For more traditional farming in one place we’d need between 8 and 80 million km2 which – at least towards the lower end – is much more realistic. But this would only work if everyone ate a plant-based diet so we could feed them efficiently on croplands. And we’d probably have to cut down many of our forests along the way. With modern farming we could feed 8 billion people on much less land. Possibly as little as 4 to 8 million km2 if we achieve very productive farming across the world and move to plant-based diets (which are very big ifs).
