Why would we want to build skyscrapers filled with lettuce when we’ve been farming on the ground for 10,000 years? Because as the world’s population grows–from 6.8 billion now to as much as 9 billion by 2050–we could run out of productive soil and water. Most of the population growth will occur in cities that can’t easily feed themselves. Add the fact that modern agriculture and everything associated with it–deforestation, chemical-laden fertilizers and carbon-emitting transportation–is a significant contributor to climate change, and suddenly vertical farming doesn’t seem so magic beanstalk in the sky.”Vertical farming could allow food to be grown locally and sustainably,” says Glen Kertz, CEO of Valcent, a tech company based in El Paso, Texas, that’s trying out the process. His firm uses hydroponic greenhouse methods to grow upward rather than out. The result saves space–vital in urban areas–and allows farmers to irrigate and fertilize with far less waste.