Agriculture
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As climate change leads to increased frequency and severity of drought in many agricultural regions, a prominent adaptation goal is to reduce the drought sensitivity of crop yields. Yet many of the sources of average yield gains are more effective in good weather, leading to heightened drought sensitivity. Here we consider two empirical strategies for detecting changes in drought sensitivity and apply them to maize in the United States, a crop that has experienced myriad management changes including recent adoption of drought-tolerant varieties. We show that a strategy that utilizes weather-driven temporal variations in drought exposure is inconclusive because of the infrequent occurrence of substantial drought. In contrast, a strategy that exploits within-county spatial variability in drought exposure, driven primarily by differences in soil water storage capacity, reveals robust trends over time. Yield sensitivity to soil water storage increased by 55% on average across the US Corn Belt since 1999, with larger increases in drier states. Although yields have been increasing under all conditions, the cost of drought relative to good weather has also risen. These results highlight the difficulty of simultaneously raising average yields and lowering drought sensitivity.

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Nature Food
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David Lobell
Stefania Di Tommaso
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High resolution satellite imagery and modern machine learning methods hold the potential to fill existing data gaps in where crops are grown around the world at a sub-field level. However, high resolution crop type maps have remained challenging to create in developing regions due to a lack of ground truth labels for model development. In this work, we explore the use of crowdsourced data, Sentinel-2 and DigitalGlobe imagery, and convolutional neural networks (CNNs) for crop type mapping in India. Plantix, a free app that uses image recognition to help farmers diagnose crop diseases, logged 9 million geolocated photos from 2017–2019 in India, 2 million of which are in the states of Andhra Pradesh and Telangana in India. Crop type labels based on farmer-submitted images were added by domain experts and deep CNNs. The resulting dataset of crop type at coordinates is high in volume, but also high in noise due to location inaccuracies, submissions from out-of-field, and labeling errors. We employed a number of steps to clean the dataset, which included training a CNN on very high resolution DigitalGlobe imagery to filter for points that are within a crop field. With this cleaned dataset, we extracted Sentinel time series at each point and trained another CNN to predict the crop type at each pixel. When evaluated on the highest quality subset of crowdsourced data, the CNN distinguishes rice, cotton, and “other” crops with 74% accuracy in a 3-way classification and outperforms a random forest trained on harmonic regression features. Furthermore, model performance remains stable when low quality points are introduced into the training set. Our results illustrate the potential of non-traditional, high-volume/high-noise datasets for crop type mapping, some improvements that neural networks can achieve over random forests, and the robustness of such methods against moderate levels of training set noise. Lastly, we caution that obstacles like the lack of good Sentinel-2 cloud mask, imperfect mobile device location accuracy, and preservation of privacy while improving data access will need to be addressed before crowdsourcing can widely and reliably be used to map crops in smallholder systems.

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Remote Sensing
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David Lobell
Sherrie Wang
Stefania Di Tommaso
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Sugar is the second largest agro-based industry in India and has a major influence on the country's water, food, and energy security. In this paper, we use a nexus approach to assess India's interconnected water-food-energy challenges, with a specific focus on the political economy of the sugar industry in Maharashtra, one of the country's largest sugar producing states. Our work underscores three points. First, the governmental support of the sugar industry is likely to persist because policymakers are intricately tied to that industry. Entrenched political interests have continued policies that incentivize sugar production. As surplus sugar has been produced, the government introduced additional policies to reduce this excess and thereby protect the sugar industry. Second, although the sugar economy is important to India, sugar policies have had detrimental effects on both water and nutrition. Long-standing government support for sugarcane pricing and sales has expanded water-intensive sugarcane irrigation in low-rainfall areas in Maharashtra, which has reduced the state's freshwater resources and restricted irrigation of more nutritious crops. Despite its poor nutritional value, empty-calorie sugar has been subsidized through the public distribution system. Third, the Indian government is now promoting sugarcane-based ethanol production. This policy has the benefit of providing greater energy security and creating a new demand for surplus sugar in the Indian market. Our analysis shows that a national biofuel policy promoting the production of ethanol from sugarcane juice versus directly from molasses may help reduce subsidized sugar for human consumption without necessarily expanding water and land use for additional production of sugarcane.

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Environmental Research Letters
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Rosamond L. Naylor
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Danielle Torrent Tucker, Stanford School of Earth, Energy & Environmental Sciences
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Generations of political support for sugar cultivation have helped India become the second-largest producer of sugar worldwide. Now, the country’s commitment to renewable energy could create additional benefits, like conserving natural resources and providing better nutrition to the poor.

Stanford researchers conducted the first comprehensive analysis of India’s sugar industry and its impact on water, food and energy resources through the lens of its political economy – that is, how entrenched political interests in sugar production threaten food, water and energy security over time. The results show that a national biofuel policy encouraging production of ethanol made directly from sugarcane juice may make India’s water and energy resources more sustainable. Using sugarcane juice instead of molasses would also free up land and irrigation water for growing nutrient-rich foods. The research was published July 24 in Environmental Research Letters.

“There are spillover effects between sectors, unintended consequences,” said co-author Rosamond Naylor, a food security expert and the William Wrigley Professor in Stanford’s School of Earth, Energy & Environmental Sciences (Stanford Earth). “It’s very instructive to think about the connection between food, water and energy because the solution may not be in the sector you’re focusing on.”

Moving toward renewables

Somewhat analogous to the corn industry in the U.S., which has shifted about 40 percent of its output to ethanol production in recent years, policymakers in India – many of whom benefit financially from the sugar industry – are currently exploring how to use sugarcane to increase energy independence and shift toward renewable energy use.

The Indian government has set a goal to increase the ethanol-to-gasoline blending rate from its current rate of about 6 percent to 20 percent by 2030 and introduced several policies to promote production of ethanol from sugarcane. The increased blending rate is a “desirable goal for improved energy security,” the researchers write. However, its effects on human health and the environment will largely depend on which sugar product ends up being the main feedstock: juice extracted from crushed sugarcane, or molasses, a by-product from sugar processing.

Figure showing irrigation water use of Indian sugar Meeting E20 by 2030: additional sugarcane, water and land resources needed, and extra sugar produced. Meeting the 20% ethanol-to-gasoline blending rate by 2030 with ethanol produced from molasses would require additional water and land resources and produce extra sugar. In contrast, ethanol produced from sugarcane juice could meet the blending target without risking water and land resources and would reduce extra sugar. (Image credit: Lee et al. / Environmental Research Letters)

India’s national policy on biofuels only recently began allowing use of sugarcane juice in ethanol production, in addition to molasses.

“If the energy industry continues to use molasses as the bioethanol feedstock to meet its target, it would require additional water and land resources and result in the production of extra sugar,” said co-author Anjuli Jain Figueroa, a postdoctoral researcher in Earth system science. “In contrast, if the industry used the sugarcane juice to produce ethanol, the target could be met without requiring additional water and land beyond current levels.”

Using sugarcane juice to create ethanol could also help alleviate government spending to subsidize sugar and sell it below cost in its public distribution system.

Entrenched incentives

The public distribution system of sugar in India dates to the 1950s, when frequent famines plagued the country. Back then, sugar helped to meet basic calorie requirements. But today – with micronutrient deficiency leading to illness, disabilities and even death – the Indian government is more concerned with nutrition.

“In India right now, even poor populations have met their basic calorie needs,” said Naylor, who is also a senior fellow at the Stanford Woods Institute for the Environment. “They have been able to buy sugar at subsidized prices, but meanwhile they don’t have access to adequate protein and micronutrients for cognitive growth and for physical well-being.”

Figure showing micronutrient content and calories of crops Micronutrient content and calories of sugar and selected crops. Sugar provides empty calories with no nutritional value. (Image credit: Lee et al. / Environmental Research Letters)

Sugarcane cultivation in India has expanded in part because of policies that incentivize production, including a minimum price, guaranteed sales of sugarcane and public distribution of sugar. These regulations have become entrenched over many generations, making the crop highly profitable to the 6 million farmers in the country, but the empty-calorie crop reduces the amount of resources available for micronutrient-rich foods. 

“Using scarce natural resources to produce a crop that doesn’t fulfill nutritional needs for the second most populated country in the world can place pressure on the global food system if more and more food imports are required to meet the rising demand in India,” Naylor said.

Balancing act

The researchers focused their analysis on Maharashtra in western India, one of the country’s largest sugarcane-producing states. Sugarcane cultivation in Maharashtra has increased sevenfold in the past 50 years to become the dominant user of irrigation water. The study found that in 2010-11, sugarcane occupied only 4 percent of Maharashtra’s total cropped areas but used 61 percent of the state’s irrigation water. Meanwhile, irrigation for other nutritious food crops remained lower than the national averages.

Figure showing irrigation water use of major crops in Maharashtra Irrigation water use by major crops or crop groups in Maharashtra from 1970–71 to 2010–11. In Maharashtra, irrigation water use by sugarcane has increased more rapidly than any other crop over time, and sugarcane has used the highest share of total irrigation water in all time periods. (Image credit: Lee et al. / Environmental Research Letters)

“Irrigation of sugarcane in our study region is about four times that of all other crops and has doubled from 2000 to 2010. This resulted in about a 50 percent reduction of river flow over that period,” said co-author Steven Gorelick, the Cyrus Fisher Tolman Professor at Stanford Earth. “Given that this region is susceptible to significant drought, future water management is likely to be quite challenging.”

As part of continued efforts to examine the Indian sugar industry and its impacts, lead author Ju Young Lee, a PhD student in Earth system science, also developed satellite imagery analyses to identify sugarcane from space.

“Despite the importance of sugarcane in the water, food and energy sectors in India, there are no reliable sugarcane maps for recent years and in time series,” Lee said. “Using remote sensing data, I am developing current time-series sugarcane maps in Maharashtra – an important step forward.”

 

The researchers worked with stakeholders in India, including NGOs, academics and government officials, to focus the goals of the project. The research is part of Food Water Energy for Urban Sustainable Environments (FUSE), an international consortium supported in part by the National Science Foundation through the Belmont Forum to address competition for scarce resources in stressed urban food-water-energy systems – including the impacts of climate variability.

Naylor is also a senior fellow at the Freeman Spogli Institute for International Studies and a professor, by courtesy, of economics. Gorelick is also lead principal investigator of FUSE and a senior fellow at the Stanford Woods Institute for the Environment.

The research was supported by the U.S. National Science Foundation.

Lead author with a group of farmers in Indian sugar field Lead study author Ju Young Lee, center, is pictured with local farmers and agricultural experts while visiting a sugarcane field in Maharashtra in western India in August 2018. (Image courtesy of Ju Young Lee)

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Researchers analyzed the interconnected food, water and energy challenges that arise from the sugar industry in India – the second-largest producer of sugar worldwide – and how the political economy drives those challenges.

Authors
Rob Jordan
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COVID-19, combined with the effects of ongoing civil conflicts, hotter and drier weather in many areas, and an unfolding locust invasion in Africa and the Middle East, could cut off access to food for tens of millions of people. The world is “on the brink of a hunger pandemic,” according to World Food Program (WFP) Executive Director David Beasley, who warned the United Nations Security Council recently of the urgent need for action to avert “multiple famines of biblical proportions.”

(Watch Beasley’s conversation on food insecurity as a national security threat with his WFP predecessor, Ertharin Cousin, a visiting scholar with Stanford’s Center of Food Security and the Environment.)

Understanding how these conditions – alone or in combination – might affect crop harvests and food supply chains is essential to finding solutions, according to David Lobell, the Gloria and Richard Kushel Director of the Center on Food Security and the Environment. Below, Lobell discusses the connection between immigration and U.S. food security, a counter-intuitive effect of COVID-19 and more.

 

How could COVID-19 affect global food security?

I think the biggest effects will probably be related to lost incomes for many low-income people. Even if food prices don’t change, potentially hundreds of millions could be pushed into a much more precarious food situation. I’d be especially worried about remittances – the money immigrants in wealthy nations send home to developing nations – falling, since these are a surprisingly large source of stability for many poor people. Beyond the income effects, there are definitely prospects for reduced supply of foods, but I think these are secondary, especially because global stocks right now are quite large.

Another counter-intuitive effect is that the drop in gasoline demand due to social distancing may be a big driver of changes in food prices. A lot of corn demand is for use in ethanol fuel, and corn prices can affect the prices of many other crops. The price of corn has dropped by about 20 percent since February.

 

What are the biggest risks in terms of food supply?

Three things come to mind. First, for crops that require a lot of labor, there are some indications that planting and harvest activities are being affected. Even though these are usually included as essential activities, they often rely on migrant populations that can no longer cross state or national borders. California is going to be a prime case study in this.

Second, some countries, like Russia, have started to restrict food exports in an effort to calm domestic consumers worried about food shortages. Even if there is enough global supply, there is a risk that supply for importing countries could be curtailed. This was a big part of the food price spikes a decade ago. Now, we have the added potential that exports will be limited by a lack of mobility to get products to the port – for instance, there are reports from South America that towns won’t let trucks through for fear of the virus.

Third, COVID-19 could really limit the ability of governments and international groups to address other crises that emerge. Nearly every year there are at least a few surprises around the world affecting food that are usually handled before they make big news. Things like livestock diseases and crop pest outbreaks, for example. But without the ability to deploy people to assess and fix problems, there is more scope for issues to go unchecked. Right now, the biggest example of this is the desert locust outbreak in Eastern Africa.

 

What current and/or likely future weather conditions might have significant impacts on food production?

As the globe warms, we continue to see more “surprises” in most years in terms of record hot or dry growing seasons. It’s a bit too soon to say if and where those will emerge this year. Since global food stocks are high, we have some ability to cope with a shock, but if governments are already nervous it may take less to induce export bans and all of the negative effects those entail.

 

Ahead of the summer harvest, what is the prospect for controlling locust swarms in threatened countries, and how might the swarms further complicate the global food security picture?

If not for COVID-19, this would likely be the biggest development related to food this year. My understanding is that they are spreading fast in Africa and the Middle East, and while they haven’t yet had big effects in the main production regions, the next couple of months will be critical. The hope is that the winds change and drive them back toward the desert areas they came from. If not, there are at least 20 million people at risk of major food security impacts in the region.

 

Could we see locust swarms in the U.S.? What can we do to prevent them?

Locusts can occur anywhere. A few years back there was a major outbreak in Israel. They haven’t been a big issue in the U.S. because control methods are available, such as widespread spraying. But again, in a time of COVID-19, these types of responses are harder.

 

What does history teach us about the situation we are in with multiple threats to food security, and how to deal with it?

I think it comes down to a combination of investing in science-based solutions to avoid problems to begin with, and then having good social safety nets for when problems arise. At that level, it’s not really any different than dealing with infectious disease. The absence of any problems is our goal. At the same time, that absence always seems to breed complacency and neglect. Hopefully, the experiences of 2020 will help strengthen support for a society based on facts, science and compassion.

 

Media Contacts

David Lobell, Center on Food Security and the Environment: (650) 721-6207; dlobell@stanford.edu

Rob Jordan, Stanford Woods Institute for the Environment: (650) 721-1881; rjordan@stanford.edu

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COVID-19 and other looming threats could make it much harder for people to access food. David Lobell, director of Stanford’s Center on Food Security and the Environment, outlines likely scenarios and possible solutions.

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Marshall Burke and fellow researchers study productivity in smallholder farms to understand variation across the adbundant but understudied firms. They use a novel framework, satellite data, and machine learning to understand such variation, and they find that output measurement error contributes significantly to this discrepancy in productivity.

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National Bureau of Economic Research
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Marshall Burke
Casey C. Maue
Kyle J. Emerick
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Researchers including David Lobell analyze how human-caused climate change has impacted a water deficit in Southern Africa and might contribute to a rising food security crisis in the region.

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Global Change Biology
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David Lobell
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Join us for a talk with agricultural and development economist Christopher B. Barrett, this quarter’s visiting scholar with the Center on Food Security and the Environment. Barrett is the Stephen B. and Janice G. Ashley Professor of Applied Economics and Management and an International Professor of Agriculture with Cornell’s Dyson School of Applied Economics and Management.

Professor Barrett will discuss food systems advances over the past 50 years that have promoted unprecedented reduction globally in poverty and hunger, averted considerable deforestation, and broadly improved lives, livelihoods and environments in much of the world. He’ll share perspectives on the reasons why, despite those advances, those systems increasingly fail large communities in environmental, health, and increasingly in economic terms and appear ill-suited to cope with inevitable further changes in climate, incomes, and population over the coming 50 years. Barrett will explore the new generation of innovations underway that must overcome a host of scientific and socioeconomic obstacles.
 
Also a Professor of Economics in the Department of Economics, Barrett is co-editor in chief of the journal Food Policy, is a faculty fellow with David R. Atkinson Center for a Sustainable Future and serves as the director of the Stimulating Agriculture and Rural Transformation (StART) Initiative housed at the Cornell International Institute for Food, Agriculture and Development.
 

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