The observers rate the intensity of damage and map its location. Pilots fly in a grid pattern with flight lines about 4 miles apart to cover every swath of the forest.
“It’s literally like mowing the lawn,” Kohler said of the flight trajectory.
The damage to fir trees was so significant researchers took to calling the blighted areas “firmageddon” as they flew overhead during aerial surveys that estimated the die-off’s extent.
The surveyors ultimately tallied about 1.1 million acres of Oregon forest with dead firs, the most damage recorded in a single season since surveys began 75 years ago.
Oregon’s dead firs are a visceral example of how drought is reshaping landscapes in Western states that have been experiencing extreme heat conditions. In many areas, these firs might be replaced by more drought-hardy species in the future, reshaping how ecosystems function and changing their character.
“When I looked at it and crunched the numbers, it was almost twice as bad as far as acres impacted than anything we had previously documented,” said Danny DePinte, an aerial survey program manager for the U.S. Forest Service. “Nature is selecting which trees get to be where during the drought.”
Fir die-off as observed during this year’s aerial survey in the Fremont-Winema National Forest in southern Oregon. (Daniel DePinte / USFS)Fir die-off as observed during this year’s aerial survey in the Fremont-Winema National Forest in southern Oregon. (Daniel DePinte / USFS)
Oregon is known for towering volcanic domes covered by a blanket of conifers that becomes sparse and patchwork on the eastern side of the Cascade Mountains before it tucks into the high desert.
The people who know the trees best say there are many signs of problems in Oregon.
“We’re seeing forms of stress in all of our species of trees,” said Christine Buhl, a forest entomologist with the Oregon Department of Forestry. “We just need to shift our expectations of what tree species we can expect to be planted where.”
Researchers have been surveying Pacific Northwest forests by air since 1947. Little about the process has changed during that time, according to Glenn Kohler, an entomologist with the Washington State Department of Natural Resources, which operates the program alongside the U.S. Forest Service and Oregon Department of Forestry.
Each summer, small high-wing planes soar about 1,000 feet above the tree canopy at about 100 mph. Trained observers peer outside both sides of the plane, looking for noticeable damage to trees.
Dead trees — conifers that are completely red or orange — are the easiest to spot, but the observers can also pinpoint trees that are barren of needles in some areas.
Paper maps of the past have been replaced today by Samsung Galaxy tablets that track the plane’s progress and make mapping easier — and probably more accurate.
Observers require a season of training, Kohler said. It can be a dizzying task.