How can we grow enough food to feed a skyrocketing population, while still leaving some room for nature? To find out, researchers ran hundreds of food production simulations under different conditions—like organic versus high-yield farming, and plant-based versus meat-based diets. They recorded whether each combination of strategies was “feasible”—whether enough food could be produced to feed the estimated 2050 world population without expanding the area of farmland people already use. Diet was the biggest determinant of success, the team reports today in Nature Communications. Of the scenarios that included everyone in the world eating a diet consisting entirely of plants, 100% were feasible. But because of the amount of land it takes to raise animals for meat—about twice as much as for crops—only 15% of the scenarios with typical meat-heavy Western diets were feasible. No other factor had that large of an effect, not even switching to farming practices like extra fertilizer use to make land more productive. The study does have lots of assumptions built in, like totally free trade between countries, which would mean that food can always get to where it’s needed. Plus, the research can’t say anything about the political and cultural challenges involved with getting people to change their diet. But it does show that, in theory, it’s possible to keep feeding the world without cutting down more forests for new farmland.