If everyone on the planet hypothetically stopped eating meat, the shift wouldn’t just reduce new emissions. A new study calculates that if animal agriculture was phased out, it would also unlock substantial “negative emissions,” helping shrink greenhouse gases in the atmosphere so dramatically that the world could reach net zero emissions for decades even if other pollution continued unabated. That’s because raising animals is a big source of methane, a potent greenhouse gas that can disappear relatively quickly from the atmosphere, and because of the potential to capture huge amounts of carbon in native forests and grasslands if they can regrow on farms currently used for animals.
The study calculates the climate impacts of different scenarios in the food system, including what would happen if the world phased out animal agriculture over the next 15 years. Pat Brown, the Stanford University biochemistry professor emeritus who coauthored the study, isn’t an unbiased source: he is also CEO of Impossible Foods, one of the pioneers of the new generation of plant-based meat designed to convert meat-lovers. But the peer-reviewed study shares all of the data that it uses so that anyone can make the same calculations.
“This is great news,” Brown says. “There has heretofore been no credible way identified to unlock the negative emissions that we absolutely need if we’re going to meaningfully address this problem.” So-called negative emissions are critical for tackling climate change, because even if we stopped burning fossil fuels today, the extra CO2 in the atmosphere would keep heating the planet. Some other negative emissions techniques, including machines that can suck carbon from the air, are still very expensive and will be challenging to implement at a large scale.
Once CO2 is in the atmosphere, it can stay there for centuries. Methane—which is emitted from manure on farms and from cow belches—has a half-life of only around nine years. It also has a bigger heating effect than CO2, so if the total amount of methane shrinks, it can quickly slow down overall global warming. Nitrous oxide, another potent greenhouse gas emitted from manure and from synthetic fertilizers used to grow crops that animals eat, also decays faster than CO2. Both methane and N₂O “are chemically unstable,” Brown says. “And so as soon as you stop those emissions, effectively you get negative emissions.”
An estimated 800 gigatons of carbon could also be pulled from the atmosphere if grazing land and land currently used for growing cattle feed and other crops for animal agriculture was allowed to return to its natural state as a forest, prairie, or grassland. Farmers who rely on subsidies now to make meat profitable could potentially make more money by selling carbon credits. “For the large majority of agricultural land in the world, at a carbon price of $50 a tonne, which is where most economists think it’s headed in the next few years, farmers could make way more money just letting the ecosystems recover,” he says. “It’s simple math.”
If the transition began now, the climate would feel the effects quickly: By 2030, we could reach net zero emissions globally, even if emissions from fossil fuels and other sources continue. Emissions would essentially pause at net zero for 30 years, buying more time to decarbonize the rest of society. Through the rest of the century, the phaseout would offset nearly 70% of the heating effect of other emissions.
Of course, it’s hard to imagine that the meat and dairy industries could actually disappear. But that’s the ultimate aim of Impossible Foods. The transition is inevitable, he argues, “once you have a product that’s more delicious, more nutritious, more affordable, better for the planet, and doesn’t involve, you know, basically eating a corpse of the slaughtered animal.”