Warming Climate Pushes Plants
To Bloom Earlier, Study Shows

WASHINGTON -- In a new measure of how climate warming is changing biology, British researchers have found that plants are blooming up to two weeks earlier in the spring and they forecast this trend will continue as temperatures rise.

A father and son team report in the journal Science that the first flowering in the spring of 385 species of British plants has advanced by between four and a half days and 15 days in a decade when compared with the flowering date of the species over the previous four decades.

"These data reveal the strongest biological signal yet of climatic change," the authors write in a study to be published Friday. The researchers are Alastair Fitter of the University of York and his father, R.S.R. Fitter of Cambridge University.

The senior Fitter started 47 years ago recording the first flowering date of the British plants in south-central England. In the new study, the researchers compared the changes in first flowering date with temperature trends in the same area over four decades.

Alastair Fitter said in an e-mail message that the mean temperatures for January, February and March -- critical months for spring flowering plants -- has warmed in the study area by 1.8 degrees since the 1960s.

"Some predictions of climate warming are 4 to 5 degrees C (7.2 to 9 degrees F), which would mean that these effects are only the beginning of a major shift," he said.

For 16% of the species studied, the first flowering date in the 1990s shifted by an average of 15 days. The greatest change was for a plant called the white dead nettle. From 1954 to 1990, its average first flowering date was March 18. From 1991 to 2000, the plant's first flowering data was around Jan. 23, a shift of 55 days. Sun spurge, a wild flower found both in the U.S. and the United Kingdom, shifted its first flowering date by about 32 days, the researchers found.

Alastair Fitter said the study supports the notion that flowering plants will be the first indicator of a warming climate.

"Plants will respond [first] by flowering earlier," Mr. Fitter said. "The next [thing] they will do will be to migrate, and I guess we will see that very soon."

He said some German studies already have shown that alpine plants are moving higher into the mountains in response to climate change.

Some other studies also have shown that the warming climate has affected insects. Alastair Fitter said he and his father found that plants pollinated by insects shifted their first flowering date more radically than those that are wind-pollinated. He said this suggests that these plants have an evolutionary history of tracking the climate-caused changes in the behavior of insects.

Stephen H. Schneider, a Stanford University climatologist and environmental biologist, said the Fitter research "is completely consistent with other studies that show climate change is not a theoretical construct, but is actually happening."

"This is precisely what you would expect in a climatic warming trend," Mr. Schneider said. "Warming is going on, and nature does respond."

However, Mr. Schneider said it is less certain how much of the warming is caused by a natural, global climactic cycle and how much is caused by humans. Many scientists believe that the planet is being warmed by an increase in the atmosphere of carbon dioxide and other so-called greenhouse gases coming from industry or from the burning of fossil fuels.

Copyright (c) 2002 Associated Press

Updated May 30, 2002 9:42 p.m. EDT