One approach to buffer vulnerable species against the effects of ongoing climate change is to prioritize the protection of land with geodiverse physical features associated with ecological and evolutionary mechanisms that maintain high biodiversity — a strategy termed "conserving Nature's stage." In this study we compare the relative effects and predictive power of geodiversity — spatial variation in abiotic processes and features — and climatic predictors of alpha-, beta-, and gamma-biodiversity of birds and trees across the United States. We quantified geodiversity across the contiguous United States with spatially continuous remotely-sensed data and generated new biodiversity maps for trees and birds from the Forest Inventory and Analysis and Breeding Bird Survey datasets. We fit separate multivariate regression models for alpha-diversity, beta-diversity, and gamma-diversity of trees and birds, accounting for the correlation between taxonomic, functional, and phylogenetic diversity and spatial autocorrelation among Nature Conservancy ecoregions. We fit and compared models including climate alone (temperature, precipitation, etc.), geodiversity alone (topography, soil, etc.), and climate + geodiversity.
Results/Conclusions
A combination of geodiversity and climate predictors predicted most forms of bird and tree biodiversity within one standard deviation, supporting our prediction that geodiversity and climate together would predict biodiversity better than climate alone. Models using geodiversity and mean climate to predict biodiversity performed better for local (alpha) and regional (gamma) diversity than turnover-based (beta) diversity. Among geodiversity predictors, variability of elevation predicted biodiversity best; interestingly, topographically diverse places tended to have higher tree diversity but lower bird diversity. Although climatic predictors tended to have larger effects than geodiversity, geodiversity improved climate-only models of biodiversity. The effect of geodiversity biodiversity was relatively stronger in the central and eastern United States for tree biodiversity and stronger in the Appalachian and Rocky Mountain ecoregions for bird biodiversity. Despite this spatial variation, geodiversity predicted biodiversity more consistently than climate across U.S. ecoregions. Taken together, our results suggest that climate change will alter biodiversity patterns of trees and birds in the U.S. but in certain contexts, geodiversity may buffer some of the effects of climate change.