Designing Sustainable Landscapes: Terrestrial barriers settings variable

Terrestrial barriers is one of several ecological settings variables that collectively characterize the biophysical setting of each 30 m cell at a given point in time (McGarigal et al 2017). Terrestrial barriers measures the relative degree to which roads and railroads may physically impede movement of terrestrial organisms. It is derived by assigning an expertderived score to each road/railroad class to reflect the increasing physical impediment of larger roads, and adjusting these scores at road-stream crossings (i.e., bridge or culvert) based either on a custom algorithm applied to field measurements of the crossing structure or predictions from a statistical model (see below for details) to reflect increased passability of terrestrial organisms through the crossing structure. Terrestrial barriers is scaled 0-5, where roads and railroads are assigned values >0 (indicating the relative degree of impediment) and all other cells are assigned 0.