Most can only appreciate nature for its asthetic properties, but there is more to nature than that. Nature is all that is created by a higher power, that which can not be explained or justified by mankind. Nature writing is expressing natural emotions, experiences, and thoughts with the written word. When I think of nature, I think about the forest, birds, animals, just everything that exists naturally, not manmade. I think of Thoreau.
Nature is life, all the species on earth.
Nature writng is writing about these things. Nature is the the bald-face hornet delivering her sting to the back of my hand through the leather glove I wore while trimming a meadow trail. Nature is the swelling of my hand and the pain, like I've been hit with a hammer. Nature is my body doing what it can to contain the poison and the curse that rolls off my tongue even before I know what's hit me. Nature is the sparrow-hawk circling overhead in the clear blue sky, and my heart leaping in that direction as I stand breathless as the hawk glides flapless.