Different studies suggest different dietary changes in response to climate change, but the ballpark is pretty clear. The most comprehensive assessment of the livestock industry's environmental impact was published in Nature in October 2018. After analyzing food-production systems from every country around the world, the authors concluded that while undernourished people living in poverty across the globe could actually eat a little more meat and dairy, the average world citizen needs to shift to a plant-based diet in order to prevent catastrophic, irreversible environmental damage. The average U.S. and U.K. citizen must consume 90 percent less beef and 60 percent less dairy. How would anyone keep track of that? No animal products for breakfast or lunch. It might not amount to precisely the reductions that are asked for, but it's just about right, and easy to remember.