Nothing is more important to human beings than an ecologically functioning, life sustaining biosphere on the earth. It is the only habitable place we know of in a forbidding universe. We all depend on it to live and we are compelled to share it; it is our only home... the earth's biosphere seems almost magically suited to human beings and indeed it is, for we evolved through eons of intimate immersion within it. We cannot live long or well without a functioning biosphere, and so it is worth everything we have.