Brown bear distribution versus human disturbance and forest fragmentation in European Russia

Brown bear population underwent dramatic declines in the past century, mainly due to the hunting, habitat loss and fragmentation, and human disturbance.  However, in European Russia it appears that brown bears are now expanding their range southward.  Our goal was to model brown bear distributions in relation to habitat availability and human disturbance indicators.  Brown bear densities were analyzed at the district level in European Russia (n = 529).  Habitat availability was assessed based on MODIS land cover and we quantified forest fragmentation indices, and forest percentage.  "Core”, “fragmented” and “edge” forests were calculated within 25, 49, 81, and 169 km² moving windows.  Indicators of human disturbance included: urban area, road density, rural population density (1991 and 2001) and distance from the nearest administrative center.  Cost-path distance represents travel cost entailed when dispersing from northern source populations to the South and is related to human disturbance.  Our results show that bear population were strongly positively correlated with forest cover, especially interior forests.  Human disturbance indices were strong negative correlates of bear population density, especially travel cost (R-square =0.48).  Multivariate models captured 61% of the variability in bear densities.  Based on these models, we can now assess the effects of rural population declines, and forest succession on abandoned farm fields for bear populations in European Russia.