Climate change and forest seed zones: Past trends, future prospects and challenges to ponder

Canada regenerates more than 400 000 ha of forest land annually through planting and seeding operations. Much of the stock for this effort is selected to be climatically suited to the planting site-a match that is often facilitated through the development of seed zones. However, if climate change proceeds as predicted, stock that is well matched under current climate will be growing in sub-optimal conditions within the next 20 to 50 years-in some parts of the country, trees may already be growing outside their optimal climates. To provide a sense of the magnitude of these changes, we present past and predicted future climate trends for Ontario and British Columbia seed zones. For Ontario, over the period 1950 to 2005, minimum temperature of the coldest month has already increased by up to 4.3 degrees C, growing season has lengthened by up to 6 days, and precipitation during the growing season has increased by up to 26%. Changes were more pronounced across British Columbia's Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) seed zones, with minimum temperature increasing by up to 8 C, a growing season extension of up to 30 days, and growing season precipitation increases of up to 40%. Projections for the end of the current century include: minimum temperature increase of 5 degrees C to 10 degrees C, growing season extension of 31 to 60 days, and growing season precipitation increases of 3% to 42% across the seed zones in both provinces. These changes are certain to have extensive impacts on forest ecosystems. We briefly discuss 3 forest management adaptation strategies intended to mitigate the negative impacts of climate change in Canada.