Transparent solar cells that could power skyscrapers

I'm not sure I get the distinction between protecting forest ecosystems and desert ecosystems.

Compare the density of plant and animal life in a desert, with a forest. Deserts are necessarily sparse, and so you can develop far more desert land while doing much less damage. Since development isn't going to stop, the LESS destructive method is preferable.

I can tell you there are lots and lots of plants in the "mostly-empty" desert.

We won't run out of creosote bushes.

The whole idea of protecting individual animals and plants is that all species play a role in the ecosystem

Actually the popularity of the endangered species act is all about people wanting to preserve their childhood, and the animals they remember. The smaller and less significant the animal, the less public interest in protecting them. In truth, many species go extinct all the time, their impact on the ecosystem is low, and nearly nobody cares when it happens. It's only when large animals disappear that people bat an eyelash.

taking one species out threatens others in ways that are often unpredictable.

That sounds a little too much like the fear-mongering mantra of anti-chemical/vaccine/GMO/nuclear groups to me. The ecosystem of Arizona didn't collapse when the Santa Cruz Pupfish (Cyprinodon arcuatus) went extinct. In fact, can you point to ANY ecosystems that collapsed as the result of a few minor plants or animals going extinct? Particularly when we're talking about one endangered minor sub-species of an animal that's otherwise doing fine, it's hard to justify all the expensive efforts to preserve it. And in the deserts, too, there are state and federal parks and preserves which will provide sanctuary for endemic species.