Historically farmers (and most people really) have sucked the area dry before getting worried. US farmers are certainly doing that right now, the incentives en

Historically farmers (and most people really) have sucked the area dry before getting worried. US farmers are certainly doing that right now, the incentives encourage it, and they're quick to lobby against changes in incentives. That's also what you get from a prisoner's dilemma, a farmer switching to conservation will increase their production prices and / or lower their yields (as they'll at least need to invest in new farming methods, probably new hardware, and will have to learn those), and they'll fall behind their neighbours to say nothing of the market as a whole.