Science Notes

Why Beetles Aren’t As Bad As You Think

Plus Four Other Complications of Climate Change & Wildfire

By Melanie Thompson

July 5, 2022

The most readily apparent and discussed relationship between climate change and wildfires is the weather. Climate change is creating a hotter, drier climate in Colorado, which in turn leads to more wildfires. But climate change and wildfires have complex relationships with our ecosystems, and tipping the balance on one will lead to cascading effects in the others. Climate change affects our ecosystems, which affect wildfires, which affect ecosystems, which affect climate change and so the cycle goes. 

Some of these connections are well known, but inaccurate, while others are obscure but true, and for some we just don’t have a conclusive answer yet. This aims to summarize five supposed effects of the climate change/wildfire relationship that you might not have thought about. Pine beetles, floods (and mudslides), invasive species, carbon emissions (and sinks), and our ability to manage it all.

Beetles Aren’t as Bad as you Think

Many people (myself included) visit areas with widespread beetle kill and think “that looks like kindling.” Although warmer temperatures driven by climate change are likely to cause more damaging beetle outbreaks, it actually doesn’t make our ecosystems more prone to wildfire.

Beetle kill has a complex relationship with wildfire and, for a long time, researchers had difficulty pinning down what that was. Some reports showed fire likelihood increasing while others observed it decreasing. Finally, a 2012 study reviewed the previous research and found that although the probability of crown fires could increase in the first 1-4 years, once the dead trees had dropped their needles the risk decreased significantly compared with live trees. This offsets the increase in the likelihood of surface fires and torching, meaning that, ultimately, beetle kill has a minimal effect on wildfires.

Source: Jeffrey A. Hicke, et al., Forest Ecology and Management. (1 February, 2012) Effect of Bark Beetle Tree Mortality on Wildfire

Expect more Floods (and Mudslides)

As we know too well, Colorado is susceptible to flash flooding in extreme rain events. Areas ravaged by wildfires are especially vulnerable after vegetation that stabilizes slopes is destroyed. For an example, look no further than the mudslides in Glenwood Canyon last summer that destroyed sections of I-70. The mudslide happened after heavy rains inundated the area burned by the Grizzly Creek Fire a year earlier in 2020.

Researchers at the National Center for Atmospheric Research (NCAR) have found that climate change is making events like these more common by driving increases in extreme wildfire and rainfall events, while bringing the fire season and rainy season closer together. 

According to the article, it can take a burn scar  3-5 years of recovery to mitigate the increased mudslide risk, and 5-8 years to mitigate flash flood. Meanwhile the likelihood of heavy rainfall within 1-2 years of a fire is increasing. Under a high warming scenario (meaning business as usual), 40-50% of extreme fire weather events will be followed by extreme rainfall within 1 year by 2050, and around 100% by 2100. Fortunately, our lot is modest compared with the 700% increase projected for the Pacific Northwest!  

Source: Danielle Touma, et al. Science Advances. (1  April, 2022). Climate Change increases risk of Extreme Rainfall following wildfire in the Western United States

Invasive Species and Forest Loss

For more than a century the US has undertaken a fire suppression policy in the West, and we’ve only recently recognized the ecological importance of fires. If you’re like me, growing up you were taught that wildfire is necessary, and that our ecosystems in Colorado actually depend on fire. The most common example being the lodgepole pine, which relies on fire to open pinecones and release its seeds. However, the benefits of fire require a balance, and as we swing from one extreme to another, it is beginning to threaten the species it once favored.

A build-up of fuels in our forests (the legacy of fire suppression), is combining with a drier climate and increasing human ignitions to drive more frequent and intense wildfires in Colorado. Those fires are giving invasive species greater opportunity. While native species are slow to regenerate following a fire, many invasive species release seeds continually, and without their natural predators or diseases present, can easily spread and take-over.

In some places, invasive species are threatening to convert ecosystems entirely. In a resilient forest, fire merely damages healthy trees, but as fires intensify they kill more trees instead. Additionally, more frequent fires are burning young conifer stands before they develop resistance. Both of these factors make it harder for ecosystems to recover and provide ample opportunity for invasive species to replace them. Although the effect is not yet widespread, this has already led forests to convert to prairie or grassland in some parts of Colorado. 

As if that’s not reason enough for concern, research now shows that some invasive species are also driving an increase in wildfires. Species like cheatgrass and other non-native grasses can double, and even triple the likelihood of fires (roughly equal with the influence of climate change). This further illustrates the cascading, and cyclical effects of a system out of balance. 

Wildfire Greenhouse Gas Emissions are Neutral… For Now

Image source: California Air Resources Board

With recent fires in Colorado many are also talking about the carbon emissions from wildfires. It’s true. Wildfires release a lot of CO2 into the atmosphere. For example, in 2020 California’s fires produced about 91 million tons of CO2, more than the state emits from power production annually. Although there is still cause for concern (just keep reading…), these numbers aren’t as bad as they seem. 

Wildfires (at least historically) are carbon neutral. Although they release huge amounts of carbon, fires also prime the ecosystem to re-absord carbon through new growth. Fires are a normal and necessary part of our ecosystem’s carbon cycle.

However, like all things, that carbon cycle relies on a balance, and wildfires activity in the US has been missing that balance for some time now. “Why?” is a combination of decades of fire suppression, increasing human ignition sources, and climate change, but in terms of carbon it comes down to this:

The increasing frequency and severity of wildfires means that they may not be as carbon neutral as they used to be, and there are two main reasons why.

  1. Forest loss: more frequent wildfires may result in some forest ecosystems converting to grasslands, which have a different sink capacity than forests. 
  2. Sink strength: Wildfire does initially reduce a forest’s ability to pull carbon from the atmosphere, or its “sink strength.” As you can imagine, more frequent fires also mean ecosystems may go through this reduced sink strength phase more frequently. Meaning the ecosystem may not remain fire-free long enough to recapture the amount of carbon lost to the previous fire.

More research is needed in this area, and we will need to continue monitoring whether wildfires become a net source of carbon emissions. But in the meantime, remember that, while wildfire GHG emissions are important to keep track of, those numbers don’t represent the full picture.

Controlled Burns and Fire Management are Getting Harder

That’s right. As climate change makes fires worse, it also makes it harder to fight them.

Controlled burns are our greatest tool for combatting the wildfire threat. This is true in any conditions, but especially  given the build up of fuels from decades of fire suppression. Controlled burns have many benefits. They reduce a fire’s ability to catch and spread, they maintain the benefits of natural wildfires, and they can limit the negative health effects of smoke. They also make our forests more resilient, so that in the event of a natural wildfire the ecosystem will recover more quickly. 

The problem is that our window for safe controlled burns is decreasing. Usually, controlled burns take place during the winter months. Snow on the ground is a prerequisite to keep controlled burns in control, but thanks to higher temperatures, snow melts more quickly and spring comes earlier. Completing controlled burns in a shorter window is spreading firefighters and their resources thin, and the backlog of burn piles increases every year.

As wildfires become more frequent and intense they will continue to stress our resources both in the on and off season. In order to keep up with these new pressures, it is especially important to fund fire mitigation efforts.


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