The Center on Food Security and the Environment is a joint effort of the Freeman Spogli Institute for International Studies and the Stanford Woods Institute for the Environment.
New work by team including FSE researchers provides a broad, cautionary understanding of why financial incentives alone are unlikely to prevent forest-clearing fires in Indonesia’s oil palm regions.
Usually, increasing agricultural productivity depends on adding something, such as fertilizer or water. A new Stanford University-led study reveals that removing one thing in particular – a common air pollutant – could lead to dramatic gains in crop yields. The analysis, published June 1 in Science Advances, uses satellite images to reveal for the first time how nitrogen oxides – gases found in car exhaust and industrial emissions – affect crop productivity. Its findings have important implications for increasing agricultural output and analyzing climate change mitigation costs and benefits around the world.
“Nitrogen oxides are invisible to humans, but new satellites have been able to map them with incredibly high precision. Since we can also measure crop production from space, this opened up the chance to rapidly improve our knowledge of how these gases affect agriculture in different regions,” said study lead author David Lobell, the Gloria and Richard Kushel Director of Stanford’s Center on Food Security and the Environment.
Nitrogen oxides, or NOx, are among the most widely emitted pollutants in the world. These gases can directly damage crop cells and indirectly affect them through their role as precursors to formation of ozone, an airborne toxin known to reduce crop yields, and particulate matter aerosols that can absorb and scatter sunlight away from crops.
While scientists have long had a general understanding of nitrogen oxides’ potential for damage, little is known about their actual impacts on agricultural productivity. Past research has been limited by a lack of overlap between air monitoring stations and agricultural areas, and confounding effects of different pollutants, among other challenges to ground-based analysis.
To avoid these limitations, Lobell and his colleagues combined satellite measures of crop greenness and nitrogen dioxide levels for 2018-2020. Nitrogen dioxide is the primary form of NOx and a good measure of total NOx. Although NOx is invisible to humans, nitrogen dioxide has a distinct interaction with ultraviolet light that has enabled satellite measurements of the gas at a much higher spatial and temporal resolution than for any other air pollutant.
“In addition to being more easily measured than other pollutants, nitrogen dioxide has the nice feature of being a primary pollutant, meaning it is directly emitted rather than formed in the atmosphere,” said study co-author Jennifer Burney, an associate professor of environmental science at the University of California, San Diego. “That means relating emissions to impacts is much more straightforward than for other pollutants.”
Based on their observations, the researchers estimated that reducing NOx emissions by about half in each region would improve yields by about 25% for winter crops and 15% for summer crops in China, nearly 10% for both winter and summer crops in Western Europe, and roughly 8% for summer crops and 6% for winter crops in India. North and South America generally had the lowest NOx exposures. Overall, the effects seemed most negative in seasons and locations where NOx likely drives ozone formation.
“The actions you would take to reduce NOx, such as vehicle electrification, overlap closely with the types of energy transformations needed to slow climate change and improve local air quality for human health,” said Burney. “The main take-home from this study is that the agricultural benefits of these actions could be really substantial, enough to help ease the challenge of feeding a growing population.”
Previous research by Lobell and Burney estimated reductions in ozone, particulate matter, nitrogen dioxide, and sulfur dioxide between 1999 and 2019 contributed to about 20% of the increase in U.S. corn and soybean yield gains during that period – an amount worth about $5 billion per year.
Future analysis could incorporate other satellite observations, including photosynthetic activity measured through solar-induced fluorescence, to better understand nitrogen dioxide’s effects on crops’ varying degrees of sensitivity to the gas throughout the growing season, according to the researchers. Similarly, more detailed examination of other pollutants, such as sulfur dioxide and ammonia, as well as meteorological variables, such as drought and heat, could help to explain why nitrogen dioxide affects crops differently across different regions, years, and seasons.
“It’s really exciting how many different things can be measured from satellites now, much of it coming from new European satellites,” said study coauthor Stefania Di Tommaso, a research data analyst at Stanford’s Center on Food Security and the Environment. “As the data keep improving, it really drives us to be more ambitious and creative as scientists in the types of questions we ask.”
Lobell is also a professor of Earth system science in Stanford’s School of Earth, Energy & Environmental Sciences, the William Wrigley Senior Fellow at the Stanford Woods Institute for the Environment, and a senior fellow at the Freeman Spogli Institute for International Studies and the Stanford Institute for Economic Policy Research. Burney also holds the Marshall Saunders Chancellor’s Endowed Chair in Global Climate Policy and Research at UC San Diego and is a research affiliate at UC San Diego’s Policy Design and Evaluation Laboratory, a fellow at the Stanford Center on Food Security and the Environment, and head of the Science Policy Fellows Program at UC San Diego.
New analysis shows crop yields could increase by about 25% in China and up to 10% in other parts of the world if emissions of a common air pollutant decreased by about half.
2021 was not the year many people hoped for. In addition to the ongoing COVID-10 pandemic and emerging coronavirus variants, last year ushered in a laundry list of unprecedented weather events.
Canada and the Pacific Northwest of the United States were scorched by a record-breaking heat wave. An extended fire season in the American West sent blankets of smoke pollution rolling across the rest of the continent. In India, China and Germany, unseasonal rain storms brought on devastating floods. According to the National Centers for Environmental Information (NOAA), July 2021 was the hottest July on Earth since global record-keeping began in 1880.
Data clearly shows that these kinds of extreme weather patterns are driven by climate change. But is that fact driving policymakers to make meaningful inroads to address the climate crisis? Marshall Burke, the deputy director of the Center on Food Security and the Environment, joins Michael McFaul on World Class podcast to review the latest data on what’s happening with the climate in the field and in the halls of Congress.
Listen here and browse highlights of their conversation below.
Click the link for a transcript of “Taking the Temperature on Climate Change."
Changes in climate are going to affect most, if not all, of us in the U.S. And public opinion has certainly changed on this in the last 10 years. Many more Americans are on board that the climate is changing and that we should do something about it. There's much more support for climate legislation across the board from Democrats and increasingly from Republicans.
Anyone who works on climate was really excited to see the platform Biden ran on, because it was really the first mainstream presidential campaign where climate had played a fundamental role. There's been a lot of discussion aboutthe importance of climate, the damages from climate that are already happening, and what we need to do is take aggressive action in the future to deal with the problem.
But there are specific industries who are going to be harmed by this legislation, and they are quite organized in fighting this legislation, and in funding politicians who fight it, and in funding organizations, either transparently or not, that are fighting climate legislation.
We are closer than we’ve ever been to really meaningful legislation on climate change. The optimistic view is that we’re on the right trajectory and that we’re going to get some part of this done eventually. But we’re not there yet.
A “COP” is a “Conference of the Parties,” which is an annual meeting of the signatories of the 1992 United Nations Framework Convention on Climate Change. The main focus of Glasgow was to get countries to be very transparent about how they are going to achieve the ambitions for combating climate change that they articulated at the last major COP summit in Paris.
Was it a success? A lot of countries did come to the table in Glasgow and made commitments in ways that they hadn't done before. There were also new, important agreements on certain greenhouse gasses that we've learned recently are pretty damaging, like methane.
Where we failed to make progress was on something that's called “loss and damage.” Many developing countries argue that they are suffering the damages from climate change even though it is a problem that they have not caused, and they are seeking compensation from developed countries who have been the drivers of climate change. That issue was on the table in Glasgow, but it got put off until next year in Egypt.
Progress is being made. Emissions are falling in the U.S. They're falling in California. They're falling in the EU. They're pretty flat around the world. And these are not just the per capita emissions, but overall emissions are now going down in many parts of the world, which is a huge success.
Where has that progress come from? In part from government policies that have been successful in mitigation. But the driving factor has really been longer decadal investments by both the public sector and the private sector in technologies that allow us to produce energy in a clean way. It’s a combination of long-term public support through taxes and subsidies for the development of these technologies alongside private sector deployment of these technologies at huge scale.
It’s important for people to know about these successes. But it’s also important for us to realize what we don’t know. Emissions in different parts of the world are falling, and that’s fantastic. But it’s also true that people are already getting sick, being harmed, and dying because of the changes we’re already experiencing. We’re poorly adapted to the climate we live in now, much less the climate of a two-degree warmer or three-degree warmer future, and the science on that needs to be much more widely understood.
I think a huge role for us as academics is not only to do the research to understand those questions, but to get that information out into the world. The great thing about the Freeman Spolgi Institute and institutions like FSI is that it's part of our mandate to translate this research out into the broader world. The translation of what we already know is important, as is the imperitive to drill down on and study the things that we don't.
Climate expert Marshall Burke joins the World Class podcast to talk through what’s going right, what’s going wrong, and what more needs to be done to translate data on the climate crisis into meaningful policy.
A major bill with bipartisan support in Congress would reward farmers for an unusual harvest. The Growing Climate Solutions Act(link is external) promises billions of dollars for climate-smart agriculture practices, such as planting cover crops to reduce erosion and sequester carbon. The bill highlights farming’s potential as a climate change solution, as well as the challenge of controlling the sector’s growing greenhouse gas emissions. Below, Stanford Earth scientists Inês Azevedo, David Lobell and Rob Jackson discuss the surprising amount of greenhouse gases emitted by farming, how farmland conservation programs can help reverse the trend and what the federal government can do to promote more climate-friendly agriculture, among other issues.
Azevedo is an associate professor in the Department of Energy Resources Engineering at Stanford’s School of Earth, Energy & Environmental Sciences (Stanford Earth). Her research examines the role of food systems in reaching de-carbonized economies. Lobell is the Gloria and Richard Kushel Director of the Center on Food Security and the Environment. He uses unique datasets to study rural areas; his research has shown how reduced soil tillage can increase yields while nurturing healthier soils and lowering production costs. Jackson is the Michelle and Kevin Douglas Provostial Professor of Energy and Environment in Stanford Earth. His work has shown that global emissions of nitrous oxide increased by 30 percent over the past four decades due mostly to large-scale farming with synthetic fertilizers and cattle ranching, and that well-managed soil’s ability to trap carbon dioxide is potentially much greater than previously estimated.
What might the average person be surprised to learn about greenhouse gas emissions from America’s agricultural lands?
Lobell: First, I think people are surprised that the food system actually uses a very small share of fossil fuels, even when you include all the fertilizer production. Second, people are surprised by how many things they think are good, like eating organic or local foods, have very little effect on emissions and can even be worse than conventional alternatives.
Jackson: Many people are aware that fossil fuel use drives most carbon dioxide emissions, but they might not know that more than half of methane and nitrous oxide emissions attributable to human activities come from agriculture.
Azevedo: I think the average person would be surprised to learn agriculture – including livestock, agricultural soils and agricultural production – accounts for about 10 percent of total U.S. greenhouse gas emissions and, in contrast to some other sectors of the economy, they have increased over time.
Does the Growing Climate Solutions Act go far enough to mitigate and reduce emissions? How could it be stronger?
Lobell: I worry that there isn’t enough emphasis on the main greenhouse gases that agriculture contributes to – nitrous oxide and methane – where progress could probably be made a lot faster than for carbon dioxide. Soil carbon is like motherhood and apple pie – nobody is against it – but I wish that half the energy I see going into how to get more carbon into soil was going into how to reduce emissions of the other gases.
How can programs that reward farmers for certain conservation practices help?
Jackson: The world’s soils contain far more carbon than the atmosphere, but agricultural activities such as plowing have released two hundred billion tons of carbon dioxide to the atmosphere from soils. Conservation programs can help us put some of that carbon back where it belongs, making our soils more fertile and better at retaining water.
Lobell: On one level, these programs can help start the process of making agriculture carbon neutral or even carbon negative. This is important if we want to meet aggressive climate goals. On another level, they can help build a broader political coalition devoted to solving climate change. This might be even more important for climate goals, especially given the disproportionate role of rural states in our federal government.
How should such programs be designed for maximum efficiency and cost-effectiveness?
Lobell: I’m concerned there is a lot of hype out there now on what specific practices can deliver, for example by companies trying to raise large funding rounds on the idea of selling carbon credits. I think it’s important that the programs have a strong system of verification and ability to adjust over time as we learn about what is truly effective.
Jackson: Rather than focusing primarily on carbon dioxide, agricultural incentives would be well served to reduce emissions of methane and nitrous oxide through practices such as better fertilizer and manure management. Methane’s warming potential is 30 times higher than carbon dioxide’s over a century, and nitrous oxide’s warming potential is nearly 300 times higher. Reducing them is a great bang for our climate buck.
From a global perspective, how important is agriculture’s role as a potential climate change solution, and how can policymakers better quantify and track it?
Azevedo: One of the recent things our recent research has shown is that although reducing emissions from fossil fuels is essential for meeting the Paris Agreement goals, other sources of emissions may also preclude its attainment. Specifically, even if all fossil fuel emissions were immediately halted, the achievement of the agreement’s 1.5 degree Celsius maximum temperature increase target would likely not be feasible if global food systems continue along their current trends.
Lobell: I think accelerating public research in this area will be critical, particularly for ways to accurately measure carbon accumulation or emissions reductions on individual farms. If this had been a well-funded area, we might be in a much better position in terms of leveraging all of the private sector enthusiasm for it. Since food is a traded commodity, it will also be important to monitor global land-use change and the extent to which our domestic policies might be having unintended consequences elsewhere.
Azevedo and Jackson are also senior fellows at the Stanford Woods Institute for the Environment and the Precourt Institute for Energy. Lobell is also a professor of Earth system science in Stanford’s School of Earth, Energy & Environmental Sciences, the William Wrigley Senior Fellow at the Stanford Woods Institute for the Environment and a senior fellow at the Freeman Spogli Institute for International Studies and the Stanford Institute for Economic Policy Research.
Stanford scientists discuss climate-smart agriculture
Despite aquaculture’s potential to feed a growing world population while relieving pressure on badly depleted oceans, the industry has been plagued by questions about its environmental impacts.
But over the years, the diverse industry – which ranges from massive open-ocean salmon cages to family farm freshwater tilapia ponds – has made significant strides toward sustainability, according to a new Stanford-led analysis.
The study notes, however, that in order for the global aquaculture sector to deliver on its full promise, more effective oversight measures are needed to help ensure that its environmentally sound systems are economically viable.
The findings, published March 24 in Nature, could help shape how consumers think about the seafood they buy, and inform governance strategies critical to global food and nutrition security.
“As the demand for seafood around the world continues to expand, aquaculture will keep growing,” said study lead author Rosamond Naylor, the William Wrigley Professor of Earth System Science in Stanford’s School of Earth, Energy & Environmental Sciences (Stanford Earth). “If we don’t get it right, we risk the same environmental problems we’ve seen in land-based crop and livestock systems: nutrient pollution, excessive use of antibiotics and habitat change that threatens biodiversity.”
Twenty years ago, Naylor led a study that sparked controversy by saying farmed fish and shellfish in some cases added pressure to ocean fisheries – instead of relieving it – because carnivorous farm-raised species required large amounts of wild fish for feed. The paper, also published in Nature, prompted a spate of news stories and academic research questioning whether aquaculture was more of an environmental problem than a solution. Environmental groups applauded the study’s focus on aquaculture’s marine ecosystem impacts, while the industry pointed to hopeful developments that were largely ignored, such as ongoing improvements in fish nutrition.
Since then, the volume of global aquaculture production has tripled. In the new paper, aquaculture specialists and scientists from Asia, Europe, South America and the U.S. assessed the state of the industry by synthesizing hundreds of studies done over the past two decades on issues ranging from value chain developments in freshwater aquaculture to the use of wild fish in feeds to seaweed market challenges.
Their analysis considered key challenges and uncertainties, such as climate change’s impact on the industry, low-income producers’ adoption of sustainable seafood certification programs and shellfish and seaweed farmers’ ability to profit from providing ecosystem services, such as carbon capture.
Among the findings: freshwater aquaculture, comprised of nearly 150 species of fish, shellfish and plants, accounts for 75% of farmed aquatic food consumed directly by humans.
“Most aquaculture is about fish people can afford to eat – and most of the farming of aquatic animals happening in Asian countries stays in those countries,” said study co-author David Little, a professor in the University of Stirling Institute for Aquaculture, in the U.K. “It’s having an important impact on food security and rural livelihoods.”
Other regions, including Africa, are increasingly benefitting from the introduction of freshwater aquaculture. But while small freshwater farms are on the rise around the world, there is little oversight of their practices.
The researchers also found that the production of high-value shrimp, salmon and other marine fish rose rapidly, contributing to a significant rise in the share of global fishmeal and fish oil used by aquaculture. Yet, the ratio of wild fish input per fed fish output has dropped almost seven-fold since 1997.
“We have been successful in converting carnivorous fish, such as salmon and trout, largely into vegetarians,” said study co-author Ronald Hardy of the Aquaculture Research Institute at the University of Idaho.
In the study, the researchers call for better management of antimicrobial use in fish farming to limit the development of drug-resistant microbes that threaten both fish and human health, and regulation of marine farm sites. They also recommended incentives for sustainably designed systems to prevent cross-contamination between fish waste and surrounding waters, and a food systems approach to governance that considers nutrition, equity, justice and environmental outcomes and trade-offs across land and sea.
“When done well, aquaculture can play a sustaining role in global food systems by providing expanded food production and livelihood benefits with relatively minimal environmental harm,” said study co-author Dane Klinger, director of aquaculture at Conservation International and PhD graduate of Stanford’s Emmett Interdisciplinary Program in Environment and Resources. “This assessment will help industry, government and other stakeholders navigate the opportunities and obstacles that remain ahead.”
The researchers shared observations from their analysis in a related seminar. Watch it here.
Naylor is also Founding Director of Stanford’s Center on Food Security and the Environment; and a senior fellow in the Stanford Woods Institute for the Environment and the Freeman Spogli Institute for International Studies. Other co-authors of the study include Alejandro Buschmann of the Universidad de Los Lagos (Chile); Simon Bush of Wageningen University (Netherlands); Ling Cao of Shanghai Jiao Tong University (China); Jane Lubchenco of Oregon State University; Sandra Shumway of the University of Connecticut; and Max Troell of the Beijer Institute and Stockholm University (Sweden).
Funding for the research was provided by the Center on Food Security and the Environment.
Twenty years ago, a Stanford-led analysis sparked controversy by highlighting fish farming’s damage to ocean fisheries. Now a follow-up study takes stock of the industry’s progress and points to opportunities for sustainable growth.
Recent dramatic and deadly increases in global wildfire activity have increased attention on the causes of wildfires, their consequences, and how risk from wildfire might be mitigated. Here we bring together data on the changing risk and societal burden of wildfire in the United States. We estimate that nearly 50 million homes are currently in the wildland–urban interface in the United States, a number increasing by 1 million houses every 3 y. To illustrate how changes in wildfire activity might affect air pollution and related health outcomes, and how these linkages might guide future science and policy, we develop a statistical model that relates satellite-based fire and smoke data to information from pollution monitoring stations. Using the model, we estimate that wildfires have accounted for up to 25% of PM2.5 (particulate matter with diameter <2.5 μm) in recent years across the United States, and up to half in some Western regions, with spatial patterns in ambient smoke exposure that do not follow traditional socioeconomic pollution exposure gradients. We combine the model with stylized scenarios to show that fuel management interventions could have large health benefits and that future health impacts from climate-change–induced wildfire smoke could approach projected overall increases in temperature-related mortality from climate change—but that both estimates remain uncertain. We use model results to highlight important areas for future research and to draw lessons for policy.
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.
