Widespread plant movement in response to 20th century warming disproportionately affects endemic species

Background/Question/Methods

The differential responses of plant species to global warming are of great interest and grave concern for scientists and conservationists. We used >650,000 herbaria records to estimate geographic and climatic shifts over >100 years in 4300 plant taxa from a wide range of bioclimatic zones, functional types, and phylogeographic origins. We applied a formal probability model to account for sampling biases, using markov chain monte carlo to estimate mean and variance along different niche axes, as well as the probability distribution of the shifts in these niches over time.

Results/Conclusions

We show that the overall tendency of the flora is to move upslope, and aridity is the strongest factor influencing the rate of elevational movement, regardless of plant functional type and geofloristic origin. Species with narrow thermal ranges, mostly endemics, are shifting upslope the most as a fraction of their historic elevation ranges, but are nevertheless experiencing warming.  In contrast, cosmopolitan species with wide thermal tolerances have large shifts both upslope and downslope, suggesting movement due to range expansion unrelated to recent climate change. These findings help explain differential observations in plant range shifts, highlighting those most vulnerable to warming.