Unnecessary and inefficient foods are farmed in California. There is a huge margin for improvement in land and water use before we come close to food shortage.
I believe that if there were a way to measure agricultural productivity besides profits, arguing in favor of less environmentally damaging agriculture would be much easier. I had to endure Atrazine polluted tap water (Panama) for my birthday last year for the first time, (officially) due to negligence of a sugarcane producing corporation. Suddenly we are faced with the difficult dilemma of having less gin and sugar or polluting the drinking water of 5% of the country.
