Well, according to Bob Holmes the first are natural but the last one is not. In his article "Imagine Earth without people" Homes writes about how humans are separate from the natural environment and can only be viewed in a negative light. Robert McHenry counters in his "Eden Without Us?" which questions Homes' views on the placing of humans outside nature. (Hat tip: Instapundit)
I guess one of the reasons I like geography so much, and the study of the ancient geographers, is the importance of the cosmological/teleological aspect. To understand the world and the cosmos one must realize that while humans are the most powerful player (that has made itself visible) it is still just an actor in the play which is the universe. We are still made out of organs, which are made out of cells, which are made out of molecules, which are made out of atoms just like everything else we scientifically know of. To think that getting rid of a "non-natural" thing like humans will "restore" the Earth to somesort of "natural" state is childish at best and absolute stupidity at worst. Think what the world has gone through. Mass extinctions, global cooling, and global warming to such extremes that Al Gore's head would explode. My own mother, with no formal paleogeographic training, is well aware that her home state has been an inland sea, desert, rain forest, desert again, savanna, under a couple miles of ice, under a giant lake, steppe, forest, and steppe again all in the last 100 million years or so all without any input from humans.
Tomorrow Catholicgauze changes gears and looks at how humans, while still part of the natural world, are at the pinnacle