This is an NYT article I've been meaning to comment on for some time, for almost a year in fact. It proposes vertical farms as a solution to food security issues.
First off, Mr. Dickson D. Despommier's initial premise is false. In spite of climate change and population growth, farming as we know it will still be around, in forty years and beyond. The only way it wouldn't be is if humans were no longer around. Despommier echoes the common lie that farming is inherently damaging to the environment, but this is simply not true, as I've explained in other posts about urban bias and about the care rural people usually give to the resources on which they depend.
A vertical farm would be a heavy consumer of fossil fuels. The materials used to build a vertical farm would be energy-intensive things like steel and glass. In addition to this, hydroponically-grown plants get all their nutrients from synthetic fertilizers that use a lot of energy to produce or to mine. Lastly, heating a transparent glass-and-steel structure uses huge amounts of energy. This is the main reason why carbon-emissions studies consistently find that produce grown in greenhouses in cold winter climates use more fossil fuels than warm-climate-grown produce shipped in from far away. All this means that vertical farming would not only not be a green, climate-friendly option for food production, but that it wouldn't even be that feasible in a world of decreasing fossil fuel resources.
The economic viability of vertical farming is impaired by this energy-intensive nature, but also because a vertical farm would have to compete economically with high-rent offices in the types of dense urban settings Despommier proposes it for. Part of the reason farming is done in rural areas with low land value, and high-rise offices are built in places with high land value, is the differential economic returns to agriculture vs. commercial office activities.
The big logical and physical problem that Despommier isn't mentioning is that we live on a flat surface, with a sun overhead. There's only so much sunlight falling on any given square meter of the earth, and if a plant intercepts that light, it's not available for other uses or plants. A vertical greenhouse could ostensibly work by capturing the morning and afternoon light that would hit vertical surfaces when the sun is in the East or the West, and even at noon in the temperate zones the building could get light from the South (or the North, if you're in Argentina). But in a downtown area, you're likely to have towers crammed together, shading each other on every side. In such a setting, the only viable greenhouses would be on the top floor of each building, which is to say that it would no longer be vertical farming but rather just horizontal greenhouses on the tops of buildings (which I think is a fair idea). In no case, even if it weren't shadowed on its sides by surrounding buildings, could a vertical building capture more light than the amount of area covered by its maximum shadow. So if you've got a vertical farm that's 100 meters high by 20 wide, you'd be better served by a horizontal greenhouse that measures 100m x 20m on the ground.
This point starts to give the lie to Despommier's claim that vertical farms would be uninfluenced by seasons and weather. In wintertime there's less light available from the sun, so many plants don't produce as well or at all. Cloudy or snowy days impair crop growth. The water used in a hydroponic system comes from somewhere, and weather affects its availability. It is possible to overcome weather limitations in a greenhouse by things like recycling water or heating the space in winter, but this always implies an expenditure of yet more fossil fuels.
Despite the author's assertions of the clean, pesticide-free nature of a vertical farm, the fact is that greenhouse agriculture uses a lot of pesticides. By assuring warmth, abundant plant growth, and humidity, you're basically creating a paradise climate for most pests, and there's no killing frost to wipe the slate clean every year. As a result, most greenhouses spray lots of poison on their plants, and both consumers and workers in greenhouses suffer the health consequences.
Even if we were to pursue the project of producing more of our food in greenhouses as opposed to open fields, the most sensible thing would be to build normal, horizontal greenhouses. These have the potential to maximize production per unit area, with fewer capital expenditures than a vertical farm tower. Despite his ignoring the fossil fuel and pesticide use of greenhouse production, Despommier is correct that it would be a good thing to produce our food more locally. But building a horizontal greenhouse in low-value vacant lots just outside of downtown areas would mean that food would still be very close to the consumer, and probably closer given that most urban dwellers don't live in the central downtown areas.
If vertical farming were ever to catch on, it would have to be for vegetables and maybe fruits (though I'm not sure how you'd cram a bunch of trees into a tower). But most land use, and land abuse, comes from large-scale grain production, which under no circumstances would be viable in urban towers. If a large share of our fruit and vegetable consumption were to move to urban vertical farming, this would mean more competition for one of the most viable, sustainable sectors for rural small farmers (and one of the friendliest agricultural land uses possible). Given that Despommier seems to envision a vertical farming dominated by large investors, with "managers and workers" as opposed to farmer-owners, this amounts to further replacing small farmers and the rural communities they support with large capital and low-wage jobs.
The author seems to be caught in the future fantasy, positing a world of unlimited synthetic resources that we can use to overcome nature. We can farm in towers, and even if this implies burning more coal, it doesn't matter, because we will no longer rely on the natural world for our well being, just on our own totally controlled, synthetic world.
Essentially Despommier is proposing factory farming for vegetables. He is applying the same philosophy as confinement animal operations do, of cramming production organisms together in industrial buildings and feeding them industrial inputs plus lots of biocides to stabilize the unhealthy ecological balance that's created.
Home gardening, windowpots, and even rooftop gardening on existing structures make sense in order to green a city, to produce local-grown, good-quality food, and to connect people with nature and one another. But industrial towers built expressly for veggies would be at best a gee-whiz oddity, and at worst the expansion of anti-rural, synthetic, industrial food production, greenwashed with a novel, vaguely ecologically-friendly patina that would make it more palatable for society.
Despommier posits a future world of reduced resource availability and increased pollution. It is precisely for this reason that I am against the promotion of more energy-intensive, polluting technologies like vertical farms.