4.5.5 Future Firescape: Western United States 

“The record of the past climate tells us that the transition from one climate state to another is rarely a smooth process” McCarthy, 2009.

While, the fact that western wildfires now typically spread to double the size as was common during the 1970s, when, on average, the wildfire season was 75 days shorter than today (Climate Central, 2012) presents humanity with a challenge, the size thereof is but modest compared with what several studies suggest may be to come. 

Analysis by the USDA (Gardner, 2014) anticipates that by 2050 national acreage burned will double that of present-day levels, rising to 20 million acres p/y, the trajectory thereof roughly correlating with earlier analysis by Spracklen et al (2009), who independently predicted a rise of 54% by mid-century. However, regional predictions vary greatly from the mean. For example, the latter’s findings suggest area burned in the Pacific Northwest will rise by 78%, whereas the Rocky Mountain region can anticipate a rise of 175% (Ibid). As discussed above, regardless of their distance to areas of human habitation, wildfires have significant impact upon regional hydrology, precipitation and weather more generally, biodiversity, and air quality, thus, should the above statistics come to pass the impact to both regional and national populations will be as diverse as they are significant. 

Having examined the western U.S. charcoal record across the period 3tya – present, Marlon et al (2012) found that during the 20th century wildfire activity dropped to the lowest level since the Little Ice Age, the causation thereof fire suppression [i.e. fire fighting], of which the result was a “fire deficit” (Ibid, online). The charcoal record also evidenced that wildfire activity peaked in periods of abrupt climate change [i.e. the onset of the Medieval Climate Anomaly (MCA) of 1tya – 700ya]. Their findings suggest that in the absence of fire suppression wildfire activity during the 20th century would have been greater than at any point in the past 3,000 years, including during the MCA. 

Relating the above to the case study sites, warming at a rate of 0.17°C per decade since 1948 (Chang, 2015), average spring and summer temperatures in Yellowstone National Park are forecast to increase 4.0 – 5.6°C by 2100 (Romme and Turner, 2015). The resulting combination of earlier snowmelt, a longer wildfire season, and higher temperatures is anticipated to increase the area burned annually by 600>% (Peterson and Littell, 2014). Whereas, modelling predicts that, should greenhouse gas emissions continue apace, northern California will see an increase in area burned of 100>% by 2085, with a state-wide increase of between 36-74% (Westerling et al, 2011), as mean annual regional temperatures increase by 4.5°C to the north of the state, and 4.4°C to the south (Krawchuk and Mortiz, 2012). However, seasonal variance is projected to be greater, with summer temperatures up by 6.4°C and precipitation down by 68% in northern California, and up 5.3°C in summer, with rainfall down 26% to the south (Ibid). 

The variance between anticipated increases in average annual burned area in the Rocky Mountains and California is in part born of the predicted impacts to the regional fire regimes, therein fuel quantity, state, and behaviour. Hydrologically, the latter is projected to swing between wildfire and floods, the juxtaposition of which is predicted to increase by 25% in northern California, and 100>% in southern (Swain et al, 2018). 

>Continue to Chapter 4.6 here.

The thesis is also available in PDF format, downloadable in several parts on Academia and Researchgate.

Note that figures have been removed from the digital version hosted on this site, but are included in the PDFs available at the links above.

Citation: Sterry, M. L., (2018) Panarchistic Architecture: Building Wildland-Urban Interface Resilience to Wildfire through Design Thinking, Practice and Building Codes Modelled on Ecological Systems Theory. PhD Thesis, Advanced Virtual and Technological Architecture Research [AVATAR] group, University of Greenwich, London.