From what I understand, the Middle East used to be lush and green, but after thousands of years of human habitation, and destructive farming practices, eventually desertified and became the giant desert we see today.
When did this happen? How green was it? What plants and animals went extinct? Give me everything.
Not to discourage further discussion, of course, but this question recently got quite a lot of good answers that you might want to check out: Why is the Fertile Crescent now desert?
/u/brigantus and /u/Prufrock451 would be happy to answer follow-up questions, I'm sure.