Expansion of subalpine woody vegetation over 40 years on Vancouver Island, British Columbia, Canada

Climate change is leading to the global loss of open montane meadows by facilitating tree and shrub encroachment at high elevations. North America’s coastal mountains are particularly vulnerable to these changes, as they are relatively low elevation compared to interior mountains and contain only small areas of alpine tundra. We compared aerial photographs from 1962 with photos from 2005 covering three subalpine regions on Vancouver Island, British Columbia, in order to document the extent of changes in woody vegetation and investigate associations between vegetation change and topography. Mean proportional woody vegetation cover increased significantly from 0.75 (± 0.03) to 0.81 (± 0.03) between 1962 and 2005 (p < 0.0001). Relative increase in woody vegetation cover was greater at higher elevations and on northerly aspects. These findings confirm an upward expansion and infilling of trees and shrubs and a reduction of the area encompassed by open alpine tundra on Vancouver Island. Loss of open meadow conditions at high elevations in this region will likely have consequences for alpine plant and animal communities.