[Tuor in Gondolin]

Interesting the Might cites his homeland of Romania, since i was about to post that since JRRT saw the Shire as being in the area of England, that would make Rhovanion in the latitude of France/Romania/the Black Sea, indicating a fairly moderate climate, and also, while a steppe, one considerably shielded from extremes by Mirkwood, the Misty Mountains, and northern Mordor.

While elves might not engage in large scale irrigation, wouldn't men?
Perhaps advised and helped by the entwives. And, as in the middle east and central Asia when peoples like the Mongols invaded, Easterlings might have destroyed them or not tended them properly, leading to some desertification.