Sparing the planet the most catastrophic effects of climate change will require a new focus on curbing the negative impact of the global food system, which accounts for nearly one-third of all greenhouse gas emissions and could doom the international Paris accord even if all other major emissions sources are eliminated, according to research published in Science.

While most of the efforts to limit global warming under the Paris Agreement focus on stemming fossil fuel production from electricity, transportation and industry through means such as renewable energy, electric vehicles and improved efficiencies, the new report published in November is the first to break down how meeting the legally binding treaty’s climate change targets will also require changing how food is produced and consumed.

The 2015 Paris Agreement, whose signatories include nearly all countries and which U.S. President-elect Joe Biden has vowed to rejoin after President Donald Trump withdrew, requires nations to minimize human impacts on the climate system by limiting global temperature rise to “well below” 2 degrees Celsius above pre-industrial levels, or more ideally, to 1.5 degrees Celsius. 

But according to the study, if food business continues as usual, it will take just 30 to 45 years for the world to blow the treaty’s more aspirational goal, and the agreement's primary target would be missed shortly after 2100.

“This is assuming we do everything else perfectly — so there are no fossil fuel emissions; we’re somehow flying planes that are electric or run on plants,” Michael A. Clark, lead author of the study and a researcher at the Oxford Martin School and the University of Oxford’s Nuffield Department of Population Health, said in an interview with The Academic Times. “We also have to talk about food in the context of climate change targets … If we don’t talk about food, we’re still going to miss them.”

Between 2012 and 2017, global food system emissions averaged about 16 billion tons of carbon dioxide annually. Food-related greenhouse gas emissions come from, for example, land clearing and deforestation that release carbon dioxide and nitrous oxide; the production and use of fertilizers and other agrichemicals that emit carbon dioxide, nitrous oxide and methane; and the combustion of fossil fuels in food production and supply chains, which emits carbon dioxide.

For their study, researchers from the U.K. and U.S. looked at how food systems have changed over time, tying them to greenhouse gas estimates based on how food is produced and consumed. The study forecasts emissions “as a function of per capita diets” — in other words, what is eaten and how much — as well as different food types’ specific contributions to emissions and, finally, global population size, assuming that food systems will continue along as they have for the past half-century.

Emissions from the current global food system were estimated by the researchers to reach 1,356 gigatons between 2020 and this century’s end.

“As such, even if all non–food system greenhouse gas emissions were immediately stopped and were net-zero from 2020 to 2100, emissions from the food system alone would likely exceed the 1.5 degrees Celsius emissions limit between 2051 and 2063,” the authors wrote.

But the estimates also show how that path could be avoided through five different methods targeting food supply and demand: more plant-rich diets, appropriate caloric consumption, higher crop yields, reducing food loss and waste by half and lowering foods’ greenhouse gas intensity.

Examining the effects of each strategy individually, “We find that cumulative food system greenhouse gas emissions from 2020 to 2100 can be reduced by 14% to 48%,” the authors said, “provided that these strategies are adopted individually and gradually such that they are fully adopted by 2050.” 

“If all five strategies were to be partially implemented together (50% adoption of each), cumulative emissions through 2100 could be reduced by 63% relative to business-as-usual,” the study continued. “Full adoption of all five strategies could result in a food system with marginally negative net cumulative emissions because of lowered emissions and net carbon sequestration on abandoned croplands.”

The impact of each transition would vary by country. For instance, food loss and waste is a particular issue in the U.S., Clark said, where the average family of four spends around $1,500 per year on food that is thrown away.

Globally, about one-third of all food produced is tossed before it’s consumed, often because of inadequacies in the labor, storage facilities or transportation networks that get the food to the people who will ultimately eat it. Food loss and waste accounts for about 8% to 10% of global greenhouse gas emissions.

“Even just being able to cut that in half is going to have a very large greenhouse gas benefit,” Clark said. “It isn’t only going to be a climate benefit for many people, it’s also financially responsible.”

Further, Clark said, if consumers around the world decided — and had the means — to shift to a healthy diet that is mostly plant-based and adheres to nutritional recommendations, that could slash greenhouse gas emissions by 40% to 50% between now and 2100.

“That’s not a small lever,” he said.

However, it isn’t only on consumers to make these choices, Clark noted.

“Government is going to have to do something in terms of what food is available, so it needs to be not only enough food but also the right types of food that are culturally appropriate, that support human well-being,” he said. “There needs to be some way to make the healthy choice and the sustainable choice also the cheapest choice, because that seems to be a very good way of getting people to change their behaviors and provides incentive to do it in ways that just information communication does not.”

The study “Global food system emissions could preclude achieving the 1.5° and 2°C climate change targets,” published Nov. 6 in Science, was authored by Michael A. Clark, Oxford Martin School and Nuffield Department of Population Health, University of Oxford; Nina G. G. Domingo, Department of Bioproducts and Biosystems Engineering, University of Minnesota; Kimberly Colgan, Department of Bioproducts and Biosystems Engineering, University of Minnesota; Sumil K. Thakrar, Department of Bioproducts and Biosystems Engineering, University of Minnesota; David Tilman, Department of Ecology, Evolution, and Behavior, University of Minnesota and Bren School of Environmental Science and Management, University of California, Santa Barbara; John Lynch, Department of Physics, University of Oxford; Inês L. Azevedo, Department of Energy Resources Engineering, Stanford University and Woods Institute for the Environment; and Jason D. Hill, Department of Bioproducts and Biosystems Engineering, University of Minnesota.