In the air and water pollution control arenas, the trading of pollution allowances has been embraced as a flexible and cost-effective way of achieving prescribed pollution reduction goals. Its advantages over prescribed technology requirements or across-the-board reduction requirements are manifest. The marketability of allowances creates an incentive for excess reductions by those who can achieve them cheaply, as well as a less costly means of achieving compliance with mandated goals by those who would otherwise face formidable compliance costs. The Clean Air Act's cap-and-trade system that has proven so successful in reducing emissions of acid rain precursors is now the presumptive best approach for reducing the threat of climate destabilization.

With the success of trading approaches in tackling air and water pollution challenges, it is natural to consider whether a similar approach might be useful in tackling the problem of endangered species. In his article, Trading Species: A New Direction for Habitat Trading Programs, Jonathan Remy Nash considers what, if anything, learned from the experiences with pollution allowance trading might be usefully applied to create an effective trading program for endangered species. His answer, not surprisingly, is essentially "not much."