October 4, 2023


The UN’s Food and Agriculture Organization (FAO) shockingly exposed the connection between animal agriculture and climate change in its study “Livestock’s Long Shadow,” which was published in 2006. As it turned out, something as obviously natural as the food we consume also sent planet-warming greenhouse gases into the atmosphere, in addition to vehicles, airplanes, and coal plants. At the time, the FAO estimated that the production of meat, dairy, and eggs accounted for 18 percent of all greenhouse gas emissions worldwide. This estimate was so high that, for many people in nations with high meat consumption, changing one’s diet was seen as possibly the most significant action anyone could take to lessen their impact on the environment.



The FAO figures have undergone a few additional revisions since then. It published its most current assessment of the carbon footprint of animal husbandry in October of last year using data from 2015 (each estimate utilizes data from many years earlier). It reduced the previous estimate of 14.5 percent given in 2013—which itself was down from the 2006 estimate of 18 percent—and put the contribution of cattle in overall yearly greenhouse gas emissions at about 11 percent. The revised estimate is lower in terms of absolute quantities as well; animal agriculture is responsible for 6.19 billion tons of carbon dioxide-equivalent emissions, down from the 7.1 billion tons the FAO estimated in 2013.

Considering the worldwide increase in the number of animals farmed for food, this conclusion is quite startling. According to FAO figures, over 83 billion land animals will be killed for food in 2021 (chickens make up the great bulk), up from roughly 68 billion a decade ago and 55 billion in 2006. This Memorial Day weekend will mark the beginning of the summer grilling season in the US, during which time it is anticipated that 818 hot dogs will be consumed per second by Americans alone.

According to a study by the Breakthrough Institute, the FAO’s latest estimate (which is not peer-reviewed) is the lowest to date when compared to various peer-reviewed studies, which place livestock emissions at between 14.5 percent and 19.6 percent of the total global emissions.

The obvious question that follows is: Why is it lower? The solution is a subject of great debate among scientists. Peer-reviewed studies continue to issue warnings that agricultural emissions, the most of which are caused by animal agriculture, may cause global temperature rise to exceed the 1.5°C Paris Agreement limit.

According to their documentation, it is difficult to determine why the latest FAO estimate is lower, according to Joseph Poore, an Oxford University expert in food sustainability analytics and co-author of a significant 2018 research on cattle emissions. Other scientists contacted for this article concurred.

According to the FAO, the revised estimate has only been released as a web app thus far, with a more in-depth study evaluating and contextualizing the findings scheduled for publication in the autumn. Poore anticipates that the FAO study will give a more comprehensive discussion of the methodological adjustments that produced the 11 percent number.

Despite the lack of openness, Poore and others proposed a number of variables that would have reduced the revised estimate, including modifications to the GWP 100 indicator for global warming potential. This crucial number is used in climate research to translate the warming impacts of various greenhouse gases into “carbon dioxide equivalents,” making it simple to compare them to one another. Methane is now estimated to be 34 times more potent than carbon dioxide, down from a previous estimate of 27 times by the Intergovernmental Panel on Climate Change. Nitrous oxide, another greenhouse gas closely linked to animal agriculture, is now estimated to be 273 times more potent than carbon dioxide, down from a previous estimate of 298 times.

Some experts have expressed a deeper worry about the FAO assessment because of what it leaves out. It excludes the significant climate benefits we’d receive if we released some of the land currently used for livestock farming and allowed forests to return, unlocking their potential as “carbon sinks” that absorb and sequester greenhouse gases from the air. It only counts emissions that the livestock industry is directly responsible for, like methane emitted by cows.

This is referred to as the potential cost of the land utilization for animal husbandry. Due to the enormous opportunity cost associated with animal husbandry, which consumes approximately 40% of the world’s livable land area, relying just on data from the FAO will unavoidably only give a partial picture of the actual impact of livestock on the climate.

In reality, models are not measures.

The Global Livestock Environmental Assessment Model, or GLEAM, which the FAO has been enhancing since 2009, generated the most recent data. The estimate has been revised downward, but this doesn’t exactly suggest that the world has succeeded in reducing emissions from animal agriculture. The dashboard states, “The various figures should not be interpreted as a time series.” It is “impossible to draw conclusions like “emissions went higher” or “livestock emissions are becoming less relevant relative to overall anthropogenic emissions,” according to the FAO.”

According to Theun Vellinga, a livestock researcher at Wageningen University in the Netherlands and a member of the team that created the first GLEAM dashboard, the revised numbers don’t significantly change the scientific understanding of how much animal agriculture matters to climate change because they are still within the ballpark of other livestock emissions estimates, with room for error in either direction. “The situation is [still] relatively serious, given the animal population continues to rise,” he said, adding that the 6.19 billion-ton projection was “still quite a worrying figure” and one that needed to be decreased.

However, the lower numbers on the dashboard are simple to misinterpret to untrained eyes. According to NYU environmental scientist Matthew Hayek, the GLEAM dashboard lacks a margin of error for its estimate, unlike the majority of scientific research, which gives it a misleading feeling of clarity. Regarding the estimations of 11.19 percent and 6.19 billion tons of CO2 emissions from cattle, Hayek commented, “Putting a decimal point on this is absurd” since it indicates an unsuitable degree of assurance.

Estimates of animal emissions “have a 30 to 50 percent error,” according to Hayek. All we can truly say is that 10 to 20 percent of the world’s greenhouse gas emissions come from animal husbandry.

That’s because, to be honest, it would be difficult for the FAO to monitor emissions from every cattle farm in the globe. They were modeled, and models are by nature imprecise.

For instance, Hayek and a colleague discovered large disparities between actual measurements of the air downwind of extensive livestock feedlots across America and modeled equivalents in a 2021 research that sought to verify the accuracy of estimates of cow emissions. They discovered that the actual methane emissions were between 39 and 90 percent greater than those predicted by models like those of the FAO. This conclusion, according to Hayek, shows that models may be underestimating the emissions from large-scale cow ranches.


a calf in a Turkish dairy farm. On dairy farms, newborn calves are removed from their mothers, unable to nurse, and housed in isolated quarters. Cows are a significant producer of greenhouse gas emissions, notably methane.

We Animals Media/Hava Zorlu

It is challenging to measure animal emissions accurately. “Biological systems (animals, plants, wetlands) are harder to assess [greenhouse gases] from because you need to model entire biological organisms and systems,” Hayek said in an email. Thermodynamics alone can largely account for fuel usage in buildings, transportation, or energy, making such modeling tasks very simple. Additionally, there are legislative restrictions. For instance, the US Environmental Protection Agency has been prohibited from utilizing funding to monitor livestock emissions, and a bill that was presented in the Senate last year seeks to explicitly prohibit the monitoring of methane emissions.

According to Timothy Searchinger, a researcher at Princeton’s Center for Policy Research on Energy and the Environment, the impact of nitrous oxide, one of the most potent greenhouse gases, is another well-known uncertainty in cattle climate models. Because the amount released varies on a number of variables, such as soil temperature, moisture content, and microbial levels, the gas, which is produced by fertilizers and other agricultural practices, is challenging to detect and model.

The risk of “the willful and unintentional misinterpretation” of the new estimates, combined with the media’s propensity to simplify data for wider communication and people’s propensity to see what they want to see about divisive topics like meat consumption, is concerning, according to Carlos Gonzalez Fischer, an agri-food systems sustainability researcher at Cornell University. Despite the fact that scientists are aware of the inherent uncertainty in emission estimates, he asserted, improved communication about what the figures actually signify is crucial for the general public and policymakers.

That might be achieved by utilizing a range rather than a single number for the percentage and tonnage estimations. Another ex-member of the GLEAM modeling team, Michael MacLeod, who studies climate change mitigation at Scotland’s Rural College, suggests presenting the estimate as a confidence interval: “six billion tons plus or minus one billion tons, with a 95 percent confidence of that range,” for instance.

Initial inquiries concerning the model’s operation received a response from the FAO, but a lengthy list of inquiries and complaints of the model received no response.

The enormous opportunity cost of using land for cattle

One of the most significant ways animal husbandry exacerbates climate change, according to some academics, is the enormous quantity of land it requires. This factor is left out of the FAO model. According to Searchinger, “livestock use 75 percent of the world’s agricultural land,” which includes both the area used to raise food to feed farm animals and the land used to house those animals. “Forest was once found in 40% of the world’s grassland. On that area, we lost a significant quantity of carbon storage.

According to Hayek, the FAO model “continues to ignore the enormous land use of animal agriculture, and the significant carbon opportunity costs of that land.” Its estimate does take into consideration fresh deforestation events, such as when untamed land is cleared to make space for cow grazing or to produce crops used as animal feed, such soy, but it ignores the possibility of carbon storage on previously deforested land used for animal agriculture.

According to Hayek, clearing some of that land would enable “large-scale reforestation and native ecosystem restoration,” capturing “multiple years’ worth of our carbon dioxide emissions into trees, shrubs, and soils, improving the terrestrial carbon sink, and buying important additional time that we need to reduce other emissions like fossil fuels.”

According to a significant research, ceasing the production of meat and dairy products over the next 30 to 50 years may offset emissions from all other industries combined, writes Kenny Torrella of Vox. Such a change would prioritize more sustainable, plant-based diets that use fewer resources to generate the same amount of calories rather than producing less food to feed the globe.


One of the largest cattle feedlots in the world, with 120,000 cows, is in Colorado. Nearly 40% of the planet’s livable land is dedicated to animal husbandry, a space that might otherwise be occupied by untamed ecosystems that absorb carbon.

RF Glowimages/Getty Images

Despite the benefits of lowering intensive livestock production being consistently found by a variety of experts, there are little indications that any meaningful changes to global climate policy are being made. Some organizations that support the environment and animal welfare are concerned that the cattle business won’t allow a sizable portion go to waste, particularly one that appears to show that more animals are producing less emissions.

“I think the livestock sector will say [the new FAO estimates mean] it’s not as bad as everyone thought,” predicted Peter Stevenson, policy consultant for Compassion in World Farming and author of a recent study on the negative effects of livestock intensification on the environment. The US cattle industry has already made a strong effort to counter the emerging understanding that significant cuts in beef output will be necessary to maintain the climate within planetary limitations.

For those who provide the feed, cages, crates, medications, and quickly growing, high-yielding animals that enable industrial production, there are billions at stake, according to Stevenson. He said, referring to the production of commodities used to feed farm animals, “The feed industry is the most valuable, worth over $400 billion annually.” They only have one consumer, highly grown animals, so it seems sense that they would wish to safeguard that industry.

Policymakers now have the enormous burden of persuading the meat and dairy sectors to accept restrictions on their business models as well as changing the consumption patterns of a population that has become used to inexpensive animal products. Although not sufficient on its own, clear science communication from organizations like the FAO will be crucial to achieving that aim.

Intensive animal husbandry and its effects on the health and wellbeing of animals, people, and the environment are topics that Sophie Kevany covers as a freelance journalist. Her work has been featured in a number of media, including the Guardian, Vox, Sentient Media, the BBC World Service, the Irish Times, and others. She formerly worked for Dow Jones and Agence France-Presse (AFP), and she graduated from Dublin City University with a master’s in journalism.

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