The world's food system depends largely on a farming system with post-green-revolution techniques: new seed varieties, substantial use of chemical fertilizers and pesticides, large-scale irrigation, machine-based cultivation, production for large markets, and separation of production from consumption by long distances. This system shows the highest productivity the world has ever seen, whether measured in terms of labor, land, or cost. And the system does a fairly good job of producing enough food for the world's 6 billion people.
But is this system sustainable?
Several large issues arise. First, the system is energy-intensive, so it poses significant demands on the petroleum economy. The use of petroleum and energy pervades the process: fuel for cultivation and transport, energy and inputs into the production of chemical fertilizers and pesticides, energy consumed in irrigation. So a part of the sustainability question has to do with the energy challenge the globe faces.
Second, industrial agriculture has massive environmental effects. Fertilizer and animal waste runoffs lead to groundwater and river pollution (extending into the Gulf of Mexico). Degradation and loss of topsoil is another large and longterm environmental effect with serious consequences for future agricultural productivity. And methane produced by large-scale cattle- and swine-rearing represents a measurable component of global warming. So the environmental effects of industrial agriculture are very large--once again raising the question of global sustainability.
Finally, industrial agriculture, and the integrated global commodity markets from which this system is inseparable, have large and destructive consequences for traditional agriculture and the communities built around traditional farming. The effect of NAFTA and the export of US corn to Mexico has been massive in its disruption of maize-based culture and communities in Mexico.
Three questions are central. First, is this system sustainable in the narrow sense, or will it collapse of its own burden of soil, water, and air pollution in the next 50 years? Second, is it a potential part of a larger sustainable global system of production and consumption from an environmental point of view? Or does global sustainability require radical change in agriculture? And finally, are there feasible alternative systems that would be less environmentally harmful, more sustainable, and less disruptive of agrarian communities? Are these alternatives scaleable to the needs of mass societies, large cities, and a global population of 6-8 billion? Can alternative systems achieve the productivity needed to feed the world's population?
Environmentalists, global justice activists, and food activists have argued that there are alternatives. The Fair Trade movement is trying to get first-world consumers to favor fair-trade-certified products in their consumption--giving greater security and income to third-world farmers. Organic farming advocates argue that a system of smaller farms, organic fertilizers, innovative pest control, and farming techniques more suited to the local environment would have a smaller environmental footprint. "Local food" activists support the idea of shifting consumption towards products that can be grown locally--thus reducing transport and refrigeration and giving more of a market for small farmers.
So there are alternatives in technique and policy that could result in different farm characteristics that are more favorable from the points of view of justice, sustainability, and community. The hard question is whether these alternatives could be scaled to the volume needed to feed a mass population. And this is a question that demands careful scientific analysis.
(An excellent current critique of industrial agriculture is Michael Pollan's The Omnivore's Dilemma: A Natural History of Four Meals.)