You make it sound like solar farms are blocking off 100% of the solar radiation over the areas they cover. Have you actually seen any large solar installations? At the ones I've seen in the Mojave desert and Central Valley of California, the actual panels never cover 100% of the surface and a lot of backscatter light gets in even in the shade. I am not an ecologist but it seems like the effect would be more like having a bunch of trees in the desert.

They do tend to remove the underbrush from around the panels, probably because it's easier to install/maintain that way. You could make a case for allowing more vegetation around/under the panels.