> I'd also argue that having large groups living out in the desert is such an absurd configuration for humans that it presupposes an indifference for any sort of sustainability.

It's easier to irrigate a flat desert with fertile soil than to move the flat terrain and fertile soil closer to a water source.

Food production is a fairly important component of sustainable human societies, and a major reason for the US (California particularly) having inhabited deserts and semi-arid regions.