Writing about historical carbon output, like most philosophers, I worry about who has done what, who is owed and who owes, whether ignorance matters or not, and so on. But in all of this debate there is an embarrassing silence about "Nature." As we worry about what (if anything) the Developed World owes the Developing World, a fair division of the pie seems still to only involve "us."
One reason for that is that we don't have room in our moral discourse for things like Nature -- because, as it were they are things and not people. "People" here need not mean just humans. In fact a humans can cease to be a person (if they are brain damaged enough) and, if there are Martians, that in itself ought not to prevent them being people (if nonetheless rather different from people we have encountered to date). If this is sounding like a non-standard use of the term 'people' it is. I am using the term to apply to anything that ought to be treated as having a claim to moral standing. What you need to have to underwrite such a claim is where the philosophical trouble starts. Is it a point of view? Something like it is to be you?
These notions impose pretty strong standards to meet -- perhaps sentience. And so on that account, both Nature and most of the things that make it up, don't qualify. On the other hand, if we weaken the condition on moral standing to having interests in some vaguely objective sense (say reproduction and survival) then stones don't have standing but flees do. Hold on! Does a flee really care if it is eaten or not? And that pushes us back into the arms of a condition of standing that it is likely that only we can satisfy. But Stone's wonderful article "Should Trees have Standing?", reprinted in a book of his essays with the same title, takes a radically different tack to break this impasse. Begin with the Law not Philosophy he argues -- and take legal rules as nothing more than rules, not as rules that express underlying moral principles. Then ask if those rules can be plausibly applied to things that do not have interests of their own.
The key move in this is the model of guardianship. Consider a profoundly brain damaged child for whom a guardian is appointed to speak on the child's behalf, to represent the child's interests. Now the philosopher wants to say, "Wait a minute! What if the child has no interests. What if the child is so brain damaged that it (literally) has no point of view?" Stone's argument is that this does not matter from the point of view of the law. All that matters is what the law decrees. ".... what the legal rules touching on the ward provide." And if those rules can accommodate the guardianship of trees, so much the better. Is this anything more than legal sophistry? Does it carry any philosophical weight? Here is why I think it does -- Stone's argument is embedded in a much broader conception of the relationship of ethics and the law. The law, he argues, develops by extension and in doing so, it offers us a social mechanism to develop our account of ethics as well.