We may not know which drives which of human population growth and agricultural growth, but we do know that Earth's population is increasing rapidly and there is a strong need for an increased food supply. Thus, because we cannot expand the amount of available cropland, we need to increase the intensity of production if we expect to increase supply.
We already have genetically modified our crops to be more productive; we use fertilizers and greenhouses to eliminate limiting resources; what now?
Vertical farming: The ultimate revolution in agriculture, conserving land while allowing for fresh food production in densely populated urban centers and requiring relatively little water and energy to grow crops in multi-story highrise "farms." And of course transportation costs would be tiny. Runoff would be eliminated. Cropland could return to a more natural state, increasing ecosystem health. Food supplies would not be subject to floods, droughts, and other disturbances. As we learned in 510, ecological systems are the basis of many human systems: vertical farming could save the environment, increase human health and reduce hunger, thereby reducing unemployment, poverty, obesity, and all sorts of other social ills.
So what's the problem? Vertical Farming doesn't exist yet. The Vertical Farm Project was developed in 1999 by faculty and graduate students at Columbia University. Vertical Farming relies on greenhouse processes, hydroponics, and careful monitoring of nutrients to determine when crops are ready to be "harvested." Vertical farming could recycle water from evapotranspiration, and the indoor nature of these farms allows for year-round production. Vertical Farmed food would all be organic, of course.
It is argued that the technology to develop Vertical Farms already exists. These farms may be a solution to environmental degradation, hunger, and inner city health issues, but a few questions still remains unanswered: What is the lifetime energy consumption of a Vertical Farm? Might all those lights and hydroponic systems actually use more energy than conventional farming systems? And would that increase in energy consumption be worth the gains in efficiency and food production?
See http://www.verticalfarm.com/index.html for some of their design proposals.