There's definitely a bit of competition between agriculture and say forests, urban areas and sustainable energy projects. But urban areas probably are the small

There's definitely a bit of competition between agriculture and say forests, urban areas and sustainable energy projects. But urban areas probably are the smallest of them all. We've seen some deforestation, and we've also seen agriculture under pressure from biofuels. The biofuels idea is mostly bankrupt (at least in terms of crops, algae etc have potential), and deforestation is in part illegal and unnecessary, not due to a dire lack of agricultural land. Our rate of human population concentration is very high, about 95% of humans are concentrated on about 10% of surface area worldwide. Meanwhile we only use 11% of land for agriculture, while about 36% of our land is suitable for farming. (which could be improved to some extent, e.g. there are various ways to take back deserts on small scales, and on large scales too if technology improves enough). And in fact, urbanisation is only growing. We've never had as much concentration of people, and as many people living in cities as today. So I don't think agricultural land is under that much threat. In fact we could probably pretty easily cut back agricultural land by 50% while increasing to a population of 9 billion if we changed our diets and our use of farmland. For example some rough numbers from 2013: > roughly 40 percent of U.S. corn is used for ethanol, (roughly 36 percent of U.S. corn is fed to cattle, pigs and chickens. Much of the rest is exported. Only a tiny fraction of the national corn crop is directly used for food for Americans, much of that for high-fructose corn syrup. Small edits by me. Now imagine what that means when you figure that corn is the nr 1 crop in the US, and a tiny fraction goes to actually feeding people. As for animals, the studies vary between chickens requiring as little as 2 kilos of plant food and cows as high as 10 kilos, to produce 1 kilo of meat. Whatever the exact accurate number is, it's a fact that making food from animals is inefficient. You put more food in than you get out, sometimes by an order of magnitude, for a different taste experience for a minute or so per day. And that's just corn, it's not alone. More than half of grain is used for livestock, too. Now obviously land is finite, if you want to live here with 50 billion people, sure. You need to go up. But the demographic projections to 2100 are to cap out at around 10 billion, and then slowly decrease again as the world moves to an average birthrate we see in OECD countries (1.7, while about 2.1 is necessary to sustain a population level). These kinds of population levels can be sustained on flat land, vertical isn't necessary. Doesn't mean that vertical can't happen. If vertical is better, who cares if it is necessary, it'll be replaced anyway. But the challenge of vertical farming is currently sustainability (large infrastructure costs are necessary to make it possible to get conditions you see on flat land for 'free' (sun, clouds and soil taking care of light, water, food, distribution, containers, germination etc) in a vertical space. And if you can't solve that problem of sustainability, it doesn't matter if there's not enough flat land anyway because we'd be doomed.