Prior to 1926 the Clearwater Valley in Wells Gray Park, British Columbia, was covered by a mature coniferous forest. By 1940 fires had denuded 380 square miles which soon supported an open deciduous vegetation. The change in vegetation was accompanied by change in the species composition of the mammalian community. Marten and caribou, among others, declined. Moose, deer, cougars, coyotes, wolves, Columbian ground squirrels and others flourished. Caribou in the area require mature coniferous forests at low elevation for winter survival. Fire reduced the area of these forests 60% or more. The decline of caribou coincided with this reduction of winter range. The northward trend of caribou decline in British Columbia since 1900 may have resulted from forest destruction, since human influences upon the forest have followed the same trend through the same period.