Intensive animal farming contributes to many environmental problems such as deforestation, loss of biodiversity, and global warming. Its climate effects are mainly due to the emission of greenhouse gases (GHGs) such as methane and nitrous oxide by “livestock” animals (especially cows, buffalos, and other “ruminant” animals), and the reduction of ecosystems such as forests to raise animals and grow their food. 

This study focused on the consequences of a transition to plant-only agriculture on global warming. Unlike previous studies on this topic, the authors considered both the reduction of GHG emissions and the absorption of these gasses if part of the land currently used for animal agriculture was transformed back into complex ecosystems like forests. Indeed, this new biomass would absorb a significant amount of carbon dioxide (CO₂) via photosynthesis, further benefiting our environment. 

In order to do this, the authors implemented several models that estimated GHG levels in the atmosphere from 2020 to 2100 using publicly available data from other studies. The reference model, which they refer to as “business as usual,” estimated GHG levels if no action was taken to change the global diet and emissions remained constant. A second model estimated GHG levels if land animal farming was immediately stopped and replaced by agriculture supporting a plant-based diet. A third model included a 15-year transition to plant-only agriculture. Several other models estimated the effects of stopping only certain types of animal production such as farming pigs, chickens, cows, etc. 

Under the business as usual model, the global temperature increase would exceed 2.0°C by 2100. To stay below 2.0°C, a reduction equivalent to 3,230 gigatons of CO₂ emissions would be required. And to stay below 1.5°C, a reduction equivalent to 3,980 gigatons would be needed. Comparatively, the model with a 15-year transition to plant-only agriculture would reduce the equivalent of 1,680 gigatons of CO₂ emissions, or forty-six years’ worth of anthropogenic CO₂ emissions. These results indicate that stopping land animal farming within 15 years, and with no other intervention to reduce GHG emissions, would be enough to achieve 52% of the emission reductions needed to limit the global temperature increase to 2.0 °C, or 42.2% of the reductions needed to limit the temperature increase to 1.5 °C. The authors note that phasing out animal agriculture in fifteen years would have a similar effect as reducing CO₂ emissions 68% by the year 2100.

In order to reduce GHG emissions, the priority is to stop raising ruminant animals, especially cows raised for beef and milk, which account for more than half of the emissions from land animal agriculture. Ending all ruminant farming — cows, buffalos, sheep, and goats — in favor of plant agriculture would be enough to achieve 90% of the benefits of stopping animal farming to fight global warming. Laying hens and chickens emit far fewer GHGs, although the authors did not account for the animal welfare harms of the chicken industry. 

It’s important to note that not all of the land recovered from animal agriculture would be transformed into complex ecosystems, as some would have to be used to grow plants for human consumption. Furthermore, the study doesn’t consider other anthropogenic pressures that could potentially be placed on the recovered land, such as using it to produce biofuels. Finally, the study is based on terrestrial animals and did not consider aquatic animals. Nevertheless, this study shows that the transition to a global plant-based diet should be a key strategy to fight climate change. Indeed, it would not only reduce GHG emissions but also free up a lot of land that could become complex ecosystems and absorb GHGs. Obviously, it must be coupled with other interventions to achieve a 1.5 or 2.0 °C temperature limit, such as switching from fossil fuels to renewable energy. 

It is well documented that plant-based diets are sufficient for a healthy life at any age. But the transition to a plant-based agriculture model will pose several challenges that must be overcome. In addition to the difficulties with political and public acceptance, the authors point out that those who make their living from livestock will need to be helped to overcome the loss of their jobs. Furthermore, there will be a need to increase the availability of plant-based products, which are very scarce in some areas. However, despite these challenges, switching to a more plant-centric system of agriculture is imperative if we want to take the climate crisis seriously.