Fires in Eastern Oregon affect crucial sagebrush rangelands

Cheatgrass and other invasive species are threatening important rangelands and helping fuel severe wildfires in Eastern Oregon. Lisa Ellsworth is an associate professor and range ecologist at the college of agricultural sciences at Oregon State University. She joins us to explain how these areas have been affected by invasive species, extreme wildfires and human activity and what that means for the future of a crucial Western ecosystem.

This transcript was created by a computer and edited by a volunteer.

Dave Miller: This is Think Out Loud on OPB. I’m Dave Miller. The Durkee Fire is now mostly contained, but it has already scorched almost 300,000 acres of sagebrush steppe in Southeastern Oregon. This land – part of an enormous swath of the American West – is much more prone to wildfires than it was in the past. Lisa Ellsworth studies the landscape as an associate professor and range ecologist at Oregon State University, and she joins us once again. Welcome back to the show.

Lisa Ellsworth: Thanks, Dave.

Miller: So, a few weeks ago, not maybe even just a week ago, the Durkee Fire was the largest wildfire in the country. Now, one in California has surpassed it. How is this fire emblematic of the situation right now in the American West?

Ellsworth: This is what we’re starting to see each year, where we have these extremely large fires. Where, 25 years ago, when I fought wildfire, it was a really big deal to have a 10,000-acre fire; and now, I had to go online and count how many over 100,000-acre fires we have in the state. So it’s very much a pattern that we’re seeing, that fires are happening earlier, they’re larger and we have more of them in these rangelands.

Miller: Let’s take those one at a time. But, first of all, if you can just remind us what wildfires, in general, were like in the past. Say, I don’t know, 100 years ago?

Ellsworth: That’s a really good question. We estimate that fire-return intervals, which is how often you see a fire in the same area, in sagebrush systems might have happened something like 50 to 100 years or more between. So it’s a very slow-growing ecosystem. There’s very little water out there to grow plants. It takes a long time for enough plant material to accumulate that it will burn again. What we’re starting to see, though, now is that there are invasive grasses that grow fairly quickly and provide fuel to create more fire.

Miller: So how are the invasive grasses – cheatgrass, I think is one that we’ve talked about in the past – different from native grasses in terms of their both response to fire and likelihood of burning, themselves?

Ellsworth: Cheatgrass and a handful of other problematic invasive grasses are annual plants. So they just come up and grow this one year, put out a ton of seeds, and then they’re done. The native grasses are perennial, clumpy, bunch grasses. And historically, we would have had these beautiful giant clumps of grass with a lot of bare ground in between them. What the invasive annual grasses do is they grow in that interspace between the plants. So where we would have had a system of clumpy plants and lots of little firebreaks between them, those invasive grasses are taking up that space and making the whole system more flammable.

Miller: You mentioned that fires are also happening earlier now than in the past. What’s responsible for the changes in the length or the timing of fire season?

Ellsworth: Good question. That is at least in part because of the annual grasses as well. They come up earlier in the spring and then dry out before the native plants do. They’re flammable earlier, so our fire season can start earlier. Climate change is a piece of that puzzle; things are getting warmer and drier. But there’s also more and more people out in these rural areas, so the potential for human ignitions is also a piece. A complicated set of answers that are all working together to make this more flammable.

Miller: As I think we maybe talked about the last time you were on, there’s an unhelpful tendency for people, even in the West where we deal with both forest fires and this kind of sagebrush land fires, to conflate them, to confuse them, to just treat them as one of the same. But it seems like one of the big differences – and I’d love you to correct me if I’m wrong here – is that when we talk about forest fires in the West, one of the big things that we now talk about is the fuel load that’s there because of historical fire suppression. Is there anything analogous when it comes to rangeland fires that we’re talking about?

Ellsworth: There’s not really a fuel build-up issue in rangelands in most cases. There are small patches of land where we’ve gone too long without fire and the shrubs are getting more dense, so there’s more likely for woody accumulation and fire spread. But that’s not the vast majority of the area. Most places, it’s a fuel continuity issue where those invasive grasses are helping to spread fire more quickly. These are dry, dry ecosystems; they get 10 to 12 inches of rain per year. So it takes a very long time to grow a plant with that little moisture.

Miller: How [is] the severity changing? I’m wondering because it’s one thing to say 300,000 acres burned; but if it’s a fast-moving fire that doesn’t penetrate that far into the soil, then whatever was there has a better chance perhaps of regrowing than if it’s just a fire of such intensity that it kind of sterilizes the ground. So what are you seeing most often these days?

Ellsworth: Yeah, that’s a good question. When you have the annual grasses that take up that space between perennial plants, it allows fire to move very, very quickly through some of those areas. A lot of times the native plants do OK. The shrubs typically die with the bunch grasses, can often survive a fire. So when we talk about severity … and on the west side, we’re usually using some sort of metric about how much tree canopy was removed, but it’s a little bit different in sagebrush ecosystems. We still think about how much of the woody plant community has been killed by the fire, but that understory of bunch grasses is what really holds the system together and makes it resilient. And those plants often do OK with wildfire.

So when we have the big continuous fires, it’s a mosaic the same way that it is on the west side, where we have higher severity patches, and we have maybe some unburned islands, even, in some areas of lower fire severity. But the size is concerning, because when we have very large fires with a lot of high severity, we lose our seed source for restoring the area after the wildfire. So there’s more interventions that need to be done in areas that are high-severity and that are very large fires.

Miller: Well, let’s turn to those interventions because you’ve been a part of some studies that have been testing out different kinds of fuel reduction treatments. Can you remind us what you’ve been looking at in different plots?

Ellsworth: Yes. So I run a large research program; it’s called SageSTEP, and that stands for Sagebrush Steppe Treatment Evaluation Project. And for 20 years, we’ve been measuring the same permanent plots all over the Innermountain West.

We have 21 plots. Crews go out every year and track how plants are responding to different treatments. So we’ve done prescribed fire treatments; we’ve done mechanical removal treatments where we cut down juniper or mow the shrubs to enhance the bunch grasses; there’s places where we’ve done herbicide treatments to suppress those invasive annual grasses.

And then we’re looking at them from multiple different perspectives. My group mostly looks at them from a fuel accumulation and fire risk perspective. Other folks are looking at native-invasive plant dynamics. Folks are looking at it from a wildlife habitat perspective. And we’re really finding that there are tradeoffs to consider. Some of the treatments that make things the least flammable in the short-term have to be done repeatedly. Something like herbicide to kill the invasive annual grasses, that treatment only lasts a couple of years. So coming up with tradeoffs to do treatments that are both effective and durable.

Miller: Then there’s also just the question of scale. If we’re talking about an area of land that’s literally bigger than many entire East Coast states combined, how do you think about what it would even mean to apply any treatments landscape-wide?

Ellsworth: That’s something that we’re wrestling with in management right now. You can’t possibly treat everything all the time. So current federal offices are strategizing, where can we get the most bang for our buck? Where can we do potentially post-fire herbicides? And then seeing where it’s actually going to have some success and we’re going to get desired plants afterwards. Where is the ecosystem resilient enough in good enough condition where maybe it can actually support some prescribed fire and we will have better fire-resilient ecosystems into the future? Where do we need to protect core habitat for important species like sage grouse and many of our songbirds that are at risk? Where are the high priority milled areas? So it’s definitely this both spatial and temporal consideration for what treatments we can do where, because we can’t do anything about all of the invasive grass all the time.

Miller: Do you see that whole suite of questions you just asked as more scientific questions – a scientific problem – or a political one?

Ellsworth: I don’t think it’s an either/or. I think that our best solutions come from scientists and managers working together to solve problems. Some of the most effective treatments are happening places where we’re all working together to solve it. And there are places where folks on the ground are doing things that science hasn’t tested yet. There are places where the science is ahead of what’s happening on the ground. But the local communities where we’re all working together to strategize is quite effective.

Miller: Lisa Ellsworth, thanks very much for your time today. I appreciate it.

Ellsworth: Yeah. Take care, Dave.

Miller: You too. That’s Lisa Ellsworth. She is an associate professor and rangeland ecologist at Oregon State University.

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