Washington Rising temperatures are causing plants to burst into bloom weeks earlier in the spring, according to British researchers who say the finding is strong evidence that global warming is changing biology.
A father-and-son research team warns that the changing thermal climate may drive some common flowering plants to extinction while permitting plants that now live only in gardens to leap from cultivation and become pesky weeds in the wild.
In a study appearing in the journal Science, the researchers report that the first flowering in the spring of 385 species of British plants has advanced from 4 1/2 days to 55 days in a decade, when comparing the flowering date of the species over the previous four decades.
"These data reveal the strongest biological signal yet of climatic change," wrote Alastair H. Fitter of the University of York and his father, R.S.R. Fitter, a naturalist and author from Cambridge, England, in the study to be published today.
Starting 47 years ago, the senior Fitter recorded the first flowering date of 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 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 Fahrenheit since the 1960s.
For 16 percent 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, its first flowering date was around Jan. 23, a shift of 55 days.