Not necessarily. It is only worth saving things that are worth saving. One would need to have a view on whether a particular species was good to have around, serves any useful purpose or is an obstacle to the welfare of what we regard as important species, like us. Otherwise our attitude to nature would be like the attitude of those deranged individuals who never throw anything away because "it may come in useful one day". Indeed it may, but it is more useful not to have trash all over the house.

Imagine someone who thinks that wild things ought to be preserved and protected -- that it is humanity's moral duty to do so. She might even be one of those good people who manages to put these "green" moral principles into action. But suppose that she does not especially enjoy being around natural things. She might well prefer "civilization" to "roughing it", and she might not even find baby seals especially cute and cuddly. Perhaps she does not even derive any pleasure from the thought that there are wild places. They may leave her utterly unmoved, or they may even inspire in her fear and terror. (An astronaut might feel that way about the surface of the moon.) Such an individual might be described as respecting nature without liking it a whole lot.

By the same token, imagine someone who likes nature. She enjoys spending time in wild places and derives deep pleasure from her interactions with wild things. To find opportunities to commune with nature might even be one of her main lifelong pursuits. She might be as strong of an advocate for the national park system as the first person I mentioned, but simply because she would like there to be parks for her to enjoy, not because she feels any moral duty towards nature. Suppose that there is no moral component at all in her attitude toward nature. She does not think that nature is valuable in any objective or transcendent sense. She may take nature to be valuable to herself, since it is something she likes, but she does not believe that nature is somehow valuable in itself. She simply likes nature, just as I like ice cream but do not think that someone who is indifferent to ice cream is morally blind. Such an individual might be described as liking nature but as having no particular respect for nature.

This is a fascinating question, in some ways, I think, it's connected to the question of whether we have responsibilities to things bigger than us in the sense of things that can continue to exist without us--e.g. things like families, nations, political and artistic movements, cultures, universities, businesses. Generally, I would say there is a moral obligation to sustain good things generally--at least where sustaining some good thing doesn't require undermining another of greater value.

To your specific question: I would say that considering the species itself, there is no obligation to sustain it, since the simple existence of the species is neither good nor bad, so long as there are other species to substitute for it. Considering the species as part of the larger ecosystems of the planet, where genetic diversity is salutary for the health of living things generally, there is an obligation insofar as the well being of living things is good. Considering the existence of the species as the necessary condition for all kinds of other goods, such as art, science, scholarship, virtue, culture, family, sport, etc., implies that an additional obligation exists as well. Of course, this last bit does depend upon the idea that the goods that the existence of human beings makes possible are not overwhelmed by the bad things their existence produces.

The eventual demise of humanity seems inevitable, so that mere prospect doesn't seem noteworthy. That our activities cause some damage to other things also seems inevitable.

Surely, however, we are responsible for enviornmental damage that we cause. Even if some damange is unavoidable, we can--and should--find ways to minimize this damage here on earth or wherever else we find ourselves.

Preparing for emigration off-world seems a hasty response to me, but not because we are likely to destroy celestial bodies. Rather, Hawking's conclusons that there is nothing we can do to avoid an environmental catostrophe here on earth seems hasty and counter-productive: we don't have the technological and financial resources to move the population to another world, but do have the means to reduce the damage that we are doing to this planet. Therefore, I would think we would be wise to focus on that.

There are many interesting philosophical questions here. For example, when assessing the environmental damage that we cause to what extent and how should we consider the interests of non-human life or even non-living things? Should we consider the interests of unborn humans or other things that do not yet exist, but might? Finally, how strong is the obligation to act to prevent an envirommental catastrophe? For example, do we have moral obligations to the enviroment or to nature that trump obligations we have to other humans? For example, is it okay to act injustly to one another if we determine that this is necessary to prevent a large-scale environmental catastrophe?

Philosophers can bring reflection on the responsibilities that contributors to global pollution have toward foreigners, future people, and animals and the rest of nature.

Foreigners. Global warming is likely to cause severe harms to foreigners -- from draughts in Africa to flooding in Bangladesh -- especially to foreigners who are poor and vulnerable (who, for this reason, are themselves only very minimal contributors to global warming). Most of us shrug off the thought that we owe them anything. We think it's alright to pollute or that our individual contribution is too small to matter. Is this an adequate response if millions die prematurely as a result of the pollution we together produce?

Future people. Global warming is likely to have devastating effects far in the future. In cost-benefit analyses, it is common to discount the interests of future people, typically by 3 percent per annum. This is thought plausible in analogy to how individuals discount future pains and pleasures -- we are much more distraught when we face death tomorrow than we when face death in 40 years. But is the discounting of future people really plausible? Are deaths in 23 years only half as important, and deaths in 53 years one-fifth as important as deaths today? Is one human death today the moral equivalent of 500 deaths in 204 years, ... of 300,000 deaths in 414 years, of 17 trillion human deaths in 1000 years?

Animals and the rest of nature. Global warming may wipe out many biological species and destroy places of natural beauty. Do these losses have any disvalue beyond the significance they have for us? Or are we human beings permitted to destroy all these beings and places so long as we are ready to do without them?

Best for whom? The enviroment may change so that a particular species of tree is no longer very successful at propagating itself. If we do nothing, it will go extinct. But it might be much better for us if we did not let that happen, because the bark of the tree contains a chemical that is highly beneficial to us.

Life is complicated, sure enough...

My advice (for what it is worth--not much, I expect) is for you to hang on to your job. Partly, this is precisely because you quitting your job (unless you have some other very clear option available to you in a "clean" occupation) won't make the least bit of difference to the project of ending waste, for the very reasons you gave: someone else will do it, and all you will have done is put yourself out of work.

Instead, why don't you consider--and urge your colleagues to consider--"greener" practices at work. For example, designs done on computers (rather than sketched on paper) create less paper waste. (An out-of-date example, I'm sure, but I hope you get the point.) Those with expertise in an industry are in the best position to find ways to cut waste and to come up with processes (and products) that are not so bad for the environment. Find these!

And where you can't find better solutions, consider finding "compensations" such as planting more trees at your place of work--or contributing trees to plant in local park areas, or somewhere else in the world--and so on. Quitting your job may seem very noble and clean--but the reality is that you are likely to end up doing something just as bad (or possibly worse), and if you stay, you may be able to make a positive difference.

I have encountered this argument before, but I don't really understand it. In short, it seems to go: We are part of nature, so nothing we do can be counted unnatural. So far as I can see, that is a simple fallacy based upon no more than word play (or, perhaps, a confusion between purely descriptive and broadly prescriptive senses of the term "natural"). The kinds of freaky creatures that now populate the landscape around Chernobyl are part of nature, too, but that does not make them "natural".

Unlike locusts, human beings can choose what they do to the Earth. They ought to choose wisely.

Perhaps you do not share the sentiment, but many people believe that we ought not needlessly drive pandas to extinction not because it is nice for us that there are pandas around but simply because it is a good thing, period, that there are pandas around. This attitude involves a certain kind of resepct for nature that is, it seems to me, difficult to explain and more difficult still to justify. But that, I would suggest, is no criticism of this attitude, which, as both defenders and critics have pointed out, has much in common with relgious faith. Indeed, I'd put the point myself by saying that "creation" is owed a certain amount of respect.

Certainly there are elements of self-interest to this position, too: Perhaps one thinks that a certain degree of humility in the face of nature is worth cultivating; the Earth is now in a certain kind of "balance" without which human habitation would not be possible, at least across very much of the planet's surface. And the Earth has not always been in that particular state of equilibrium. Since the costs of upsetting that balance would, for humans, be catastrophic, perhaps it is best to err very much on the side of caution.

I agree with Nicholas that where we can take natural to mean 'conducive to human flourishing', in Aristotle's sense, there will be a connection between being natural and being good. But there are natural functions that do not carry this meaning. In biological cases, functions often correspond to 'selected effects'. Thus the function of the white fur of a polar bear is camoflage, and that coloration is the result of natural selection. Bears in that environment with white fur did better at reproducing than their more colourful cousins. Selected effects are in that sense natural: they are what the trait is for.

From a moral point of view, however, selected effects may be bad and unselected effects may be good. Thus we may have evolved a tendency to deceive other people in certain circumstances, even if this is not morally decent behaviour, and someone who decently resists this temptation may be bucking that evolved inclination. Selected effects may be conducive to what we might call 'reproductive flourishing', but as Nicholas emphasizes, this is not what Aristotle meant by 'flourishing' and it is not the same as what is morally valuable.

I agree with Peter Lipton that most cases of people associating unnaturalness with badness are cases that provide no such connection. Usually, however, I find in such faulty associations a false conception of what is and is not "natural."

For example, many people have claimed that homosexual sex acts are "unnatural," for the reason that the biological function of sex is reproduction. So homosexual sex acts would be ones, to use Peter Lipton's expression that appropriated "something that has one function [reproduction] in order to perform a different function [giving and receiving pleasure, for example]." While I concede that homosexual sex acts cannot serve the function of reproduction (at least directly--I can come up with cases where it does so indirectly), I do not at all concede the claim that the natural function of sex is reproduction, since plainly that would make most sexual activities unnatural, including (but not limited to) kissing, caressing, oral or manual sex, and most of the rest. Indeed, if reproduction were all that was at stake, rape would be more "natural" than oral sex.

If we do not take such a blinkered conception of what is natural, however, at least some philosophers are actually inclined to think that there is a connection between something being natural and its being good, and accordingly, between being unnatural and its being bad.

Aristotle, for example, famously (in Nicomachean Ethics I.7) that human beings have, as a natural function, the desire to gain eudaimonia, which is variously translated as "happiness," or "well-being," or "flourishing." Now, if we all do, by our very natures wish to flourish, then anything that we do that will lead to the opposite result (wretchedness or misery) will be contrary to our natures. Measured by our shared interest in flourishing, moreover, doing something that will make us more wretched will also be bad, on the ground that what makes something good or bad is just what makes it conducive to flourishing or wretchedness, respectively.

By this measure, notice, homosexual sex will (among eagerly consenting adults and well performed) be both natural and also good, and good because it is natural. That is, consenting adult homosexuals performing well will act in ways that are very much conducive to their own flourishing (as well as to the flourishing of those who care about them). Similarly, all of the other sex acts the narrow reproductive conception of naturalness would condemn also, in this alternative theory, would reasonably be seen as contributing to human flourishing, and thus both natural and good, and good because it is natural. Laws or other restraints on things that are conducive to human flourishing would now be revealed as both unnatural and bad, and bad, again, precisely because they were contrary to our natural human desire to flourish.

I am not claiming that this theory is beyond all criticism, though I admit to finding it an attractive way to connect the natural and the good. But it does seem to me that the sense of natural at work in this view is actually the same sense as the one Peter Lipton was using--that of having a natural function--and it does provide some reason for thinking that good and bad can be understood in terms of something's natural function.