New study finds certain tree species in Humboldt struggle to adapt to climate change

ARCATA, Calif. — As fire crews work to extinguish wildfires across Northern California, a recent study has found that certain conifer trees are declining as a result of this fire suppression and climate change.

The study by researchers from Cal Poly Humboldt, the University of Wyoming and the U.S. Forest Service found that human fire suppression in the Klamath Mountains has actually stunted certain tree species' ability to grow.

"When we suppressed fires, it led to a huge increase in one particular tree called White Fir, which does really well when fires are absent, and because it's doing so well, it's filled in all of the gaps in between the large trees," Cal Poly Humboldt Professor Erik Jules said.

Jules is one of the lead researchers in this study, which was initiated in the 1960s by Humboldt State University professors John Sawyer and Dale Thornburg. The study wasn't revisited until recently after Sawyer's wife discovered her husband's findings after his death.

According to the study, the incline of shade-tolerant species like the White Fir has led to a massive decline in drought-resistant, fire-adapted species, like the Sugar Pine.

Without human interference, these fire-adapted species would naturally move upslope so they can stay in the same temperature range. But with fire suppression efforts allowing the White Fir to dominate these areas, the trees that would typically migrate upslope are unable to do so.

"All these other tree species are being thwarted in their attempt to move upward," Jules said.

These species include those that have become historic features of Northern California, like the Ponderosa Pine.

"It's going to lead to a lot of mortality of the big old-growth trees that have been there for several hundred years," Jules said.

This also means that the forests are more sensitive and less adaptable to drought and fires, both of which are likely to increase as the planet continues to warm.

"That's led to a forest that's very maladaptable to future climate change," Jules said.

The most recent findings in this renewed study are even more extreme than the original findings from the 1960s, Jules said. But because fire suppression is oftentimes a necessary practice to protect nearby communities, there isn't a clear solution to the issue.