Obviously, the Wine Country fires are yet another of the many signs of the coming climate Apocalypse, right?
I’ll spare you all the suspense and say yes,wildfires probably are increasing due to climate change, but the picture is a little more complicated than it might appear. Let’s explore some of these extra details a bit, shall we?
First of all, a fire season can be “bad” in many different ways, just as a hurricane season can be, and in order to even assess whether fire seasons are getting worse, we need to first decide what kind of “bad” we’re even looking at. For example, a fire season can be bad because:
- There are a lot of fires
- A lot of acreage burns
- The fire season is very long
- The fires are unusually hot, thus causing more damage per acre burnt
- Fire behavior is less predictable than normal, making the fire harder and more dangerous to fight
- More places humans care about burn
- Fighting fires costs more than usual
- An unusual number of people die in fires
Obviously, several items on the menu can occur at the same time–a year might see a lot of very large, hot fires that behave unpredictably, kill lots of people, destroy lots of property, and cost a lot of money during a time of year when fire danger is normally low. But it’s also possible to see a huge number of very small fires, a small number of very large fires, or a season that seems bad only because beloved places burn, while fire behavior is otherwise fairly mild.
Also, some of the variables in play are clearly linked to climate, such as the length of the fire season. But other forms of “bad” are partly or wholly caused by other factors, such as where suburban development is occurring, how forests are being managed, and how wildfires are being fought.
As with hurricanes, the challenge is to tease out a consistent, relatively uncluttered dataset so you can compare apples to apples from year to year–for enough years for statistical relevance. Unfortunately, most of the articles don’t address where their information is coming from, even when the site is quite reputable, so it’s hard for a non-expert like me to judge how much we really know and how much is logically sound conjecture.
Wildfire Is Getting Worse Because of Climate Change
A simple online search brings up lots of articles on how climate change is definitely making wildfires worse (meaning “longer and more intense”). There are several mechanisms involved. Most directly, higher average temperatures drive more evaporation, and earlier snowmelt, meaning that fuels are drier for a greater part of the year even if precipitation remains the same. Indeed, fire seasons are usually two months longer now than they were a few decades ago. Longer fire seasons mean more fires and also a greater drain on national firefighting resources.
A hotter climate also increases the chance that firefighters may have to work in dangerously hot weather. Hot weather at night can be especially damaging, because heat injury is cumulative. If the body can’t rest from the heat, then heat stroke becomes more likely.
Changes in precipitation patterns, another aspect of climate change, are also important, and not only because some areas are increasingly vulnerable to drought. Climate change involves a concentration of precipitation, so that a greater proportion of the rain that does fall comes in intense cloudbursts, with longer gaps in between. Even if average precipitation holds steady or goes up, this “never rains but it pours” situation is bad news. The rainstorms trigger lush plant growth, which then dries out in the long periods between rains, increasing fuel loads.
The number of acres burned per year has gone up over the past forty years, although the year-to-year variation is very large as well and tends to complicate the picture.
And of course, changes in land-use patterns play their own roles, since there are more houses being built in wooded areas than there used to be, and those houses burn if the woods do.
Wildfire Might Not Be Getting Worse
I’ve also found a few articles arguing that wildfires aren’t getting worse at all. One article argued that America’s forests are getting too dense because there aren’t enough fires and that Congress should provide immediate relief by encouraging logging. Unfortunately, I have not been able to re-find that article, so I can’t verify either its methods or its politics. The other simply points to the lack of trend and leaves it at that.
In some ways, it’s a pretty solid piece–it even links back to several original research papers, and the website, which belongs to a group of public radio stations has no obvious political agenda. A close reading of the article, and its sources, resolves the apparent contradiction.
The author, Tom Banse, acknowledges that fire seasons have been trending worse in recent decades, as other authors describe, yet he frames his own article as providing “contrast” by discussing three scientific papers that “question that prevailing wisdom” by looking at longer time scales.
Time scale is important. It’s possible to create trends out of nothing, or erase trends that actually exist, simply by looking at data from either a too-short interval or a too-long interval. Reading Mr. Banse’s article, it looks as though such obfuscation may be occurring with respect to wildfire, at least in the Western United States. Reading the papers he cites….
The link to one of those three papers is broken. The other two do say the things that Mr. Banse says they say, but not in any way that contrasts with the narrative of climate-induced fire severity.
One paper (actually a report by the United States Forest Service) concludes that, at least in some parts of California, fires were more frequent before the European-American conquest than they have been in modern times, defined as since 1908. In other words, it does not comment at all on changes in fire frequency over the past forty years–the study did not look at trends at all, at any time scale. Instead, the study’s methods involved dividing the study area up into ecologically defined sub-units and comparing the fire frequency for each unit before conquest to the fire frequency after 1908. Thus, all the fires in all the years since 1908 are subsumed into a single number.
There is nothing wrong with that method, but it was designed to address a very different question than the one Mr. Banse is using it to address. It’s a non-sequitur that happens to include the requisite words that wildfires used to be more frequent.
The other paper demonstrates that prior to conquest, fires were often more intense than conventional wisdom among conservationists maintain. Note that the authors of this paper aren’t talking about modern fire behavior at all. They are comparing their understanding of pre-conquest fire severity with somebody else’s understanding of pre-conquest fire severity.
Mr. Banse does quote one of the paper’s authors as saying that fire severity is less now than what “early settlers were dealing with,” but it’s unclear where this quote comes from–it does not come from the paper, since the language of the quote is not formal. Without the original context, we can’t tell what Dr. DellaSala was really talking about in his quoted remarks, or what information he was basing his remarks on. He does not seem to be arguing against the idea that climate change is causing larger, hotter, or more frequent wildfires, only that, from a strictly ecological perspective, more fire isn’t the disaster people seem to think it is.
A very interesting point–but relative to Mr. Banse, it’s another convenient non-sequitur.
Does Tom Banse have a climate-denier agenda? Maybe. The article is certainly structured as a counterpoint against the use of wildfire as evidence of the reality of climate change. I suspect that in the three years since its publication, it has been linked to by climate deniers more often than by the climate sane. But without more information, I cannot judge Mr. Banse. It’s possible he just felt that a counterpoint to prevailing wisdom seemed more interesting.
What’s Going on with Wildfire?
The actual fire we see is a result of a combination of climate, land management (including fire management), and other factors. The research Mr. Banse references hints at that complexity, though probably not in the way he intended.
While the quoted researchers seem to treat the conditions found by settlers as natural, it is likely that the lands in question were being managed intensively with fire prior to conquest–fire was a common management tool in many areas of North America, though I don’t know the details for the areas in those studies (if we don’t normally think of Native Americans as having their own land management practices, it’s because we’re racist; the idea that any part of the American was untouched by humans prior to white people showing up implicitly assumes that Native Americans aren’t human). After conquest, management with fire stopped, and was, within several decades, replaced by active fire suppression (when I was doing fuels reduction cutting in Arizona, I was told that grazing by cattle dramatically reduced fire frequency well before fire suppression began–close-cropped grass did not carry flame well). Of course there were fewer fires–that was the idea.
Decades of fire suppression increased fuel loads dramatically, thus increasing fire risk. Land managers have in more recent decades responded by conducting controlled burns and by allowing some fires that do not threaten developed areas or infrastructure to burn freely. Between one thing and another, fire frequency and severity have increased again, and would have increased anyway whether climate change intervened or not.
It’s not that I don’t believe climate change is a factor–in fact, I don’t see how climate change could avoid being a factor, given that it directly affects both fuel load and fuel moisture content, as well as making firefighting more dangerous due to the risk of heat stroke, as mentioned. But neither the fact that more acreage is burning, nor the fact that this year’s fires are particularly bad is itself the proverbial smoking gun.
What I’d like to see–and I’m sure this exists, I just haven’t seen it this week–is an article, written for a general readership, that presents the changes in fire behavior that result from climate change as separate from those that result from changes in land management and fire management practices. And I mean observed changes, not simply a discussion of what climate change ought to be doing based on our general knowledge of it.
That Mr. Banse may have had an agenda doesn’t make him wrong; that he is wrong makes him wrong. Most people have an agenda of one kind or another, and even those who profess to being utterly objective generally reflect somebody’s viewpoint or priority system (for example, who is paying for their objective scientific research and why?). The point isn’t to avoid those who have agendas, the point is to avoid lies, misleading statements, and agendas that are irrational, dysfunctional, or immoral in some way. Mr. Banse was honest enough to give us the tools to evaluate his talking points–he included links to peer-reviewed scholarship. That’s why we can say that his article was close to meaningless. I find myself wishing that more writers whose agendas I might like better were equally helpful and honest, if only so I could be certain they are right.
So, to summarize: wildfires are burning more acres per year, on average, than they did when I was born, and fire seasons are longer. Fires are also more dangerous to fight because of the increased likelihood of heat waves. Climate change is part of this picture, because it gives us longer summers and longer dry periods between wet periods. But other factors are also changing fire behavior, and at the moment one of the areas that happens to be on fire is beautiful and famous and populated, so we really care about it.
And at 11:31 PM of the day I’m supposed to post this, I can’t tell you what the relationships among all those factors is, or whether anyone knows.
(Note; actually, someone might know, and that someone might be me; I’ve written about fire in this blog before, but since I’ve been chasing information online today without much success, I haven’t had the time to reread my own work and hunt down my earlier sources. The result is this article that comments on the need for better science communication as much as on climate change itself)