I stand by what I said. You're looking at how we meet our needs for food and water today. I'm looking at how we'll do so for 10 billion people, with a larger percentage of them consuming more resources like us Westerner's enjoy.

Vertical farming hardly enters the picture today, and we currently pick a lot of the low hanging or unsustainable fruit where water is concerned. But we're going to have to do a lot of desalinization going forward, and we're also going to need to take a good percentage of farming indoors because we just don't have the land and water resources to do otherwise.

Vertical farming works for more than just lettuce and tomatoes - the thing is it's uneconomical so far. The technology needs to get cheaper and more widespread, and the inputs of energy, water, and fertilizers need to get cheaper. Advances in materials, building technology, and transportation would also help. Cheaper energy helps with everything.