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A global shift to flexitarian diets would buy critical time to meet key climate targets

DAILY SCIENCE

A global shift to flexitarian diets would buy critical time to meet climate targets

A new study demonstrates how dietary shifts could build wiggle room into a fast shrinking global carbon budget.
April 5, 2024

Let the best of Anthropocene come to you.

Adopting a flexitarian diet could be a uniquely powerful way to help us keep warming levels below the 1.5°C target of the Paris Agreement, finds new research. The gains from reducing agricultural emissions and freeing up former farmland could be so powerful in fact, that such dietary shifts could significantly increase the remaining global carbon budget we have left to achieve that goal.

It’s widely known that a ‘flexitarian’ diet, where plants rather than animal products dominate—popularized by the EAT-Lancet planetary health diet—is a surefire way to reduce dietary impacts on the planet. But few studies have looked specifically at how these dietary changes could shape the global carbon budget, the net amount of CO2 we can still emit while keeping global warming below a certain limit—and how dietary changes may therefore trickle through to influence other things, like the level of decarbonization needed in the energy sector. 

The interplay of dietary shifts with these other big-picture climate goals is what the new Science Advances study set out to explore. Using a variety of models, they took one emissions scenario—known as SSP2 or, more colloquially, the ‘business-as-usual’ pathway—and then applied three different conditions to that scenario to explore how much closer or further way it would take us from the target of 1.5°C by 2050. 

For the first condition they looked at how nationally-determined contributions (NDCs)—nations’ individual emissions reduction targets—would affect that goal. Second, they looked at the role of taxing greenhouse gas emissions, on top of NDCs. Finally, they looked at what a worldwide shift towards the EAT-Lancet planetary health diet, on top of NDCs and taxes, would mean for the 1.5°C goal.

The scenario that included NDCs alone fell far short of what would be needed to keep 1.5 alive, but when greenhouse gas emissions taxes were added into the mix, it became achievable, with warming peaking at 1.56°C by 2045. 

However, these two scenarios are outstripped by what could be achieved if a plant-rich global diet is layered on top of these actions. In this third scenario, the reduction of animal-based foods would lead to less livestock farming, less methane, less conversion of wild habitat into pasture, and plenty of freed land that, ideally, could be returned again to the wild. This shift would not only succeed in locking tons upon tons more carbon into the ground, but it would also drastically reduce methane from livestock, a short-lived but potent greenhouse gas that has a warming effect several times that of CO2.

What’s really interesting about this is that it builds some wiggle room into our global carbon budget, the researchers find. The second scenario where NDCs and taxes were applied leaves us with a remaining carbon budget of 500 gigatons of CO2 before we hit 1.5°C. But under the third scenario where diet is factored in, that budget increases to 625 gigatons of CO2 before the threshold is met. 

“Our results  show  that  dietary  shifts  do  not  only  reduce  impacts  from  food production within the land system, but  also  relax  the  1.5°C  compatible  peak carbon budget by 125 Gt CO2,” the researchers explain. 

Effectively, by mitigating the enormous emissions impact of our diets—especially by dampening the outsized effects of methane on climate—we could create a little bit of breathing room to help us meet our climate targets. 

For example, this could reduce the need for carbon dioxide removal by 39%, and might result in “less stringent CO2 emissions reductions in the energy system,” the researchers write. Energy prices would also decline, and the pace at which we’d need to reduce emissions would be slowed down, which is linked in the study to increased economic welfare gains in many countries. In this less pressured market, the cost and taxes attached to greenhouse gas emissions would decline by 43% by 2050, the study also showed. 

This raises questions about whether all of these are effects that we want to see. Reducing the need to curb emissions, or lock away more CO2, isn’t necessarily a good mindset to take into the next two decades. And the researchers acknowledge that our remaining carbon budget is a figure that still involves a lot of uncertainty, and could change. Beyond that, there are also questions about how to go about universally shifting diets: the researchers raise the possibility of a tax on products from the most methane-emitting animals like cattle and sheep. 

Either way, a global change in what we eat would be a gargantuan feat. But for now perhaps, the larger takeaway is this: there is power in our everyday diets to achieve change at a truly planetary scale. 

Humpenöder et. al. “Food matters: Dietary shifts increase the feasibility of 1.5°C pathways in line with the Paris Agreement.” Science Advances. 2024.
Image: ©Anthropocene

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