One of the most iconic trees of the Pacific Northwest has been showing signs of distress for years. Western redcedars are a water-loving tree, and it appears that drought and rising temperatures may be impacting their health. Columbia Insight previously reported on the results of a two-year study on the dieback of Western redcedar trees by the Oregon Department of Forestry, the Washington Department of Agriculture and the U.S. Forest Service. Joey Hulbert leads a citizen-science research project at Washington State University collecting data on western redcedars throughout their range. Christine Buhl is a forest entomologist at the Oregon Department of Forestry and a co-author of a recently published report on the dieback of Western redcedar trees. They join us to talk about their research and the threats Western redcedars face.
The following transcript was created by a computer and edited by a volunteer.
Dave Miller: One of the most iconic trees of the pacific Northwest has been showing signs of distress for years now. Western redcedars are a water loving tree and it appears that drought and rising temperatures may be impacting their health. Joey Hulbert is a postdoctoral fellow. He leads the Citizen Science Research Project at Western State University collecting data on western redcedars throughout their range. Christine Buhl is a forest entomologist at the Oregon Department of Forestry. They both join us now to talk about their research. Thanks for joining us. Joey Hulbert first. On your website for your project, it says that western redcedars are nature’s superheroes. What does that mean?
Joey Hulbert: Well as you mentioned earlier, they’re water loving species. So they grow in a lot of environments where there’s a lot of water. And in those areas they’re providing critical services like providing shade for streams. So our salmon can thrive in these cooler river systems.
Miller: What do they mean culturally?
Hulbert: So refuge is really important. As a cultural species it’s known as a really generous species because of all the gifts that it’s provided to Indigenous communities since time immemorial. And it’s really critical that we understand what’s going on with this tree so we can protect those services and the tree can continue to provide these gifts to future generations.
Miller: Christine Buhl, why is your team and Joey Hulbert and others, why the focus on Western redcedars now? In the big picture what’s happening?
Christine Buhl: You could consider Western redcedar is a bit of a canary in the coal mine species because it is not very drought tolerant. It does like cool shaded moist conditions. So with these increasing temperatures, reduced precipitation for long periods of time, that’s one of the first species in which we’re seeing damage of climate change. And this is a very important species, as Joey had mentioned, to Indigenous peoples but also ecologically in our riparian areas and even in our urban areas. And so it’s kind of an indication of where things might be headed in terms of where we can expect to see this and other species that are not as climate-change adapted.
Miller: Joey Hulbert, what did you set out to find out with the help of citizen scientists?
Hulbert: Thanks for that question. It’s a great opportunity to hear from Christina as well. So Christina and her collaborators had led a kind of inter agency effort to understand where trees are healthy and unhealthy. And we worked with them to extend that effort to the public through a community science project called Forest Health Watch. So through working with Christine and her collaborators, Betsy Goodrich and Melissa Fisher, based in Washington, we extended an effort they had to understand where redcedar were unhealthy, into a tool called iNaturalist which allowed the public to participate and learn with us. So we really are eager to seek the help of more community scientists and to better understand where trees are healthy and where they are unhealthy. So we can then evaluate which factors might be useful for predicting where trees are going to be healthy and where they’re going to be unhealthy in the future.
Miller: So what did you find looking region wide, Western U.S., in terms of broadly places where Western redcedars are doing well and places where they seem to really be in trouble?
Hulbert: Generally, the purpose of this effort is to understand where trees are vulnerable. If we continue to have longer and hotter drought, and Christine can speak to their use of the iNaturalist data and the community scientists’ effort to do some analyses, and start understanding which trees may be vulnerable and which trees should thrive. But generally, and Christine feel free to correct me,we were seeing dieback throughout the range of redcedar, happening in British Columbia all the way down to southern Oregon. And we’re seeing as far east as western Montana.
Miller: Christine Buhl, I know that there are always going to be sort of micro climates and little slices here where things may be better or worse for any given creature. But in general, where are Western redcedars likely to do well going forward?
Buhl: So going forward, but also currently, we are seeing Western redcedars still thriving in areas that are cooler and more moist, such as along the coast range, higher elevations in the Cascades, they seem to still be doing well. There are some areas within those ranges that they are starting to struggle. But usually it’s kind of the lower elevation areas that are really sun exposed that they tend to fail first. However, an interesting thing that we found in doing this mapping and more indepth research is that we had a lot of Western reds here dying in shaded areas that are right along streams where we thought they should be doing well. It’s a little bit more complicated. But to kind of generalize, what we think might be happening in those areas, is that even though there is still flowing water right alongside these trees, in many cases, maybe it’s not as much as what they had been used to historically.
Those water levels have still dropped and Western redcedar does not have a tap root. It has more shallow wide branching roots and so it can’t simply dive deeper when moisture levels are lower or they’re less consistent. And even if there’s some shading, there’s still a high temperature element even though it’s not in direct sunlight. So we do have some pockets in which Western redcedar looks like it’s in the correct microclimate, but it’s still getting more stressed as are all of the trees in our state due to ongoing high temperatures, low or erratic precipitation.
Miller: My understanding Christine, and as I noted, you are an entomologist, a forest entomologist with the Oregon Department of Forestry. And one of the points of this research was to rule out that insects or fungus were primarily responsible for the decline. Were you able to do that?
Buhl: Yes. So my other collaborators that Joey had mentioned - Betsy Goodrich with the Forest Service is a pathologist with Region 6 and Melissa Fisher is an entomologist with Washington Department Natural Resources - we have quite a wealth of information and background on insects and diseases that attack Western redcedar. And what we know historically is that Western redcedar is a very insect and disease resistant species because it does have chemical compounds that it utilizes when it’s healthy to resist or tolerate any of the attacks by insects and diseases which are often opportunistic, meaning they only attack trees that are already struggling or dying. And it’s very common for Western redcedar to have stem rot. But oftentimes that’s attacking tissues that are already dead within the tree. It’s kind of like if your hair falls out or it’s not really supporting you and your well being.They’re just tissues that are old and dying back anyway.
And so what we did was we tried to investigate if there were new insects or diseases that were emerging or maybe the intensity had ramped up so populations were higher. And we did not find that. We saw the usual suspects that we would expect to see for insects and disease in the struggling trees. We did not see anything novel. We did not see healthy trees being heavily attacked. There were many cases where we had Western redcedar dieback and no insect or disease activity to speak of. And so then we started looking at some abiotic or other factors that might be at play here. And as with many of our trees, as I mentioned, climate change is very damaging. And we’ve been seeing it in many species. So we assume that that was at least one of the characters that play.
Miller: So climate change seems to be the main culprit here. As you said, this is a kind of canary in the coal mine tree, very susceptible to drought and to heat. So that’s a question of global greenhouse gas emissions. But more specifically in terms of these trees and what could be done in the short to medium term, what could be done? I mean, are we looking at planting saplings on north facing slopes or at higher elevations or higher latitudes? I mean, what would it take to have these trees survive?
Buhl: I think Joey would agree with me in that we want to retain Western redcedar on the landscape wherever possible. We are not stating that this is a loss of the species. It could be a range shift or range shrinkage. But we can still retain Western redcedar even in these dieback areas where there are some microclimates that can support it. In areas that can’t support it we want to think about what are some alternate species that we might want to plug into those areas. Incense cedar is a great option, for example, that serves many of the same ecological purposes that Western redcedar does, although it cannot fully supplant Western redcedar.
But even in those areas where we do have Western redcedar not doing well, there are some ways to retain it on site, at least for a bit longer, by reducing competition for water resources, such as reducing invasive species that might be coming into the area and out competing Western redcedar or even some native species. Maybe tree stocking is a little high and we can reduce that so that we can give the Western redcedar as much access to moisture as possible.
Miller: Joey Hulbert, what should people do if they want to take part, if it’s still possible, in this citizen science and to help map out the health of Western redcedars in the west?
Hulbert: Yeah. Thanks Dave. Absolutely. We would love more participation. And a lot of the results that we’ve spoken to have been only achievable because of the incredible participation of many community scientists. So more than 250 people have shared observations of trees and indicated, but there was a healthy tree, an unhealthy tree. And we hope that people will continue to do that because that information is really useful. And with more observations, we can do more fine scale comparisons, trying to identify some of those other factors within a site where a tree may be healthy here and unhealthy over there.
But generally, there’s a lot more opportunity to contribute and people can find more information at foresthealth.org/map. There’s some guides for how to use iNaturalist and I’ll say that it’s really a pleasure to be here with you and Christine. They’re doing incredible work and it’s great to see this community science effort turn into some tangible information and results. So thank you both.
Contact “Think Out Loud®”
If you’d like to comment on any of the topics in this show, or suggest a topic of your own, please get in touch with us on Facebook or Twitter, send an email to thinkoutloud@opb.org, or you can leave a voicemail for us at 503-293-1983. The call-in phone number during the noon hour is 888-665-5865.
