(1) The effects of man and climate on fire frequency have been studied using historical data and a fire-history model in Glacier National Park in British Columbia, Canada. (2) Glacier National Park experienced a change in fire cycle in the 1760s, which could be related to the occurrence of the Little Ice Age. Before 1760, the fire cycle was 80 years and after 1760 it was 110 years. The longer fire cycle after 1760 was clearly related to the cooler, moister climate which also resulted in the advance of glaciers at that time in the Park. (3) The construction of the Canadian Pacific Railroad through the Park corresponded to a period in which the area burnt by man increased (1883, 1885 and 1886) and many lightning fires occurred. There has not been a decrease in the fire frequency since the establishment of Glacier National Park in 1888, despite a fire-suppression policy. (4) Large, high-intensity, rapidly spreading fires caused by lightning are associated with a characteristic synoptic weather pattern which consists of two parts: (i) intense fuel drying associated with a stationary high-pressure system blocking access of moist Pacific air, and (ii) one or more periods of breakdown of the high-pressure system into low-pressure systems, which create lightning and high winds. (5) To have supplanted climate as a major determinant of fire frequency, man must either have used regular management burning or suppressed fires during critical weather periods. Because this has not occurred in Glacier National Park, the present fire regime is largely natural.

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This study examines the influences of fuel, weather and topography on lightning-caused forest fires in portions of southern British Columbia and Alberta, Canada. The results show a significant difference in lightning and lightning-caused fires east and west of the Continental Divide. In British Columbia, on average there was one fire for every 50 lightning discharges whereas in Alberta there was one fire for every 1400 lightning discharges. Elevation, the distribution of lightning strikes, the Daily Severity Rating (a component of the Canadian Forest Fire Weather Index System) and vegetation composition were identified as primary agents controlling lightning fire occurrence. However, the multivariate analysis does suggest that there are other factors influencing fire occurrence other than the biophysical factors we tested. The implications of the lightning and lightning-ignited fires for land managers are discussed.

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The subject of this article is the fire history of seven contiguous national and provincial parks in the Canadian Rocky Mountains, four to the east of the continental divide and three to the west. Seven centuries of time-since-fire data were combined and arrayed in three sets: all seven parks together, then the east-side and west-side groups separately. Fire cycles were estimated by four different methods: two of them statistical and two deterministic. Statistical evidence of distinct changes in fire regime, always toward a lower burning rate, was uncovered, with transitions in 1760 and 1940 on the east side, and in 1840 on the west side. The principal conclusions were: The seven parks as a unit supported a fire cycle of 60–70 yr for nearly five centuries before 1760. The burning rate then dropped sharply and a longer cycle of about 175 yr prevailed until 1940. Fire history in the combined large parks on the east side was similar to the above. By contrast, the smaller west-side parks group sustained a fire cycle of about 90 yr for at least five centuries before 1840; the burning rate then decreased irregularly to 2000. On the east side, the near absence of burned area after 1940 was attributed to the onset of effective fire protection. Possible prior causes of the earlier transitions on east and west sides include changes in climate or aboriginal fire practices, but this issue is left unresolved.