Conserving biodiversity through offsets? Findings from an empirical study on conservation banking

Abstract

Biodiversity offsets are used internationally to compensate for impacts on the environment, but research on the effectiveness of this instrument in conserving biodiversity is scarce. Conservation banking under the US Endangered Species Act is a long established and strictly regulated offsetting program. An analysis of the implementation of this program can hold implications for biodiversity banking anywhere. This paper describes and analyzes the implementation of species and habitat conservation banking in the state of California. First, we identify aspects of effective offset program design and implementation from previously published literature. In a second step, this paper uses empirical evidence from 30 expert interviews to analyze how these aspects are applied in conservation banking. The analysis covers a no net loss policy goal and additionality, equivalence and accounting, uncertainties and ratios, site selection, landscape-scale mitigation planning, advance mitigation, adherence to the mitigation hierarchy, leakage & trade-offs, oversight, transparency and monitoring. The positive attitude of all stakeholders towards conservation banking suggests that the program yields some benefits, but its contribution to species recovery is unclear. Limited standardized metrics reflecting key biodiversity values for species recovery (e.g. habitat size, connectivity, quality) at the impact and bank site are needed to allow for program evaluation. In addition, transparent tracking across impact permit and crediting processes as well as across agencies is necessary. Once implemented and evaluated in California, results could lead to changes in the implementation of the ESA across the US. We reflect the results considering best practice from academic literature and raise questions for future empirical research.