The publisher regrets the below corrections in the article: The abstract of the article was missing. Abstract In the United States, the most recent regulatory tool for carrying out biodiversity offsets for wetlands is the mitigation banking system. This system aims to compensate for many small impacts on wetlands by carrying out restoration projects on fewer but larger wetland areas in order to reach the goal of no net loss of biodiversity. Mitigation banking has been criticized based on its categorization as an environmental “market”. This paper discusses the real nature of biodiversity offset markets, using three complementary approaches: a conventional economic approach, an empirical sociological approach, and a new institutional economics theory approach. To accomplish this, we carried out a field research study in Florida. The results show that the mitigation banking system is a hybrid organizational form halfway between a market and a hierarchy. Compared to permittee responsible mitigation, it has interesting specific features resulting from political tradeoffs, which seem adapted to implement public policy dealing with the complex and poorly predictable issue of biodiversity. Thus, it may be a useful organizational innovation to implement ecological compensation more efficiently, provided it is properly regulated.