Guest Commentary: Tracer bullets or climate change? A retrospective
What do Durango’s 416 Fire, southeastern Colorado’s Spring Creek Fire, and Basalt’s Lake Christine Fire all have in common? They were all started by people and they all occurred during one of Colorado’s warmest and driest summers in the past 125 years.
As we reflect on these disastrous fires one year later, many of us are grappling with the question: Were these fires actually man-made or were they natural disasters? The question is not as simple as it might appear; wildfire is a natural part of our local ecosystem. These fires were started by humans. And, they also were started during a particularly hot and dry year. So, what’s the right answer?
Fire is a necessary part of almost every ecosystem in Colorado. But, in many areas, large wildfires occur infrequently (at least on human time scales). High elevation spruce and fir forests can average 400 years between wildfires. Even lodgepole pine, one of the most fire-adapted species in Colorado, can average over 50 years between wildfires. In short, it takes a rare set of conditions for wildfires to occur. First, conditions need to be dry enough — for high elevation forests this means an exceptional drought. Second, there needs to be enough fuel on the landscape — in the time between fires, the amount of burnable material builds up. And finally, there needs to be a spark. Human impacts are making all three of these more likely.
According to Western Water Assessment’s 2014 report “Climate Change in Colorado,” the average annual temperature has increased 2.5 degrees over the past 50 years. Warming temperatures have several important implications for wildfires. In Colorado, the highest fire danger often occurs in June and early July (all 10 of Colorado’s largest wildfires have started during that time period). June is one of our driest months, and in years with deep snowpack (like this year), slower snowmelt prevents plants from drying out during this period. But in dry years like 2018, most of the snow will melt in late May or early June and conditions will get progressively drier until the monsoons arrive in July. Higher temperatures can mean less snow and an earlier melt-off, thus lengthening the most dangerous time for wildfires in Colorado.
Humans are not just warming the climate; we’re also increasing fuels and ignitions on the landscape. In their 2017 article, “Human-started wildfires expand the fire niche across the United States,” Balch et. al. examined the role humans have had on fire ignitions in the past 40 years. In Colorado, human ignitions are responsible for 30% of wildfires and have extended the fire season from 43 days to 93 days. Additionally, after a century of fire suppression, many forests have built up large amounts of fuel.
In the end, the events of the Lake Christine Fire might be best categorized as a climate disaster triggered by human actions. While this is still not a simple answer, it is one that will likely be heard around the West more and more. The combination of more people living and recreating in Colorado, along with continued warming from climate change, means that we will almost certainly witness more events like the Lake Christine Fire. If we want to protect our communities, we need to address the three areas where we can have an impact. We need to reduce carbon emissions and limit the impacts of climate change. When safe to do so, we need to allow some fires to burn. And we need to be more responsible individuals, fire hardening our homes, and using fire more responsibly.
Adam McCurdy is the Forest Programs director at the Aspen Center for Environmental Studies. Adam started working at ACES as a summer naturalist in 2008 and has a background in environmental science and studying climate change impacts.
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