Temperature measurements indicate that Earth is gradually warming. But are these changes large enough that plants and animals are responding? Recent articles in Nature suggest they are. Parmesan and Yohe (2003) study more than 1,700 species and found 279 species that demonstrated long-term trends. They showed that, on average, species are moving poleward at a rate of 6.1 km per decade (or temperature-equivalent distance up mountain slopes) to find comparably constant temperatures. Spring events occur on average 2.3 days earlier per decade.
In a second article published in the same issue of Nature, Root et al. (2003) studied 143 species, ranging from mollusks to mammals and from grasses to trees. They observed that more than 80% of the species studied showed changes in the direction that are consistent with a warming planet. The combination of temperature rise and other stresses such as habitat destruction could alter composition of ecosystems over much shorter periods of time than occurs naturally.
These two studies seem to provide very strong evidence of impacts of climate change on species. However, Jensen (2003) suggests that biologists tend to study global regions where changes are expected and therefore tend to find what they are looking for. However, to be objective they also should look at regions where no effect or opposite effects might occur.
Reference
Jensen, M. N., 2003: Consensus on ecological impacts remains elusive. Science, 299, 38.
Parmesan, C., and G. Yohe, 2003: A globally coherent fingerprint of climate change impacts across natural systems. Nature, 421, 37-42.
Root, T. L., J. T. Price, K. R. Hall, S. H. Schneider, C. Rosenzweig, and J. A. Pounds, 2003: Fingerprints of global warming on wild plants and animals. Nature, 421, 57-60.