I'm thinking of the Nile valley, and how it supported Egyptian civilization for thousands of years. But it was fed by the annual flooding. Maybe damming and controlling river flow disrupts the natural processes that replenish the soil.
Discussion
Yes, I imagine so.
And my impression is that much of the Middle East used to be much more fertile - but I could be wrong!
Certainly in the US, we're doing a number on the soil by growing corn, grain and soy in the way that we do. I remember hearing that the biggest export of the US - by weight - is topsoil.
Goodness that's rather depressing.
I imagine with all the knowledge we have of biology now, we ought to be able to work out more sustainable methods of agriculture. It just seems there aren't incentives to do that on a national/global scale.