Spatial synchrony of local populations has increased in association with the recent Northern Hemisphere climate trend

Eric Post*,† and
Mads C. Forchhammer‡

^*Department of Biology, Pennsylvania State University, 208 Mueller Laboratory, University Park, PA 16802; and ^‡Department of Population Biology, Biological Institute, University of Copenhagen, Universitetsparken 15, DK-2100 Copenhagen, Denmark

Edited by David W. Schindler, University of Alberta, Edmondton, AB, Canada (received for review August 7, 2003)

Abstract

According to ecological theory, populations whose dynamics are entrained by environmental correlation face increased extinction risk as environmental conditions become more synchronized spatially. This prediction is highly relevant to the study of ecological consequences of climate change. Recent empirical studies have indicated, for example, that large-scale climate synchronizes trophic interactions and population dynamics over broad spatial scales in freshwater and terrestrial systems. Here, we present an analysis of century-scale, spatially replicated data on local weather and the population dynamics of caribou in Greenland. Our results indicate that spatial autocorrelation in local weather has increased with large-scale climatic warming. This increase in spatial synchrony of environmental conditions has been matched, in turn, by an increase in the spatial synchrony of local caribou populations toward the end of the 20th century. Our results indicate that spatial synchrony in environmental conditions and the populations influenced by them are highly variable through time and can increase with climatic warming. We suggest that if future warming can increase population synchrony, it may also increase extinction risk.

Footnotes

↵ † To whom correspondence should be addressed. E-mail: esp10{at}psu.edu.
This paper was submitted directly (Track II) to the PNAS office.
Abbreviations: GAM, generalized additive model; NAO, North Atlantic Oscillation.