It is clear that veganism is one of the most effective personal consumption choices to reduce our carbon footprint. A vegan diet reduces the yearly greenhouse gas emissions of an average person in a high-income country with close to 1 ton of CO2-equivalents. As a comparison, the total carbon footprint of a rich person is around 15 tons of CO2e per year. Living car free or avoiding a yearly intercontinental flight saves around 2 ton CO2e per person per year.
However, these climate benefits of vegan diets are highly underestimated, because they do not include the carbon storage opportunity costs. The 1 ton CO2e per year per person carbon footprint reduction only takes into account the yearly emissions of greenhouse gases, in particular methane emissions from ruminants, nitrous oxide emissions from animal manure, some CO2-emissions from burning fossil fuels on factory farms and CO2-emissions from deforestation and land clearing for livestock feed crops. Those emissions contribute to 15% of global greenhouse gas emissions, according to the UN-FAO. Not included in those estimates, is the loss of a huge carbon sink: agricultural land that was once forest.
With a global vegan diet, less agricultural land is required. Roughly 7 million km² can be reforested spontaneously (i.e. with natural seed dispersion instead of actively planting trees). Those new grown forests (including the soil and litter) can absorb 750 gigaton CO2. That means the new forests can absorb more than half of the total amount of CO2 that was added to the atmosphere and oceans since the industrial revolution (1750): 1300 gigaton CO2. In other words, vegan diets allow us to eliminate more than half of all previous net-emissions from the burning of fossil fuels in human history. (Another, higher estimate of CO2-sequestration from vegan diets, which requires active reforestation of the freed agricultural land, is 1100 gigaton CO2. All currently available cropland is sufficient to feed the world in the future (10 billion people) with a vegan diet. That means all the grazing land in the world is no longer needed. Current global livestock agriculture uses 50 million km² of grazing land. At least 20 million km² of this grazing land can be reverted to forests that can absorb more than 1000 gigaton CO2.)
Even more striking: the total carbon sequestration of reforestation due to a global vegan diet is 2,3 times more than our carbon budget, i.e. the maximum emissions to stay below 1,5°C warming with 66% likelihood (this budget is 340 gigaton CO2). Hence, with a global vegan diet, our remaining carbon budget becomes more than three times higher, increasing above 1000 gigaton. The current global level of greenhouse gas emissions is around 50 gigaton CO2-equivalents per year. That means, if we want to stay below 1,5°C with a 66% likelihood by linearly reducing the global emissions towards zero, with the current non-vegan diet we only have 14 years to reduce global emissions to zero, which is impossible. But with a global vegan diet, we have 40 years, which is not impossible (if we sufficiently invest in clean energy technologies).
Vegan diets offer us the opportunity to use the most effective and cheapest carbon capture and storage method: reforestation. Hence, eating animal products has a huge opportunity cost: with livestock farming, we cannot store so much carbon in a cheap way. (Next to reforestation, agricultural land that is no longer needed if the world went vegan can also be used for other climate purposes, such as the production of bio-energy or the installation of solar and wind energy farms.)
Taking into account this carbon storage opportunity cost of different diets, we see that a vegan diet does not only safe 1 ton of CO2 emissions per person per year, but there is a second benefit: the sequestration of 6 tons of CO2 per person per year. The total climate change impact of food reduces from 9 tons of CO2e per year per person for an average omnivorous diet to 2 tons for a vegan diet: a total reduction of 7 tons. This double benefit (lower emissions and higher absorption of greenhouse gases) makes a vegan diet by far the most effective personal consumption choice to reduce climate change.
The good news is: with current technological innovations such as cellular agriculture and precision fermentation, we can expect that the livestock industry will collapse in a few decades. For example, RethinkX predicts that: “The fastest, deepest, most consequential disruption of food and agriculture in history, driven by technology and new business models, is underway. By 2030, modern food products will be higher quality and cost less than half the price of the animal-derived foods they replace, the dairy and cattle industries will have collapsed, and the rest of the livestock industry will follow. […] By 2030, demand for cow products will have fallen by 70%. Before we reach this point, the U.S. cattle industry will be effectively bankrupt. By 2035, demand for cow products will have shrunk by 80% to 90%. Other livestock markets such as chicken, pig, and fish will follow a similar trajectory.” (Catherine Tubb & Tony Seba, 2019. Rethinking Food and Agriculture 2020-2030. The Second Domestication of Plants and Animals, the Disruption of the Cow, and the Collapse of Industrial Livestock Farming. A RethinkX Sector Disruption Report.)
In a decade almost 50% of the land currently used for livestock and feed production in the US will be freed for other uses, such as reforestation (carbon sequestration). It is possible that livestock farmers, when facing a strong decline in demand and a decline in land value of their land, have enough political power to delay the collapse of the livestock industry for a few years (e.g. by misleading the public that the clean meat and precision fermentation animal free products are unhealthy, unsustainable or unsafe). To prevent such resistance, livestock farmers and feed crop farmers could be paid or subsidized to turn their agricultural land into forests. These subsidies could ideally be financed with a carbon tax. This carbon tax, used in part for reforestation, is a kind of CO2-offset. The expected collapse of the livestock industry, and the coupled opportunity for reforestation, is an extra reason to introduce a carbon tax.
If you want to support this transition towards cellular agriculture, precision fermentation and cultivated meat, you can support organisations such as the Good Food Institute, New harvest, the Cellular Agriculture Society or the Modern Agriculture Foundation. These are also the most effective charities to reduce animal suffering.