A recent headline on the front page of the Wall Street Journal hailed the opening of the nation's first "butterfly bank." The "deposits" in this unusual bank are conservation credits earned by preserving an important area of habitat for the Quino checkerspot butterfly, an endangered species restricted to California. The bank's intended customers are other landowners who hope to develop other sites where the butterfly occurs. In order to do so, they can buy credits from the private entrepreneur who established the butterfly bank.

Meanwhile, just a week earlier on the nation's other coast, the state of North Carolina announced that it was purchasing a large tract of land containing a number of endangered red-cockaded woodpeckers. The state's intention is to earn conservation credits that it can use to meet future mitigation requirements when the state's transportation department builds new roads in woodpecker habitat elsewhere. The California and North Carolina examples illustrate two forms of a new phenomenon, generally known as either conservation banking or mitigation banking for endangered species.