been fairly somber affairs this summer. (The general store has changed hands, but unfortunately, the watery coffee and the stale cookies have not improved.)  Farmer faces were grim even before the storm, mainly because of what has happened to corn prices.  In August 2012, local farmers were being offered $7.65/bushel [56 pounds] of corn; in August 2013, the price was $6.20/bushel, and on August 20, 2014, the price was $3.60/bushel.  Suddenly the rush to buy new pick-ups and large harvesting equipment slowed drastically.  John Deere, the major farm-equipment manufacturer, has already laid off hundreds of workers at various Iowa sites.

Orders have not stopped entirely, however, largely because of crop insurance.  Virtually all farmers have either 75% or 85% revenue protection. If a combination of yield and/or price declines cause revenue to be less than 75% (85%) of normal, farmers are reimbursed by private insurance companies. The premiums for this revenue-protection insurance are heavily subsidized by the federal farm program. Taxpayers underwrite more than 60% of the total insurance premiums, which last year resulted in subsidies to farmers of about $9 billion. Historic yields are used in the insurance contract, and this year the early insurance lock-in price was $4.62/bushel. That price looked low in the spring, but now looks extremely favorable.  Unfortunately, many of my neighbors chose the “wrong” insurance option. They were able to purchase 75% revenue protection for about $4.50/acre, whereas the 85% protection cost about $19/acre. For a farmer with 1500 acres of corn, the difference in insurance premiums was more than $20,000.  But given declining corn prices, the cheaper insurance option for 2014 will surely turn out to be the most costly choice at the end of the season.  Farm decision making these days is mostly about risk management, and that is why crop insurance was such a big element in the new farm program.

Perhaps the hottest topic of conversation at morning coffee centered again on wind, but not of the tornado variety.  It turns out that “the wind comes sweeping down the plain” in Iowa as well as in Oklahoma. Iowa is the third-largest producer of wind energy, and wind power supplies a hefty 27 percent of Iowa’s total energy use. So why are my neighbors upset?  It is something called the Rock Island Clean Line (RICL), and a bit of history is in order.
 

Image

The old Rock Island Line was a rail company—made more famous than it really deserved to be by Johnny Cash. The line ran five miles south of our farm, and yes, it was a “mighty fine line” that did carry cows, sheep, pigs, and mules. But it went bankrupt in 1975. The Rock Island Clean Line originally planned to use some of the old right-of- way for quite a different purpose—transporting wind-generated power from northwest Iowa on huge towers, with cables carrying direct-current electricity into the Illinois market to the east. It turned out, however, that too much of the old right of way went through urban areas and was unsuitable, so RICL will purchase some 500 linear miles of farmland right-of-way for the towers.

Farmers are rationally and irrationally furious. (The line was originally scheduled to go across the full length of our farm, so we have been directly involved in the discussions.) It has been extremely difficult to get straight answers about the line, with the company and the Iowa Utilities Board doing a dance in which neither wants to lead. There is no doubt that these140-foot towers create an ugly line of sight; they complicate farming with large machinery; and they seriously impact adjoining fields during the construction phase.  The company believes that it is offering generous one-time compensation—the equivalent of $10,000 to $15,000 per acre in most cases—but it then retains easement rights to this land forever, including the authority to sell the rights. Farmers are livid—they basically do not want the line from which they will receive no benefits—but they are being faced with potential eminent domain proceedings if they do not agree to sell. All sorts of NIMBY arguments are being brought forward, from the “government can’t tell us what to do,” to “the lines will emit electrical forces that will cause health effects,” to “they are not paying enough,” to “why should we use good Iowa soil to transport electricity rather than to produce food for the hungry?” The last of these comments is the one I have heard most often. When I inquired as to whether the coffee group was also against ethanol—since 40% of Iowa corn is going into gas tanks rather than hungry mouths—I was NOT regarded as a helpful contributor to the conversation!

In the end, I suspect that the Rock Island Clean Line will prevail, and that farmers and their families will learn to accommodate the power towers. Many farmers will grumble publically, but smile privately en route to their banks with rather large checks. However, both the process and outcome have stirred up deep passions about who controls the land.

Not all farmers are sad this summer, and the winds of good fortune have blown in the direction of cattle feeders.  The structure of cattle feeding in Iowa has changed enormously in recent times. I am the son of a mid-sized feeder, and spent a good deal of my youth working with cattle and driving cattle trucks.  Most east Iowa farms these days are strictly grain farms, in large part to free farmers from the 24/7 burden of animal care. My neighbor talks about his corn-Texas crop rotation—growing corn in the summer and going to Texas for the winter.
 

Two black angus calves.

There are only two large cattle feeding operations left in Linn County where I live, and both are within four miles of our farm.  I was invited by one of the owners to attend a cattle auction with him, and to see for myself just how much things had changed.  He owns his own 18-wheeler, and almost every week takes a load (36 head) of prime beef to the auction.  Cattle are taken to the auction pens the night before the sale and are taken off of feed and water. These steers weigh between 1400 and 1500 pounds, and buyers want assurance that the animals have not gorged on feed and water just before crossing the scales. The cattle are weighed early the morning of the sale, and weights are then flashed on a scoreboard as the animals enter the sale ring.

There is still an amazing amount of ritual at a cattle auction—I had forgotten just how much! Prime steers are typically sold in lots of 12 animals. They enter the ring from one side, and are moved about by a “ring man” so that buyers can get a good view of them. Part of the ritual is where various people sit.  A small group of farmers/sellers sits in one section, typically bantering about whom has the best cattle and whose will “top the sale.” The buyers sit near the top of the bleachers, in the same spot each week, but separated from each other.  (They would not want a casual conversation between them to be construed as collusion!) There is also the auctioneer with his chatter, mile-a-minute delivery, and selling antics. The sale itself happens very rapidly. There are typically two to four bidders for a particular lot of animals, and the bids go back and forth among them at lightning speed. The bidding cues are highly personalized—one buyer uses the flip of his tally sheet, another raises his index finger, and one simply arches his eyebrow.  In less than 45 seconds, the winning buyer has spent $27,000! And then the next lot appears.  Cattle from this sale went to packing plants in Wisconsin, Iowa, Nebraska, and Illinois.

On the 25-mile ride home, my neighbor talked about how pleased he was with what had happened. His steers had gained well and had topped the market in terms of price at $1.57 per pound. He said that corn was very cheap, as was distiller’s grain—the high protein by-product from making corn-based ethanol—which is now an important part of cattle feeding rations. There would be a healthy profit from this load of steers that had grossed about $80,000. 

But then he turned somber.  What should he do about next year? The price of 600-pound calves that he would put into the feedlot for feeding and sale next year are selling at the astronomical price of $2.50 per pound and even higher.  Perhaps next year, he said, was the year to stay out of the ring and go to Texas or Arizona for the winter. Risk had reared its ugly head once again. But my neighbor is first and foremost a cattle feeder, with a cattle feeder’s mindset toward risk. My conjecture is that he will somehow find a rationale for purchasing replacement calves, and that he will do everything all over again next year.                                                 

“The answer my friend, is blowin’ in the wind,

The answer is blowin’ in the wind.”

(Bob Dylan, 1962)

Corn yields in the central United States have become more sensitive to drought conditions in the past two decades, according to a new study in the journal Science from a team led FSE associate director David Lobell.

"The Corn Belt is phenomenally productive," Lobell said, referring to the region of Midwestern states where much of the country's corn is grown. "But in the past two decades we saw very small yield gains in non-irrigated corn under the hottest conditions. This suggests farmers may be pushing the limits of what's possible under these conditions."

He predicted that at current levels of temperature sensitivity, crops could lose 15 percent of their yield within 50 years, or as much as 30 percent if crops continue the trend of becoming more sensitive over time.

As Lobell explained, the quest to maximize crop yields has been a driving force behind agricultural research as the world's population grows and climate change puts pressure on global food production. One big challenge for climate science is whether crops can adapt to climate change by becoming less sensitive to hotter and drier weather.

"The data clearly indicate that drought stress for corn and soy comes partly from low rain, but even more so from hot and dry air. Plants have to trade water to get carbon from the air to grow, and the terms of that trade become much less favorable when it's hot," said Lobell, also the lead author for a chapter in the U.N. Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report, which details a consensus view on the current state and fate of the world's climate.

Rain, temperature, humidity

The United States produces 40 percent of the world's corn, mostly in Iowa, Illinois, and Indiana. As more than 80 percent of U.S. agricultural land relies on natural rainfall rather than irrigation, corn farmers in these regions depend on precipitation, air temperature and humidity for optimal plant growth.

According to the research, over the last few decades, corn in the United States has been modified with new traits, like more effective roots that better access water and built-in pest resistance to protect against soil insects. These traits allow farmers to plant seeds closer together in a field, and have helped farmers steadily raise yields in typical years.

But in drought conditions, densely planted corn can suffer higher stress and produce lower yields. In contrast, soybeans have not been planted more densely in recent decades and show no signs of increased sensitivity to drought, the report noted.

Drought conditions are expected to become even more challenging as temperatures continue to rise throughout the 21st century, the researchers said.

Lobell said, "Recent yield progress is overall a good news story. But because farm yields are improving fastest in favorable weather, the stakes for having such weather are rising. In other words, the negative impacts of hot and dry weather are rising at the same time that climate change is expected to bring more such weather."

Extensive data

Lobell's team examined an unprecedented amount of detailed field data from more than 1 million USDA crop insurance records between 1995 and 2012.

"The idea was pretty simple," he said. "We determined which conditions really matter for corn and soy yields, and then tracked how farmers were doing at different levels of these conditions over time. But to do that well, you really need a lot of data, and this dataset was a beauty."

Lobell said he hopes that the research can help inform researchers and policymakers so they can make better decisions.

"I think it's exciting that data like this now exist to see what's actually happening in fields. By taking advantage of this data, we can learn a lot fairly quickly," he said. "Of course, our hope is to improve the situation. But these results challenge the idea that U.S. agriculture will just easily adapt to climate changes because we invest a lot and are really high-tech."

Lobell and colleagues are also looking at ways crops may perform better under increasingly hot conditions. "But I wouldn't expect any miracles," he said. "It will take targeted efforts, and even then gains could be modest. There's only so much a plant can do when it is hot and dry."

This animation shows the increasing sensitivity of U.S. corn to drought over time. Animation by Carlo Di Bonito.

Growing agave and other carefully chosen plants amid photovoltaic panels could allow solar farms not only to collect sunlight for electricity but also to produce crops for biofuels, according to new computer models by Stanford scientists.

This colocation approach could prove especially useful in sunny, arid regions such as the southwestern United States where water is scarce, said Sujith Ravi, who is conducting postdoctoral research with professors David Lobell and Chris Field, both on faculty in environmental Earth system science and senior fellows at the Stanford Woods Institute for the Environment. David Lobell is associate director and Chris Field is a core faculty affiliate at the Center on Food Security and the Environment.

“Colocated solar-biofuel systems could be a novel strategy for generating two forms of energy from uncultivable lands: electricity from solar infrastructure and easily transportable liquid fuel from biofuel cultivation,” said Ravi, lead author of a new study published in a recent issue of the journal Environmental Science & Technology that details the idea.

Photovoltaic (PV) solar farms run on sunlight, but water is required to remove dust and dirt from the panels to ensure they operate at maximum efficiency. Water is also used to dampen the ground to prevent the buildup and spread of dust. Crops planted beneath the solar panels would capture the runoff water used for cleaning the PV panels, thus helping to optimize the land. The plants’ roots would also help anchor the soil, and their foliage would help reduce the ability of wind to kick up dust.

Computer simulations of a hypothetical colocation solar farm in California’s San Bernardino County by Ravi and colleagues suggest that these two factors together could lead to a reduction in the overall amount of water solar farms need to operate. "It could be a win-win situation," Ravi said. “Water is already limited in many areas and could be a major constraint in the future. This approach could allow us to produce energy and agriculture with the same water.”

But which crops to use? Many solar farms operate in sunny but arid regions that are very not hospitable to most food crops. But there is one valuable plant that thrives at high temperatures and in poor soil: agave. Native to North and South America, the prickly plant can be used to produce liquid ethanol, a biofuel that can be mixed with gasoline or used to power ethanol vehicles. "Unlike corn or other grains, most of the agave plant can be converted to ethanol," Ravi said.

The team plans to test the colocation approach around the world to determine the ideal plants to use and to gather realistic estimates for crop yield and economic incentives.

“Sujith’s work is a great example of how thinking beyond a single challenge like water or food or energy sometimes leads to creative solutions,” said Lobell, who is a coauthor on the new study. “Of course, creative solutions don’t always work in the real world, but this one at least seems worthy of much more exploration.”

Ker Than is associate director of communications for the School of Earth Sciences.

Contact: Sujith Ravi, 703-581-8186, sujith@stanford.edu; Ker Than, 646-673-4558, kerthan@stanford.edu 

FSE’s David Lobell finds that an increase of more than two degrees Celsius in average global temperature is likely to cause yields of wheat, rice and maize to fall throughout the 21st century. Early adaptation could increase projected yields by up to 15 percent.

If global temperatures continue to rise, the amount of crops farmers can harvest will sharply decline during the next 100 years.

Stanford professor David Lobell and an international team of climate scientists modeled future crop yields under several global climate scenarios throughout the 21^st century. They found that if average global temperatures rise by more than two degrees Celsius, farmers are likely to get less wheat, rice and maize out of each plot of land. Yields are expected to fall by an average of 4.9 percent for every one degree Celsius rise in average temperature. Year-to-year variability of harvests is also expected to rise, as drought and flooding become more frequent. Crop yield losses will speed up throughout the century, with declines in yield beginning around 2030 and with the fastest drop happening in the second half of the century.

Lobell, an associate professor of Environmental Earth System Science and the associate director of the Center on Food Security and the Environment at Stanford, reviewed over 1,700 published studies with a team of climate scientists from the United States, United Kingdom and Australia. The team found that if farmers adapt to climate change within the next few years, they have a better chance of avoiding or even reversing the predicted decline of wheat and rice yields in some regions. Agricultural adaptation strategies like irrigating fields and developing new crop breeds could increase projected yields between 7 percent and 15 percent.

The new study also highlights the need for better data on the potential future impacts of other factors that affect crop yields, like the prevalence of pests and plant diseases, and the availability of water supply. A full version of the study can be found online at Nature Climate Change.

By Terry Nagel, Stanford Woods Institute for the Environment

David Lobell, an associate professor of environmental Earth system science and a senior fellow at the Freeman Spogli Institute for International Studies, has been named a 2013 MacArthur Fellow and one of Foreign Policy Magazine's 100 Leading Global Thinkers of 2013.

MacArthur "Genius Grant"

Lobell, who is also the associate director of FSI’s Center on Food Security and the Environment, was cited "for unearthing richly informative, but often underutilized sources of data to investigate the impact of climate change on crop production and global food security." He received his doctorate degree from Stanford in 2005 and was appointed to the faculty in 2009.

A pioneer of the emerging field of crop informatics, Lobell is revolutionizing the understanding of the environmental factors controlling crop yields, with a particular emphasis on adaptation to climate change.

His work provides decision makers, for the first time, with critical information about how to adapt agricultural development to climate change.

"I was completely surprised by this recognition, but am really excited by the opportunity it presents," said Lobell, who is also a senior fellow at Stanford Woods Institute for the Environment. "To have the MacArthur Foundation recognize the value of taking new approaches and the importance of the topics of hunger and food production is deeply gratifying."

Lobell's research focuses on identifying opportunities to increase yields of crops including wheat and corn in major agricultural regions, with projects currently underway in Africa, South Asia, Mexico and the United States. 

"I'm interested in how to feed the world and protect the environment at the same time," he said. "While there are many theories about how to do that, my work tries to test these theories, often using data that were collected for completely different reasons."

The citation emphasized Lobell's work on understanding the risks of climate change, and options for adaptation. "Climate change is one of the reasons for concern about feeding people in the future, but it's not insurmountable if good decisions are made," he said. 

When asked how he would use the funding, Lobell said he would not rush the decision. He said that some of the award would likely relieve him of writing grant proposals. In addition, he said he would consider using some toward more travel.

"A lot of my better ideas in the past have started with travel and interactions with international collaborations," he said.  "And there's always a tradeoff between my work travel and family.  I now might take my wife and young sons with me on some extended trips."

Foreign Policy's Leading Global Thinkers

In December, Foreign Policy named Lobell one of the 100 Leading Global Thinkers of 2013. The recognition comes for his work "helping farmers feed the world" in a changing climate. Lobell is joined on the magazine's list by fellow researchers working on climate issues, along with prominent public figures like German Chancellor Angela Merkel, U.S. Secretary of State John Kerry, and Pope Francis.

Widely sought throughout the world to provide expert advice, Lobell is a lead author for the Intergovernmental Panel on Climate Change Fifth Assessment Report chapter on food security, to be published in 2014. The IPCC, which won the Nobel Prize in 2007, also made Foreign Policy's 2013 Leading Global Thinkers list alongside Lobell, "for showing that humanity is on the brink of catastrophe" if climate change is not addressed quickly and aggressively.

Lobell studied applied mathematics at Brown University, and before receiving his bachelor's degree in 2000, he spent the summer of 1999 as a research intern at Stanford, developing remote sensing algorithms. He then pursued graduate studies at Stanford, receiving his doctorate in geological and environmental sciences in 2005.

He was a postdoctoral fellow at Lawrence Livermore National Laboratory from 2005-2007, and returned to Stanford as a senior research scholar in the Program on Food Security and the Environment in 2008-2009.  He accepted an appointment as assistant professor in the Stanford School of Earth Sciences in 2009. 

In addition to his research, Lobell teaches several courses open to both undergraduates and graduate students, including "Feeding Nine Billion," "Climate and Agriculture," and "Global Land Use to 2050," as well as modeling and statistical methods classes.

Lobell received a NASA New Investigator Program Award for 2008-2011. He received the James B. Macelwane Medal from the American Geophysical Union in 2010, awarded for significant contributions to the geophysical sciences by an outstanding scientist under the age of 36.

Nancy Peterson is the chief communications officer for Stanford's School of Earth Sciences. Laura Seaman, communications manager for the Center on Food Security and the Environment, contributed to this article.