In the case of the US, we turned much of the richest farmland into subdivisions. The breadbasket of the nation is powered by an aquifer that will be depleted in my kids lifetime. Most of our green goods come from the deserts of California and Arizona, and won’t exist if the Colorado River water system breaks down.
That aquifer is being depleted because of farm subsidies not in spite of them.
The US’s domestic demand for food is vastly below the actual production, exports and biofuels need not be maintained in a war.