As cooler, wetter weather comes to the Northwest, wildfire season is rapidly coming to a close.
This year’s fires are leaving behind more than just charred forests. They’re setting the stage for what’s expected to be a fundamental shift in the landscape. Because of a changing climate, what grows back could permanently look very different than what was there before.
Much of the forestland above the Illinois River in Southwest Oregon is a tangled mess of manzanita, shrubby hardwoods and ceanothus. Bushwhacking through it is a branch-to-the-face, boot-snagging, poison-oaky horror.
And this is one of the easy spots, says Charles Maxwell.
Charles Maxwell: “Yeah, this one is a pretty accessible site relatively, some quite a bit further in.”
This is where the Biscuit Fire burned 13 years ago, and one of dozens of research plots the Portland State PhD student catalogued this summer.
Charles Maxwell: “This is typical thing we would see. Fairly diverse number of species but again not too much in the way of conifer regeneration.”
In fact the shrubs here are decidedly in control. Maxwell and his colleague Melissa Lucash are trying to figure out if this is going to be permanent.
Melissa Lucash: “With climate change, we might be headed more towards that tipping point of increasing more shrubs.”
Some modeling has shown that these Klamath and Siskiyou forests could experience a substantial long-term shift from conifer to this shrub-heavy chaparral.
Portland State’s Robert Scheller, who’s leading the study, says established trees can likely survive some warming. Where climate change really kicks in is after large forest die-offs from wildfire, disease or bug infestation.
Robert Scheller: “It's little trees - you know like, little trees - those are the ones that really get hammered by drought. And so if you get big wildfire, then you get some droughty years following that, that's where you get the replacement with shrub chaparral. They can keep a location in this shrub/chaparral state for decades, even centuries.”
Scheller hypothesizes that any place in the Northwest outside of the moist Coast Range is at risk of flipping to some other forest system.
This has major implications for the region, says University of British Columbia Forestry Professor Nicholas Coops
Nicholas Coops: “Ultimately, the species that inhabit that forest, the biodiversity that’s in that forest, the ground cover, all of that will ultimately be shifting. Now the caveat is it probably won't shift in one person's lifetime, but the trail that your grand kid walks will be a very different trail.”
Landscape shifts to shrub could mean changes for the timber industry as well, says Mike Cloughesy with the Oregon Forest Resources Institute.
Mike Cloughesy: “If you're owning it, you're not going to get any type of income off that piece of ground.”
But Roseburg Forest Products Manager Eric Geyer says they have not changed how they’re managing their land in anticipation of shifting forest types.
Eric Geyer: “As people that look at forest as long term process, we don’t really think about smaller shifts, we think about big shifts. And that's anybody's guess as to what the climate may do over the next 30-40 years.”
The data gathered this summer by Portland State scientists will be used to help better predict what forests will look like in the future.
But even now, the consensus is that forest type shifts are happening. And Lucash says intense wildfire can hasten the process.
Melissa Lucash: “You have scenarios where you have increasing fire, then you have more and more shrubs. Then you have increasing fire, and you have, you know sort of resetting and you have shrubs dominating again. You end up in this sort of self-reinforcing loop.”
And to help Northwest forests weather the coming climate change, scientists and forest managers will need to figure out how to break that cycle.