In Google Earth satellite view, go find the entire plateau of dry land wheat farming (non irrigated) on the masive plateau surrounding Waterville, WA. We have already significantly modified the desert environment there for other purposes. Look at all the square areas of wheat farming.
Go find "Atomic City, ID" in a satellite view and look at the desert brush land surrounding it for an area that's so arid that humans haven't even tried to irrigate it or do something like dry land wheat farming.