Fire Ecology Professor Says Ecosystem In ‘Uncharted Territory’
The National Interagency Fire Center Tuesday bumped the national preparedness level up a notch to its next-to-highest rating.
The agency says this is the second earliest it reached that level on the 1-5 scale since 1990. It's also only the fourth time in the last 20 years to reach that level in June.
This development comes on the heels of a recent University of Montana study that finds Rocky Mountain forests are now burning more than at any point in the past 2,000 years. Edward O’Brien sat down Tuesday with the report’s lead author, who describes the findings as among the most sobering of his professional career.
Edward O'Brien The 2020 fire season punctuated a decades-long trend of growing fire activity across the western United States.
Phil Higuera I said that it's a record-breaking, record-breaking fire season.
O'Brien That's University of Montana professor of fire ecology Phil Higuera.
Higuera 2020 was exceptional for a number of reasons. I mean, in California, they had six of their largest fires occur last year. In Colorado, which is in the area where we focused, they had three of their largest fires last year. They're not just breaking their fire size record once, they're doing it multiple times in a season.
O'Brien The fire season smoke also impacted the health of millions of people. Higuera and Study coauthors Bryan Shuman of the University of Wyoming and University of Montana doctoral candidate Kyra Wolf wondered if they were witnessing something unprecedented. So they started digging into the history of fire in northern Colorado and southern Wyoming's high-elevation forests. Their findings surprised them.
Higuera We use records from lakes on the landscape to reconstruct how often fires have burned in the past and how forest vegetation has changed in the past. And we can also use these records to learn about how climate has changed in the past.
O'Brien What do you mean, lakes? What are you getting [from] lakes?
Higuera Yeah, so, we like to think of lakes as kind of these "field notebooks" that record what's gone on in the past. Everything that falls on the lake surface, like charcoal when wildfires burn or tree needles, that material gets waterlogged, falls to the bottom of the lake, and it gets incorporated into the sediment at the bottom of the lake. And because there's little or no oxygen down there, that material is preserved really well for thousands of years. So we collect cores, tubes of mud from the lakes. I describe it sometimes, like sticking a giant straw into the bottom of the lake, putting your thumb over the top to create a seal, pulling that up. And we end up with these meter-long cores and we collect multiple cores in a lake to go back as far as we're interested in. We slice those cores up into half-centimeter increments. Each one of those little slices from the core represent somewhere around a decade of time in the past. We've spent collectively 15-plus years developing these lake sediment records to learn about fire history in the past. And it just so happens that the area that was experienc[ing] extensive burning last fall overlapped with this area where we had this really well-resolved understanding of fire history.
O'Brien How alarming was the data you all collected?
Higuera One of the first key findings is, after 2020, we can now see that these forests are burning at about twice the rate at which they burned on average over the past 2,000 years. So they're experiencing twice as much fire as they've experienced on average. The second key finding is when we look in the past, there are periods of past climate variability. And some of the previous work that my colleague has done in this region in Colorado highlighted how a period about a thousand years ago when Northern Hemisphere temperatures were a little bit warmer than what they were for most of the 20th century. That period corresponded to a period of extensive burning in sub-alpine forests that used to be the record-setting high. If you think of the record over the last 2,000 years, we've now exceeded that as well. So we're experiencing about, say, 20% more burning than what these forests used to have as a maximum rate of burning over the last 2,000 years.
O'Brien To those who would say, look, we're a couple of decades into the 21st century, doesn't even rate as a blip on the cosmic scale, let's not go Chicken Little here — you would say what?
Higuera You know, I appreciate that perspective in particular, because much of my career has been based in understanding how ecosystems change over these long timescales. You know, putting together the observations over the last several decades, the predictions from the scientific literature, it's clear now that our ecosystems are kind of moving into uncharted territory in response to the warming of the climate. It's particularly alarming or concerning to me. And I think it's really important to know that, you know, we're not just moving outside of what we've experienced in the last 30 to 50 years. These ecosystems are moving outside of what they've experienced for the past several thousand years. And our study stopped at 2,000 years, not because something happened different before that, but that just happens to be when our records end. So it's likely that we're moving into territory that's even outside of the range of, say, the last 6,000 or more years, basically the time period that these forests have existed.
O'Brien Can we extrapolate the results of your team's study and apply them to this heatwave that's enveloping the western U.S. and these fires that have swept through areas like Red Lodge, towns on the Crow reservation in the Bighorns, or is that a reach that you're not quite prepared to make?
Higuera I'm prepared to make a little bit of a reach there. I mean, certainly, the drought and the heatwave that the West is experiencing right now does have a direct connection to the findings of our study. The link there is that as forests experience increasingly intense drought and/or drought over long time periods, that drought dries the vegetation, whether it's live vegetation, but in particular dead vegetation. So sticks, twigs, logs, any dead vegetation. And it is that dry vegetation that makes it easy for ignitions to occur. And once those fires start, they'll spread more quickly. So what we like to say is that climate, for example, drought, enables the possibility of large fires to occur. The more time that the West is experiencing drought, and the more intense that drought is, kind of the more time each year and in cumulative years, over time, that the dice are loaded for large fires to occur.
O'Brien Before we sat down and rolled tape, you described this study in a very unsettling way. What did you say?
Higuera I was saying that in my career, which is going on 20 years now, I think this was one of the most sobering studies to put together because rather than making some prediction about what was going to happen in the future or kind of warning about the impacts of climate change on fire activity and forest ecosystems, this was kind of one of the first times in my career where, when we put the data together, we could kind of see that we're now looking in the rearview mirror and able to say, "Things have changed and we've now entered into uncharted territory." Unfortunately, even as 2021 is unfolding, we can see that it's not going to be the last example that we have of that.
Copyright 2021 Montana Public Radio. To see more, visit Montana Public Radio.