The Think globally- eat locally – San Francisco Foodshed Assessment study starts by asking if the city of San Francisco (not the entire Bay Area) could feed itself with local food produced within 100 miles of the Golden Gate. It identifies a production of 20 million tons of food per year, as compared to 935.000 tons consumed in San Francisco and 5,9 in the whole Bay Area. But for eggs, citrus fruit, wheat, corn, pork and potatoes, the food produced whithin the 100 miles range would be enough to current demand, altough in some cases seasonality would be a problem.
But it is not possible to know the actual proportion of local food consumed today in the city or the Bay Area. Irrigated croplands into the aforementioned circle are just 18% of total farmland, but produce 3/4 of the agricultural value; these irrigated areas are threatened by urban growth, at a rate of an acre for each 9,7 residents (a bit less than 25 residents per hectare). Food traceability should be encouraged.