Jun 16, 2011 9:25 PM GMT
Personally, I'm not a locavore.
But while neighborhoods benefit from the occasional communal garden, it is a mistake to think that metropolitan areas could or should try to significantly satisfy their own food needs. Good environmentalism is smart environmentalism that thinks through the total systemic impacts of any change. Farm land within a metropolitan area decreases density levels and pushes us apart, and carbon emissions rise dramatically as density falls.
In 2008, two Carnegie Mellon researchers analyzed the reduction in carbon emissions that might come from moving to local food. They found that American food consumption produces greenhouse gas equivalent to 8.9 tons of carbon dioxide per household per year. Food delivery represents .4 tons of that total; all agricultural transportation up and down the food chain creates one ton of carbon dioxide per household annually.
We must weigh the environmental benefits from shipping less food against the environmental costs of producing and storing local food in a state that doesn’t exactly have ideal conditions for every kind of produce. One recent UK report found that the greenhouse gas emissions involved in eating English tomatoes were about three times as high as eating Spanish tomatoes. The extra energy and fertilizer involved in producing tomatoes in chilly England overwhelmed the benefits of less shipping. Even New Zealand lamb produced less greenhouse gases than English lamb. Berkeley graduate student Steven Sexton estimates that an American switch to more local corn production would require 35 percent more fertilizer and 22.8 percent more energy.
But the most important environmental cost of metropolitan agriculture is that lower density levels mean more driving. Today, about 250 million Americans live on the 60 million acres of this country that are urban — which is about four people per acre. By contrast, America uses 442 million acres for cropland and 587 million acres for pastureland, which is about 1.4 and 1.9 acres per person respectively. If we allocated just 7.2 percent of this agricultural land into metropolitan area, we would halve metropolitan area densities.