As the world heats up, trees are stuck. To migrate or adapt to a new climate takes them generations—and climate change is happening too fast for them to keep up.
One challenge is that we don’t fully understand how trees adapt to climate in the first place. Now, a study conducted by researchers in Canada has revealed that two distantly related conifers use the same set of 47 genes to deal with climate variables like temperature and precipitation—a clue that might make a difference for forestry management in the future.
The researchers set out to understand the genetic basis for how the two most planted trees in western Canada, lodgepole pine and interior spruce, adapt to climate. The two species are prized by the timber industry, which is obligated to reforest public lands they’ve harvested. “In British Columbia alone, we plant 250 million trees every year,” said Sally Aitken, a professor at the University of British Columbia and corresponding author on the paper.
Aitken and her team wanted to “understand how trees have adapted to climate so we can better match the trees that get planted with new climates in a type of assisted migration,” she said, which would involve planting new trees farther north than their population currently grows, but still within the species’ range.
“We know that already the trees are about 150 kilometers on average from the climates that they have historically adapted to,” Aitken said.
Lodgepole pine and interior spruce trees are distant relatives, having diverged 140 million years ago. Since climate adaptability traits come from many genes rather than just one, the researchers expected that the species might have developed genetically different ways of adapting to climate, said Sam Yeaman, an assistant professor of biology at the University of Calgary and one of the authors of the study. However, after sequencing some 23,000 genes in 600 trees, the researchers noticed some significant overlap. They were then able to narrow it down to a group of 47 genes linked to climate adaptation in both species.
This shows that there may not be many genetic paths a species can take to developing climate adaptability traits, Yeaman said. “The fact that out of thousands of genes in the genome they’re using the same few of them to do this adaptation to temperature suggests that there is some kind of constraint,” he said.
This particular project was expensive, Aitken said, and it simply wouldn’t be possible to carry out a similar study for every species. But the apparent evolutionary constraint at play in lodgepole pine and interior spruce trees may help scientists looking to analyze other tree species. The study “might give us a small set [of genes] to go after in other species to get a quick look at those patterns of climate adaptation,” Aitken said. The group has already begun working with other species.
While the set of 47 genes may provide a starting point for other studies, the specific traits are what could guide assisted migration for an individual species.
“[The study] provides evidence of a genetic basis for cold hardiness and for adaptation to the climate,” said Brad St. Clair, a research geneticist with the U.S. Forest Service, who was not involved in the study. “It’s the kind of thing we’ve been trying to look at for a long time.”
While cold hardiness may seem irrelevant in a warming world, Aitken said adaptation to low temperatures is the most important historical climate factor when it comes to reforestation efforts.
“As we think about shifting trees across the landscape, we’ve got to make sure they can handle the cold temperatures that they’re going to experience early in their lives,” she said. “We have to be careful about moving too far too fast.”
Extensive testing and trials are being conducted by the Canadian government in British Columbia and Alberta, Yeaman said. Although assisted migration efforts are being carried out “slowly and tentatively,” he said there is growing support. But the world isn’t waiting, and the trees are becoming less adapted to their climate with each passing year.
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