Even though I'm sure that the sky was monochromatic like that when shot, it feels almost out of place with the color of the lower half. I would try converting it to black and white and see how that works.
I wouldn't change a thing. Whether the sky truly was mono or not, it's perfect.
The ground is the only thing with color -"life"- in it, as that life is sucked from it and all surrounding foliage (notice the barren tree) and expelled into the sky in the form of monochrome, all-encompassing grey.
The grain in the image, more visible in the sky, adds to the uncomprimising yet bleak depiction of this scene. This is an image that's natural, political, artistic and silent all at once.