IANABotanist either, but your real problem isn't finding the right species of ground cover. It's coming up with sufficient water in the Mojave desert.

Might be an interesting terraforming project: bring some water along with the electrical infra, plant drought resistant shrubs and watch as they start covering soil, capturing moisture and so on...

Or maybe just leave the desert ecosystem alone?

I am not sure why people think that a desert is bare and empty, I guess most just assume that because you can't see it as easily as you can in a forest that there is nothing there, but desert ecosystems are much more fragile than most other ecosystems and do not adjust easily to random interference.

But you have to grapple with the counterfactual. The status quo of not building some of these projects is we keep pumping tons of coal soot and gas fumes into the air. We are currently on course to destroy the ecosystem of the entire planet.

I won't pretend that I know these projects are well-sited or they couldn't easily be done in a better way to lessen their impact. But, you can't use "it has a new harm" as an a priori veto of changes when the status quo is so deeply, deeply harmful.

Any human activity had an impact on the earth. At some point even the most well-intentioned of us have to accept that some big benefits may come at some (ideally lesser) costs.

I would ask those locals if they are ok with having no electricity other than what they can generate themselves on their own houses.

Desert may be a fragile area, but what is the real impact of its disruption? Everywhere there are tradeoffs.

Phosphorous from Saharan desert sands fertilizes the Amazon.

Messing with ecosystems on a large scale will probably have serious side effects which we haven’t investigated; better to err on the side of caution.

Define large scale...