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New model explores link between animal agriculture and climate change

Phasing out animal agriculture around the world, combined with a global shift to plant-based diets, would effectively halt the rise of atmospheric greenhouse gases for 30 years and give humanity more time to end its addiction to fossil fuels, according to a new study by scientists from Stanford University and the University of California, Berkeley.

A new model suggests that phasing out animal agriculture over the next 15 years would have the same effect as a 68% reduction in carbon dioxide emissions by 2100. (Image credit: Getty Images)

“We wanted to answer a very simple question: what would be the impact of a global elimination of animal agriculture on atmospheric greenhouse gases and their impact on global warming?” noted patrick brown, Professor Emeritus in the Department of Biochemistry at Stanford University. Brown co-authored the article with Michael Eisen, professor of genetics and development at UC Berkeley.

Based on the model, published in the open access journal PLoS climate, phasing out animal agriculture over the next 15 years would have the same effect as a 68% reduction in carbon dioxide emissions through 2100. This would provide 52% of the net emission reductions needed to limit global warming to 2 degrees Celsius above pre-industrial levels. levels, which scientists say is the minimum threshold required to avoid disastrous climate change.

The changes are said to come from the spontaneous breakdown of the potent greenhouse gases methane and nitrous oxide, and the recovery of biomass in natural ecosystems over 80% of the Earth’s footprint, say the authors. of humanity currently devoted to livestock.

“Reducing or eliminating animal agriculture should be high on the list of potential climate solutions,” Brown said. “I hope others, including entrepreneurs, scientists and global policymakers, will recognize that this is our best and most immediate chance to reverse the course of climate change and seize this opportunity.”

Brown is also the founder and CEO of Impossible Foods, a company developing alternatives to animals in food production. Eisen is an advisor to the company. Both Brown and Eisen stand to benefit financially from the reduction in animal agriculture.

Release negative emissions

Brown and Eisen are not the first to point out that continued emissions from animal agriculture contribute to global warming. But what hasn’t been recognized before, they say, is the far more impactful “climate opportunity cost” – the potential for unlocking negative emissions by eliminating livestock.

“As methane and nitrous oxide emissions from livestock decline, atmospheric levels of these potent greenhouse gases will actually drop dramatically within decades,” Brown said. “And the CO2 that was released into the atmosphere when wild forests and grasslands were replaced with forage crops and pastures can be converted back to biomass as livestock are removed and forests and grasslands recover.

Brown and Eisen used publicly available data on animal production, livestock-related emissions, and the potential for biomass recovery on land currently used to support livestock to predict how phasing out all or part of global animal agriculture production would change the net anthropogenic or human-made production. emissions relative to 2019 levels. They then used a simple climate model to project the impact of these changes on changing levels of greenhouse gases in the atmosphere and warming for the rest of the century.

They looked at four dietary scenarios: an immediate replacement of all animal agriculture with a plant-only diet; a more gradual and, according to the authors, more realistic transition, over 15 years, towards a global plant-based diet; and versions of each where only beef has been replaced with plant-only products.

For each hypothetical scenario, the scientists assumed that non-agricultural emissions would remain constant and that land formerly used for livestock would be converted to grasslands, grasslands, forests and the like that will absorb atmospheric carbon dioxide.

“The combined effect is both incredibly large and – equally important – rapid, with much of the benefit realized by 2050,” Brown said. “If animal agriculture were phased out over 15 years and all other greenhouse gas emissions were to continue unabated, the elimination would create a 30-year pause in net greenhouse gas emissions and offset nearly 70% of the heating effect of these emissions. until the end of the century. »

While the complete elimination of animal-based agriculture was expected to have the greatest impact, 90% of emissions reductions could be achieved by replacing only ruminants such as cattle and sheep, according to the model.

Although their paper does not explore the specifics of what a global elimination of animal agriculture would entail, the authors acknowledge that “the economic and social impacts of a global shift to plant-based diets would be acute in many many regions and localities” and that “It is likely that substantial global investment will be required to ensure that people who currently live from livestock do not suffer from its reduction or replacement.”

But, they write, “in either case, these investments must be weighed against the economic and humanitarian disruptions of significant global warming.”

To change the mentalities

Many will scoff at the idea that billions of people can be convinced to switch to a plant-only diet within 15 years. To these skeptics, Eisen points out that other revolutions have occurred in less time. “We went from no cellphones to ubiquitous cellphones in less time than that. Electricity, cars, solar panels – everything became mainstream in a relatively short time,” Eisen said.

What’s more, Brown added, societal attitudes toward food are far from fixed. “Five hundred years ago, no one in Italy had ever seen a tomato. Sixty years ago, no one in China had ever drunk coke. Mutton was once the most popular meat in America,” he said. “People all over the world readily adopt new foods, especially if they are delicious, nutritious, convenient and affordable.”

The scientists have made all of the raw data they used, along with their calculations and the computer code used to perform the calculations, publicly available so that others can make up their own minds.

“The great thing about science is that ultimately it all comes down to whether the conclusions are supported by evidence,” Brown said. “And in this case, they are.”