Centuries-old trees are dying at a shocking rate in Oregon

Some of the oldest trees in Oregon are vanishing – and fast. In the Malheur National Forest in Eastern Oregon, old-growth pine, fir, and larch trees are dying off at a shocking rate. Many of these trees are more than 500 years old.

Between 2012 and 2023, one in four trees over the age of 300 died in remote areas of the forest. A mix of drought, insect damage, and overcrowding from younger trees appear to be the main causes.

“It’s sad to see so many old trees dying,” said lead researcher James Johnston, an assistant research professor in the University of Oregon’s Institute for Resilient Organizations, Communities, and Environments.

Old trees dying fast

The new study builds on research that started over a decade ago. Back then, Johnston was working on his doctoral dissertation and collected core samples from old-growth trees in untouched, roadless parts of the Malheur.

These were forests that hadn’t been logged or disturbed, offering a clear look at how the trees live – and die – when left alone.

Ten years later, Johnston returned to the same sites with a research team from the University of Oregon. They relocated 1,617 trees from the original survey. Their ages ranged from just a few decades old to over 600 years.

The results were stark. One-third of trees aged 150–300 years were gone. A full quarter of those older than 300 had died.

“We’re talking about trees that easily live to be 500 years old, and a quarter of them died in just 10 years. That’s really alarming,” Johnston said.

Young trees compete with older ones

The team found a pattern. Trees that had slowed in growth in the last five years were more likely to die. Those in forests that hadn’t seen wildfire in more than 130 years were also at higher risk.

Wildfires, it turns out, play a key role. They thin the forest naturally by removing younger trees. Without fire – or human thinning – newer vegetation grows unchecked, competing with older ones for light, water, and nutrients.

“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.”

Drought and pests play a part

And it’s not just about space. Malheur is a dry forest system. While these trees are used to some drought, recent conditions have gone beyond what they can handle. The region has grown significantly drier over the past decade.

At the same time, pests like the western spruce budworm and Douglas-fir tussock moth have taken a heavy toll. These insects strip forests of their needles, weakening them further.

A bleak forecast without action

Looking ahead, the outlook isn’t promising unless something changes. Using statistical models, the team projected that fewer than one in four of the old-growth trees will still be standing in the next 50 to 60 years.

One major reason is that it takes centuries to grow a replacement. “You can’t replace a 300-year-old tree in 10 years or 20 years,” Johnston said.

Still, there’s hope – if the right steps are taken. Thinning younger trees to reduce competition could help the old ones hold on longer. In forests where thinning is allowed, the researchers believe outcomes could be more positive – but there’s not enough long-term data yet to be sure.

“We need significantly more research about the fate of old trees and dry forests,” Johnston said.

Why old trees matter

Old-growth trees aren’t just impressive for their size or age. They’re essential. They store large amounts of carbon, support biodiversity, and help filter and hold water through their deep roots.

Losing them doesn’t just mean fewer ancient trees – it could mean more fragile ecosystems and a harder time adapting to climate change.

As the forest keeps changing, researchers from the University of Oregon warn that we’ll need to rethink how we protect these old giants. It won’t be enough to just leave them alone. Some may need our help in order to survive.

The full study was published in the journal Forest Ecology and Management.

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates. 

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–