[latefordinner]

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Are you looking for a deontological explanation or a consequentialist explanation?

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HMK: I think you could make both, but I don't think it has to be deontological (as an aside, do you make deontological arguments for AC or do you think it is the best simply from a consequentialist POV?)

For instance, one could make the argument that, from a utilitarian standpoint, humans have only quite recently gained the capability to alter their environment on a scale that is not sustainable in terms of sustaining human life at its current levels. (ie; 500 years ago you could pretty much do whatever the [censored] you wanted with whatever technology you had to whatever species you wanted and it wouldn't affect the capability of another human being that you didn't even know existed to maintain her biological survival requirements). However, our ability, as humans to understand/predict those results is not in an equal place with our ability to create those changes. (I realize you could make the argument that a human, or the human species in aggregate, can never know/predict the ultimate effects of their actions on their survival/wellbeing, hence the "accidental/random" nature of natural selection and the reasoning behind a market economy in determing what is best for everyone) - therefore the only sane/safe course of action is to realize that any species currently living on earth could be essential for human survival (though our understanding of biology/ecology is certainly at a point where we could say that some species are more likely than others to be essential) therefore, from a utilitarian standpoint, to maximize our chances of survival we should, as humans, do our best not to willfully cause the extinction of another species for economic reasons.

or to put it another way - the market economy can only make use of the information that is priced into it. However it is possible in the case of ecology/sustainability (whether we are talking about the existence of other species, global warming, whatever) that by the time the market has received enough information to price it in at a reasonable level for a market correction to occur we will have already overshot ecological limits to human survival in a large and irreversible way thus ensuring a rather massive die-off of humans and other species.