Canadian Forest Fires Research Articles

Direct carbon emissions from Canadian forest fires, 1959-1999

Direct emissions of carbon from Canadian forest fires were estimated for all Canada and for each ecozone for the period 1959–1999. The estimates were based on a data base of large fires for the country and calculations of fuel consumption for each fire using the Canadian Forest Fire Behaviour Prediction System. This technique used the fire locations and start dates to estimate prevailing fire weather and fuel type for each of about 11 000 fires. An average of 2 × 106 ha·year–1 was burned in this period, varying from 0.3 × 106 ha in 1978 to 7.5 × 106 ha in 1989. Ecozones of the boreal and taiga areas experienced the greatest area burned, releasing most of the carbon (C). The mean area-weighted fuel consumption for all fires was 2.6 kg dry fuel·m–2 (1.3 kg C·m–2), but ecozones vary from 1.8 to 3.9 kg dry fuel·m–2. The mean annual estimate of direct carbon emissions was 27 ± 6 Tg C·year–1. Individual years ranged from 3 to 115 Tg C·year–1. These direct fire emissions represent about 18% of the current carbon dioxide emissions from the Canadian energy sector, on average, but vary from 2 to 75% among years. Post-fire effects cause an additional loss of carbon and changes to the forest sink condition.

Direct carbon emissions from Canadian forest fires, 1959-1999

Direct carbon emissions from Canadian forest fires, 1959-1999

The influence of canadian forest fires on pollutant concentrations in the united states

High carbon monoxide (CO) concentrations from uncertain origins occurred episodically in the southeastern United States during the summer of 1995. We show that these episodes were caused by large forest fires in Canada. Over a period of 2 weeks, these natural emissions increased CO concentrations in the southeastern United States as well as along the eastern seaboard, a region with one of the world's highest rates of anthropogenic emissions. Within the forest fire plumes, there were also high concentrations of ozone, volatile organic compounds, and aerosols. These results suggest that the impact of boreal forest fire emissions on air quality in the mid-latitudes of the Northern Hemisphere, where anthropogenic pollutant sources have been considered predominant, needs to be reevaluated.

Satellite detection of smoke aerosols over a snow/ice surface by TOMS

A recently developed technique of using satellite UV radiance measurements to detect absorbing tropospheric aerosols is found to be effective over snow/ice surfaces. This method takes advantage of the wavelength dependent reduction in the backscattered radiance due to the presence of absorbing aerosols over snow/ice surfaces. An example of the aerosol distribution derived from Total Ozone Mapping Spectrometer (TOMS) data is shown for an August 1998 event in which smoke generated by Canadian forest fires drifts over and across Greenland. During this event, the TOMS observed 360 nm reflectivity over the snow/ice surface dropped drastically from 90‐100% down to 30‐40%. We investigated the history of smoke events over snow/ice and found that there is a large interannual variability in the amount of smoke aerosols observed over Greenland.

Ozone and aerosol distributions in the summertime troposphere over Canada

Measurements of ozone (O3) and aerosol distributions were made with an airborne lidar system in the lowland and boreal forest regions of eastern Canada during July–August 1990 as part of the NASA Global Tropospheric Experiment/Arctic Boundary Layer Expedition (ABLE) 3B. Aerosol and O3 profiles were measured simultaneously above and below the Electra aircraft from near the surface to above the tropopause on long‐range flights over these important ecosystems. A broad range of atmospheric conditions were encountered during repeated flights over intensive study sites in the Hudson Bay lowlands near Moosonee, Ontario, and over the boreal forest near Schefferville, Quebec. The tropospheric composition in this high‐latitude region was found to be strongly influenced by stratospheric intrusions. Regions of low aerosol scattering and enhanced O3 mixing ratios were correlated with descending air from the lower stratosphere. Over 33% of the troposphere (0–12 km) along our flight track at latitudes from about 45° to 55°N had significantly enhanced O3 due to stratospheric intrusions, and in the middle to upper troposphere the extent of the enhanced O3 generally exceeded 40%. Ozone mixing ratios of 80 parts per billion by volume (ppbv) near 6 km were common in strong intrusions. In the boundary layer over the lowlands, O3 was in the 20–30 ppbv range with a vertical O3 gradient of 6.7 ppbv km−1 to about 45 ppbv at 3 km. Above 6 km the background tropospheric O3 profile was nearly constant with an average value of 53 ppbv. Due to forest fires in Canada and Alaska, plumes from biomass‐burning sources were observed on many flights. Biomass‐burning plumes influenced about 25% of the free troposphere below 4 km, and in some of the plumes, O3 was enhanced by 10–20 ppbv over ambient levels of 30–45 ppbv. Several air masses transported from the tropical Pacific were observed over Canada in the middle to upper troposphere with O3 levels 10–20 ppbv below background values of 50–55 ppbv.

Effects of biomass burning on summertime nonmethane hydrocarbon concentrations in the Canadian wetlands

Approximately 900 whole air samples were collected and assayed for selected C2‐C10hydrocarbons and seven halocarbons during the 5‐week Arctic Boundary Layer Expedition (ABLE) 3B conducted in eastern Canadian wetland areas. In more than half of the 46 vertical profiles flown, enhanced nonmethane hydrocarbon (NMHC) concentrations attributable to plumes from Canadian forest fires were observed. Urban plumes, also enhanced in many NMHCs, were separately identified by their high correlation with elevated levels of perchloroethene. Emission factors relative to ethane were determined for 21 hydrocarbons released from Canadian biomass burning. Using these data for ethane, ethyne, propane,n‐butane, and carbon monoxide enhancements from the literature, global emissions of these four NMHCs were estimated. Because of its very short atmospheric lifetime and its below detection limit background mixing ratio, 1,3‐butadiene is an excellent indicator of recent combustion. No statistically significant emissions of nitrous oxide, isoprene, or CFC 12 were observed in the biomass‐burning plumes encountered during ABLE 3B. The presence of the short‐lived biogenically emitted isoprene at altitudes as high as 3000 m implies that mixing within the planetary boundary layer (PBL) was rapid. Although background levels of the longer‐lived NMHCs in this Canadian region increase during the fire season, isoprene still dominated local hydroxyl radical photochemistry within the PBL except in the immediate vicinity of active fires. The average biomass‐burning emission ratios for hydrocarbons from an active fire sampled within minutes of combustion were, relative to ethane, ethene, 2.45; ethyne 0.57; propane, 0.25; propene, 0.73; propyne, 0.06;n‐butane, 0.09;i;‐butane, 0.01; 1‐butene, 0.14;cis‐2‐butene, 0.02;trans‐2‐butene, 0.03;i‐butylene, 0.07; 1,3‐butadiene, 0.12;n‐pentane, 0.05;i‐pentane, 0.03; 1‐pentene, 0.06;n‐hexane, 0.05; 1‐hexene, 0.07; benzene, 0.37; toluene, 0.16.

Global warming and forest fires in Canada

The looming possibility of global warming raises legitimate concerns for the future of the forest resource in Canada. While evidence of a global warming trend is not conclusive at this time, governments would be wise to anticipate, and begin planning for, such an eventuality. The forest fire business is likely to be affected both early and dramatically by any trend toward warmer and drier conditions in Canada, and fire managers should be aware that the future will likely require new and innovative thinking in forest fire management. This paper summarizes research activities currently underway to assess the impact of global warming on forest fires, and speculates on future fire management problems and strategies.

Blue moons and large fires

Theoretical analysis of simulations of optical effects from the 1950 Canadian forest fires has revealed what conditions are necessary for large fires to cause blue moons and suns. This study shows how large fires can be used to improve our understanding of long range pollution transport on a global scale as well as the evolution of aerosol radiative effects so important to global climate studies. The most important aerosol characteristics are the initial submicron smoke particle concentration and areal extent of the fire and its effect on fire plume dispersion. Capping clouds above the fire and near saturation humidity effects are simulated and found to help establish anomalous optical effects. Data are included showing probable anomalous extinction events associated with concentrated fire plumes.

Forest Fire Control Aircraft in Canada

SummaryThe economic losses occasioned by forest fires in Canada are serious. Although the forest lands are largely under the jurisdiction of the provincial governments the forest resources are of national interest. For this reason the federal government, through the Department of Forestry, carries out a national programme of forestry research. The research in forest fire control encompasses the use of aircraft. This paper reviews the early developments in the use of aeroplanes in Canadian forestry operations. The more recent developments of direct fire suppression techniques, such as water dropping, are discussed in detail.

WARTIME INFLUENCE ON FOREST FIRES IN CANADA

Canada's forest-fire protection forces were seriously handicapped during the war years by reduced or inexperienced staff, owing to enlistment in the armed services, and by difficulty of securing equipment and supplies. In partial compensation the weather was, on the average, no worse than normal, and the number of fires attributable to campers, settlers and incendiaries was considerably reduced. Railway fires unavoidably showed a marked increase.The total number of fires during the 5-year period 1940-44 was 10 per cent less than in the pre-war fire seasons of 1935-39, but the size of the average fire (which has been used as a measure of the effectiveness of fire control) was 7½ per cent higher.So far as the war period is concerned this represents a creditable achievement on the part of the forest protection services of the country. When considered over a longer period, however, the situation is far from reassuring. During the last ten years the average fire was 20 per cent larger than in the previous decade, and in the past five years the average fire size was 52 per cent greater than it was in the period 1930-34 in spite of the fact that there were 19 per cent fewer fires to control.A long and gratifying down-trend in the average size of forest fires in Canada ended in the mid-1930's. More intensive fire-control measures must be taken in the post-war period if the former favourable situation is to be restored.