For Pollan, the key question isn't whether you can feed the world sustainably, but whether you can do it on the current model of industrial-scale food production. And he has serious doubts that you can, not least because climate change has challenged its long-term sustainability. So long as the climate remains relatively stable, then the current model can be sustained, as farmers and agribusinesses have learned over the years how best to protect the environment. But with a change in climate, that becomes a much more difficult task, with serious knock-on effects for large-scale food production.

As regards population, Pollan points out that we're currently growing enough calories of food to feed a much larger population than we have right now. And yet over a billion people worldwide still regularly go hungry. The main problem is who controls the food supply. The technology to feed a much bigger world population is certainly there, but there's a distinct lack of political will at the very highest level of Western governments to ensure that this happens.

If anything, the current model of industrialized food production needs a huge increase in population to sustain it over the long-term. As Pollan points out, Wall Street wants to see food companies grow by about five percent a year, and yet the population of the United States only grows by about one percent a year. This means that, in order to remain profitable, food companies have encouraged consumers to eat more. Any further increase in population is likely to accelerate this process further, as food companies overproduce in order to exceed growing demand instead of just meeting it.