Aerial survey reveals massive fir tree die-off in Oregon

An aerial survey conducted this past summer by the U.S. Forest Service and the Oregon Department of Forestry found more than 1 million acres with dead or dying fir trees in Oregon, the largest amount of fir mortality since the aerial surveys began 75 years ago. News of the tree die-off, which has been called “firmageddon” by some of the survey researchers, was first reported by Columbia Insight. The affected trees were mainly white and Shasta firs, with the bulk of the tree mortality concentrated in the southern part of the state. Danny DePinte is a forest health specialist and aerial survey program manager for the U.S. Forest Service. Christine Buhl is an entomologist with the Oregon Department of Forestry who participated in the survey. They join us to talk about what’s behind the tree die-off and its implications for the state’s forest canopy in an era of more intense wildfires and hotter droughts driven by climate change.

Note: The following transcript was created by a computer and edited by a volunteer.

Dave Miller: This is Think Out Loud on OPB. I’m Dave Miller. Aerial surveys on forest land throughout Oregon this summer revealed a nasty surprise. More than a million acres had dead or dying fir trees. It was the largest fir die-off ever recorded in 75 years of surveys by the U.S. Forest Service and the Oregon Department of Forestry. It was bad enough that it earned a nickname “firmageddon”. For more on this die-off, I’m joined by Danny DePinte who is a forest health specialist and aerial survey program manager for the U.S. Forest Service and Christine Buhl, an entomologist with the Oregon Department of Forestry. It’s good to have both of you on the show.

Christine Buhl: Thank you.

Danny DePinte: Yeah, thanks for having us on.

Miller: Danny DePinte, can you just give us a sense for what you saw from those airplanes this summer?

DePinte: Yeah. Flying over the forests, you head over mountains and hilltops and we’re looking at the forest canopy below and we get our normal level of die-off, little pockets here and there and then you come over a certain ridge and it starts to become more intense and almost a blanket, and some parts of just red, dead, fir trees across the landscape and it just continued on. And as we start to realize how large this is, that’s where it started to get the name “firmageddon,” as in designating that as a more severe area of fir mortality than normal.

Miller: Christine Buhl, what was going through your mind when you would see some of those areas?

Buhl: Well, historically we have seen dieback in multiple different tree species such as Douglas fir and True fir, in certain areas it’s been more intense than others. So, initially, it looked like more of the same, that this is just a harder hit area. But then once hearing what other surveyors were finding later in the season, looking at the rest of the state, the True fir mortality was indeed quite a bit higher than what we have seen historically.

Miller: Danny DePinte, can you give us a sense for what that means? How much worse was this than other years? Because as you’ve both said, it’s not like you’re not used to die-offs, this is just a fact of life and death in forests. So how much worse was this?

DePinte: Twice as large as what we have previously seen. When I looked back at the historical data, starting around 1952, specifically for fir, the periods of bad die-offs before, were typically around 500,000 acres, with mortality, to some degree. Whereas last year, 2022, we recorded over one million acres with some level of mortality. And that’s twice as big as anything we’ve ever recorded before.

Miller: What areas were hit the worst in Oregon?

DePinte: The worst areas that we’ve noticed start around the center part of Oregon, around the Ochoco and the Malheur National Forests and then it continues southwards towards the California border. And this is mostly east of the Cascades. The drought kind of swoops into the Medford area, Ashland kind of area, but it’s mainly down there and then it goes to the California border, so basically from the center of Oregon to the California border.

Miller: Christine Buhl, I wonder if we can go from 1,000 ft in the air down to the ground. What happens when you look at these trees when you’re standing at the foot of them?

Buhl: So oftentimes, we’re looking for signs and symptoms of what could be occurring on the ground from things that we see up in the air. The first thing we want to look at is what tree species are being affected. If we are seeing multiple different types of species that are being affected, then that kind of lends itself to something abiotic. A lot of our insects and diseases that are passed tend to target specific tree species. And so if you see multiple species being affected, it likely could be something else or an underlying stressor. Particularly, when you see species that are maybe less drought tolerant, that are damaged or have some mortality, then you start thinking about, “well, is drought stress an issue? Is that something we’ve been seeing in the data collection from the climate center?”

And then taking a closer look, beyond looking at the exterior of symptoms of the tree such as red needles, any sort of damage along the bark, etcetera, we can look under the bark, we can do a little bit deeper digging. But oftentimes, you can kind of see if the signs and symptoms of insect or disease are present or not exteriorly and if not, you might dig deeper or just start thinking about abiotic underlying stressors.

Miller: What tree species were most affected? What are the trees that died off in great numbers this year?

Buhl: As Danny had mentioned, historic levels of True fir die-back. And I want to distinguish that from our state tree, which is Douglas fir, which is not a True fir, so taxonomically, it’s in a different group. But we have multiple species of True fir, often seen as Christmas trees in our homes. These include Grand fir, White fir, Pacific Silver, Noble fir, California Red, Subalpine, and they occur at different areas of the state depending upon their requirements. Oftentimes this species, however, is pretty drought intolerant and they tend to reside specifically in higher elevation areas. So when you go up in the mountains and you go skiing, you’re seeing a lot of Subalpine and Noble fir, for example. But we have had quite a bit of Grand fir, in particular, that’s become very common in lower lying areas, particularly in areas where we practice a lot of fire suppression. And so it’s allowed those True firs to populate a bit more densely than they typically should in some of those areas that are a little bit more harsh for them.

Miller: So because of, among other things, our fire suppression tactics, trees have started growing in places where, maybe traditionally and and more so with climate change, they’re really not adapted?

Buhl: That’s in some cases that, where we have paired not only wildfire suppression, but we haven’t done that typical cleanup that we should pair with any sort of suppression, which is reduction of fuel. So prescribed fire, for example, those are things that need to be paired, if we’re not going to allow natural fire cycles to take place. And so in some areas, yes, some trees have populated and can kind of proliferate, sometimes more densely than they would have naturally. And especially with our changing climate, with ongoing hot droughts, those areas are becoming even more intense, making a kind of fringe habitat for some of these species.

Miller: I feel like the phrase “hot drought” is maybe self explanatory, but it also seems like you’re using that in a very specific forestry science way. So what do you mean by hot drought and why is it such a problem for some trees?

Buhl: Oftentimes we just talk about drought and we don’t talk about temperature and so drought is a reduction in total precipitation, but we’re also seeing that paired with increasing temperatures. And so that’s kind of a 1-2 punch for trees, that not only are they receiving less moisture or less consistent moisture, but it’s drying out really quickly or being pulled from the trees into the atmosphere more quickly.

I want to make really clear that when we talk about hot droughts or climate change, there are some very specific points here to recognize that we do have some record high temperatures some years, for example, that don’t compete with what we might have in a milder year, but it’s still an intense drought period or hot drought period because it’s the duration of the hot droughts or the temperature and precipitation changes. It’s the timing. It’s how frequently this is occurring. Those things all play a role in how these trees are being stressed and it’s kind of an ongoing stressor in that these trees are not able to access moisture and even if they could, some of their tissues, to transport it throughout the tree, have been damaged from previous drought. So they’re just kind of being pummeled by ongoing high temperatures and inconsistent or low precipitation.

Miller: What’s the connection between drought stricken trees and susceptibility to beetles or fungus?

Buhl: I’ll start with beetles. We oftentimes will map the damage that we see as beetle-caused damage, because historically we thought that that was exclusively what was causing the damage and didn’t pay attention to some other underlying factors such as root diseases that can predispose trees to insect attack or drought stress. Oftentimes, these beetles are natural components of a functioning ecosystem, they’re native, widely present on the landscape, but they are opportunistic. So whenever that tree is stressed, such as the defenses are down, those beetles can take over the tree and then they can build into populations that are unnaturally large and spill over and overcome the defenses of adjacent healthy trees.

Drought stress in particular is really damaging for tree defenses because it reduces sap flow and sap is a main mechanical and chemical barrier to prevent insect entry into trees and allowing them to populate. There are also a myriad of other impacts that drought causes that can predispose trees or weaken them to diseases that they may have been otherwise able to fight.

Miller: Danny DePinte, I’m assuming that most of these trees are still standing and could be standing for a while now, even though they are dead or dying. What’s going to happen to them?

DePinte: That really depends on each land manager. We survey all forested lands and so this problem is so wide and broad that it’s really up to each land manager.

Miller: Meaning it could be National Forest Service land or BLM land or state forests or private land, which is a big patchwork?

DePinte: Exactly. It’s a huge patchwork. So each individual person or organization that’s managing that little piece of the land, really gets to decide on what they want to do. Do they want to sequester that carbon and turn that into boards or do they want to leave it for habitat for animals? Is it something they can tolerate? They have to just kind of imagine fire going through their landscape and seeing if this is hazardous or is this a beneficial component of their landscape now for wildlife or something like that.

Miller: Can you describe the worst case scenario, in terms of fire danger, in places that have big stands of dead firs with dry crowns?

DePinte: The worst case scenario would be, if you’re in an area with more than 50% mortality, dead standing trees with needles on them and then on top of that, if you had on the ground, what we call surface fuels or ladder fuels, something that would actually carry the flames up high enough to reach those dry needles, that would be the worst case scenario. And then, aspect and slope, if you’re on a hillside. These are all different factors that go into modeling that kind of fire behavior.

Miller: Christine Buhl, what does a die off like this suggest about what kinds of trees different land managers should be planting or thinking about in Southwestern or Central or Eastern Oregon going forward?

Buhl: I’m gonna tend to give a silver lining here. Whenever we’re talking about widespread mortality, it’s really an opportunity to kind of retool what species we’re putting on the landscape and think about what we expect to see where. There are some really great seed lot selection tools online that can assist a landowner in selecting the right, not just tree species, but the genotype within that species that may be more tolerant in the current and future conditions of a site. So placement of those species correctly, not just regionally within the state, but looking at the microclimate within your specific site. If it’s a drought intolerant species, maybe you want to place it in a draw or a shaded area or an area where there’s gonna be less water loss or more access to moisture. And so we do have an opportunity to kind of shift our thinking in terms of what species we can expect to persist where. In the meantime, our landscapes are going to change and we’re going to see that happen sometimes more suddenly as we saw this year, but we just need to change our thinking to adapt for it.

Miller: Christine Buhl and Danny DePinte, thanks very much.

Buhl: Thank you.

DePinte: Thank you.

Miller: Christine Buhl is an entomologist with the Oregon Department of Forestry. Danny DePinte is forest health specialist and aerial survey program manager for the U.S. Forest Service.

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