A new study demonstrates substantial changes in agricultural practices will be necessary to achieve the goals of the Paris climate accord, the 2015 international agreement designed to avert catastrophic global warming.
The paper, published Jan. 27 in Nature, provides the most thorough inventory yet of greenhouse gas emissions connected to the way humanity alters Earth’s landscapes. Led by researchers at the University of California, Irvine and coauthored by Stanford University scientist Rob Jackson, the study estimates carbon dioxide, nitrous oxide and methane emissions from 1961 to 2017, taking into account emissions from agricultural production activities, deforestation and other modifications to the natural landscape.
“We estimated and attributed global land-use emissions among 229 countries and areas and 169 agricultural products,” said lead author Chaopeng Hong, UCI postdoctoral scholar in Earth system science. “We looked into the processes responsible for higher or lower emissions and paid particularly close attention to trends in net CO2 emitted from changes in land use, such as converting forested land into farm acreage.”
The researchers learned that poorer countries in Latin America, Southeast Asia and sub-Saharan Africa experienced the most pronounced surge in emissions resulting from changes in land use.
East Asia, South Asia and the Middle East produced fewer greenhouse gases as a result of land-use change, according to the study, but the regions’ agricultural emissions were growing strongly as output raced to keep up with population expansion. And more affluent North America, Europe and Oceania showed emissions from changes in land use have declined over the past 50 years. The trend reflects continued yield improvements leading to abandonment of agricultural lands, more efficient fertilizer use, and reduced per capita meat consumption in Europe and the U.S., Jackson explained.
“While the situation in low-income countries is critical, mitigation opportunities in these places are large and clear,” said senior author Steve Davis, UCI associate professor of Earth system science. “Improving yields on already cultivated land can avoid clearing more carbon-dense forests for cultivation of soybeans, rice, maize and palm oil, thereby drastically reducing land-use emissions in these countries.”
The authors suggest that nations in emerging and developed markets also can lessen the emissions intensity of agriculture by adopting more efficient tilling and harvesting methods, improving management of soil and livestock waste, and by reducing food waste.
In addition, dietary changes could help, according to the study, which says that while red meat supplies only about 1 percent of calories produced globally, it’s responsible for up to a quarter of the world’s land-use greenhouse gas emissions. “Eating less red meat would be good for our health and our planet. Producing red meat releases one quarter of land-based greenhouse gas emissions but supplies only one-hundredth of the calories we consume," said Jackson, the Michelle and Kevin Douglas Provostial Professor at Stanford and a senior fellow at the Stanford Woods Institute for the Environment.
Europe has the lowest land-use emissions, at half a ton per person per year, the researchers note, but the figure is substantially higher almost everywhere else, and as the planet’s population continues to increase, farmers and policymakers will need to meet and exceed current best practices.
The paper highlights some promising technological solutions, such as new ways of cultivating rice that create less methane and dietary supplements for cattle that reduce their harmful emissions by up to 95 percent.
“Feeding the planet may always generate substantial greenhouse gas emissions,” said Davis, a member of the executive board of UCI’s Solutions that Scale initiative, which seeks answers to the planet’s most pressing climate and environmental problems. “Even if we get emissions down to European levels worldwide, with expected population growth, we could still be looking at more than 5 gigatons of land-use emissions per year in 2100, an amount at odds with ambitious international climate goals unless offset by negative emissions.”
The project received funding from the National Science Foundation, the German Research Foundation, and the Gordon and Betty Moore Foundation.
Jackson is also a senior fellow atStanford’s Precourt Institute for Energy. Additional coauthors are affiliated with the University of California, San Diego; Colorado State University; and Germany’s Max Planck Institute for Meteorology.