ANCIENT MARINE LOCATION-SHIFTS IN RESPONSE TO CLIMATE-CHANGE: A LONG-TERM PERSPECTIVE

Modern climate warming is associated with dramatic range shifts both on land and in the oceans. Although there are exceptions, there is a general tendency of species to move poleward with or without retractions at the southern edge of their range. Thus climate warming is expected to increase the average latitudinal positions of species, whereas cooling should have the opposite effect.

We used occurrences of marine invertebrate fossils recorded in the Paleobiology Database to trace latitudinal location shifts through late Paleozoic-Cenozoic times. The stage-to-stage variation in mean paleolatitudinal positions was calculated for genera occurring in two successive stages. The mean latitudinal location shift of all occurrences was subtracted from this mean to adjust for plate-tectonic movements and changing sampling foci.

The resulting pattern suggests substantial location shifts ranging between up to 5.5° poleward and 4.5° equatorward. The greatest volatility is observed in the late Paleozoic and early Mesozoic, whereas location shifts were less than 1.5° throughout the Cenozoic. Substantial poleward shifts are evident in the aftermath of two big mass extinctions – the Permian-Triassic and the Triassic-Jurassic – both or which have been linked to massive climate warming. Not all fossil location shifts can be attributed to climate change alone, but there is generally a good agreement between location shifts and independent proxy data of climate change.