The 20th-century industrialization of agriculture has increased the amount of greenhouse gases emitted by the food system by an order of magnitude; chemical fertilizers (made from natural gas), pesticides (made from petroleum), farm machinery, modern food processing and packaging and transportation have together transformed a system that in 1940 produced 2.3 calories of food energy for every calorie of fossil-fuel energy it used into one that now takes 10 calories of fossil-fuel energy to produce a single calorie of modern supermarket food. Put another way, when we eat from the industrial-food system, we are eating oil and spewing greenhouse gases.
While the surfeit of cheap calories that the U.S. food system has produced since the late 1970s may have taken food prices off the political agenda, this has come at a steep cost to public health.
Cheap energy has underwritten a globalized food economy in which it makes (or rather, made) economic sense to catch salmon in Alaska, ship it to China to be filleted and then ship the fillets back to California to be eaten; or one in which California and Mexico can profitably swap tomatoes back and forth across the border; or Denmark and the United States can trade sugar cookies across the Atlantic.
Whatever we may have liked about the era of cheap, oil-based food, it is drawing to a close. Even if we were willing to continue paying the environmental or public-health price, we’re not going to have the cheap energy (or the water) needed to keep the system going, much less expand production. But as is so often the case, a crisis provides opportunity for reform.
we now need to learn how to run an industrial economy without cheap fossil fuel, we have no choice but to find out whether sustainable agriculture can produce enough food. The fact is, during the past century, our agricultural research has been directed toward the goal of maximizing production with the help of fossil fuel. There is no reason to think that bringing the same sort of resources to the development of more complex, sun-based agricultural systems wouldn’t produce comparable yields.