Considering that there are archaeological sites in the American Southwest that are posited to have been abandoned due to the disappearance of their water supply, it is hard to blame all the aridness on “white folks”. Moreover, when I cycled through the Anza-Borego State Park in California, several of the information boards discussed how hardscrabble the existence of the Native American peoples in this area was, because it was already very much desert and required special strategies to survive.
This is a solid point. I was at Mesa Verde, the national park with the cliff dwellings. Apparently the people who lived there just up and left, well before Columbus showed up on the other side of the continent. One theory is that the current Hopi people are their descendants.
It's pretty clear that bad things happen, even when white people aren't around.
It's not really a "theory" as anyone normal uses that term. We know beyond any reasonable doubt that there's significant genetic, cultural, and political ancestry tying modern Puebloan groups to the the people who inhabited Mesa Verde (and other earlier pueblos). "Most" went east to the Rio Grande area, but plenty went west too. Some Hopi ancestry also comes from other groups to the north, west and south (into modern Mexico) where Puebloan groups no longer exist.
With that said, Spanish and American colonization of the Southwest has radically changed the landscape. Much of what's now low brush used to be substantially more vegetated, similar to organ pipe national monument. Mesquite was rare outside intentional cultivation. It's actually an invasive species from the separate Chihuahuan deserts in Texas that was spread alongside cattle. Another fun fact is that prior to colonization, no part of AZ+NM was more than a day's walk from water (~20mi), which was important to long distance travel and later the Apache wars. That's no longer true due to groundwater depletion.
Do you have a citation on mesquite spreading from Texas with cattle? I ask because the aforementioned information boards in the Anza-Borrego State Park speak of the local Native American population consuming mesquite, and Wikipedia, too, says the same about those Cahuilla people of southern California. From what I gather, it is only certain species that have later been invasive?
To be fair, North America used to have a lot of megafauna like wooly mammoths and they were hunted to extinction by "native Americans" when they showed up via the land bridge at Alaska.
