How do we know if habitat restoration is working? The case of Karner blue butterfly recovery in New York

In response to precariously low population numbers of the federally endangered Karner blue butterfly (Lycaeides melissa samuelis Nabokov) in east-central New York State, USA, intensive habitat restoration efforts were initiated in the Glacial Lake Albany (GLA) Federal Recovery Unit. We report on the use of The Nature Conservancy’s Conservation Action Planning framework to assess the long-term viability of the Saratoga Sandplains metapopulation in GLA and, additionally, to ascertain the short-term success of habitat restoration efforts. The framework includes a set of key ecological attributes, associated indicators, and ranges of acceptable variation that were identified based on the state and federal Karner blue butterfly recovery plan objectives, published literature, and expert opinion. Key ecological attributes include metapopulation size, connectivity of subpopulations, and amount and distribution of suitable habitat. We defined habitat suitability based on host plant abundance, nectar diversity, and within-patch structural heterogeneity. Overall, key ecological attributes in the Saratoga Sandplains Karner blue butterfly metapopulation fell below the acceptable range of variation, indicating the need for additional habitat restoration to avoid potential extirpation of the metapopulation. Over the last five years the metapopulation size increased, but consistently fell below the threshold established by the federal recovery plan. However, habitat restoration efforts have been successful in restoring over 30 acres of suitable habitat in the past three years. We suggest that use of an adaptively managed project cycle that assesses long-term and short-term success will improve endangered species recovery efforts.