Since the glaciers receded, fire has been the most dominant recurring event affecting natural processes in the boreal forest. In this region, the effects of fires on aquatic systems are not well understood, but are likely to be important. Intensive fire suppression and forest harvesting are changing historical disturbance regimes.
In the last 30 years, commercial forestry has increased dramatically in the WBF. Governments have encouraged development by granting cutting rights to vast areas of forest. Forest Management Agreements and other licenses provide exclusive access to Crown Lands for large forestry companies, typically for tenures of 10 to 20 years in Canada, and up to 50 years in Alaska. Recent technological improvements in harvesting methods, road building, and the use of aspen for pulp production have enabled timber harvest to increase dramatically. The vast majority of the commercially valuable timberland in the central WBF has been allocated and scheduled for harvest over the next 40 years.
Oil, gas and mineral extraction
Extraction of petroleum resources is the primary threat to boreal habitats where little marketable timber is present. The fourth largest oil field in Canada is located at the heart of the taiga plain at Norman Wells, NT. Alberta, however, possesses the bulk of the region's oil and gas fields. There are over 88,000 well sites located in Alberta's portion of the boreal forest alone, and >885 km2 have been cleared for those well sites. Between 1986 and 1995, approximately 500,000 km of seismic lines were approved to be cleared in Alberta, and by 1998, more hectares of land were cleared each year for oil and gas pipelines, seismic lines, roads and well sites than were cleared by forest logging. Although most of this activity is in the south central portion of the WBF, these combined impacts illustrate the level of fragmentation that can occur in more remote regions if they contain extractable minerals. In addition to land clearing, petroleum production and oil sands mining promote a high degree of habitat fragmentation, hydrologic interruption, and air and water pollution.