Big-Tree Loss in Portland’s Wind and Ice Storms: What’s in Our Control and What’s Not in an Era of Climate Unpredictability?
Local arborists share their takes on tree failure during this year’s severe storm, helping to put it into broader perspective and advising what can be done to reduce risk to trees in future events.
By Kyna Rubin
“It was like a war zone over there,” says Chad Honl of Honl Tree Care, referring to Southwest Portland, where this year’s January’s windstorm hit hardest. “There were trees I was working on where every third house had a tree on it.” He saw failures from a bit north of Skyline Drive all the way down to Lake Oswego.
Storm-related tree emergency calls Urban Forestry received in January 2024. Note the concentration of calls from the city’s southwest. Map: Portland Parks & Recreation/Urban Forestry.
Oregon Tree Care owner Damien Carré observed “the most uprooted failures I’ve seen at once in 25 years.” Like many local arborists, Will Koomjn, owner/operator of Emergent Tree Works, didn’t take a day off for three weeks. He found the West Hills, Raleigh Hills, Cedar Hills, and West Portland Park “really bad.”
This winter’s intense storm arose from a triple slam for trees—saturated soils from previous rain followed by high winds and, a few days later, ice. In hilly areas, ice and downed powerlines delayed some arborists’ accessibility.
Though airport gauges showed gusts between 40 and 50 mph, some West Hills residents recorded hurricane-force winds on their own private devices, in one case, 80 mph. Wind at ground-level faces friction, which slows it down, but it speeds up when aloft, explains Rick Till, a local ISA Board Certified Master Arborist. The eastern winds that smacked higher elevations like the West Hills (and the eastside’s Mount Tabor) seem to have sped up there, moving through the landscape with patterns affected by local topography. But wind behavior can be erratic. Qualified tree risk assessor Brian French, principal, Arboriculture International, found that in the Southwest areas where he worked to clear trees, the winds from the gorge entered from the north and northeast.
From January 12 until about the end of that month, Portland Parks & Recreation’s Urban Forestry, which throughout the year averages about five emergency calls a week, received calls from 770 residents, says City Forester Jenn Cairo. Some callers reported more than one downed tree. Urban Forestry prioritized public and right-of-way trees, as well as removing the sections of private-property trees that blocked roads and sidewalks. The City waived until March 8 the application fee for retroactive tree removal permits, which are designed to apply to emergencies, says Cairo.
As of at least early March, arborists were still finding compromised trees. Residents who had been away during the storm, or whose ivy-covered tree bases hid uplifting root plates, or who were unable to even walk into iced-over backyards didn’t summon arborists to assess tree damage until weeks after the storm. Importantly, the wind and ice caused long-term consequences for some trees that tree owners won’t be able to see until the trees leaf out, notes one arborist.
But fear-based, precipitous reaction to this weather event by residents taking out even big healthy trees will create negative, long-term consequences for their health and that of the city.
What Species Were Most Affected?
Large, sometimes healthy conifers such as Douglas-firs, Western redcedars, grand firs, shore pines, giant sequoias, and some spruces took the brunt of the January windstorm, say arborists. Deodar cedars more commonly suffer limb or trunk failures, observes Chad Honl, but in this storm he witnessed five deodar cedars totally uprooted. Some elms, too, were affected (see photo below).
An uprooted elm on NE 22nd Avenue north of Knott Street whose post-cut stump had been placed upright. The tree fell across the street, grazing a neighbor's porch facade. Its tight planting strip for a tree of its size could have contributed to its vulnerability. Photo: All photos by Trees for Life Oregon unless otherwise noted.
Due to physics and the architecture of trees, severe winds tend to damage tall evergreens, whose foliage acts like wind sail. (Watch a video on arboriculture biomechanics and tree failure here.) January’s wind forces upended the entire root plates of 150-foot trees. In contrast, harsh ice storms such as the one we had in 2021 are more likely to strike broad-structured deciduous trees such as Oregon white oaks whose horizontal branches can fail from unbearable ice load. Rather than causing full tree failure, ice more often generates branch breakage, sometimes taking off the tops of trees.
The January storm brought wind, then ice. “As the storm changed, we saw other types of trees being affected,” observes Brian French. The ice that came in the wake of the wind damaged normally robust large oaks, some maples, and other winter-bare species, but not to the extent of the ice event four years ago.
From the horrific photos we saw of upended Douglas-firs on top of Portland-area homes and cars it is easy to fear that our state tree has become a threat to homes, lives, and property. Since January, several letters to the editor in The Oregonian have suggested that Douglas-firs should be removed from our city, that “smaller deciduous trees fit the bill” to cool our impermeable surfaces, or that “choosing the trees which are dying in our changing climate over the taxpayers and their children who can and will die from treefall during storms is bad science.”
“The great majority of Portland’s more than 4 million trees did not fail in this storm. ”
Like the great majority of its species citywide, these east-facing private-property Douglas-firs, in Alameda, remained intact during the January storm.
Plenty of Douglas-firs did topple, and tragically, two people in Portland died from fallen trees.
Douglas-firs have been growing here for centuries. As one of the tallest of our native trees, it is exposed to higher winds and greater lever forces on its root plate. Concluding that these trees had a higher failure rate than other trees in this storm is anecdotal and “still speculation,” says arborist Rick Till, who saw pines snap in half and mature oaks uproot. “To know the statistical relevance of that observation, we’d need to compare the number of failed trees to the overall population.”
Douglas-fir is the most abundant conifer and one of the longest-lived in our landscape. It is one of our most precious and robust native climate soldiers. Hoyt Arboretum holds more than 6,000 trees. Of the 12 large trees it lost from the storm, only one was a Douglas-fir. The arboretum’s other 649 Douglas-firs remain standing. Among its other downed trees were grand firs and hemlocks, said Hoyt Arboretum Curator Martin Nicholson at a late February talk for volunteers.
Trees Adapt to Their Growing Environment
The experts with whom I spoke about the most recent tree loss repeated a crucial big-picture message: The great majority of Portland’s more than 4 million trees did not fail in this storm. A tree might have fallen in one yard, but how is it that other trees in the same yard or the neighbors’ yard did not?
South-facing Douglas-firs in a front yard on NE Dunkley Street that held firm in the latest windstorm.
One factor is that trees are wired to maintain strength by adapting. Portland Arboriculture’s Casey Clapp, a qualified tree risk assessor, explains how this works on his website. Trees “build self-optimized structures, piece by piece, year by year, responding to the forces of wind and gravity.” Their bending and swaying in the wind dampen their loads across all tree parts, helping them to strengthen their wood where stress is highest. Tree roots, even in a forest, don’t go very deep for strength, they grow laterally. Roots grow strong by “dispersing the loads from the stem [trunk] above far and wide through a vast network with a massive surface area” below ground.
All trees, Clapp writes, whether Douglas-firs, oaks, maples, or pines, grow and adapt to their conditions, whether an open yard or a closed forest. The great majority of the city’s large trees, including Douglas-firs, remain standing after the storm, both in small and big yards and in parks and natural areas.
However, some trees cannot adapt fast enough when abrupt surrounding conditions such as wind- and ice-producing storms occur. And all trees have “failure loading thresholds,” says Tom Ford of Shasta View Tree Care. Several arborists mentioned that trees can adapt to regular wind patterns, but that the January winds came from the east rather than the more typical southwestern direction.
The Complexity of Tree Risk Factors
“A host of previously existing natural and human-caused tree weaknesses, often invisible to the lay eye, can make a tree susceptible to weather extremes.”
The wind and ice storms of January 2024 arrived on top of highly water-saturated soils. The single, roughly 140-year-old Douglas-fir that Hoyt Arboretum on Fairview Boulevard lost had survived many storms and, like all Douglas-firs, was very hardy in cold weather. But prior to the wind and ice events, high rain levels had created loose, mushy soil. The root plate rotated and the wind flipped the bottom piece into the air, according to the arboretum’s curator, Martin Nicholson.
Combined, these weather catalysts were the main cause of tree loss from what one longtime Oregon-based ISA-certified arborist calls “an unusual and statistically very unlikely event.”
An Urban Forestry arborist loading massive, cut chunks from an elm tree. Photo: Portland Parks & Recreation
But a host of previously existing natural and human-caused tree weaknesses, often invisible to the lay eye, can make a tree susceptible to weather extremes. Disease and pests come readily to mind, but other less obvious issues matter too.
Longer, dryer, and hotter summers have shrunk root masses, undermining stability, says arborist Damien Carré. “A lot of structural roots have died in the last 15 to 20 years,” he says. “Not the whole thing, but instead of branching out every year they’re not sustaining and may be declining some.” Massive oak trees he saw fail in January should have had more roots sticking out of the ground when they uprooted, but they did not. Along the same lines, Rick Till speculates that the 2021 heat dome may have reduced some trees’ ability to respond to stress by adding wood strength where it’s needed.
Another hidden factor is soil depth. Chad Honl says that Portland’s westside soils are thinner than eastside Willamette Valley soils. Thinner soils and higher wind owing to elevation contributed to westside tree vulnerability.
Contiguous tree groves, which facilitate interconnected root systems, fared best in the January storm, noted Damon Schrosk, a qualified tree risk assessor and the urban forest director at A Plus Tree. As he says, “it’s hard to prove a negative.” But edge effect can weaken trees. This refers to when a tree in a grove fails or was removed for construction. Its sudden absence can undermine the remaining trees’ stability by exposing them to changes in wind-loading patterns.
Still another threat to a tree’s health is insufficient soil volume (think small tree wells or planting strips) and soil condition changes from human-introduced compaction or installation of grass sod and irrigation. Poor drainage is another culprit.
“Think about caring for our trees the same way we attend to our own bodies.”
As well, and of great importance, poor structural pruning and lack of regular tree maintenance can contribute to poor storm outcomes.
All that said, pinpointing exactly what causes trees to fail in storms can be tricky, cautions Will Koomjn. “A lot of trees failed just because the forces they experienced were greater than their strength.”
Advice for Reducing the Risk of Tree Failure in Storms
We can’t control factors such as climate events, whose unpredictability is likely here to stay. But we can take action to lower the risk of losing our beloved large trees in the next storm. Think about caring for our trees the same way we attend to our own bodies, because, after all, trees contribute to our health.
Get to really know your trees. Trees are not an amenity. We require them for human and environmental health. The only way to completely remove all risk of a tree failing and harming people or property is never to mix people and trees, an unrealistic and undesirable scenario. One arborist has observed that homeowners can take trees for granted, assuming trees will, unassisted, always provide shade, cooling, clean air, and a noise buffer. But generally speaking, some kind of failure will happen if a tree gets no maintenance. In an urban context, in particular, we need to foster a reciprocal relationship with our trees by regularly watching and maintaining them over time to manage potential weak points. Trees grow in relation to their micro-environment, for instance, soil volume and quality or the presence of trees near them now or in the past. To get to know a tree we should not only learn what species it is but its history. When was it planted and what plants and other trees might have once grown next to it? Has a neighbor removed a nearby tree or done construction work that would have affected its growing conditions? Chad Honl suggests carefully observing our trees over time. Is the tree still straight? Does the trunk contain cracks? Has there been movement around the trunk base? Any upheaval in the soil? Broken limbs? Brian French points to included, or ingrown bark as a textbook sign of tree weakness. If he had his way, every elementary school student learning about tree biology would be taught how to identify it. Tree owners unsure if their trees are showing signs of stress should hire an arborist.
Get your trees evaluated on a regular basis and have them pruned as needed. “It’s all about gravity, tension, and compression. More than half of failed trees could have survived [this past storm] had they been properly pruned,” says Damien Carré. The taller and heavier a tree is, the more force is being applied to the base. Take some end weight off the end branches of the upper third of a Douglas-fir’s canopy, which will greatly reduce wind sail and reduce tension on the root plate, he advises. Arborists warn, however, that topping a tree can destabilize it.
Make sure the builder of your new home, addition, or ADU uses techniques to protect nearby tree roots. Terry Flanagan, principal and consulting arborist at Teragan & Associates, says that most of the large Douglas-firs that fell on the westside were likely native to or germinated naturally on a site before homes were built. Unless a builder is familiar with and willing to use construction methods to avoid tree roots during excavation, trees can be indiscernibly compromised and may die 5 to 10 years later. Or they may not fail until the next storm comes, which can be even later.
When replacing trees, replant only with high-quality nursery stock. Planted and maintained properly, these trees will have a greater chance of remaining strong and reaching their full life potential. Frequent storms cull out weak trees, says Terry Flanagan. He says we tend to plant a lot of weak trees because nursery-grown trees are often not pruned for stability but for aesthetic desirability, that is, to sell. We need to be more judicious when buying a nursery tree, he cautions. He also points to “false tops” on nursery-grown root balls, which, for a lay person who doesn’t know how to fix this problem during planting, can hinder proper planting depth. Planting too deeply can result in roots girdling a tree. Having a trusted arborist select a nursery tree “would be worth its weight in gold,” says Flanagan. Finally, when planting, choose the right placement. For one, to minimize soil saturation, make sure home downspouts aren’t draining into the tree roots. Mulch in the root zone to help incorporate organic material into the soil to create a better rooting environment and stronger trees, advises Damon Schrosk. In yards, avoid planting near driveways and don’t park cars near tree roots.
Water your trees in hot, dry summers. This can’t be said enough: climate is changing and in summer most Portland-area trees need more water than they did in the past. Mulch and water them during drought periods. See here for specifics about suggested methods and frequency.
Forge an ongoing relationship with a qualified arborist. Proper maintenance can help keep trees safer during most storms. As trees change in response to climate, tree owners need to view tree care and risk assessment as a regular investment, not an expense, and one that will bring peace of mind. Arborists have different qualifications and specialties. (See this list of Urban Forestry tree care providers and this list of Friends of Trees’ arborist partners. Both of these lists have been screened for certain qualifications.) It’s best to work with the same arborists over time so they can get familiar with your trees. Tree owners concerned about risk of failure during storms should be looking for an ISA (International Society of Arboriculture) TRAQ (Tree Risk Assessment Qualification) arborist. Many area arborists have this credential. Between now and spring, Will Koomjn suggests that concerned tree owners hire a TRAQ-qualified arborist to assess their trees. Even trees that didn’t fail during the storm have likely suffered some degree of stress that might undermine their strength. Trees are dormant right now, making them unable on their own to address internal damage until spring or later.
Alternatives to Removing Damaged or Felled Big Trees
On the heels of the winter storm, out of fear and caution some tree owners who’ve had their trees well-maintained for years now want them taken out. Damon Carré’s says he and his staff’s moral compass steers them to do their best to talk clients out of unnecessary removals. In fact, scrupulous arborists will very rarely recommend removing a healthy tree as a first resort. And for trees that are damaged or that have genuinely failed, some arborists offer alternatives to full removal.
Terry Flanagan prefers to restructure rather than take out a tree that’s been stressed but is still stable in the ground. And if a city allows it, Damon Carré might reduce a tree by half to leave it as a snag for wildlife habitat, something that Brian French also strongly supports.
More difficult calls are sometimes made to preserve trees like Western redcedars, a big native tree that provides enormous services. This species has been undergoing climate stress. Some of Chad Honl’s clients don’t want to remove big trees like this that uprooted a bit. Outside of Portland, where, he recognizes, topping a tree is frowned upon, he has topped a Western redcedar to keep it “alive as an organism.” Arborists and clients choosing this route will need to carefully monitor a topped tree for signs of becoming hazardous. As we move through climate change, Honl feels we should be looking at ways to preserve rather than remove.
Getting a Perspective
As humans, we accept risk. We cross busy streets, bike, drive, and fly. Rare winds could tear off our roofs. Severe river flooding could destroy our homes. In response, we don’t stop moving or roofing our houses, nor do we typically drain our rivers, because these things benefit us.
During and after January’s storm, the arborists with whom I spoke have been dismayed by residents whose new terror of large-form trees, especially mature conifers, are driving them to remove them, even the healthy ones that withstood the storm. Unfortunately, there are always some arborists motivated by money rather than ethics who will agree to take down healthy trees without a permit and without offering appropriate alternatives.
Portland is already losing canopy. Doing away with the big conifers that make up the most valuable part of our canopy will just increase our longer, dryer, hotter summers. Terry Flanagan, who is seasoned enough to have witnessed the 1995 storm, whose high winds and wet soils wrought more tree failures than this past one did, worries that after a storm like this people will start replacing big trees with even more small ornamental trees than they already do. Small trees simply don’t generate the volume of health and environmental benefits that big trees do.
“Trees are not inherently hazardous. Experts already understand how to assess and lessen trees’ risk of failure. ”
Powerful storms can push some trees beyond their physical limits, which is understandably scary to people, says Casey Clapp. The unsettling reality is that even if inspected pre-storm, says Tom Ford, some of the trees that fell in this event would not have been assessed as obvious hazards. Still, our urban forest “saves far more lives and money than what happens during these extreme weather events,” according to Rick Till. Statistics bear that out. Extreme heat events in areas that lack cooling shade from big trees cost many times more lives than do falling trees.
Climate change is here. We need our big trees to shade and cool us. Trees are not inherently hazardous. Experts already understand how to assess and lessen trees’ risk of failure. While we learn more about how weather extremes affect trees, Casey Clapp reminds us, “We should apply what we already know, and remember that our trees are some of our greatest assets and they are worth keeping around.”