Global warming has begun to affect a wide array of species in the United States, from plants that now flower earlier to red foxes that are venturing farther into Canada, says a report released today by the Pew Center on Global Climate Change. The authors say their analysis is the first to directly link regional biological changes to anthropogenic climate change.
Although anecdotes abound suggesting that plants and animals around the world are responding to global warming, the first rigorous papers that analyze the scientific literature for a worldwide biological "fingerprint" of climate change--versus other factors that could explain species shifts, such as habitat destruction--were published in Nature only last year (ScienceNOW, 2 January 2003). Now, a co-author of one of those studies, ecologist Camille Parmesan of the University of Texas, Austin, and environmental scientist Hector Galbraith of the University of Colorado, Boulder, have done a similar ecological analysis for the United States, where since 1900 temperatures have warmed 2°C and precipitation has risen 5% to 10%. Using different criteria than the global study, they reviewed more than 40 studies that included shorter-term observations and single species and sites.
The report finds "strong evidence of a direct link" between climate change and ecological effects. "We're seeing responses everywhere from Florida to Alaska, from the East Coast to the West Coast, in all kinds of species," Parmesan says. For example, the Edith's checkerspot butterfly has moved northward and disappeared from parts of Mexico and many lower elevations on the West Coast, and red foxes are moving northward in Canada. Citing studies in the past year linking warming in North America to the global rise in greenhouse gases, the authors say there is an "emerging link" between these ecological observations and human-induced warming. As global warming continues, the effects may be most severe for rare and endangered species in the United States, especially because a dearth of wilderness will hinder species from moving northward.
Economist Gary Yohe of Wesleyan University in Middletown, Connecticut, who co-authored the Nature paper with Parmesan, says that linking regional ecological changes and global climate "is the last remaining step" to show that global warming is causing such changes. He hasn't seen the Pew report yet, but he says if Parmesan has established the first regional link, "she's done the world a service."