Will freshwater fishes keep pace with climate change?

Julian D.Olden (1)    

1    School of Aquatic and Fishery Sciences,University of Washington, Seattle, Washington USA, olden@uw.edu, @oldenfish

Climate  change is poised to challenge the future persistence of organisms across the globe, and many uncertainties remain to whether, and if so how, species will cope. Despite mounting   evidence in terrestrial and marine ecosystems that the rapidity of climate  change  may exceed  the dispersal ability of many species, the question of whether freshwater species will be able to keep respond  has not been considered. My presentation provides the first evaluation of whether freshwater fishes will keep pace with projected climate warming in contemporary riverscapes   where dams represent ubiquitous barriers to dispersal and habitat may simply run out  at  watershed  divides. By linking  geographic  patterns  and  variability in  climate change  velocity  to   spatially explicit estimates of maximum dispersal rates and physiological  tolerances,  I quantify the fate of 862 fish species in over 6 million river kilometers across the contiguous United States. I illustrate that freshwater fishes will be required to disperse considerable distances to track geographic shifts in isotherms and that  many species lack the dispersal  ability to keep pace with   stream warming. Large dams will only serve to worsen the situation by blocking  upstream movement. Non-­‐native fish species show, on  average, five times greater dispersal ability compared    to native species. Time lag responses between projected climate velocity and fish dispersal abilities highlight the species and locations where adaptive capacity may allow for resilience to   climate change versus where barrier removal/passage and species translocation via assisted colonization may be necessary to  ensure  the future persistence of freshwater fishes.

Climate change is poised to challenge the future persistence of organisms across the globe,  and many uncertainties remain to whether, and if  so how,  species will cope. Despite mounting   evidence in terrestrial and marine ecosystems that  the rapidity of  climate change may exceed the dispersal ability of  many species, the question of whether freshwater species will be able to   keep respond has not been considered. My presentation provides the first evaluation of whether freshwater fishes will keep pace with projected climate warming in contemporary riverscapes   where dams represent ubiquitous barriers to  dispersal and habitat  may simply run out at  watershed divides By linking geographic patterns and  variability in climate change velocity to spatially explicit estimates of maximum dispersal rates and physiological tolerances, I  quantify the fate of  862 fish  species  in over  6 million river kilometers across the contiguous  United States. I   illustrate that freshwater fishes will be required  to  disperse  considerable distances  to track geographic shifts in isotherms and that many species lack the dispersal ability to keep pace with   stream warming. Large dams will only serve to worsen the situation by blocking upstream movement. Non-­‐native fish species  show, on  average,  five times greater  dispersal ability  compared   to native species. Time lag responses  between projected climate velocity and fish dispersal abilities highlight the species and locations where adaptive capacity may allow for resilience  to   climate change versus where barrier removal/passage and species translocation via assisted colonization may be necessary  to  ensure  the future persistence of freshwater fishes.

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