Solar Arrays in the Desert

A few years ago I read an article in Science or Scientific America about the idea of putting a gigantic solar array in the desert areas of the Southwest US. I thought it was a horrible idea then, still think it's a horrible idea. I read an another article today that said the BLM has started selling development rights to federal land in the Southwest US specifically for the purpose of putting in huge solar arrays. The area is large, "empty" and the sun shines over 300 days out of the year. It's actually a great place for solar power, but at whose expense.
The BLM has allowed one company to actually start development before the impact on the desert tortoise was researched. Uh, DUH! So, after this company has started putting their arrays in, the government scientist find out that, oops, this huge array that you are putting in will have a negative impact on a federally protected species. again, I say, Uh, DUH!! The solar array was to impact 5000 acres, 3500 of which was desert tortoise habitat. 
The BLM originally intended for solar development to take place on 700,000 acres of public land in six southwestern states, but has dropped the number to 300,000 because of complaints from many conservation groups and industry. However, they are still moving forward without any research. Although, they have launched one of the largest research projects to discover the impact on the tortoise, big horn sheep, mule deer, and many other species that use those areas for migration, foraging, or residence. Kind of like shutting the barn door once the horses have already left the building, putting the cart before the horse, and how many other million cliches about doing something "bass ackwards!"
So again, I bring up the point. What about all the buildings and parking lots in the southwest US? Nothing lives on them, other than our gas guzzling SUV's. Nothing uses them for migration, other than the random squirrel, or our gas guzzling SUV's. Nothing forages on them, not even our gas guzzling SUV's. So, why are we letting all that space go to waste? Why is it, the first thing anyone thinks of destroying is virgin/raw land? Why don't people think about using areas that we've already ruined and making them multi-use? We've already put buildings up in the middle of the desert, and created a heat sink that guzzles more water than was ever intended to go there. Why don't we make something positive out of it? Why not put up solar arrays, but put them over the parking lots, and on top of the buildings. Make use of "wasted space."
Oh, wait, I know, that kind of thing would take a little more thought and a little more money because they would have to find a way to work around people, instead of defenseless, endangered, or threatened animals. Instead of just coming in and mowing everything down and putting up what they want, they would need to stop and think and improvise. That might be a little to hard for them.