Annual DNR Forest Health Report Highlights Impact of Record Heat on Trees in Western Washington
March 31, 2022
Damage caused by extreme temperatures, increased detection of sooty bark disease of maple among key findings of DNR, USFS scientists
The Department of Natural Resources Forest Resilience Division released its annual Forest Health Highlights report this week following a 2021 calendar year that included some of the hottest temperatures ever recorded in Washington, the worst drought event since 2015, and one of the most active fire seasons recorded in the Evergreen State.
Forest scientists from the Department of Natural Resources (DNR) and the U.S. Forest Service (USFS) returned to the skies last year to survey about 19 million forested acres across Washington for their annual insect and disease aerial detection survey (ADS). The COVID-19 pandemic grounded survey flights in 2020 for the first time since 1947.
The 2021 ADS recorded some level of tree mortality, tree defoliation, or foliar disease on about 555,000 forested acres across Washington – a decrease of about 100,000 from 2019. However, the 2021 survey omitted nearly 3 million acres due to fire activity and limited aircraft availability.
“This comprehensive accounting makes clear the impacts our worsening climate crisis have on our forests and the urgency of our efforts to combat our forest health crisis in Washington,” said Commissioner of Public Lands Hilary Franz. “Forests weakened due to drought, insects, or disease outbreaks are less resilient and pose a greater risk for catastrophic wildfires, which is why I fought so hard to pass House Bill 1168 last year to improve forest health and accelerate forest restoration across Washington.”
Scientists determined the record-breaking heatwave that occurred in late June of last year to be responsible for at least 84,000 acres of desiccation damage to conifer crowns, primarily in western Washington. This was likely an undercount, and the severity of the damage will become more known this year. The highest concentrations of observed damage were in the Cascade foothills of Snohomish, King and Lewis counties, the west side of the Olympic Peninsula, and western Pacific County.
Confirmed samples of sooty bark disease of maple were recorded outside of the greater Seattle area last year for the first time. The dieback-causing fungal infection was found as far north as Bellingham, as far south as Olympia, and as far east as Rattlesnake Lake in King County. A full survey of western Washington is planned for this year, as studies in Europe have shown the fungus to thrive after hot, dry summers.
Data trends for beetle-caused tree mortality were mixed in 2021. Mortality due to Douglas-fir beetles decreased to 51,700 acres from a 10-year high of 69,100 in 2019, and mortality attributed to pine bark beetles fell to 92,500 acres – the lowest amount recorded since 2015. Tree mortality due to western pine beetle reached a 15-year high of 37,800 acres.
Read the complete 2021 Forest Health Highlights report here.