Climatic and biotic velocities for woody taxa distributions over the last 16,000 years in eastern North America

Background/Question/Methods

At present, there is intense interest in whether rates of species distribution shifts will be able to keep pace with the projected rates of climate velocity. However, it is an open question whether rates of response to rising temperatures will be faster for northerly (expanding) or southerly (contracting) populations within a species distribution. We estimated the latitudinal velocity (km/decade) of northern and southern boundaries of core distributions for 30 woody taxa over the last 16,000 years (biotic velocities) using networks of fossil pollen records, and compared these to climate velocities estimated from CCSM3 simulations

Results/Conclusions

Biotic velocities were faster during periods of rapid temperature change (i.e., 16 to 7ka) than times of relative stability (i.e., 7 to 1ka), with a consistent northward movement of northern and southern boundaries. For most taxa, biotic velocities were faster for northern than for southern boundaries between 12 and 7ka, resulting in expanding distributions. For individual time periods, biotic velocities were as fast or faster than climate velocities calculated using multivariate approaches. These results indicate that climate change paced the rate of distribution shifts in both northern and southern populations while suggesting that northern populations were more sensitive. A similar sensitivity and pacing is expected under 21^st-century climate change.