Update on additivity

Note that my last post on additivity, and this one, are both examples where I'm thinking out loud.  I'm still trying to sort out my views on these things.

I think Glenn's comment in the last post refers to the phenomenon of "leakage" or "slippage", which I have written and blogged about (see here).  I don't have a problem with this jargon.  Nor do I have a problem with any of the theoretical and empirical issues that dance around carbon offsets and similar policies that pay for conservation.

I guess my main concern is that the term "additive" may be too generic: it doesn't help to clarify where and how policies may be inefficient.

But, as Glenn points out, one of the big overarching issues here is that many conservation programs tend to put a price on environmental services in some contexts but not price them in other contexts.  Or, almost equivalently, environmental gains are priced but environmental loses are not priced, or vice versa. It's very much like taxing pollution in one country and not taxing in another country.  This is a big potential challenge with PES, especially for global environmental problems.