Global Change Projections for Taiwan Island Birds: Linking Current and Future Distributions

Abstract

The earth is warming rapidly. Species around the world must adapt to the increasing heat and to the rapid rate of temperature change. Decision makers and managers must aid species to adapt and to keep up with the changes if they are not able to do so on their own. Special attention needs to be paid to small islands because they are at high risk for the loss of unique and threatened systems and species, and face habitat loss as a consequence of climate-induced rises in sea level. In this study, we examined 17 endemic avian species on the island of Taiwan. Bird observations from 1993 to 2004 were compared to modeled distributions for 2020, 2050, 2080 and 2100. We used 5 general circulation models (CCCMA, CCSR, EHAM4, GFDL, and HADCM3) for the Intergovernmental Panel for Climate Change A2 and B2 scenarios. Results show that the distributions of 15 out of 17 species are predicted to shift up in elevation with warming. As the lower distributional limits contract to higher elevation, the upper edge of their current distributions cannot shift up in elevation because they were already near or at the tops of the mountains. Consequently, their distributions are predicted to shrink over time. The median elevation of each of these species’ distributions is higher than the median elevation of all available habitats on Taiwan. In addition, we find that a few common species are predicted to become rare species under climate change. Two of the 17 species examined are not near the tops of the mountains and are the only species that have median elevations of their distributions lower than the median of all available habitats on Taiwan. These 2 species are predicted to expand the upper-elevation distribution limit but not to contract the lower-elevational limit, which results in a widening of their distributions. Hence, we suggest that the median elevation of a species’ current distribution plays a key rule and can be further used as an index of the response birds most likely will exhibit as the temperature increases.