Determining sustainable levels of cumulative effects for boreal caribou

Direct and indirect effects of industrial development have contributed, in part, to the threatened status of boreal ecotype caribou (Rangifer tarandus caribou) in Alberta and Canada. Our goal was to develop a model that would allow managers to identify landscape-scale targets for industrial development, while ensuring functional habitat for sustainable caribou populations. We examined the relationship between functional habitat loss resulting from cumulative effects of natural and anthropogenic disturbance, and the rate of population change (lambda) for 6 populations of boreal caribou in Alberta, Canada. We defined functional habitat loss according to 2 variables for which we had a priori reasons to suspect causative associations with lambda: 1) percentage area of caribou range within 250 in of anthropogenic footprint, and 2) percentage of caribou range disturbed by wildfire within the last 50 years. Multiple regression coefficients for both independent variables indicated significant effects on lambda. The 2-predictor model explained 96% (R-2) of observed variation in X among population units (F-2,F-3 = 35.2, P= 0.008). The model may be used to evaluate plans for industrial development in relation to predicted wildfire rates and goals for caribou population growth rates.