As this post and this article in Nature suggest, going all-out renewable will gobble up some major habitat--if it's not done right. There are two money quotes in Amanda Leigh Mascarelli's excellent Nature piece. The first is from Jimmie Powell, a policy expert at The Nature Conservancy:
If we are to prevent serious, damaging climate change, it will require one of the largest land-use changes in the history of the country.
The second is from conservation biologist Martha Groom:
I'm someone who believes that habitat change is as big a threat to our world today and our society as is climate change.