The Icarus challenge: Predicting geographical and taxonomic patterns of vulnerability to climate change in near-coastal species

Background/Question/Methods Like Icarus, the world’s oceans are “flying too close” to the sun. Increases in temperature and sea level and reductions in pH will affect many, if not most, near-coastal species. The type and severity of the effects will vary both by species and regionally due to geographical differences in the extent of climate alterations. To determine the patterns of this environmental threat, we developed a climate risk assessment framework that combines species’ traits, such as preferred depth ranges and regional abundances, with effects thresholds that relate different levels of risk with projected changes in the climate stressors. For sea level rise (SLR) and pH, the effects thresholds were derived from a literature synthesis. For temperature, the effects thresholds were derived both from historical temperature ranges in the warmest occupied ecoregion (WOE) and from a comparison of the WOE to the next warmest unoccupied ecoregion. To evaluate regional patterns, the effects thresholds were overlaid on projected values of temperature, pH, and sea level rise at the scale of the Marine Ecosystems of World (MEOW) ecoregions. To avoid the potential limitations associated with expert solicitations of biases, lack of transparency and repeatability, we developed an “algorithm-based” approach, where vulnerability in an ecoregion is automatically calculated from synthesized information using a set of a priori rules. The web-based tool Coastal Biodiversity Risk Analysis Tool (CBRAT, http://www.cbrat.org/) synthesizes the biotic traits, environmental projections, and rules, allowing assessments using different climate scenarios

Results/Conclusions

We are applying the approach to the brachyuran and lithodid crabs (387 species), rockfish (74 species) and bivalves (884 species) over 12 MEOW ecoregions, from the Gulf of California through the Beaufort Sea. Patterns emerging from preliminary analyses include: 1) impacts of increased sea-surface temperature are primarily limited to the southernmost occupied ecoregion (WOE) of a species; 2) species in the Arctic tend not to be highly vulnerable to temperature increases because most extend southward, indicating a thermal tolerance, 3) sea level rise will have minor impacts on crabs in Alaska compared to those in Puget Sound through Southern California; 4) while adult decapods appear more resilient to ocean acidification than certain other taxa they are potentially at risk in the Arctic.