Climate change is altering both the suitable habitat and phenology of plant species around the world, with cascading effects on people and animals who rely on those plant species as food sources. Here, we ask how the ranges and phenology of food-producing shrubs of the Pacific Northwest, USA, are changing as the climate changes. To address this question, we utilized a wide variety of citizen scientist observations, US Forest Service monitoring plot data, and gridded climate data to identify climate variables that best predicted the current bioclimatic niches and the timing of flowering and fruit ripening of four culturally-important food-producing shrubs: black huckleberry, salal, Oregon grape, and hazelnut. We then used multi-model future climate projections for 2 time periods (2040-2069 and 2070-2099) and 2 emissions scenarios: RCP 4.5 (which assumes emissions will be reduced), and RCP 8.5 (which assumes emissions will continue on the current pathway), to predict how species ranges and the timing of flowering and fruiting of the four species would change in the future.
Results/Conclusions
The modeled bioclimatic niches for the current time period were good matches for our observations with the model predicting a high probability of occurrence where the species were observed. Suitable habitat for the highest elevation species, black huckleberry, was predicted to substantially shrink across the Northwest USA in the future, and losses in predicted probability of occurrence were most common on the lower elevation and drier portions of the current range of the species. We found that flowering dates of all species were best predicted by mean or maximum spring temperatures, whereas timing of fruit ripening was best predicted by mean summer temperature and accumulated growing degree days. Preliminary phenology models for these species indicate that the ripening of fruits and nuts will advance an average of 25 days by 2055 based on RCP 8.5 climate projections. Additionally, we found that flowering dates for at least one species have already advanced considerably over the recent past. An exceptionally long record of flowering observations (1963- 2016) of Oregon grape in Salem, Oregon shows that flowering has advanced by 5 days per decade, with flowering occurring an average of 50 days earlier now than it did in the 1960s. These large shifts in phenology have the potential to greatly alter trophic relationships and the timing and location of traditional harvests in the future.