Swallows, geraniums and spruce
In their analysis, Root and her co-workers revealed that nearly 1,200 species - roughly 81 percent of the total number analyzed - have undergone biological changes that were "consistent with our understanding of how temperature change influences various traits of a variety of species and populations from around the globe."
Their overall analysis of studies involving temperate-zone species revealed that springtime events - such as blooming, egg laying and the end of hibernation - now occur about 5.1 days earlier per decade on average.
The North American tree swallow offers a good example. Field biologists, who kept track of some 21,000 tree swallow nests in the United States and Canada over the last 40 years, concluded that the average egg-laying date for female swallows has advanced by nine days - a phenomenon that mirrors other North American studies confirming higher temperatures and the earlier arrival of spring.
Similar long-term observations of flowering plants in Wisconsin revealed that wild geraniums, columbine and other species are blooming earlier than before. Studies in Colorado also showed that marmots are ending their hibernations about three weeks sooner than they were in the late 1970s.
Other studies confirmed that a variety of species - including butterflies and marine invertebrates - have shifted their ranges northward as temperatures increased. Measurements taken in Alaska revealed that growth in white spruce trees has been significantly stunted in recent years - another expected consequence of a rapidly warming climate, Root said.
"Climate change models predict that the poles will warm more quickly than the equator, so it's not surprising that we're getting the strongest signals of biolog
'"/>
Contact: Klas Bergman
kbergman@stanford.edu
650-723-8490
Stanford University
1-Jan-2003