SALEM, Ore. – If you look up this month and see a slow-flying plane crisscrossing the skies over Oregon it’s likely just researchers looking for signs of damage in Oregon forests from insect pests and other threats. The Pacific Northwest Aerial Detection Survey of Oregon’s forests has been conducted by the Oregon Department of Forestry and the USDA Forest Service since the 1940s, except during the 2020 pandemic. It is the longest continuous annual survey of its kind in the United States.
To complete the survey, airborne researchers take off in fixed-wing aircraft with one on each side of the plane. They use laptops to record where trees appear to be in trouble. Survey flights typically fly between 1,500 to 2,500 feet above ground level, following a systematic grid four miles apart and traveling at 90 to 140 miles an hour.
“Oregon has about 30 million acres of forest so flying in a grid pattern over it allows us to find problems even in remote areas hard to reach by vehicle or on foot,” said ODF Forest Entomologist Christine Buhl.
“For several years this survey has identified a trend in increasing tree deaths as a result of drought stress and subsequent opportunistic beetle attack, which finishes off these stressed trees,” said Buhl. “Trees that are most stressed are those that are less drought-tolerant or have spread into fringe habitat and don’t have time to adapt to the rapidly changing conditions. Beetles might be the immediate cause of a tree’s death but the underlying cause is often drought.”
Other causes of trees being injured or killed can also be viewed from the air, such as damage from storms and wildfires.
Last year’s report showed drought, insect pests, and tree diseases continue to be the biggest threats to the state’s trees. That report is available at https://www.oregon.gov/odf/forestbenefits/documents/forest-health-highlights.pdf.
“Best management practices are to plant the right tree species and seed zone in the right place for projected climate and keep stocking density to a level that can be supported during drought,” said Buhl.
Due to persistent dry conditions, she said she expects the 2025 survey to see more of the same trends in higher tree deaths in Oregon’s driest areas, such as in southwest Oregon and east of the Cascades.
Buhl emphasized the importance of on-the-ground collaborators to help round out the full picture of forest health in Oregon. “In addition to information ODF and the USDA Forest Service gather, we rely on Oregon State University Forestry Extension staff from across the state, and collaborate with other natural resource agencies, universities, public and private forest landowners, and members of the public to gather information on the ground,” she said.
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