Responding to SecularAnimist @183 on RealClimate Unforced Variations:
"I am most concerned about 'saving' the Earth’s biosphere from utter destruction."
Saving the biosphere is a laudable goal, but the question stands: what are we saving the biosphere for?
The biosphere is ephemeral. Bacteria will ultimately inherit Earth, and witness its destruction. This is arguably just, since bacteria are the most adaptable, the most abundant and have been here the longest. Even within your body, bacteria grossly outnumber your cells. To say that we exist in symbiosis with bacteria is a charitable interpretation. It's more accurate to say that we exist at the behest of tiny but exceedingly powerful and numerous organisms which are completely indifferent to our fate.
If we're saving the biosphere for bacteria, we needn't bother, because they don't need our help. It's we who need help, along with our fellow apex predators. There's an ethical argument that other organisms enjoy existence as much as we do, and therefore have intrinsic value and an inalienable right to exist. This closely relates to arguments previously advanced for universalism and civil rights. In the 20th century many nations became sufficiently enlightened to extend intrinsic value to all human beings, regardless of their race, color or creed, at least in theory. In the 21st century we're in the process of adding sexual orientation to the list, and non-humans could well be next.
Most civilized people support animal rights to some extent, but few would accept that plants also have rights, let alone bacteria. Obviously humans relate to mammals most easily, because we're biologically so similar to them. People can easily tell that their cat or dog is asleep, bored, or in pain, but they're less likely to identify with the internal states of non-mammals. Are we saving Earth for mammals then? E.O.Wilson would surely object, "What about ants?"
If we're saving the biosphere for its intrinsic value, then we have to face not only its impermanence, but also its incompatibility with many aspects of human society. Should we all become vegans? Many think so. Are we willing to abandon our machines, shrink our population, and worship nature as our aboriginal ancestors did? Or embrace Jainism and avoid harming even insects? Very few would go this far, but people are increasingly aware that we can't continue to have everything our way, that urgent choices need to be made.
For better or worse, humans run the show at the moment. The blade of natural selection that normally trims away failure is temporarily blunted. We routinely nourish organisms that would otherwise fail, and exterminate organisms that would otherwise succeed. In other words, we play god, by deciding what lives and what dies. Playing god is the essence of being human, and we'll keep doing it until we tire of it, or wreck things badly enough to be forcibly demoted. We need to be honest, and admit that we're primarily saving Earth for ourselves, so that the cultural odyssey in which we've invested so much time and energy can continue.
Saving culture is not merely a technical problem. It's not just our ingenuity, but our honor and integrity that are being tested, our willingness to make sacrifices for progress towards shared goals. Our aim is more than survival: it's to survive with dignity, while upholding our commitments to hard-won truths and principles. If we're saving Earth at all, we're saving it for future generations, so that they can fulfill our ambitions, by building a wiser and more enlightened society.