When US tanks crossed the Iraqi border on 20th March 2003, they trundled along sandy roads and desert-scapes. How do we square this with the Fertile Crescent of Antiquity, that cradle of civilization running between the Tigris and the Euphrates that gave us the legendary Hanging Garden of Babylon?

There are two explanations. Firstly, climate change over several tens of thousands of years gradually warmed the area, reducing rain flow and restricting plant life. The second explanation is that human agriculture damaged the fragile ecosystem of the area. Irrigation channels dug led to the accumulation of salt and other minerals in the topsoil. Over time this reduced the soil’s ability to absorb water, led to flash floods, and desertification. The specifics of each explanation are beyond me, but if you are interested in reading more I recommend the following Ask Historians thread.

The human-agency explanation is most intuitive (and popular) but is apparently controversial. It is rooted in early colonial writers, who unable to understand how the cities of antiquity could have developed amongst the deserts they saw, assumed the unenlightened natives had ruined it all. Detractors argue low-intensity ancient methods could not have had such a profound impact on the region.
Today, we’ve resolved the debate by the dubious privilege of satisfying both explanations at once; industrialisation has allowed us to undermine local ecosystems while also changing long-term climate patterns.
The Fertile Crescent reminds us that politics has historically been intimately linked to questions of water and food. Industrial agriculture has consigned that to distant memory for many in the developed world (although not for many others). One of climate change’s consequences is likely to be the steady repoliticization of these issues again.