Development of a Climate Change Index of Stress Using Future Projected BEC: Proof of Concept for the Nadina TSA

As the climate changes, some species within existing plant communities will become maladapted to local conditions. Immigration of climatically-suited species is unlikely to keep pace. This study investigated methods of using 1) community similarity between current and projected future plant communities as an indicator of ecosystem stress due to climate change, and 2) geographic distance to climatically-suited species as an indicator of potential recovery. We analysed potential shifts in plant communities under three climate-change scenarios in the Nadina Forest District in Central BC, focusing on the SBSdk, SBSmc2 and ESSFmc biogeoclimatic variants. Patterns arising from analyses of community similarity, changes in species pools and geographic distance corresponded: a Slightly Warmer scenario (<2°C increase in temperature) likely poses low stress to all variants; a Warmer and Wetter scenario (+2.6C) may pose higher stress to the drier SBSdk than to SBSmc2 and ESSFmc variants; a Much Warmer scenario (+3.5C) likely poses high stress to all variants, with low potential for recovery. Geographic distance between variants was correlated with community similarity. At the site scale, analysis suggested that the wettest and driest ecosystems may experience highest stress. Challenges to analysis included a necessity to consider multiple scales, data uncertainty, difficulty in interpreting geographic distance, and limitations of climate projections (e.g. lack of consideration of extreme events). We do not suggest that climate projections can predict future ecosystems, but we suggest that analysis can estimate relative stress to ecosystems. The pilot study points to the most fruitful avenues to explore for analyses expanded to consider the entire province, including communication of potential ecosystem stress by drawing trajectories on ordinations of similarity, estimating stress related to a broader suite of scenarios, investigating the relationship between geographic distance and community similarity and investigating the relationship between similarity and soil moisture regime.