A Stanford-led team has discovered how to estimate crop yields with more accuracy than ever before with satellites that measure a special form of light emitted by plants. This breakthrough will help scientists study how crops respond to climate change. 

As Earth's population grows toward a projected 9 billion by 2050 and climate change puts growing pressure on the world's agriculture, researchers are turning to technology to help safeguard the global food supply.

A research team, led by Kaiyu Guan, a postdoctoral fellow in Earth system science at Stanford's School of Earth, Energy, & Environmental Sciences, has developed a method to estimate crop yields using satellites that can measure solar-induced fluorescence, a light emitted by growing plants. The team published its results in the journal Global Change Biology.

Scientists have used satellites to collect agricultural data since 1972, when the National Aeronautics and Space Administration (NASA) pioneered the practice of using the color – or "greenness" – of reflected sunlight to map plant cover over the entire globe.

"This was an amazing breakthrough that fundamentally changed the way we view our planet," said Joe Berry, professor of global ecology at the Carnegie Institution for Science and a co-author of the study. "However, these vegetation maps are not ideal predictors of crop productivity. What we need to know is growth rate rather than greenness.

The growth rate can tell researchers what size yield to expect from crops by the end of the growing season. The higher the growth rate of a soybean plant or stalk of corn, for instance, the greater the harvest from a mature plant.

"What we need to measure is flux – the carbon dioxide that is exchanged between plants and the atmosphere – to understand photosynthesis and plant growth," Guan said. "How do you use color to infer flux? That's a big gap."  
 

Solar-induced fluorescence

Recently, researchers at NASA and several European institutes discovered how to measure this flux, called solar-induced fluorescence, from satellites that were originally designed for measuring ozone and other gases in the atmosphere.

A plant uses most of the energy it absorbs from the sun to grow via photosynthesis, and dissipates unused energy as heat. It also passively releases between 1 and 2 percent of the original solar energy absorbed by the plant back into the atmosphere as fluorescent light. Guan's team worked out how to distinguish the tiny flow of specific fluorescence from the abundance of reflected sunlight that also arrives at the satellite.

"I think of it like crumbs falling to the ground as people are eating. It's a very small trail," said co-author David Lobell, associate professor of Earth system science at Stanford's School of Earth, Energy, & Environmental Science. "This glow that plants have seems to be very proportional to how fast they're growing. So the more they're growing, the more photosynthesis they're doing, and the brighter they're fluorescing." Lobell is also deputy director of the Center on Food Security and the Environment.

The research team saw an opportunity to use this new data to close the knowledge gap about crop growth, beginning with a major corn- and soybean-producing region of the U.S. Midwest.

"With the fluorescence breakthrough, we can start to directly measure photosynthesis instead of color," Guan said.

The fact that fluorescence can now be detected from space allows researchers to measure plant growth across much larger areas and over long periods of time, giving a much clearer picture of how yields fluctuate under changing weather conditions.

"One of the really cool things about fluorescence is that it opens up a whole new set of questions that we can ask about vegetation, and often times it's these new measurements that drive the science forward," Lobell said.  
 

Next steps

The research team has already identified a number of potential uses of this approach by agricultural scientists, farmers, crop insurance providers and government agencies concerned with agricultural productivity.

If there is a day when the plant is really stressed, the fluorescence will drop significantly, Lobell said. Capturing these short-term responses to environmental changes will help scientists understand what factors plants are responding to on the daily time scale.

"That helps us, for example, figure out what we need to worry about in terms of stresses that crops are responding to," Lobell said. "What should we really be focusing on in terms of the next generation of cropping systems? What should they be able to withstand that the current crops can't withstand?"

At this early stage, fluorescence measurements are relatively low-resolution (a single measurement covers about 50 square kilometers) and because it is only collected once per day, cloudy skies can interfere with the fluorescence signal. For now, researchers have to supplement the data with other information and with on-the-ground observations to refine the measurements.

"Now that we have demonstrated the concept, we hope to soon be orbiting some new satellites specifically designed to make fluorescence measurements with better spatial and temporal resolution," Berry said.

The team plans to continue its research on U.S. crop yields while expanding measurements to other parts of the world.

"In the future, we hope to directly use this technology to monitor global food production, for example in China or Brazil, or even in your backyard," Guan said.

David Lobell is also deputy director of the Center on Food Security and the Environment, and William Wrigley Senior Fellow at the Freeman Spogli Institute for International Studies and the Stanford Woods Institute for the Environment. The study was also co-authored by Youngguan Zhang of the International Institute for Earth System Sciences at Nanjing University and the German Research Center for Geosciences (GFZ); Joanna Joiner of the NASA Goddard Space Flight Center Laboratory for Atmospheric Chemistry and Dynamics; Luis Guanter of GFZ; and Grayson Badgley of Stanford's Department of Earth System Science and Department of Global Ecology at the Carnegie Institution for Science.

CONTACTS:   
 

p> Kaiyu Guan, Stanford School of Earth, Energy, & Environmental Sciences: kaiyug@stanford.edu

Laura Seaman, Stanford's Center on Food Security and the Environment: lseaman@stanford.edu, (650) 723-4920

Read the original post on Medium.com:

A Global Perspective on Food Policy

I applaud Mark Bittman, Michael Pollan, Ricardo Salvador, and Olivier de Schutter for advocating the introduction of a national food policy in the U.S. Greater emphasis in our current farm legislation on nutrition, health, equity, and the environment is clearly warranted and long overdue. As the authors note, Americans’ access to adequate nutrition at all income levels affects educational and health outcomes for the nation as a whole. Poor nutrition thus plays a role in determining the level and distribution of economic and social wellbeing in the U.S, now and in the future. It is surprising that no one within the large circle of Presidential hopefuls has raised the topic of food, not just agriculture, as a major political issue for the 2016 election.

The U.S. is not unique. Virtually every country with an agrarian base has, at some point in history, introduced agricultural policies that support farmers and provide incentives for them to produce major commodities. At the time, governments have been able to justify these policies on several grounds: national security (avoiding excess dependence on foreign nations for food), economic growth (using agricultural surpluses as an engine of economic growth), and social stability (keeping its population well-fed to avoid social unrest). Once agricultural policies are implemented, they typically give rise to institutions and vested political interests that perpetuate a supply-side orientation to food and agriculture. In the U.S., the political institutions that govern food and agriculture have their roots in historical political precedents that date back to the 1860s, and later to the 1930s when the New Deal was promulgated. Farm interests have been entrenched in the U.S. political system for quite some time, and they cannot be easily removed.

There is a general rule for successful policies: Align incentives with objectives. A corollary to this principle is that objectives change over the course of economic development. For the United States in earlier eras, and for many developing economies in recent decades, meeting basic calorie needs has been the first order of business. This objective has been largely achieved through public investments in infrastructure (irrigation, roads), research and development, commodity support programs, incentives for private agribusiness development, and other supply-side measures.

With successful agricultural growth and rising incomes, many countries face a new set of food and nutrition challenges: eliminating “hidden hunger” (deficiencies in iron, vitamin A, calcium, zinc and other micronutrients), and abating the steady rise in obesity that results from a transition to diets rich in energy-dense carbohydrates, fats, and sugar. Hidden hunger affects some three billion people worldwide. It is prevalent among low-income households in almost all countries, impairs cognitive and physical development (especially among infants up to two years of age) and thus limits a nation’s educational and economic potential. Meanwhile, rates of obesity now surpass rates of energy-deficient hunger throughout the world, even in developing nations.

The objectives of food and agricultural policies in virtually all countries need to shift, on balance, from promoting staple food supplies to enhancing nutrition. I am not suggesting an abandonment of agriculture, but rather an enrichment of agriculture with more crop diversity to support the nutritional needs of all people. If improved nutrition is the objective, what are the correct incentives? Proper incentives will differ among countries, but will inevitably require a fundamental change in institutional structure. With a shift from supply- to demand orientation, there needs to be a transition from Ministries of Agriculture to Ministries of Food. After all, the main goals of a Ministry of Agriculture are to increase the volume of agricultural production and to improve economic growth in the agricultural sector. The main goal of a Ministry of Food, by contrast, is to enhance the nutrition and food security of the entire population.

Bittman, Pollan, Salvador, and de Schutter emphasize that replacing the U.S. Department of Agriculture (USDA) with a “U.S. Department of Food, Health, and Wellbeing” would be difficult at best. It would require unprecedented political will and cooperation among parties. The same can be said for institutional change in agricultural ministries throughout the world. Regardless of the challenges, however, nothing will change until the conversation surrounding food policies, politics, and institutions takes a major turn.

FSE director Roz Naylor will give the opening plenary lecture at the 2nd International Conference on Global Food Security on October 12, 2015 at Cornell University. Naylor is William Wrigley Professor in Earth System Science, and senior fellow at the Stanford Woods Institute for the Environment and the Freeman Spogli Institute for International Studies at Stanford. 

In addition to Naylor's lecture on "Food security in a commodity-driven world," several FSE researchers will give talks and poster sessions during the five-day conference, including professors Marshall Burke and Eric Lambin, visiting scholar Jennifer Burney, postdoctoral scholar Meha Jain, and doctoral candidate Elsa Ordway.

It is the end of summer and time for another Iowa report. My wife and I own a medium-sized farm in East Central Iowa that produces corn and soybeans, and beef from a cow/calf herd. My day job is as Professor of International Agricultural Policy at Stanford University, typically working on hunger problems in Asia. The summer keeps me in direct contact with rural life in the Midwest. 

My previous Iowa postings have been dominated by weather—severe drought in 2012, massive flooding in 2013, and tornados in 2014. In a different way, weather features again this year. We had 10 inches of rain and a hailstorm during the first 10 days following my June return from California. But after that episode, the weather has been nearly perfect for our locale. Things could still go wrong—a typical farmer comment—but at the moment, we are looking at near-record yields on our farm. My guess is 210 bushels per acre for corn, and 65 bushels per acre for soybeans, both about 10% higher than for recent years. 

Crops throughout the region look generally good, and the following couplet is a standard feature of local conversations: 

“Don’t the crops look great?”  
“Yeah, but they aren’t worth nothing.”  

A sharp run-up in corn prices the last two weeks of June—from $3.50 to $4.40 per bushel—left farmers hopeful with what would turn out to be faulty expectations. As many waited for further price increases before selling, the good weather and the economic slow down in China caused corn prices to tumble. By Sept 1, prices were back at $3.50. These low prices left many farmers with dashed expectations, substantial amounts of 2014 corn in farm storage, and the prospects of a large upcoming October harvest. Nor will crop insurance help very much. The combination of yields and prices this year will leave most farmers just outside the range that would qualify them for 75%-revenue-protection payments. 

Few outside the farming community realize that marketing decisions are often more important than production in defining a successful farm year. Few also appreciate the differential impact on Iowa’s general prosperity from the $7 corn that prevailed in 2012-13, versus the current $3.50. 
 

Gloom is not the only thing that has been rolling across the landscape. Two parades really had to be seen to be appreciated. Each year since 1973, the state has hosted a bike ride across Iowa called Ragbrai. It is a weeklong activity that starts at the Missouri River to the west, and ends 500 miles to the east at the Mississippi River. It has grown into a massive affair that attracts some 15,000 riders.  

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Photo Credit: C. Benz 

This year’s ride was special, at least for us. This mass of rolling humanity came within two miles of our farm, and it included a sizeable number of Stanford faculty and students (including my boss, pictured below) who, among others, made mini-detours to visit us. What were most interesting to my wife and me were the impressions expressed both by the bikers and the local hosts. 

The riders marveled at the rolling topography of Iowa; the vast expanses of corn and soybeans; the welcoming hospitality of Iowans; the infinite ways pork could be served on a stick; and the best sweet corn in the world! The locals were bemused that so many sane people of all shapes and sizes would voluntarily ride 500 miles in the heat and rain; amazed by the short-term chaos that 15,000 cyclists could cause in small rural communities that were attempting to move machinery and feed cattle; and pleased by the magnitude of the expenditures. The latter was deftly described by a neighbor as “our own economic stimulus package,” and more pointedly summarized by a local headline, “Circus, Economic Windfall, or Occupying Army?” 
 

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 Photo Credit: R. Naylor

Politicians formed the second parade (charade?) that has been rolling across the state. Iowa—with the dubious honor of having the first primary/caucus—is a genuinely purple state. It voted for President Barack Obama in 2012 and for Senator Joni Ernst in 2014. Iowans pride themselves on being able to pick winners and on being stubbornly independent. The prevailing general mood at the moment, however, is some combination of confusion and disgust. Donald Trump draws the most comments. And while he leads the polls, I have yet to hear anyone (literally) this summer say that he or she favored him. Time will tell what Iowans really believe.

Nowhere was the comedy and chaos more vivid than at the recently completed Iowa State Fair. Some 15 presidential candidates showed up. Most of them spoke at the fair’s “Soapbox Corner” before conspicuously casting their kernel-of-corn vote at the straw (corn?) ballot table. They also had the obligatory pictures taken with the life-sized cow sculpted in butter, the fair’s largest bull (there must be some symbolism here), and the fair’s heaviest pig. The latter was a 500-pound specimen named Mac. (I was disappointed that an earlier winner, my namesake “Wally”, was not in the competition.) And to no one’s surprise, all candidates thought that corn-based ethanol was a really good idea. Most of them even expressed favor with the fair’s latest cuisine contribution—the Bomb—brisket, wrapped in bacon, served on a stick! 
 

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Photo Credit: R. Naylor 

Readers of previous reports will be pleased to know that the 1868 Waubeek general store and restaurant still serves as the morning gathering place. It has changed hands, but continues its long tradition of watery coffee and stale pastry. (By request, I have included pictures; I am California hatless, plus a shot of the outside.) Besides prices, bikers, and politicians, three new topics of conversation have cropped up: water, cover crops, and weeds. All three are environmental issues that are distinctly operational. They also remind me of just how much information is exchanged around tables such as this one, though on any given morning that conclusion is not always obvious!

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By far the most controversial topic of the summer has been water. (And to be clear, the issue is about water quality and the nutrients carried in the water, not about water supplies or allocations.) Many farmers realize that nutrient runoff from livestock operations and from fertilizer applied to fields is a very serious problem; most of them are also loathsome about EPA efforts to redefine and regulate what constitutes water flows in the U. S. 

During the last week in August, the EPA announced new clean-water rules that would give the agency new jurisdiction over bodies of water (and land), including many in agriculture, which were previously unregulated. But it remains to be seen which bodies of waters would be covered, and which specific agricultural situations that would be exempted from the rules. Six states have sued the EPA, and the question of when or if the rules will be implemented is now caught up in the courts. The Farm Bureau has declared an all-out offensive against the rules, and farm publications have added further fuel to the fire. To complicate matters even more, the Des Moines Water Works has brought suit against three counties upstream of its water plant that would require farmers to change practices and/or make investments to reduce nutrient flows (particularly nitrates) into the Raccoon River. 

Most scientists and many farmers believe that nutrient runoff constitutes the largest remaining environmental problem facing agriculture. Thus the fight, in many ways, is less about the problem, and more about philosophy. Most farmers prefer voluntary solutions arranged with the state or the USDA. They typically dislike mandatory rules of any sort, and they are particularly concerned that regulations might be of the one-size-fits-all character. The discourse is inflamed by uncertainty: the EPA has yet to write all of the regulations, and farmers simply do not know what to expect. In the absence of information, they fear the worst. Everyone I talked with had a relevant question. Will we need to get a permit to spread manure? How will drainage tiles that empty into or near creeks be handled? Will we need to file a nitrogen plan for every farm that specifies amounts and timing of fertilizer applications? On our farm, for example, we have a flowing creek that traverses a large permanent pasture. The creek provides water for the cowherd, which has direct access to it. What, if anything, will need to be changed in that arrangement? All of us wonder about the flexibility in timing and scope that will be accorded farmers who may be faced with large corrective investments. Many also fear that the regulators will know little about agricultural practices. In short, what waters are to be regulated, for what purposes, and with what instruments are issues still to be resolved? At the moment, there is considerable heat, but very little light about the answers. 

Virtually all Iowa farmers have transitioned to minimum tillage systems; plowing has become a field operation of the past. This change in tillage also creates new cropping opportunities. 
 

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Photo Credit: USDA

Five years ago, there was virtually no talk about or use of “cover crops.” These crops are sown in residues immediately after corn or soybean harvest. Certain of them survive the winter, but others do not. Radishes (shades of the English agricultural revolution, circa 1700!) produce long roots that punch holes in clay layers of the soil, thereby assisting drainage. They can also be grazed. Small grains are also being seeded, which add to add organic matter and can sometimes be chopped as forage for dairy or beef operations. 
 

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Photo Credit: Mühlhausen/landpixel

Cover crops are clearly still a work in progress, but they provide an interesting example of active on-farm experimentation. Best solutions seem to vary from farm to farm—from no cover, to radishes, to triticale—and seem importantly dependent on particular crop-livestock combinations. Discussions about the use of triticale—a cross between rye and either bread wheat or durum—were of particular interest to me. I worked with Norman Borlaug at the International Wheat and Maize Improvement Center in Mexico during the 1980s to develop modern varieties of this crop, but it has been slow to find appropriate niches in cropping systems around the world. In the 1980s, I never even contemplated that Iowa might be such a place. 

Several forces drive the new concern about weeds. Falling crop prices have squeezed profit margins severely, causing farmers to look seriously at each cost component. For the first time, I have heard farmers question new seed varieties (virtually all GMOs), both because of their cost and their effectiveness. They increasingly wonder if the $200 seed-cost-per-acre for corn is justified. The current year, with its excellent growing season, meant there was less need for certain stacked traits such as drought resistance. Moreover, the year was equally good for weeds, whose resistance to major herbicides like Roundup seemed to be spreading. 

Water hemp, in particular, gave soybean farmers grief, and is causing them to rethink seed-weed strategies. They worry about the consequences from applying new combination-herbicides (some still under various reviews) that attack both grasses and broad-leafed weeds. They are particularly concerned that spraying some of the new products will also destroy the grasses in waterways left specifically to prevent water erosion. 

My conjecture is that most farmers will still use the specialized seeds next year. I predict, however, that they will also be searching more carefully for lower-cost ways—both via seeds and herbicides—to manage weeds. The growing weed resistance problem has begun to scare them—a recent Greenwire Poll indicates that 90% are worried—and has belatedly driven home the difficulties that arise from overuse of only one or two herbicides. 
 

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No Iowa report is complete without some cattle commentary. 

My father was a cattle feeder, and some of those “cattle genes” carried forward a generation. I grew up knowing a lot about purebreds, about corn and soybean-meal feed rations, and about 2-pound-per-day rates of gain that produced 1100-pound animals for sale. Fast forward to 2015. When I look around, virtually all cattle have been crossbred for size and vigor (though in the market they may still be advertised as Angus!). Soybean meal has dropped completely out of the rations being fed in our county, having been replaced by the high-protein distillers grain, the by-product of making corn sweeteners and ethanol. Rates of gain are now 3.25 pounds per day, and finished animals are sold at 1500 pounds. What has not changed, however, is the riskiness of the enterprise. Even with cheap corn, buying 700 pound feeders for $2.25 per pound, and selling 1500 pound steers at $1.45 per pound has not been a great way to get rich in 2015! 

My final impression of the summer is a memorable one: rolling down the Mississippi River on a paddle boat, celebrating my wife’s and my birthdays with good friends, viewing a glorious sunset, and eating world-class prime rib. Now that’s the way to get ready for a new year of Stanford classes.

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Photo credit: flickr/Lance and Erin