Restoration and recovery: Do restoration actions lead to stable populations of rare species?

Background/Question/Methods

Habitat restoration has long been used as a tool for recovering populations of rare or endangered species because it is believed to create new, robust source populations.  However, restoration actions may also create habitats that are sinks or ecological traps for existing populations, and few programs have evaluated the long-term ramifications of habitat modification on the population dynamics of the target species.  We tested the effect of habitat restoration on the dispersal behaviors and population dynamics of the Appalachian Brown satyr butterfly (Satyrodes appalachia) as a surrogate for the disturbance dependent, federally endangered St. Francis’ satyr (Neonympha mitchellii francisci).  Habitat restoration within existing forested riparian corridors comprised of either removing all trees, installing temporary dams, or both in 30m x 30m plots.  Each restoration action was chosen to capture the different primary phases of wetland succession found in active and historic St. Francis’ satyr population sites.  To estimate survival rates of larvae and the effects of predation, caterpillars of mixed age were experimentally added to host plants that were either open or closed to predation in all plots.  In addition, we tracked naturally occurring and experimentally released butterfly movements to estimate dispersal rates in each restored habitat type. 

Results/Conclusions

We found that larvae survival rates were not affected by restoration actions when protected from predation.  However, larvae survival was significantly lower in the presence of predators in plots that had all trees removed; suggesting that some types of restoration actions can have strong negative effects on population dynamics over time.  In plots that had trees removed, we also found greater potential host plant abundance than in plots of intact riparian forest; a result that is thought to benefit butterfly populations.  Plots that included dams alleviated predation pressure on larvae, resulting in positive effects on butterfly populations.  Dispersal behavior of butterflies did not differ between habitat types.  Our results suggest that recovery of the endangered St. Francis Satyr is complex and that restoration actions can have both positive and negative effects on population dynamics depending on the type of habitat modification undertaken.