Spotlight: Assisted migration as a climate change adaptation tool

Climate change is expected to exert pressure on species to either adapt or move. Climatic ranges for many tree species in Canada are expected to shift northward by roughly 300 kilometres (km) over the next 50 years. Given that tree species have an average migration rate of about 5 km per 50 years, it is unlikely that they will be able to keep up with these projected shifts. Tree species therefore may no longer be suited to their environment, which could reduce forest health and productivity and have related impacts on forest biodiversity.

Conservation concern versus risks

Assisted migration is the human-assisted movement of plants and seeds to new locations where they will be suited to projected future climate conditions. Some species are thought to be particularly vulnerable to climate change, and proponents of assisted migration suggest that this approach may be the only means to save them. But there are well-documented risks associated with the movements of species, including invasive spread of the species and introduction of new pests and diseases throughout the new location, as well as wasted resources associated with failed attempts to move species. These risks have led to debate about whether there is an appropriate role for assisted migration in biodiversity conservation efforts.

Lower risk with commercial tree species

However, a different style of assisted migration has emerged in the context of forest management. Because major tree species generally have large geographic ranges, assisted migration of seeds or seedlings can occur within, or slightly beyond, existing current range limits, significantly reducing the risks. In Canada, while provincial resource management agencies have previously restricted the movement of seeds to ensure that sites are regenerated using locally adapted sources, interest in assisted migration is growing, and several provinces have recently modified policies to allow expanded northward and “upslope” seed movements (i.e., using seeds at higher elevations).

Scientific advances in this area are being made through the use of data from forest genetics trials, which provide insights into how seed sources may respond to rapid climate change. Given that hundreds of thousands of hectares of forest are regenerated annually in Canada, assisted migration of commercial tree species could represent a relatively low-risk and potentially effective approach to introducing a degree of climate change resilience into Canadian forests in the future.

Photo of a man standing next to a young oak tree at an assisted migration trial site
An oak tree at an assisted migration trial near Pickering, Ontario. In this collaboration between Natural Resources Canada and the Ontario Ministry of Natural Resources and Forestry, a variety of hardwood species have been planted from seed sources 200–600 km south of the trial site to test both the species’ and the population’s response to a different climate.