A new study published in the Proceedings of the National Academy of Sciences on Monday reveals that Western forests are not adapting fast enough to match the current rate of climate change.
The study was co-authored by Kyle Rosenblad, a campus doctoral candidate in integrative biology, and integrative biology professor and dean of Rausser College of Natural Resources David Ackerly, alongside Kathryn Baer, a research ecologist at the U.S. Forest Service’s Pacific Northwest Research Station.
“We know that climate change is happening really rapidly,” Rosenblad said. “That led us to wonder, to what extent are the forests adapting to that change and adapting quickly enough? In order to answer that, we had to think hard initially about what it means to “adapt” quickly enough.”
To explain this phenomenon, Rosenblad noted different tree species prefer different climates, adding that these preferences can be mapped to where each tree species has historically lived.
According to Rosenblad, if forests keep up with climate change, it is expected that there would be a growth in the number of tree species that prefer warmer climates. This process only works when new species’ seeds are brought in by wind, animals or water.
“If we’re hoping that our forests are keeping pace with climate change, then we don’t just hope to see that these new tree species with higher temperatures preferences are coming in,” Rosenblad said. “More specifically, we would want to see that the rate of this process matches the rate at which the climate is changing.”
To assess the success of Western forests’ adaptation to climate change, the study analyzed data from the U.S. Forest Service’s Forest Inventory and Analysis National Program, which keeps track of different plots of forest. In each plot, the Forest Service records the size of each tree and their species over time, among other characteristics.
The study pulled data from about 50,000 plots from the year 2000 and onward, specifically looking at how forests changed over 10 years.
“There’s so many plots out there that even a relatively small time slice like 10 years — with relatively subtle changes going — will show a pattern, and that’s what our analyses were able to detect,” Rosenblad said.
The study compared their forestry data to data which quantified how much the climate had been changing at different locations. To do so, they used different public climate datasets to measure temperature and precipitation changes.
Through analyzing these datasets, the study found that for every 10 degrees of warming, there was just a 1 degree increase in the average temperature preferred by trees.
“And what’s even more concerning on top of that is the 1 degree increase that we’re seeing in temperature preference is not actually coming from an influx of new species that prefer warmer temperature,” Rosenblad said. “It’s coming from die offs of the trees that have the lowest temperature preferences.”
Climate change policy can be split into two main categories: mitigation and adaptation. In terms of aiding the survival of Western forests, Rosenblad stated, it is a matter of incorporating both.
Mitigation wise, Rosenblad added that it is necessary to create “a culture and an economy” that does not run on fossil fuels. This means divesting from fossil fuels and removing its influence from the U.S. political system.
In regards to adaptation strategies, this could mean scientists help trees that prefer warmer temperatures migrate.
“We’re going to have to recognize that some areas that are currently forested are just not going to be able to stay forested in the future because the climate is changing too drastically,” Rosenblad said. “We’re going to have to think hard about how to adapt to that as well because there’s a lot of local cultures, local economics that depend on very specific aspects of these ecosystems.”