Another hazard that still lies ahead is peak wildfire season. CapRadio’s Manola Secaira spoke to Zack Steel, a research scientist who has studied changing wildfire patterns in California. While last winter’s heavy rains and snowfall boosted the state’s water resources, Steel said it could also play a part in how and where wildfires manifest this year.
This interview has been edited for length and clarity.
What did fire historically look like in California forests? And what’s changing now?
The first thing to understand with a lot of the ecosystems in California, in the West overall, is that these are ecosystems that are really built to burn. There was a lot of fire in these areas historically.
If we look back, prior to European colonization, there was a lot of Indigenous fire management on the landscape. There's a lot of lightning ignitions. And so the way that the vegetation and the ecological communities more broadly were structured is really around frequent, but low-intensity, fires.
What we're seeing now is … highlighted by a couple of big changes in the last couple hundred years. One is how we've been managing these forests — putting out those small, low-intensity fires [via fire suppression] and then we're also layering, on top of this, climate change. That leads to some of the big, severe fires that we're seeing now, which were historically uncommon and really not what these ecosystems are adapted to.
So, it’s the intensity of wildfires that’s changing and not an increase in the number of them?
On any given year over the last few decades, we've actually had a lot less fire [in recent decades] than we thought we used to on an average year, you know, 200 years ago.
2020, I think, was the first year that we actually kind of reached that historic average, and we had a lot of fire that year. But the problem is the type of fire that we're seeing now tends to be more severe. You have larger patches of complete or nearly complete mortality of the vegetation and this is occurring near human communities.
The cycling between multiple drought years and an occasional wet winter, like the one we just saw, isn’t out of the ordinary. But many researchers I’ve spoken to have told me the extremes are becoming more extreme. Can you tell me how this relates to wildfires?
There is a lot of interannual variation from one year to the next of drought and wet years, like we've seen in the last few years. That's intensifying because of climate change. But climate change also influences how the ecosystems respond to these disturbances, both drought and wildfire.
So if you have a couple of really dry years like we've recently experienced, then your forests are going to be stressed. You're going to start to see conifer mortality or other trees dying on the landscape due to a combination of drought and beetle attack. So when the fire does come through, you have a lot of dead material, fuels, which tend to dry out faster and burn hotter. That can contribute to the next fire.
And so there is an interaction of these different disturbances. That kind of goes back to this dual problem of global warming events that's amplifying the underlying problem, but also the overly dense forests that we have in a lot of places where we have excluded fire and so when you have a dense forest, it's more susceptible to both drought and to wildfire and eventually, the combination.
It’s easy to understand how drought conditions feed a fire. But what does a wet winter mean for peak wildfire season?
All the rain and the snow certainly helps a lot. But the way that's going to play out will likely vary a lot by the ecosystem type that we're focused on. In that higher elevation Conifer forest, which is where I do most of my work, you're going to have snow in those systems for a while. It's going to remain wet and not susceptible to fire for a longer part of the season, so the fire season is going to be shorter.
But lower elevations where you don't have the snowpack, it's going to dry out sooner. There's less of that truncation of the fire season.
The other part is that when you have these wet winters, you get this pulse of vegetation growth. Think of the weeds in your yard — they really took off this year. Once those dry out and kind of get cured as the summer goes on, that's a lot of fuel that's ready to burn. So, we are still going to have a fire risk later in the season. It's just going to be, probably, delayed and come in a different form. Where we're likely to see these fires might be a little different than we have in past years.
It sounds like there are some predictions we can make based on this past winter, but it’s not set in stone.
It's difficult to predict where and how much fire we're going to see — other than the fact that California's going to burn again. It’s part of the system.