I always wondered if this happened in the middle east, with essentially the same cause. It seems hard for me to imagine that the "cradle" of civilization began in such an arid place, though it would be quite fitting if civilization transformed it.
2. The Euphrates floodplain is still quite green, like the Nile's. It's not like the US midwest where you have thousands of square miles of grass, but you do have a strip of extremely reliably fertile land (and for civilization-building, reliable seasons are super important).
Deforestation is a common cause of desertification worldwide. Trees help to capture moisture from the air and bring it to ground. Cut them down, and the moist air blows past. Trees are commonly cleared for farmland, and then the farmland has to be abandoned when it gets too dry.
In the Amazon basin and along the northwest coast of North America, trees were the basis of productive agriculture, carefully chosen mixes of trees of different sizes and species. To this day the Amazon basin is dominated by tree species that were once cultivated throughout, supporting tens of millions until they were wiped out by smallpox and other pandemics. In North America, such tree gardens can still be found centuries after they were abandoned.
Trees alone do not help. There are a lot of tree farms which do not capture moisture and are prone to forest fires. We need forests with good ecosystems not tree plantations.
Also certain places, e.g, Israel, were actual forests just 10-12,000 years ago.
I have no knowledge about the eastern portion of Egypt (Sinai?) being richer than the western one, afaik the wealth of Egypt was always centered around the nile and nile delta (even today). That's probably what the breadbasket refers to.
Wheat yields progressively fell as salt accumulated in the ground. They switched to barley until that crop failed too.
According to the book, almost all ancient agriculture was unsustainable. If not because of the irrigation, it was because plowing caused too much soil erosion. The only places that could get away with it long-term were Egypt and China, because of the flooding and lime replenished the soil.
Language is great.
There is evidence of lush farms in what is now the Sahara desert and civilizations that existed there had significantly more resources.
Early Egyptians documented this as well. ...and the Carthaginians were likely the last holders of that fertile land before civilization moved north in the Roman Empire.
Global temperatures rose causing desertification along that entire latitude.
I would think that the the cause is complex but humans removing trees until they are gone is probably part of the problem.