Print PageFuture climate change is expected to be a major driver of biodiversity loss, but how do climatic changes projected for coming decades compare with those experienced historically? I explored this question by considering how past climate changes experienced by the world’s global biodiversity hotspots compare with those projected for the 21st century using two different, but complementary, approaches. One approach involved modeling the current distributions of 33 biodiversity hotspots using ensembles of species distribution models (SDMs), which were projected to identify the probable size and geographic location of hotspots in the past and future. This method is likely a better measure of historic impacts as results should be insensitive to migration rates of species. Second, I used a new statistical technique to measure the similarity of the current climatic conditions within hotspots to those characterizing the same region in the past and future. This approach likely is a better assessment of the impacts of future climate change. For both approaches, I considered multiple climate scenarios for multiple times in the future (2020, 2050, and 2080) and the past, including the Last Interglaciation (~120,000 years ago), the Last Glacial Maximum (~ 21,000 years ago), and the Mid-Holocene (~ 6,000 years ago).
Results/Conclusions
In terms of changes in area (from SDMs), across all climate scenarios, hotspots on average were projected to be smallest during the Last Interglaciation (~ 120,000 years ago), the last time that global temperatures were as warm or warmer than today. The majority of hotspots were projected to contract to similarly small extents under future warming, especially by 2080. Although some hotspots were predicted to expand, such expansions will occur only to the extent that migration limitations do not prevent species from colonizing these newly suitable areas. In terms of climate similarity, my results suggest that by 2080 climatic conditions within most hotspots will be more different from present climates than present climates are from those experienced at any time during the last 120,000 years. Interestingly, the magnitude of climate change experienced during the Last Glacial Maximum (~21,000 years ago) was found to be most similar to that projected for many hotspots by 2080, but different in direction (cooling versus future warming). However, SDMs suggested that historic cooling had relatively benign impacts in terms of changes in area as compared to warming, suggesting that future climate change may have particularly severe impacts on the world’s biodiversity hotspots.
