Landscape permeability is the ability of a land area to allow organisms to move and disperse, equivalent to what some authors call “habitat connectivity.” This project evaluated and mapped the relative landscape permeability for terrestrial organisms across the eastern United States and southeastern Canada, taking into account features that impede natural connectivity such as roads and other development. The analysis assigned locations to categories of diffuse flow (intact, permeable areas that facilitate high levels of dispersal), concentrated flow (large quantities of flow are concentrated through a narrow area), constrained flow (low permeability, with flow following a weak reticulated network), or blocked flow (lack of permeability). The analyses were conducted using the Circuitscape program. The regional permeability results were compared to the results of over 20 independent, smaller-scale studies of connectivity and the majority were found to be in good agreement, with the remainder in moderate agreement with the regional analysis. Alternative versions of the regional analysis incorporated climate change by considering preferential flow upslope and northward to track a warming climate. An additional analysis identified areas where major road crossings occurred in areas of concentrated flow, which could form the greatest barriers to range shifts and species movements.
