K. A. Logan

CLIMATE CHANGE AND PEOPLE-CAUSED FOREST FIRE OCCURRENCE IN ONTARIO

Climate change that results from increasing levels of greenhouse gases in the atmosphere has the potential to increase temperature and alter rainfall patterns across the boreal forest region of Canada. Daily output from the Canadian Climate Centre coupled general circulation model (GCM) and the Hadley Centres HadCM3 GCM provided simulated historic climate data and future climate scenarios for the forested area of the province of Ontario, Canada. These models project that in climates of increased greenhouse gases and aerosols, surface air temperatures will increase while seasonal precipitation amounts will remain relatively constant or increase slightly during the forest fire season. These projected changes in weather conditions are used to predict changes in the moisture content of forest fuel, which influences the incidence of people-caused forest fires. Poisson regression analysis methods are used to develop predictive models for the daily number of fires occurring in each of the ecoregions across the forest fire management region of Ontario. This people-caused fire prediction model, combined with GCM data, predicts the total number of people-caused fires in Ontario could increase by approximately 18% by 2020–2040 and50% by the end of the 21st century.

Relative importance of fuel management, ignition management and weather for area burned: evidence from five landscape–fire–succession models

The behaviour of five landscape fire models (CAFE, FIRESCAPE, LAMOS(HS), LANDSUM and SEM- LAND) was compared in a standardised modelling experiment. The importance of fuel management approach, fuel management effort, ignition management effort and weather in determining variation in area burned and number of edge pixels burned (a measure of potential impact on assets adjacent to fire-prone landscapes) was quantified for a standardised modelling landscape. Importance was measured as the proportion of variation in area or edge pixels burned explained by each factor and all interactions among them. Weather and ignition management were consistently more important for explaining variation in area burned than fuel management approach and effort, which were found to be statistically unimportant. For the number of edge pixels burned, weather and ignition management were generally more important than fuel management approach and effort. Increased ignition management effort resulted in decreased area burned in all models and decreased number of edge pixels burned in three models. The findings demonstrate that year-to-year variation in weather and the success of ignition management consistently prevail over the effects of fuel management on area burned in a range of modelled ecosystems.

Fire weather index system components for large fires in the Canadian boreal forest

Canadian Fire Weather Index (FWI) System components and head fire intensities were calculated for fires greater than 2 km 2 in size for the boreal and taiga ecozones of Canada from 1959 to 1999. The highest noon- hour values were analysed that occurred during the first 21 days of each of 9333 fires. Depending on ecozone, the means of the FWI System parameters ranged from: fine fuel moisture code (FFMC), 90 to 92 (82 to 96 for individual fires); duff moisture code (DMC), 38 to 78 (10 to 140 for individual fires); drought code (DC), 210 to 372 (50 to 600 for individual fires); and fire weather index, 20 to 33 (5 to 60 for individual fires). Fine fuel moisture code decreased, DMC had a mid-season peak, and DC increased through the fire season. Mean head fire intensities ranged from 10 to 28 MW m −1 in the boreal spruce fuel type, showing that most large fires exhibit crown fire behaviour. Intensities of individual fires can exceed 60 MW m −1 . Most FWI System parameters did not show trends over the 41-year period because of large inter-annual variability. A changing climate is expected to create future weather conditions more conducive to fire throughout much of Canada but clear changes have not yet occurred.

Fire activity in Portugal and its relationship to weather and the Canadian Fire Weather Index System

The relationships among the weather, the Canadian Fire Weather Index (FWI) System components, the monthly area burned, and the number of fire occurrences from 1980 to 2004 were investigated in 11 Portuguese districts that represent respectively 66% and 61% of the total area burned and number of fires in Portugal. A statistical approach was used to estimate the monthly area burned and the monthly number of fires per district, using meteorological variables and FWI System components as predictors. The approach succeeded in explaining from 60.9 to 80.4% of the variance for area burned and between 47.9 and 77.0% of the variance for the number of fires; all regressions were highly significant (P < 0.0001). The monthly mean and the monthly maximum of daily maximum temperatures and the monthly mean and extremes (maximum and 90th percentile) of the daily FWI were selected for all districts, except for Braganca and Porto, in the forward stepwise regression for area burned. For all districts combined, the variance explained was 80.9 and 63.0% for area burned and number of fires, respectively. Our results point to highly significant relationships among forest fires in Portugal and the weather and the Canadian FWI System. The present analysis provides baseline information for predicting the area burned and number of fires under future climate scenarios and the subsequent impacts on air quality.

Impact of climate change on area burned in Alberta’s boreal forest

Eight years of fire weather data from sixteen representative weather stations within the Boreal Forest Natural Region of Alberta were used to compile reference weather streams for low, moderate, high, very high and extreme Fire Weather Index (FWI) conditions. These reference weather streams were adjusted to create daily weather streams for input into Prometheus – the Canadian Wildland Fire Growth Model. Similar fire weather analyses were completed using Canadian Regional Climate Model (CRCM) output for northern Alberta (174 grid cells) to generate FWI class datasets (temperature, relative humidity, wind speed, Fine Fuel Moisture Code, Duff Moisture Code and Drought Code) for 1 ×, 2 × and 3 × CO2 scenarios. The relative differences between the CRCM scenario outputs were then used to adjust the reference weather streams for northern Alberta. Area burned was calculated for 21 fires, fire weather classes and climate change scenarios. The area burned estimates were weighted based on the historical frequency of area burned by FWI class, and then normalized to derive relative area burned estimates for each climate change scenario. The 2 × and 3 × CO2 scenarios resulted in a relative increase in area burned of 12.9 and 29.4% from the reference 1 × CO2 scenario.

Forest Fires and Climate Change in the Northwest Territories

Fire is the major stand-renewing disturbance in the circumboreal forest. Weather and climate are the most important factors influencing fire activity and these factors are changing due to human-caused climate change. Under a future warmer climate, we expect more severe fire weather, more area burned, more ignitions and a longer fire season, although there will be large spatial and temporal variation in the fire activity response to climate change. Results indicate increases of 25 to 300% in area burned and a lengthening of the fire season by 30 to 50 days over a large portion of the Northwest Territories, Canada. This field of research allows better understanding of the interactions and feedbacks between fire, climate, vegetation and humans, and identification of vulnerable regions. Projections of fire activity for this century can be used to explore options for mitigation and adaptation.