Assisted migration to address climate change in British Columbia: Recommendations for interim seed transfer standards

Climate change is expected to result in trees in most regions of British Columbia becoming increasingly maladapted to the climates in which they are planted. Consequently, planting seedlings adapted to future climates (assisted migration) is recognized as a key strategy to address climate change, as it will help maintain healthy, productive forests, and ensure capture of gains obtained from decades of seletive breeding. To examine opportunities to incorporate assisted migration into British Columbia's seed transfer system, the feasibility of increasing the upper elevational transfer limit of British Columbia's Class A and Class B seed was assessed by calculating the climatic transfer distance associated with elevational transfers. A rationale was developed for quantifying an appropriate climatic distance and range to migrate seed, and was used to evaluate elevational transfer increases of 100 and 200 m. Results indicate that of the 30 Class A Seed Planning Units (SPUs) examined, eight should retain their current upper elevation limits, one should have their upper elevation limit increased by 100 m, and the remainder should have their upper elevation limits increased by 200 m for eight species, by 100 m for two species, and should remain unchanged for three species. Specific recommendations are provided in Tables 2 and 3. Deployment of orchard seed in the lowest 200 m of the western white pine - Maritime and interior spruce - East Kootenay SPUs is discouraged, as is transfer of Class B seed of amabilis fir and western hemlock more than 200 m downward and western redcedar more than 300 m downward.