How will subalpine conifer distributions be affected by climate change? Impact assessment for spatial conservation planning

The objective of this study was to assess the impact of climate change on keystone subalpine conifers, Tsuga diversifolia and Abies veitchii, incorporating the uncertainties of general circulation models (GCMs) for spatial conservation planning in Japan. Potential habitats for T. diversifolia and A. veitchii under current and 20 GCMs in 2080-2100 were predicted using generalized additive models. We counted the number of GCMs under which current potential habitat was predicted to lose by a spatial unit and used them as indices of vulnerability and prediction uncertainty. Gaps between protected areas and potential habitats under the future climates were identified. Reasonably accurate models revealed that T. diversifolia and A. veitchii require cool and wet summers with low winter precipitation. Only less than 1 % of current potential habitats for the species were predicted to be sustainable with low GCMs-related uncertainties. Most of these certainly sustainable habitats were designated as protected areas. Of current potential habitats for T. diversifolia and A. veitchii, 88 and 97 % were predicted to be non-habitats under future climates with low GCMs-related uncertainties. These certainly vulnerable habitats included the southern and low elevated northern range limits of the species, of which 70 % were designated as protected areas. These results suggest that subalpine conifers are vulnerable to the climate change irrespective of GCMs variation. Strengthening of monitoring may be necessary, especially at unprotected and certainly vulnerable habitats in lower subalpine areas where influences of the climate change will appear first. Active management including assisted regeneration may be necessary for preserving the vulnerable and genetically endemic populations.