Tree populations need at least 100 and perhaps 200 years to respond to the changing climate – far too slow to keep pace with current global warming. That is according to a study, “Coupled, decoupled, and abrupt responses of vegetation to climate across timescales“, published in Science earlier this month, tracking pollen in lake sediments and showing how trees responded to climate change over a 600,000-year period.
Led by David Fastovich, a postdoctoral researcher at Syracuse University, who, working with, Tripti Bhattacharya, the Thonis Family Professor of Paleoclimate Dynamics and associate professor in the university’s Department of Earth and Environmental Sciences, analysed how and when tree species migrated south (during Ice Ages) and north again as global temperatures cooled and warmed again over thousands of years.
“We’ve known these time lags have existed, but no one could put a firm number on them,” according to Fastovich. “We can intuit how long a tree lives. We can count the rings on a tree and estimate from there. But now we know that after one to two centuries—very close to how long a tree lives on average—entire forest ecosystems begin to turn over as trees die and are replaced in response to climate.”
Using spectral analysis, commonly used in physics and engineering, researchers established long-term ecological data, allowing them to compare the relationship between tree populations and climate over decades and millennia. One goal was to understand how closely tree population migrations, tree mortality, and forest disturbances from things like wildfires match climate changes over time, developing a unified statistical approach that connects how natural forest adaptation evolves from days to thousands of years. “This gives us a common language for people who observe forest change—ecologists, paleoecologists, and paleobiologists—to talk to one another about those changes, no matter if we study forests on annual or millennial timescales,” Fastovich said, adding that it can take up to eight centuries for forest changes to become larger, tied to natural climate variability.
“With this new technique, we can think about ecological processes on any timescale and how they are connected,” he said. “We can understand how dispersal and population changes interact and cause a forest to change from decades to centuries and even longer timescales. That hasn’t been done before.”
According to Fastovich, the study suggests that forests will need much more human intervention to keep them healthy, who said that “assisted migration” – where foresters plant warmer climate trees in traditionally colder climates – would be crucial in helping woodlands adapt and flourish despite the heating of habitats due to climate change. “Forest adaptation to climate will be a slow, complex process requiring nuanced, long-term management strategies,” Fastovich notes. “There’s a mismatch between the timescales at which forests naturally change and what’s happening today with climate change,” he said. “Population-level changes aren’t going to be fast enough to keep the forests that we care about around. Assisted migration is one tool of many to keep cherished forests around for longer.”
Where’s the Wood? Climate Scientists Fear for the Future of Beech
Last year, Wood Central reported that English Oak trees could become the cornerstone of reforestation projects and timber plantations across Europe, with a study warning that the trees are one of the only species to survive global warming. Published in Nature Ecology & Evolution, A climate-induced tree species bottleneck for forest management in Europe, the study looks at the changes to European forests expected to occur over the next 100 years – adding to a squeeze on timber, expected to grow fourfold over the next 30 years, and compromising the EU’s push to build more with wood.
Led by Johannes Wessely and Stefan Dullinger from the University of Vienna, scientists tested 69 of the most common European tree species to see how they would react to warmer temperatures. It found that depending on the region, one-third to half of all tree species found today will no longer be able to cope with climate change: “This is an enormous decline,” according to lead author Johannes Wessely, “especially when you consider that only some species are of interest for forestry.”
Scientists found that just nine of 69 species are fit to withstand the future climate in Europe, compared to four in the UK. “Trees planted now for reforestation must survive under current and future conditions,” Dr Wessely said, “This is difficult because they have to withstand the cold and frost of the next few years and a much warmer climate at the end of the 21st century. There is only a minimal overlap,” they said.
For more information: David Fastovich et al. ,Coupled, decoupled, and abrupt responses of vegetation to climate across timescales, Science 389, 64-68 (2025). DOI:10.1126/science.adr6700
