Climate change shifts in habitat suitability and phenology of huckleberry (Vaccinium membranaceum)

Climate change is altering the suitable habitat and phenology of plant species around the world, with cascading effects on people and animals reliant upon those plant species as food sources. Huckleberry (Vaccinium mem-branaceum) is one of these important food-producing plant species that grows in the Pacific Northwest of North America. Here, we modelled how the range and phenology of huckleberry may change as the climate changes. To address this question, we first utilized citizen scientist observations, long-term plot data, and gridded climate data to identify climate variables that best predicted the current bioclimatic niche and the timing of flowering and fruit ripening of huckleberry. We then used multi-model future climate projections for 2 time periods (2041-2070 and 2071-2100) and 2 greenhouse gas emissions scenarios (RCP 4.5 and RCP 8.5) to predict how the range and the timing of flowering and fruiting would change. The modelled bioclimatic niche for the current time period was a good match for our observations, with the model predicting a high probability of occurrence where the species was observed (AUC = 0.88). Suitable habitat for huckleberry was predicted to shrink by 5-40% across the northwestern USA by the end of the 21st century, and this reduction in predicted probability of occurrence was greatest at lower elevations, across drier portions of the current range of the species, and under the higher emissions scenario. Suitable habitat was predicted to expand at higher altitudes (>3,050 m) and in more northern locations in British Columbia by 5-60% by the end of the 21st century. To predict how future phenological dates might shift, we developed thermal sum models for flowering and fruiting under current climate conditions and then used those models to predict how these events would change based on climate predictions. Our phenology models suggested flowering would advance 23-50 days (mean 35 days) and fruiting would advance 24-52 days (mean 36 days) by the end of the 21st century under the RCP 8.5 scenario; greater advances in phenology were shown over more northerly and higher altitude regions. These large shifts in potential range and phenology could greatly alter trophic relationships and the timing and location of traditional harvests in the future.