Fig 1.
Map of the contiguous United States showing large core protected areas and Protected Areas Database of the U.S. units not included in our definition of core protected areas.
Fig 2.
Linear (top) and non-linear (bottom) versions of resistance surfaces based on wildness (left) and human modification (right) used to model connectivity between large protected areas.
See S1 Fig for distribution of resistance surfaces in relation to original indices.
Fig 3.
Normalized least cost corridors (after removing the linkages >300 km shown in S3 Fig and the 10% worst linkages shown in S4 Fig) from Linkage Mapper connectivity models based on linear (left) and non-linear (right) versions of resistance surfaces using wildness (top) and human modification (bottom).
Fig 4.
Composite corridor value between large protected core areas, which was calculated by summing and reclassifying normalized least-cost corridors shown in Fig 3.
Black polygons are large core protected areas used in our analysis. Raster data are available as S1 File.
Fig 5.
Mean composite corridor values (classified into deciles) among non-core Protected Area Database land units (A) and federal inventoried roadless and wilderness study areas (B).
Roadless and wilderness study areas are shown in greater detail for the Northern Rockies and Southern Appalachian Mountains.