Foresters need to take a proactive approach to keeping their forests climate-ready, says the author of two studies on assisted migration in the forests of the Canadian province of Alberta.
Assisted migration, the conscious movement of one species of life -- plant or animal -- to another region, has been used for several years as a survival technique against climate change. In forests, this means planting heartier trees in regions vulnerable to high heat, drought and pests. Assisted migration bridges the gap of "evolutionary lag," the wait time between environmental changes like global warming and the evolutionary processes to adapt naturally to shifts.
"Assisted migration is mainly put forth to increase the productivity of trees, helping them mitigate [losses]," said Laura Gray, a Ph.D. candidate at the University of Alberta.
Gray is the author of two recent papers on the issue. One article, published in PLoS ONE, mapped out 18 different climate scenarios in the 2020s, 2050s and 2080s, for six different conifers. The second study, published in the journal Ecological Applications, makes specific recommendations for aspen -- a commercially important tree with uses ranging from matches to animal bedding. Aspen populations have suffered recently from drought in the region, said Gray.
For white spruce, a resistant variety often used for paper pulp and Christmas trees, the future is more certain. For another conifer, Douglas fir, suitable habitats in the future are much less sure. Researchers offered the most confidence for success for ponderosa pine across a wide variety of climate change scenarios.
Taking risks with species
Models on assisted migration could be used as a guide for foresters who want to maximize productivity on land in the next 40 years -- where certain species in regions may thrive or, as Gray put it, "just not where I'd put an investment."
"From a reforestation angle, we're focusing on an area where [no one is] sure what will occur," she said. "We give practitioners their own choice for what risk they want to take with their species."
In Alberta, there are state-regulated "seed zones," areas designated to capture the genetic diversity of the region. The zones dictate how seeds can be transferred from one area to another. But these lines may become less easily enforceable with climate adaptation needs.
"We're asking for a more flexible framework to be put in place," said Gray. "We're not recommending to redraw the seed zones, but to make the guidelines on transferring [seeds] between them a little more flexible."
The evolutionary lag can have serious implications for species diversity and local economies, said Brad St. Clair, a research geneticist with the U.S. Forest Service's Pacific Northwest Research Station in Corvallis, Ore.
"You have a lot of loss of productivity in these forests while they catch up with climate," he said. "These species will be maladapted for some time before they become more adapted."
Assisted migrations or 'sort it out on their own'?
The idea of "assisted migration" does not sit well with all conservationists, said Laurie Wayburn, president of the Pacific Forest Trust, which advocates for conservation measures on private forestland. While some may suggest planting Tennessee hickory to replace the dwindling New Hampshire maple trees in the face of climate change, others prefer a "sort it out on their own" approach, she said.
"The fact is, we do not know how climate change will impact specific areas with precision," she said. "Leaping to conclusions may not be the best answer in the variability of climate change -- but keeping the pieces is certainly a good idea."