No Fire on the Mountain: Has Fire Suppression Caused Population Declines of an Imperiled Ground Squirrel?​

The Northern Idaho Ground Squirrel (Urocitellus brunneus) is listed as threatened under the Endangered Species Act. A prevailing hypothesis suggests that one reason for the species decline is encroachment of trees into its habitat due to fire suppression. However, this hypothesis has not been rigorously tested. Using geographic information systems and aerial imaging, I compared changes in abundance of the squirrels\u27 populations to changes in forest canopy coverage over the past 40 years. These comparisons allowed me to test the prevailing hypothesis for the population declines of this rare species by testing the prediction that forest fire suppression has allowed tree growth and encroachment into the squirrel’s habitat. This hypothesis predicts that the areas with the most pronounced population declines of Northern Idaho Ground Squirrels will have the most pronounced forest encroachment among colonies of these squirrels. Data indicates that there is a 50% increase in tree cover over the colonies and the historical range for the last 40 years