Hi RobTM,
Obviously I didn't make myself clear. I think that without man to observe it, nature, landscape in this case, from the point of view of man, doesn't exist. Oh, yes, as far as physics are concerned it exists, as do galaxies beyond the range of our sensing devices, but at that level it's an abstraction. I think the relationship between man and nature is what's important, and from the standpoint of visual art if you take man out of the picture you essentially have nothing very interesting.