Sustainability as a moral obligation is a general obligation, not a specific one. It is not an obligation to preserve this or preserve that. It is an obligation, if you want to make sense of it, to preserve the capacity to be well off, to be as well off as we. That does not preclude preserving specific resources, if they have an independent value and no good substitutes. But we shouldn't kid ourselves, that is part of the value of specific resources. It is not a consequence of any interest in sustainability.
Secondly, an interest in sustainability speaks for investment generally. I mentioned that directing the rents on non-renewable resources into investment is a good rule of thumb, a reasonable and dependable starting point. But what sustainability speaks for is investment, investment of any kind. In particular, environmental investment seems to me to correlate pretty well with concerns about sustainability and so, of course, does reliance on renewable resources as substitutes for non-reliable ones.
Third, there is something faintly phony about deep concern for the future combined with callousness about the state of the world today. The catch is that today's poor want consumption not investment. So the conflict is pretty deep and there is unlikely to be an easy way to resolve it.
Fourth, research is a good thing. Knowledge on the whole is an environmentally neutral asset that we can contribute to the future. I said that in thinking about sustainability you need to be as inclusive as you can. Investment in the broader sense and investment in knowledge, especially technological and scientific knowledge, is as environmentally clean an asset as we know.
And the last thing I'd like to say is, don't forget that sustainability is a vague concept. It is intrinsically inexact. It is not something that can be measured out in coffee spoons. It is not something you could be numerically accurate about. It is, at best, a general guide to policies that have to do with investment, conservation, and resource use. And we shouldn't pretend it is anything other than that.
"Sustainability: An Economist's Perspective," Robert M. Solow