A national assessment of green infrastructure and change for the conterminous United States using morphological image processing
Green infrastructure is a popular framework for conservation planning. The main elements of green infrastructure are hubs and links. Hubs tend to be large areas of ‘natural’ vegetation and links tend to be linear features (e.g., streams) that connect hubs. Within the United States, green infrastructure projects can be characterized as: (1) reliant on classical geographic information system (GIS) techniques (e.g., overlay, buffering) for mapping; (2), mainly implemented by states and local jurisdictions; and (3) static assessments that do not routinely incorporate information on land-cover change. We introduce morphological spatial pattern analysis (MSPA) as a complementary way to map green infrastructure, extend the geographic scope to the conterminous United States, and incorporate land-cover change information. MSPA applies a series of image processing routines to a raster land-cover map to identify hubs, links, and related structural classes of land cover. We identified approximately 4000 large networks (>100 hubs) within the conterminous United States, of which approximately 10% crossed state boundaries. We also identified a net loss of up to 3.59 million ha of links and 1.72 million ha of hubs between 1992 and 2001. Our national assessment provides a backbone that states could use to coordinate their green infrastructureprojects, and our incorporation of change illustrates the importance of land-cover dynamics for green infrastructure planning and assessment.