Fig. 1. The Canadian boreal forest faces growing threats from human activity, as illustrated by this time series of aerial photographs from the Swan Hills in west-central Alberta. The region was essentially wilderness circa 1950 (top left). As early as 1964 (top right), numerous well pads had been constructed for extracting natural gas, connected by a network of gravel roads and pipeline corridors. These developments were preceded by the construction of a network of narrow (5-8m) seismic lines used for exploration seismology, which are visible as faint straight lines in the image. By the early 1980s (bottom left) forest harvesting had been added to these earlier disturbances, together with expansion of the primary road network. All these developments intensified over the following decade (bottom right), a process which continues to this day. Photos were reproduced with permission from "Alberta Sustainable Resource Development, Air Photo Distribution". Images are protected under the Copyright Act of Canada.
Fig. 1