Everyone hates wildfires and the damage that they can do (Figure 1). But climate change is a decidedly slipperier and more divisive issue. It seems that some of the blame for this lies with the fact that climate change is a slow and ongoing process. So it can be a bit like watching the hour hand on a clock for a few minutes and concluding that it does not move. Mind you this phenomenon of not noticing the insidiousness of slow and constant change is not a valid excuse. After all, we have detailed geological and historical records available to us that supplement and improve our personal observations.
Luckily (or unluckily for some) we also have an observable climate-change canary that is screaming its head off as it flies past most other warnings at about 600 miles/hour, leaving a swath of cinders and dead Bambi-moms in its wake: wildfire occurrence and intensity.
Background on wildfire increase in the USA:
Simple historical measurements of burned acreage show a clear increase in wildfire damage in the USA. Records from the National Interagency Coordination Center (https://www.nifc.gov/fireInfo/fireInfo_statistics.html) show a clear increase in the amount of damage caused in the western USA. Figure 2 shows a plot of the acreage burned in the western USA from 1960 to 2015. This plot reveals the obvious increase in wildfire damage over time.
Discussion on causes of wildfire increase:
Pinpointing the direct cause of increased wildfire activity is trickier than you might guess. (Like most things tend to be when you take a really good look at them.) Certainly, and paradoxically, the successes of previous forest firefighters are partially to blame. This is because as wildfires in previous years were effectively fought and curtailed, the amount of unburnt fuel (wood and other flammable debris) in the forests increased (Marlon et al., 2012).
But other factors also contribute to wildfire activity. Many quality peer-reviewed studies have shown that climate has direct effects on the occurrence of wildfires (e.g. Littell et al., 2009; Morton et al., 2013). One of the most important ways that climate affects wildfire activity is by controlling how dry the landscape is (and thus how flammable the fuel is). This dryness is referred to as “fuel aridity” and a new study suggests that this drying of burnable material is responsible for 76% of the modern increase in area burned by wildfire in the western USA (Abatzoglou and Williams, 2016).
Conclusion—why wildfire increase is important:
Climate change aside, the increase in wildfire activity is important to anyone who lives near arid, forested areas. Moreover, recent studies on the “wildland–urban interface” (or, the zone where human development meets nature) predict that continued urban sprawl will cause increased risks from future wildfires (Liu et al., 2015). Therefore the infrastructure we humans depend on will be at increasing risk of fire damage (Figure 3).
But saving ourselves and our stuff from fire isn’t the only consideration for improving our understanding of increased wildfire activity. Since climate change has been shown to affect wildfire activity, we should also improve our knowledge of changing wildfire regimes. This will help enable us to improve our understanding of climate change. In effect, with proper understanding, wildfires can be used to measure climate change and improve predictions. If that isn’t enough motivation for you, consider that new research suggests that 44% of the increased fuel aridity is likely the result of human-caused climate change (Abatzoglou and Williams, 2016).
Abatzoglou, J.T., & Williams, A.P. (2016). Impact of anthropogenic climate change on wildfire across western US forests. Proceedings of the National Academy of Sciences, 201607171.
Littell, J.S., McKenzie, D., Peterson, D.L., & Westerling, A.L. (2009). Climate and wildfire area burned in western US ecoprovinces, 1916–2003. Ecological Applications, 19(4), 1003-1021.
Liu, Z., Wimberly, M.C., Lamsal, A., Sohl, T.L., & Hawbaker, T.J. (2015). Climate change and wildfire risk in an expanding wildland–urban interface: a case study from the Colorado Front Range Corridor. Landscape Ecology, 30(10), 1943-1957.
Marlon, J.R., Bartlein, P.J., Gavin, D.G., Long, C.J., Anderson, R.S., Briles, C.E., Brown, K.J., Colombaroli, D., Hallett, D.J., Power, M.J. & Scharf, E.A. (2012). Long-term perspective on wildfires in the western USA. Proceedings of the National Academy of Sciences, 109(9), E535-E543.
Morton, D.C., Collatz, G.J., Wang, D., Randerson, J.T., Giglio, L., & Chen, Y. (2013). Satellite-based assessment of climate controls on US burned area. Biogeosciences, 10(1).
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