Visit somewhere in California where a pristine mountain side with trees and red rock was just 10 years ago, and not it is nothing but wall of spinning white blades of bird killers.
Wind is like water. You can't just slow it down with your turbines and expect no environmental impact. Putting them on the windward side of a mountain reduces the rain fall on the opposite side. Birds die in the blades. It isn't all rainbows and butterflies.
"Previous studies had suggested that cats kill about 500 million birds a year. Marra's group came up with something very different. "We estimate that cats kill somewhere between 1.4 and 3.7 billion birds a year," Marra says. "For mammals, it's upward of about 15 billion."
"Marra says based on those new figures, cat-caused mortality far exceeds deaths from other sources, like collisions with cars or wind turbines.
As these things go, it's one of the more unobtrusive options. Compare it to, for example, an open cast coal mine. (It's even probably cheaper to knock down the turbines than it is to fill the pit back in.)
Wind is like water. You can't just slow it down with your turbines and expect no environmental impact. Putting them on the windward side of a mountain reduces the rain fall on the opposite side. Birds die in the blades. It isn't all rainbows and butterflies.