Gradual warming over the past century has forced a global movement of animals and plants northward, and it has sped up such perennial spring activities as flowering and egg hatching across the globe - two signals that Earth and its denizens are responding to a minute shift in temperature, according to two studies published today.
One study shows that animals have shifted north an average of nearly 4 miles each decade. Another shows that animals are migrating, hatching eggs and bearing young an average of five days sooner than they did decades ago, when the average global temperature was 1 degree lower.
That 1 degree, according to the studies, has left "climatic fingerprints" - pushing dozens of butterfly and songbird species into new territories, prompting birds and frogs to lay eggs earlier and causing tree lines to march up mountain slopes.
In some cases, the shifts have been big. The common murre, an arctic seabird, breeds 24 days earlier than it did decades ago. And some checker-spot butterflies shifted their range north by nearly 60 miles.
Although many individual shifts in timing and range have been reported by field biologists, the studies published in today's issue of Nature are the first to establish that a variety of organisms in myriad habitats are responding in similar ways to climatic change.
"There is a consistent signal," said Terry L. Root, a biologist at Stanford University and lead author of one report. "Animals and plants are being strongly affected by the warming of the globe."
Root said she was surprised the two Nature studies were able to detect the effect. She said she thought the increased temperature was too small to cause widespread change. Root also said she expected that any damaging effects of climatic change would be unnoticeable amid the enormous habitat destruction in modern times caused by development, pollution and other human activities.
Many scientists have debated whether plants and wildlife have been widely affected by climatic change. Some scientists have argued that no widespread response has occurred.
The new studies attempt to override such criticism by analyzing thousands of reports of biological change in animals and plants and correlating them with climatic change.
Usha Lee McFarling is a reporter for the Los Angeles Times, a Tribune Publishing newspaper.