[M]ost of the familiar candidates for alternative food would have trouble operating on the kind of scale necessary for a world of 6.7 billion people. Consider what it would take to make our farm system entirely organic. The only reason industrial organic agriculture can get away with replenishing its soils with manure or by planting nitrogen-fixing cover crops is that the industry is so tiny--making up less than 3 percent of the US food supply (and just 5.3 percent even in gung-ho green cultures like Austria's). If we wanted to rid the world of synthetic fertilizer use--and assuming dietary habits remain constant--the extra land we'd need for cover crops or forage (to feed the animals to make the manure) would more than double, possibly triple, the current area of farmland, according to Vaclav Smil, an environmental scientist at the University of Manitoba. Such an expansion, Smil notes, "would require complete elimination of all tropical rainforests, conversion of a large part of tropical and subtropical grasslands to cropland, and the return of a substantial share of the labor force to field farming--making this clearly only a theoretical notion."
That doesn't mean sustainable agriculture can't happen. But if we want to build large-scale capacity, we're going to need to broaden our definitions of sustainable practices.
(via bittman)
