[aerohead]

That's not germane to the conversation.

But, yes, they did in a way. They consumed more and more local vegetation for fuel as their population grew, denuding the landscape, and requiring longer and more distant overnight foraging missions to bring back fuel.
It's the prolonged drought that got them. And right now, New Mexico is in a 1,200-year drought.
So as AeroStealth says: with the first law of holes, when the hole's too deep, stop digging!
If you're in a drought, it's folly to behave in ways which aggravate drought.
One cannot plant apple trees with the expectation of harvesting oranges.