Compensatory mitigation for injury to a threatened or endangered species: scaling piping plover restoration

Abstract

Conducting natural resource damage assessments and adopting compensatory restora- tion plans for endangered and threatened species have special constraints. These constraints are illustrated by the agency responses to evaluate impacts of the North Cape oil spill on piping plovers Charadrius melodus in Rhode Island, and to establish appropriate compensatory restoration. Adopt- ing a precautionary principle implies that strict adherence to an α-value of 0.05 in formal tests for injury on endangered species, where rarity implies low statistical power, would result in overlooking many true impacts. Criteria for concluding that injury took place must nonetheless exist, including (1) existence of a conceptually valid mechanism to link exposure to the stressor and the documented negative responses; (2) field data supporting the existence of the stressor-response link; and (3) sam- pling designs that consider impacts of potentially confounding factors such as natural temporal change. Choosing restoration options is also challenging for endangered species because ethical considerations and risks associated with some interventions preclude otherwise acceptable actions for common species. For the piping plover, a synthesis of population limitations done for the species recovery plan was used to design compensatory restoration of protection of nesting on newly colonized beaches, an action difficult to scale in advance to match the estimated injury from oil, but adaptively adjustable if monitoring shows a need.