Using landscape connectivity to inform prioritization of restoration areas in the Delaware Estuary watershed

Background/Question/Methods Regional restoration planning is emerging nationally as a means to promote better coordination among restoration practitioners, planners, and project decision-makers to ensure that the most meaningful ecological outcomes are realized. From an ecological perspective, the suitability of potential restoration sites is based on both species ecology and habitat availability (either current or planned for in the future). From a regional perspective, an additional consideration for mobile species or propagules is the value that a restored site can contribute to habitat connectivity in the broader landscape.

In the Delaware River watershed, the Regional Restoration Initiative (RRI) spearheaded by the Partnership for the Delaware Estuary is coordinating a project registry of potential restoration sites. The restoration sites will be prioritized based on a variety of scientific, policy, and economic factors. Habitat connectivity is one of the scientific factors, and here we consider the landscape connectivity modeling predictions in a case study of six urban waterfront restoration sites in Philadelphia along the Delaware River.

Integral Consulting completed landscape connectivity modeling for three avian species of concern (black duck, least bittern, and marsh wren) for each of the six restoration sites using the LandGraphs modeling software.  Literature-based species-specific dispersal distances were used as model inputs along with GIS habitat layers from the USFWS/USGS Maryland, Delaware, and New Jersey Gap Analysis Project.

Results/Conclusions

The modeling results indicated that the landscape was very well connected for black duck and marsh wren, and poorly connected for least bittern. More specifically, 1) the black duck habitat patch data was not amenable to modeling but nevertheless showed that all of the restoration sites would be valuable for dispersal across the landscape; 2) the marsh wren results indicated that all of the restoration sites would be valuable for dispersal, and that two sites in particular had elevated dispersal values; 3) the least bittern results indicated low dispersal value for all restoration sites, however, two sites in particular could be valuable for the connection of isolated least bittern populations.

Based on the model results from this case study, a consideration of the restoration priorities that should be represented by the connectivity valuation in the RRI project registry will be completed and applied to other potential restoration sites under consideration.