16-07-2025
Eastern Oregon's old-growth trees are dying at ‘alarming' rates, UO finds
PORTLAND, Ore. () — Older trees in an Eastern Oregon forest are perishing 'at an alarming rate,' .
A new study led by James Johnston, an assistant research professor for the University of Oregon, found that about 25% of trees over 300 years old died in the Malheur National Forest from 2012 to 2023.
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Scientists noted the 1.7-million-acre site is known to host some of the state's most ancient trees, some dating back more than 500 years. But drought conditions, pests and competition between trees of different ages have created a 'triple whammy' for the older trees in roadless areas.
'In the moistest and most productive Douglas-fir-dominated forests in Western Oregon, setting forests aside as protected reserves has proven to be a successful strategy for protecting old trees,' Johnston said. 'But this research shows that we need active management to remove younger trees in order to protect old trees in dry forests of Eastern and Southern Oregon.'
Scientific journal will publish Johnston's findings in its October 2025 issue. He, who serves UO's Institute for Resilient Organizations, Communities, and Environments, first launched the study for his doctoral dissertation about a decade ago.
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When researchers revisited the area, they located 1,617 trees that were recorded for the original project. UO reported that about 33% of the trees between 150 and 300 years old had died in the time since, in addition to the 25% of ancient trees that had withered away.
According to the university, trees that hadn't been burned in a wildfire in the past 130 years were more susceptible to death. Scientists said wildfires help thin out forests, therefore removing younger trees and diminishing competition for the ancient trees that need water and other nutrients.
The study also noted it is 'generally' illegal to cut down trees in federally protected lands. Similar to a , researchers listed drought conditions and insects as other causes of the Malheur National Forest's alarming tree deaths.
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'Although Eastern Oregon's forests are considered dry forests, meaning they've adapted to seasonal dry spells, they still need water to survive,' UO wrote. 'And the area is significantly drier than it once was. To top it all off, several species of defoliating insects, such as western spruce budworm and Douglas-fir tussock moth, chowed down on the trees during the study period.'
Researchers estimate that less than 25% of ancient trees will remain through the next 50 to 60 years.
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