GIS analysis of spatial and temporal patterns of human-caused wildfires in the temperate rain forest of Vancouver Island, Canada

Abstract

This study examines the spatial and temporal pattern of human-caused wildfires (HCWs) in the temperate rainforest of Vancouver Island (VI). A Geographic Information System was used to locate HCWs that occurred on VI from 1950 through 1992, to divide VI into 1 km×1 km grid cells, and to determine for each grid cell the climate and distances to various human-built infrastructures. Logistic regression was used to build a predictive model of the probability of HCW occurrence in each of the grid cells, using climate and distances as predictor variables. A total of 6329 wildfires occurred on VI over the 43 years study period, and 2747 of the grid cells contained at least one fire. The probability of a grid cell burning was positively correlated with summer temperature, and negatively correlated with precipitation and distances to municipalities, campgrounds, dirt roads, railroads and paved roads. Grid cells were grouped into five classes of HCW probability: <20, 20–39, 40–59, 60–79, >80%. The lower the probability of HCW occurrence, the lower the number of fires per km 2 per year, the longer the fire cycle in years, and the larger the mean fire size. The unexpected larger mean fire size in areas with low HCW probability is due to logging fires being the most common type there, and logging fires being significantly larger than other types on all portions of VI. Where the HCW probability was highest, recreation and miscellaneous fires were most common, and these types of fires tended to be significantly smaller. The annual number and annual area burned by HCWs on VI has been decreasing. These decreases have occurred primarily in the areas that have a high HCW probability, while increases have occurred where the HCW probability is low. These results indicate that HCWs are a significant part of the temperate rainforest ecosystem and that the spatial variation in their occurrence could be used to delimit fire management zones.