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Playing with matches: Incorporating human activity into wildfire forecasting

The Fort McMurray wildfire in Alberta. Canada, now at well over half-a-million acres in size and still out of control as of the time of this post (May 12, 2016), has brought a discussion about the intersection of climate change, wildfires, and demographics back to the global stage. The fire has resulted in the evacuation of an estimated 88,000 people and has led to downgrade in the forecasted growth of Canada’s gross domestic product (GDP). Scientists have issued repeated warnings for decades that climate change will result in increased wildfires. It is becoming apparent also that human activity is contributing to increased wildfire occurrence. A recent study published in PLOS ONE by George Washington University Professor of Geography, Michael L. Mann and colleagues, finds that the incorporation of human activity and demographics into forecasting fire probabilities reduces model uncertainty and highlights the human contribution to the increased prevalence and occurrence of wildfires.


Humans are driving wildfire occurrence in part because there are simply more of us, but also because we are building in areas of the forest and landscape we haven’t built before. The wildland-urban interface (WUI) is the area where houses and development meant the forests and the wildlands, and has become the locus of many environmental conflicts from declines in biodiversity to wildfires. California alone sports 5.1 million housing units classified as within the WUI. This many structures in the WUI has led to increased exposure to fire. California has averaged $160 million dollars in fire-related damage to buildings and structures from 1999 to 2011. While climate change and weather are driving much of the severity of wildfires in California and other regions, in California, people alone are responsible for the ignition of 95% of all wildfires.


Just recently, Wayne Huntsman was fined $60 million dollars and sentenced to 20 years in prison after pleading guilty to starting the 2014 King Fire—which the man lit in order to get a “fire selfie.” The fire burned over 100,000 acres, destroyed 12 homes and over 100 other structures, and resulted in nonlife-threatening injuries to many firefighters.


In their research Mann and his colleagues find that the inclusion of human activity and human drivers into modeling wildfire probability increases the performance of wildfire models and decreases uncertainty through comparisons of data over the past century. In Southern California, human activity explains about half of all wildfires. This is an important contribution for many reasons as Mann and his colleagues point out. Many fire prediction models exclude urban areas and focus only on “natural” areas. This is a common occurrence in many studies and models, not just those focusing on forecasting fire probabilities. Urban areas can be difficult to incorporate into any model and many existing models lack the capability to even consider urban landscapes.

Contribution to 25 year expected fire count by natural and human factors. Contribution of natural (A) and human (B) variables, ceteris paribus, to the expected fire count predicted during the 1976–2000 period. Natural variables are defined as all variants of AET, CWD, lighting, elevation and slope. Human variables include distance to population centers, neighboring maximum housing density, distance to populated places, and distance to campsites.
Contribution to 25 year expected fire count by natural and human factors (from Mann et al. 2016). Areas in red indicate increased fire probability–southern California shows an intersection of both human and natural forcings that increase fire probability.

The incorporation of urban areas here is also important because it demonstrates the possible overestimation of the influence of climate change alone on wildfire occurrence. Which by no means should serve as a solace, but rather an indictment on what we are doing to our environment and ourselves. From cigarettes tossed from moving cars, to campfires not properly extinguished, humans are clearly a major source of wildfire ignition. As Mann remarked recently in the National Observer, “Individuals don’t have much control over how climate change will affect wildfires in the future. However, we do have the ability to influence the other half of the equation, those variables that control our impact on the landscape.”


Climate change is already profoundly changing our forests and our landscape—especially in the southwestern US were increased drought and tree mortality is evident. We have written about these issues here at PLOS Ecology before, from Katie Barry’s excellent post from November, 2015:  “Climate change and the catastrophic wildfire,” to one of my own from August, 2015:  “Changing Ecosystems in Changing Climates: Three articles from the PLOS Ecological Impacts of Climate Change Collection.” Personally, living in the Mid-Atlantic region of the US, I don’t encounter wildfires too often. Until recently. The Rocky Mount fire here in Shenandoah National Park affected nearly 10,000 acres of backcountry forest that has not burned in nearly 100 years. However, unlike the Fort McMurray fire that has devastated lives and landscape, the Rocky Mount fire was small, easily contained, and ultimately beneficial to the forest. I cannot possibly imagine the extent of what is occurring in Alberta and other areas that have been impacted by similar fires and my heart goes out to all affected. It was awe-inspiring to walk through the forest after even a small fire such as this was. The smell of char and smoke still lingers several days after the fire has been out, despite constant rain. If anything, small fires such as the Rocky Mount fire will serve as reminders of how much fire suppression we have seen in areas like the eastern United States and the possible consequences. The state of Connecticut alone has over 70% of its housing within the WUI, potentially exposed to wildfire threats were drought and climate effects as pronounced as seen in the southwestern US.

Rocky Mount Fire near Grottoes, VA
A picture of a fire break near Two Mile Run in Shenandoah National Park. The low-intensity, Rocky Mount fire burned nearly 10,000 acres of backcountry forest. (Photo J. Atkins)

Canada, Australia and California have become the possible canaries-in-the-coalmine where demographics and climate are intersecting and the discussion is most heated. Canadian Prime Minister Justin Trudeau has taken a middle-of-the-road approach to linking climate change with increased wildfire occurrence, “It’s well known that one of the consequences of climate change will be a greater prevalence of extreme weather events around the planet,” he remarked, “there have always been fires. There have always been floods. Pointing at any one incident and saying: ‘This is because of that,’ is neither helpful, nor entirely accurate.” Trudeau’s remarks came in response to Canadian Green Party Leader Elizabeth May who had previously said, “The fact that the forest fire season has arrived so early in northern Alberta is very likely a climate event – very likely related to extreme high temperatures and very low humidity, very low precipitation.” She continued, “. . .  it’s a disaster that is very related to the global climate crisis.” While May has faced criticism over the politicization of the disaster, there is a discussion to be had on what we can do.




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