Forest Investment Account (FIA) - Forest Science Program
FIA Project Y091111

    Wildfire Risk in a Changing Climate
 
Project lead: Taylor, Stephen (Canadian Forest Service)
Contributing Authors: Meyn, Andrea; Taylor, Steve W.; Flannagan, Mike D.; Thonicke, Kirsten; Cramer, Wolfgang; Regniere, Jacques; St. Amant, Remi; Van der Kamp, Derek W.; Moore, R. Dan
Subject: Forest Investment Account (FIA), British Columbia
Series: Forest Investment Account (FIA) - Forest Science Program
Description:
The purpose of this project is to forecast the effects of climate change on wildfire activity and impacts on its impacts on forest resources in British Columbia, which was identified as a key uncertainty in a review of climate change impacts on forest management (BCMOFR 2006). Through their impact on forest age structure and species composition, forest fires can impact the sustainability of timber supply and other resource values (Armstrong 2004). Average global temperature increases are expected to increase between 1.3 and 1.7 degree by 2050 over 1980-1999 levels (Field et al 2007), although there will be regional variation in temperature and precipitation changes, with higher temperature increases in northern regions. Flannigan et al (2002) predicted an increase in the seasonal fire danger severity rating and an increase in fire season length of 2-3 weeks in BC by the year 2085. Recent work by Flannigan et al (2005) suggested a 74-118% increase in average area burned in Canada by the end of this century (3xCO2 scenario) without taking into account changes in vegetation, insect outbreaks, ignitions, fire season length and human activity. However, results for BC were less conclusive. Further work is needed to improve predictions of impacts in BC to guide mitigation strategies. Furthermore, while weather is a strong driver of fire activity, as area burned increases, there may be negative feedback due to an increasing proportion of less flammable vegetation in the landscape that is not included in most climate change projections. Little work has been done to examine changes in potential fire severity measures, such as the number of days with crown fire vs surface fire activity, and forest floor depth of burn, which will have important ecological consequences.

Between 1919-2007 approximately 20 million ha were burned in BC (Fig 1). However, the annual area burned in BC, as elsewhere, is highly variable, and follows a negative exponential distribution (Fig 2). This variation, which is mainly due to weather, has a great influence on timber supply and other resource values. For example, the amount of winter precipitation determines whether forest fuels are saturated at the beginning of the fire season, while the amount of snow and timing of the spring melt influences the length of the fire season. Westerlink et al (2006) found correlations between forest fires and spring snowmelt timing, which they also linked to summer drought conditions at mid-elevation locations in the western USA. During the fire season, the flammability of forest fuels depends on the frequency, duration and intensity of drying periods and precipitation events; large forest fires are associated with atmospheric circulation patterns characterized by a prominent ridge with a strong meridional flow (Skinner et al. 2002).

Stahl et al (2006) classified synoptic circulation patterns over BC into 13 types (Fig 3) and examined their frequency in relation to the El Nino Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO). Positive PDO was associated with warm dry winters in mainland BC. Preliminary analyses suggest that forest fires are mostly associated with synoptic Types 1 and 2 (the dominant types in summer) and that there is a higher frequency of fires in Type 7 than there are Type 7 days (Fig 4). More work is needed to examine the relationship between large scale circulation types (ENSO, PDO), synoptic circulation patterns, fire weather and fire activity. An understanding of the effects of the various modes of variability on local climate is also important to effective downscaling of GCMs (Stahl et al 2006).

This project will address three key research questions:

1.How may predicted changes in temperature and other weather variables due to global climate change and large scale circulation patters affect future fire weather?

2. How will changes in fire weather influence changes in fire risk, and fire severity? Are there potential feedbacks?

3.How will changes in area burned frequency distributions impact sustainability of forest resources?

Realizations of future fire weather will be developed from a) an ensemble of GCM model output and b) from stochastic weather simulation from monthly weather normals, adjusted for predicted future anomalies (Regniere and St. Amand 2006). The simulation of future fire weather with be informed by an analysis of the effects of winter synoptic circulation patterns on snowmelt timing and early season fuel moisture indices, the effects of summer synoptic circulation patterns on fire weather, atmospheric stability indices and lightning ignition risk, and potential large-scale teleconnections and modes of variability such as ENSO. The fire weather scenarios will also be used to examine potential changes in fire severity measures, particularly the number of days of potential crown fire activity.

Spatio-temporal fire risk models will be developed from historical spatial fire perimeter, fire weather and other covariate data (eg Preisler et al 2004). Potential negative feedbacks of increasing area burned will also be examined.

Changes in area burned frequency distributions will be incorporated into a stochastic timber supply modeling framework for a pilot timber supply area to examine potential impacts on forest structure and harvest levels.

The results of this work will provide:
• an increased understanding of underlying climate/weather processes affecting fire risk;
• new methods and spatial representations of future fire risk;
• demonstration of methods to estimate impacts of changed fire regimes on forest management.

The results will be applied by timber supply analysts, fuels management specialists, conservation planners, fire suppression specialists, and forest based communities, including First Nations.

References

Armstrong GW. 2004. Sustainability of timber supply considering the risk of wildfire. For. Sci. 50:626-639

[BCMFOR] BC Ministry of Forests and Range. 2006. Preparing for climate change: Adapting to impacts on British Columbia’s forest and range resources. Victoria, B.C.

Flannigan, MD, Logan, KA, Amiro, BD, Skinner, WR, and Stocks, BJ. 2005. Future area burned in Canada. Climatic Change 72: 1-16.

Flannigan, MG, Wotton, BM, Todd, B, Cameron, H, and Logan, K. 2002. Climate change implications in British Columbia: Assessing Past, Current and Future Fire Occurrence and Fire Severity in BC. Report prepared as part of the Collaborative Research Agreement by the Canadian Forest Service for the British Columbia Ministry of Forests, Protection Program.

Meehl, GA, TF Stocker, WD Collins, P Friedlingstein, AT Gaye, JM Gregory and others. 2007. Global Climate Predictions. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the International Panel on Climate Change. Solomon, S, D Qin, M Manning, Z Chen, M Marquis, KB Averyt, M Tignor and HL Miller (eds). Cambridge University Press, Cambridge and New York

Preisler, HK DR Brillinger, RE Burgan, and JW Benoit. 2004. Probability based models for estimation of wildfire risk. Int. J. Wildland Fire 13:133-142.

Régnière, J, R St-Amant. 2007. Stochastic simulation of daily air temperature and precipitation from monthly normals in North America north of Mexico Int. J. Biometeorology 51: 415-430.

Skinner, WR, MD Flannigan, BJ Stocks, DL Martell, BM Wotton, JB Todd, JA Mason, KA Logan, and E M Bosch. 2002. A 500 hPa synoptic wildland fire climatology for large Canadian forest fires, 1959-1996. Theoretical and Applied Climatology, 71: 157-169 doi: 10.1007/s007040200002

Stahl , K, RD Moore , and IG Mckendry. 2005. The role of synoptic-scale circulation in the linkage between large-scale ocean-atmosphere indices and winter surface climate in British Columbia, Canada. Int. J. Climatology 26: 541 – 560

Westerling, AL, Hidalgo, H.G., Cayan, DR. and TW Swetnam. 2006. Warming and earlier spring increases western U.S. forest wildfire activity. Sci. 313:940-943.
Related projects:  FSP_Y102111

    Deliverables:

Executive summary (1.1Mb)
Fact sheet - Relationship between fire, climate oscillations and surface weather in British Columbia, Canada (0.1Mb)
Fact sheet - Stochastic simulation of seasonal fire danger from monthly climate normals - an Early Warning application (0.1Mb)
Poster - Prediction of future lightning frequency in British Columbia (0.9Mb)
Meyn, A. et al. 2009. Relationship between fire, climate oscillations, and drought in British Columbia, Canada, 1920-2000. Global Change Biology 16:3 977-989

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Updated August 16, 2010 

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