I've been reading, and was interested in how the center of civilization has shifted dramatically over the last few thousand years. In particular, regions that are currently known to be arid and relatively infertile to be host to powerful empires such as the Achaemenid Empire, the Bactria Kingdom, Carthage or the various Caliphates.
So I was wondering, how do the agricultural regions of the past compare to its present day counterparts? From Asia, the Middle-East, Europe, Africa etc.
follow-up question: When there were reductions in arable land, can we trace human causes in some cases? Has deforestation promoted desertification? Has flood prevention turned nutrient-rich soil into nutrient-poor soil?
Agricultural regions depends on water and that in turn depends on the weather systems. And weather systems changes over time. During the time when an area receives enough rain there are more arable land, population expands and is able to support urban centers and artisans as well as other careers that is not involved in food production. An arid land today might be flourishing hundreds of years before.
When the land stops being productive whether stripped bare from overuse of just plain the rain stopped coming the population dwindles and moves away, and the then current government is vulnerable to attacks or internal collapse.
Can I recommend Floods, famines, and emperors El Niño and the fate of civilizations by Brian Fagan?