Philippe Ciais is research director at the Laboratory of Climate and Environmental Sciences ; Élodie Vieille Blanchard is a doctor in social sciences and president of the Vegetarian Association of France.
To avoid catastrophic climate change, the signatories of the Paris Agreement have committed to significantly reducing their greenhouse gas emissions by 2050. France’s National Low Carbon Strategy is part of this segment, promising advances in industry and housing. But it remains unambitious for the agricultural sector, which, however, also harbors considerable potential for emission reductions.
If it is necessary to improve yields in order to occupy less territory, limit excessive consumption and waste or even reduce livestock emissions, it is by starting a global food transition for plants that we will be able to obtain the most significant results, revealed the 1er February a study published in the scientific journal Plos climate .
An essential delay in the face of the climate emergency
Livestock farming has well-known negative effects on our climate. Deforestation and, more broadly, the transformation of ecosystems destined for grazing livestock and crops that supply livestock would be the cause of almost a third of global human emissions of greenhouse gases emitted to date. Livestock and plant-based agriculture that feed animals also contribute significantly to man-made methane emissions (up to 34 %) and nitrous oxide (66 %), two gases with very strong global warming potential.
Therefore, it would be important to accurately assess the impact that a transition to plant-based diets could have on global climate change mitigation strategies. But today, this solution remains underestimated, because most estimates do not take into account the substantial consequences that the release of agricultural land would have.
“ Greenhouse gas emissions would be stabilized for thirty years »
In 2013, the Food and Agriculture Organization of the United Nations (CAM) put livestock emissions at the equivalent of 7.1 billion tons of COtwo per annum. But recent estimates suggest that the equivalent of 800 billion tons of COtwo would be fixed by photosynthesis if natural biomass could be replenished over the 30 % of the Earth’s surface that is currently devoted to livestock.
During this century, taking into account the avoided emissions and the refueling of COtwo atmosphere, we could subtract between 330 and 550 billion tons of COtwo the replacement of animal production by plant-based agriculture.
- The rapid elimination of livestock globally has the potential to stabilize greenhouse gas levels for thirty years and offset 68 % of emissions CO2 of this century. Plos climate
To put this number in perspective, total anthropogenic emissions of COtwo since the beginning of the industrial age are estimated at about 1,650 billion tons. The effects of the partial disappearance of methane from the atmosphere and the reconstitution of the biomass would quickly synergize, so that greenhouse gas emissions would be stabilized for thirty years after the cessation of ‘creation’.
By achieving half of the emission reductions needed to meet the Paris Agreement targets, the transition to plant-based foods would give us time to rethink our energy system currently based on the use of fossil fuels.
Constraints preferable to those of climate inaction
This transition will necessarily face cultural and economic barriers: meat, dairy and eggs are still an important component of the global human diet, and livestock are an integral part of rural economies worldwide – more than a billion people derive all or part of their livestock livelihood.
Although animal products currently provide 18 % of calories and 40 % of protein in the human diet, the sharp reduction in livestock is expected to lead to an overall increase in food availability. Thus, they would replace animal-derived nutrients, greatly reducing the impact on land, water, greenhouse gases and biodiversity, and would require only minor adjustments to optimize nutrition.
However, investments will be needed to prevent food insecurity in areas where large-scale access to a healthy plant-based diet is lacking and to ensure that people who rely on animal fertilization for their crops or who live off livestock are not replaced.
It should also be noted that the large impact of the sharp reduction of livestock on the climate would not be enough on its own to avoid catastrophic global warming. Likewise, the complete replacement of fossil fuels in energy production and transport would no longer be enough to avoid a warming of 1.5°C. The challenge we face, therefore, is not to choose one of these two levers, but to determine the best way to overcome the social, economic and political challenges involved in their joint implementation, even if partial.