'Dead tree after dead tree.' The case of Washington's dying foliage

When Jim and Judy Davis moved to their property in Granite Falls two and a half years ago, the trees in their 25-acre forest were healthy.

Then the hemlocks started to turn brown.

Now, “if we were to walk this path completely -- it’s about a quarter of a mile -- this is what you would see,” Jim Davis said, “just dead tree after dead tree.

“It’s just a feeling of sadness and helplessness."

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So the Davises called in Kevin Zobrist.

“I feel like I'm always coming out to a crime scene, you know: another dead tree, another one lost, coming out to investigate,” Zobrist said.

Zobrist is a forestry professor at Washington State University. He said this isn’t just a problem on the Davis’ property.

“When I drive up and down the highways around western Washington, I just see dead and dying hemlocks all up and down the roads,” Zobrist said. “We first noticed it right around 2016, and now I just see it everywhere.”

And it’s not just hemlocks. Western red cedars and big-leaf maples are struggling as well. All three species are native to western Washington.

Zobrist isn’t the only one seeing this: KUOW’s listeners have been writing in to ask about why they’re seeing so many dead trees.

Zobrist thinks the answer lies in climate change.

“At this point in time, my top suspect is drought — drought stress from climate change,” he said. “We've seen records being set for heat and drought in a number of years in a row now, starting with 2012.”

“This summer was a little bit better,” he said. “But that cumulative drought stress is really taking its toll.”

Thirst can weaken trees’ immune systems, and then something else, like an insect or fungus, can kill them.

It's not just happening in places we can see it, like gardens, parks and roadways. It’s happening deep in the forest as well.

Glenn Kohler, a forest entomologist for Washington’s Department of Natural Resources, and his colleagues fly over every forested acre of the state every year and measure how many trees have died.

“So the individual trees or a patch of dead trees are going to have the same kind of red color that's easy to see from an airplane,” Kohler said. “That's what we're mapping.”

“The amount of that is increasing right now,” he said.

In 2018, Kohler and his colleagues found that nearly 500,000 acres of Washington’s forests had some level of damage. That’s an area bigger than all of Kitsap County.

In short, western Washington’s forests are changing, Zobrist said. Some trees may be lost in places where they used to be able to survive.

“This is, I think, the first really visible impact of climate change in our area,” Zobrist said. “And it's kind of a warning of things to come.”

Jim and Judy Davis say, now that the initial shock of the dying hemlocks has worn off, they’ve come up with a plan. They’re going to take out some of the dead trees and limbs to reduce fire risk around their house, and they’ve started to plant new trees, choosing drought-tolerant native species.

Zobrist said other homeowners can do the same thing.

Also, he said, take a look around the tree, at what else might be competing for water.

“Grass is the worst,” he said. “I see lots of situations where there's a lawn or tall grass all the way up to the edge of the tree and that grass layer robs all the water, so get the grass out of there. Replace that with a good three to four inches of mulch.”

The Davises hope measures like these will help their forest survive for decades to come, for their kids and seven grandkids.

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