I'd further add that destroying food supplies is a pretty old strategy in war. Theoretically, it would result in less death, because most opponents would surrender before letting their people starve.
It is prohibited to attack, destroy, remove or render useless objects indispensable to the survival of the civilian population, such as foodstuffs, agricultural areas for the production of foodstuffs, crops, livestock, drinking water installations and supplies and irrigation works, for the specific purpose of denying them for their sustenance value to the civilian population or to the adverse Party, whatever the motive, whether in order to starve out civilians, to cause them to move away, or for any other motive.
This was not an attempt to starve the civilian population.
http://en.wikipedia.org/wiki/File:Aerial-herbicide-spray-mis...