Increase in wildfire frequency and severity – is it real?

By Kelly Ramirez, PhD

While Colorado’s wildfire season is really only just beginning, the state has already been struck by multiple serve fires, including the WaldoCanyon and HighPark fires.

As I write this post, 9 wildfires are ablaze in the state in varying degrees of containment and control, and that number is far from static. Each lightning storm brings a wave of fire outbreaks and a fear that any strike could result in devastation. With the already seemingly substantial increase in fires this season, we begin to question what we as a community can do and what steps we should take in the future to prevent the loss of homes, our land, and even human life. Here is an interesting, thought-provoking editorial, addressing the fact that homes in the wild-urban interface (WUI) are especially susceptible to wildfire.

As an ecologist and researcher, I have more fundamental questions about the nature and frequency of fire:

  • Is the frequency of fires we have seen this year ‘normal’?
  • If not, is this a new normal, will we continue to see an increase in fire frequency and severity?
  • And just why is this season so much more susceptible to fire risk?

Dr. Max Moritz, a researcher at the University of California, Berkley, has recently addressed some of these questions in a paper published here in ESA Journal’s Ecosphere:

His group found that fire activity is increasing across the world, not just in Colorado. While Dr. Moritz used his research to examine fire prevalence and future distribution across the entire globe, we can apply much of what his paper discusses to our own fire danger in Colorado- and across the west (New Mexico, Montana, Wyoming are all in the midst of battling fires, as well).


Fire frequency is strongly controlled by the climate (hot, dry, and windy areas are, not surprisingly, more susceptible to wildfire), the resources that burn (the forest and, in devastating instances, houses) and the ignition source (whether that be lightning or human caused).

Here is a dorky conceptual diagram from Moritz et al. 2012, just to make clear that the controls on fire activity are pretty straightforward:

In Colorado, we have the trifecta this year- continuous days of hot, dry, and windy weather (this has been the driest/warmestyear on record since 2002, the year of the Haymanfire); a forest parched and overstressed from current and past stressors (a low snow-pack year, pine beetle attack, and fire suppression – many of our forests haven’t had a fire in over 200 years!); and lightning– we are hit by a lot of lightning.

To predict where wildfire frequency will increase or decrease across the globe, Moritz andcolleagues begin simply by first mapping out fire occurrence from 1997-2007.

Their map isn’t surprising – it is intuitive that fires would break out most frequently in certain locations (i.e. dry hot areas of the Western US) and not in others (i.e. the cold, wet Arctic).

Next, getting a little more complicated, the authors compare climate and vegetation distribution maps (where is it hot/dry? where are areas with best fuel?) to past fire occurrences. This allows them to make predictions about where fires can and may occur (based on fire history and potential).

Then, to predict future global fire frequency (will it increase or decrease), they apply where fire history and potential to climate change predictions. For example, with climate change, some areas (like Colorado) are expected to get warmer and drier. We would therefore predict fire frequency to increase in these areas (especially if a dense, dry forest is present).

Now that we have a baseline of information for prediction, we can really start to dork out and look at how fires will change over the next 30 years (or even 80 years) in conjunction with climate and vegetation changes. To do this, the authors compare current fire regimes to future climate projections. When these maps are compared, they find an increase in fire across the globe. By 2039, there will be a small increase in fire occurrence, but by 2099 there could potentially be a 25% increase in fire activity in some areas.

The work by Moritz and colleagues cannot tell us where fires will break out or how severe they may be, but it does tell us that overall fire danger and frequency will likely increase in Colorado.

Now, as a community, we must decide: what are the next steps we will take? Although fire is capable of destroying so much, it should not pit our community against nature. How can we learn to live with fire, especially as wild-urban interfaces are only expected to increase?

**All figures pulled from Moritz et al. 2012

** For a bit more on the ecology of our forests and wildfires, this is a great post from two of our other Early Career Ecologists (posted at NREL’s EcoPress).