I seem to think they are a huge benefit, I do know the lack of cover is detrimental to the proliferation of baitfish which in turn will decrease size in predator fish, I used to have a pond to fish in that the owner didn't like the looks of trees showing and also there weren't any trees around close to the pond, then he had a fellow come in with a long reach trackhoe and dig out the entire perimeter of the pond as far as he could reach, 60+ ft, thereby eliminating all cover for yoy, the fishing went south fast.

All the really good ideas I've ever had came to me while I was milking a cow.