BOISE, Idaho — It is a question many people have asked over the past few years, and a story KTVB has covered several times.
Why are all the trees dying along Highway 55? An Idaho lawmaker is working to get an answer.
"I'm hoping to get a study done to find out what is happening to the trees along 55, particularly along the river...," said Idaho Senator Rick Just. "We just need to find out what it is. That's the main thing I'm concerned about."
Sen. Just said he is planning to request funding to test tree tissue samples, and find out what is killing them.
"It's just like if you were to go to the doctor and they did a blood sample, they can see a lot of things based on that sampling. So, a tree would be no different," University of Idaho Professor, Audra Cochran said. She teaches Farm and Forestry topics.
Professor Cochran explained what this study may look like.
"So, it's a bit of an extensive process. You would be looking at a research trial, because you would want to get tissue samples from a collective sampling across the state so that you could get a good idea to see what the trees are working with and what they're fighting off," she said.
For the past two years, the U.S. Forest Service said a combination of factors are to blame, including climate change and drought. Now, scientists want to examine if the salt mixture used to melt snow on wintry roads has something to do with it.
"So deciduous trees are better able to handle the road salt load, because they do shed that foliage every year, where our conifer species aren't necessarily shedding needles every year," Cochran said. So they have a little harder time dealing with that road salt. Tree stress in general can take on a lot of different shapes and forms. But typically. you can start telling by the needle color."
Conifer species include pine trees, like those along Highway 55.
"Typically, what we see if we think that road salts are affecting it, is you can kind of see the spray pattern. A lot of times it is around the base of the tree and that lower foliage, so it accumulates and that's where we're going to start noticing the color changes as much," she said.
Cochran added road salt will eventually make its way down into the soil and affect the roots too.
The Idaho Transportation Department (ITD) has used a variety of salts and salt mixtures over the years on Highway 55. ITD used a salt and sand mixture since at least the late 1970's, then a salt and magnesium chloride.
For the past two winters, ITD has been using a new product called IceKicker. They say it is a type of sodium chloride that is less corrosive and more efficient at melting snow. However, even though road salt may be one of the causes of stress on the trees, it is not the only one.
"And that's what I think we've been seeing as it's been since 2020, it's been three years of drought, stress, and just environmental factors that are really affecting those trees," Cochran said.
Sen. Just said he heard about the effect these dying trees were having on our community at an ITD meeting and was surprised at the emotional turn the meeting took.
"During the question and answer session, a couple of people from Horseshoe Bend got up and said 'You really need to cut those trees down.' And they were emotional about it. And I was a little puzzled by that. And then, as they talked I found out that a young man had been killed by a falling tree," Just said.
Sen. Just is referring to 8th grader Coltin Jones who died in June of this year. His family was driving on Highway 55 when a tree fell on the passenger side of their car.
After the meeting the senator said he went home and wrote up a newsletter that he regularly sends to his constituents, including this topic.
"I just assumed the die off was due to bugs or blister rust or something. And one of my constituents, wrote back and said, 'No, it's not it's the road salt' " the senator said. "And so I got poking around a little bit, asked the Idaho Conservation League, I asked ITD as well, 'What's going on there?'"
ITD said they do not have any evidence to show it is the road salt.
"But I wasn't satisfied with that. I don't care what it isn't. I want to know what it is." Just said.
The senator plans to make a budget request in the Joint Finance Appropriations Committee in April. That budget would have to pass during the legislative session, and if it does, it would not take effect until July 2024.
This issue is not exclusive to Southern Idaho. Areas in Northern Idaho are seeing dead trees right now too. In November, a 68-year-old woman died in Coeur D'Alene when a tree fell on her car. Coeur D'Alene Police are calling it a freak accident. They said weather was not a factor, as there was no wind that day.
KTVB is waiting for more information to be released by the city about the condition of the tree and what may have caused it to fall down.
Our changing climate has intensified the stress on trees. All across the Northwest, there is disease, bark beetles, wildfires and drought. Is salt the latest stressor that is pushing it over the edge?
"There's an irony there because they [ITD] put salt on the highways as a safety measure. I'm not suggesting we just stop things. We do need to find out what it is. Maybe there's a different application method? Maybe there's a different formula? I don't know, maybe it's not the salt at all? Let's find out," Just said.
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