Texas scholar produces major assessment of potential impacts of global warming on ecosystems
Camille Parmesan, a professor at the University of Texas-Austin, has produced a landmark study that indicates a consensus may be forming around the estimated mean global advancement in the timing of spring events and potential consequences for ecosystems. The trend is estimated to be between 2.3 and 2.8 days per decade advancement. Significant differences in the magnitude of the response were evident across species, with amphibians in particular showing the strongest response by far.
Many studies have been published documenting changes in phenology among plant and animal species in response to regional climate temperature and precipitation trends. Although the vast majority of such studies demonstrate that species are responding as expected, the magnitude of the response varies by an order of magnitude across species. Camille Parmesan used two existing globally comprehensive datasets of phenological responses to recent climate warming - papers published by Root et al., and by Parmesan and Yohe, both in 2003, to determine the cause of the more than two-fold difference in estimates of the mean global advance in timing of spring events between the two studies: 2.3 days per decade found by Parmesan and Yohe and 5.1 days per decade found by Root et al. Her results showed that the difference in estimated response is primarily due to differences in the methodologies used by the two studies. Once the methodology differences are accounted for, the studies generated more similar conclusions.
Parmesan also presents an analysis of a new, expanded dataset of 203 species. These new results together the previous studies document a consensus estimate of a mean response of between 2.3 and 2.8 days per decade advancement of spring events across all species included in the study. Amphibians had a significantly stronger shift toward earlier breeding than all other taxonomic groups, advancing more than twice as fast as trees, birds and butterflies, and nearly eight times as strong as that for herbs, grasses and shrubs. The author suggests this may be due to the sensitivity of amphibians to changes in precipitation as well as changes in temperature. Latitude did not explain much of the variability in phenological response.
Source: Parmesan, C. 2007. Influences of species, latitudes and methodologies on estimates of phenological response to global warming. Global Change Biology 13: 1860-1872.