Every summer I watch the wildfire season with trepidation knowing my home will be engulfed in smoke for a time from forest fires. This year has been especially awful. I live in the wildland-urban interface (WUI) south of Columbia Falls, Montana and forest fire is part of my life. As a brief introduction; “a wildland-urban interface is an area where houses meet or intermingle with undeveloped wildland vegetation” (Lampin-Maillet et al., 2010, p. 732). In 2011 the Montana Department of Natural Resources produced Figure 1 detailing the WUI parcels for Montana (DNRC, 2017).

Each year as the smoke envelopes us I wonder; will climate change increase forest fire severity or not?  If forest fire severity does increase would this negatively affect the WUI? To answer these questions I reviewed current literature, focusing primarily on peer-reviewed journals, in regards to;
● Historical increases in fire severity.
● Climate change modeling and potentials for increased forest fires.
● Factors that could mitigate or exacerbate forest fires.
● Growth of risk and mitigation in the WUI.

Increasing Fire Severity

Fire has been an integral part, and primary disturbance force, of North American forests since the last ice age (Soja et al., 2007) but severity appears to be increasing. Figure 2 presents data from the U.S. National Interagency Fire Center (2016) which illustrates that 9 of the 10 largest number of acres burned in the U.S. since 1960 occurred after 1999.

Siberia and Canada also experienced extreme fire seasons between 1998 and 2007 (Soja et al., 2004). In Canada the area burned by forest fires has been increasing (Gillett et al., 2004) and five of the eight largest fire years since 1921 occurred between 1989 and 2005 (Soja et al., 2007). Locally warming climatic conditions are driving the Western North American forest fire severity (Gillett et al., 2004; Kurz et al., 1995; Westerling et al., 2006) but these local changes do not necessarily equate to anthropogenic climate change (Westerling et al., 2006). If warmer climatic conditions fuel severe forest fires one would assume anthropogenic climate change would too. Is this true?

Climate Change Modeling and Increasing Risks

General circulation models (GCM) are commonly used to project spatial change in climate conditions  (Dale et al., 2000) and can help evaluate links between climate change and forest fire severity. These models indicate a substantial increase in future fire risk for North America and Russia (Aber et al., 2001; Flannigan, Stocks and Wotton, 2000; Soja et al., 2007).  Gillett et al. (2004) found increased temperatures from climate change indicate an increased likelihood for large forest fires and increased areas burned. Aber (2001); Flannigan, Stocks, and Wotton (2000); and Moriondo et al. (2006) recognize that local effects could result in localized risk reduction but agree that in general, over the landscape, risk will rise. Knowing forest fire risk is likely to rise, are there other factors that could reduce or increase these risks?

Mitigation or Exacerbation Factors

To explore this is to explore the carbon cycle of a forest. Forest ecosystem are large reservoirs of carbon (Kurz et al., 1995) and changes in fire can affect the carbon cycle (Soja et al., 2004). Fires could be critical in shaping whether forests are carbon sinks, potentially mitigating climate change, or carbon sources which would increase fire risk (Flannigan, Stocks and Wotton, 2000).

Wildfires themselves have the ability to increase the risk of more fires.  Severe fire seasons in the U.S. and Siberia have the potential to release large amounts of carbon into the atmosphere (Aber et al., 2001; Soja et al., 2004) which risks creating a positive feedback loop with increased CO2 from fires increasing global temperatures and therefore the risk of severe fires (Balzter et al., 2005; Soja et al., 2007; Westerling et al., 2006).  Forest age classes also change under increased fire frequency and this shift in the age of the plants can result in forests acting as a carbon source and therefore feed climate change (Kurz et al., 1995; Soja et al., 2004).

At the same time these warmer climates with higher CO2 levels could aid in greater carbon storage in forests.  Aber et al. (2001) found warmer climates could extend growing seasons and higher concentrations of CO2 could lead to increased forest growth both of which increase carbon sequestration by the forest.  Complicating these factors, fire does not act alone in disturbing forests but interacts with human management, disease, insects, etc. compounding the effects (Agne, Woolley and Fitzgerald, 2016; Flannigan, Stocks and Wotton, 2000; Kurz et al., 1995).  As a result, it is hard to predict how various factors in our changing climate will affect wildfire severity.  In the end, climate change favors instability which favors the factors (like drought which results in large fire seasons) that turn forests into carbon sources (Kurz et al., 1995).  The most likely outcome of climate change is that forest fires are likely to breed conditions favorable to more forest fires.  If you live in the WUI what does this mean for you?

The Wildland-Urban Interface

Currently over one third of all housing in the U.S. is in the WUI (Radeloff et al., 2005) and the WUI worldwide has been increasing and is projected to increase further (Lampin-Maillet et al., 2010).  I look around our beautiful valley and see a very large number of our homes in the WUI. 

Figure 3. The Waldo Canyon Fire; an example of the destructive capacity of a wildfire in the WUI.  In 2012, this single fire near Colorado Springs killed two people, burned 346 homes, and resulted in insurance claims in excess of $450 million (One Republic, 2012; Waldo Canyon Fire Wikipedia, 2016).

Lampin-Maillet et al. (2010) found areas of the WUI would experience increasing fire risk under an increased forest fire regime and created a categorization tool (Figure 4) to analyze risk.  Use of this tool would allow for prioritization of regional/local fire mitigation efforts to achieve the greatest increase in safety for least cost.  This tool could also be used to aid in county level housing development planning to reduce fire risk for new developments.

Figure 4. Categorization of wildfire risk by housing density and vegetation cover. (Lampin-Maillet et al., 2010)

Safford, Schmidt, and Carlson (2009) found risk could be mitigated by reducing fire intensity through fuel treatment but with limitations (Dale et al., 2000; Kurz et al., 1995; Lampin-Maillet et al., 2010). As important as creating safe zones for homes in the WUI is fuel reduction in the WUI tends to be more expensive than forest fuel mitigation in areas outside the WUI (Nowicki, 2002; Safford, Schmidt, and Carlson, 2009).  Ultimately, the WUI and its fire risk are expected to grow and mitigation can be expensive.

Conflagration or Hot Air?

In summary: Climate change is likely to increase global temperatures and the risk of severe forest fires creating a potential positive feedback loop. This will require mitigation work to pro-actively create safe zones in the WUI. The potential increase in risk to homes in the WUI under climate change with increasing fire severity is not just hot air but has the potential for very serious consequences. With the smoke engulfing my home I am taking a critical  look over the safe zone around my home.  If you want to learn more about protecting your home and property visit Fire Safe Montana.

Protect yourself, your family, and your friends: Get involved locally and nationally and learn how to reduce your contribution to climate change.

References

Aber, J., et al. (2001) ‘Forest processes and global environmental change: Predicting the effects of individual and multiple stressors we review the effects of several rapidly changing environmental drivers on ecosystem function, discuss interactions among them, and summarize predicted changes in productivity, carbon storage, and water balance’, BioScience, 51(9), pp.735-751.
Agne, M.C., Woolley, T. and Fitzgerald, S. (2016) ‘Fire severity and cumulative disturbance effects in the post-mountain pine beetle lodgepole pine forests of the Pole Creek Fire’, Forest Ecology and Management, 366, pp.73-86.
Balzter, H. et al. (2005) ‘Impact of the Arctic Oscillation pattern on interannual forest fire variability in Central Siberia’, Geophysical Research Letters, 32(14).
Dale, V.H. et al. (2000) ‘The interplay between climate change, forests, and disturbances’, Science of the Total Environment, 262(3), pp.201-204.
DNRC (2017) Montana Department of Natural Resources and Conservation Available at: http://dnrc.mt.gov/divisions/forestry/fire-and-aviation (Accessed: 31 August 2017)                   Flannigan, M.D., Stocks, B.J. and Wotton, B.M. (2000) ‘Climate change and forest fires’, Science of the total environment, 262(3), pp.221-229.
Gillett, N.P. et al. (2004) ‘Detecting the effect of climate change on Canadian forest fires’ Geophysical Research Letters, 31(18).
Kurz, W.A. et al. (1995) ‘Global climate change: disturbance regimes and biospheric feedbacks of temperate and boreal forests’, in Woodwell, G., Mackenzie, F. (eds.) Biotic feedbacks in the global climatic system: Will the warming feed the warming, New York: Oxford University Press, pp.119-133.
Lampin-Maillet, C. et al. (2010) ‘Mapping wildland-urban interfaces at large scales integrating housing density and vegetation aggregation for fire prevention in the South of France’, Journal of Environmental Management, 91(3), pp.732-741.
Moriondo, M. et al. (2006) ‘Potential impact of climate change on fire risk in the Mediterranean area’, Climate Research, 31(1), pp.85-95.
National Interagency Fire Center (2016) Available at: https://www.nifc.gov/fireInfo/fireInfo_stats_totalFires.html (accessed 10 October 2016)
One Republic (2012) Available at: http://techland.time.com/2012/06/29/how-to-track-the-colorado-springs-waldo-canyon-super-fire-and-others/ (Accessed: 10 October 2016)
Nowicki, B. (2002) The community protection zone: defending houses and communities from the threat of forest fire. Center for Biological Diversity, pp.1-8. Available at: http://www.biologicaldiversity.org/publications/papers/wui1.pdf (Accessed: 5 October 2016).
Radeloff, V.C. et al. (2005) ‘The wildland–urban interface in the United States’, Ecological applications, 15(3), pp.799-805.
Safford, H.D., Schmidt, D.A. and Carlson, C.H. (2009) ‘Effects of fuel treatments on fire severity in an area of wildland–urban interface, Angora Fire, Lake Tahoe Basin, California’ Forest Ecology and Management, 258(5), pp.773-787.
Soja, A.J. et al. (2004) ‘Estimating fire emissions and disparities in boreal Siberia (1998–2002)’, Journal of Geophysical Research: Atmospheres, 109(D14).
Soja, A.J. et al. (2007) ‘Climate-induced boreal forest change: predictions versus current observations’, Global and Planetary Change, 56(3), pp.274-296.
Westerling, A.L. et al. (2006) ‘Warming and earlier spring increase western US forest wildfire activity’, Science, 313(5789), pp.940-943.
Waldo Canyon Fire Wikipedia (2016) available at: https://en.wikipedia.org/wiki/Waldo_Canyon_Fire (Accessed: 20 October 2016)