Limited net poleward movement of reef species over a decade of climate extremes

Abstract

Warming seas are expected to drive marine life poleward. However, few systematic observations confirm movement among entire communities at both warm and cool range edges. We analysed two continent-scale reef monitoring datasets to quantify changes in latitudinal range edges of 662 Australian shallow-water reef fishes and invertebrates over a decade punctuated by climate extremes. Temperate and tropical species both showed little net movement overall, with retreat often balancing expansion across the continent. Within regions, however, range edges shifted ~100 km per decade, on average, in the poleward or equatorward directions expected from warming or cooling. Although some species responded rapidly to temperature change, we found little evidence for mass poleward migration over the decade. Previous studies based on extreme species observations, rather than tracking all species through time, may have overestimated the prevalence, magnitude and longevity of range shifts amongst marine taxa. The authors use 12 years of broadscale survey data across 838 temperate and tropical coastal sites to investigate shifts in marine taxa range edges at the community level. They show that while some species respond rapidly to change, evidence for mass poleward migration is limited.