The whole point of these renewable energy projects is to be considerate to the environment. Covering up the desert, inhabited by tons of species (this is not the Sahara) in a greenhouse is an environmental disaster in a new skin.
Land use efficiency is a concern now for the environment. If renewable technologies have to cover up 60,000+ square miles of land not inhabited by humans, then coal and nuclear are the environmentally friendlier options.
From a strictly pragmatic perspective, I would argue that the loss of some desert habitat in an ecosystem that is not significantly linked with those used by humans for habitation, carbon sequestration, or agriculture is acceptable compared to the damage to higher-value ecosystems caused by air pollution from coal power. This assumes that environmental damage that causes long-term consequences for humans is considered more egregious than environmental damage that has no negative consequences for humans.
Personally, I think a thorium nuclear power plant in an isolated desert is a much more environmentally preferable approach than most renewable power sources.
It's better to make coal powerplants run cleaner too. Thorium will require serious effort to develop, a decade perhaps, but sure would be nice to have. Modern uranium is not that bad either.
There was some solar thermal project in California that ran into a lot of problems trying to use the desert land. Old power companies are paying environmental groups to protest those sprawling projects. Divide and conquer those hippies!
High altitude wind is the best source of renewable energy. It's concentrated and takes up airspace instead of land. They're taking their time though.
Land use efficiency is a concern now for the environment. If renewable technologies have to cover up 60,000+ square miles of land not inhabited by humans, then coal and nuclear are the environmentally friendlier options.