Climate displacement vectors of the contiguous United States during the 20th century: Implications for identifying climate refugia

Background/Question/Methods

Concerns about climate change impacts on biota stem largely from uncertainty about the rates of recent climate change and species capacity to ameliorate these changes through migration, adaptation, and the use of climatic refugia. In addition to supporting relict climates, climatic refugia should buffer against rapid climatic changes or they will be short lived. Additionally, a reasonable expectation is that species are constrained by multiple interacting climatic factors that will be important for identifying refugia. Here we assess climate displacement rate and direction (“climate velocity”) for minimum temperature (t_min), actual evapotranspiration (AET), and deficit over the contiguous United States during the 20^th century in order to identify regions that exhibit climatic inertia and that minimize divergence between these individual climate vectors. 

Results/Conclusions

Climatic refugia were identified with low displacement rates and minimal divergence between vectors of t_min, AET, and deficit. These areas were principally in the mountainous western region of the country in areas that exhibited complex topography. Climate displacement vectors for these variables demonstrate a complex mosaic of patterns that not only vary spatially and temporally across the last century, but also result in divergent patterns across the variables considered. Quantifying divergence in climate displacement vectors over time may provide mechanistic insights into how non-analog climates are formed.  Moreover, divergent climate displacement vectors between temperature and water balance would likely result in taxonomic variability in phenological responses to climate change, taxon specific differences in range shifts, and potential asynchrony in species interactions. These phenomenon are likely drivers of non-analog biotic communities.