Rising Temperatures Tied to Flowers’ Earlier Bloom

The results of a new study suggest that rising temperatures are leaving a mark on the world. According to a report published in the current issue of the journal Science, the first flowering of plants in Britain has changed by as much as 55 days over the past few decades in response to warmer weather. The results, the scientists say, are the “strongest biological signal yet of climatic change.”

Alastair Fitter of the University of York and his father, naturalist Richard Fitter, analyzed 47 years of data that the senior Fitter collected from a single location in England. They determined that, on average, the first flowering for 385 plant species in the past decade occurred 4.5 days earlier than it did between 1954 and 1990. For 16 percent of the species, the date of the first bloom advanced by 15 days and one particularly affected plant, the white dead nettle, bloomed 55 days earlier than it had three decades ago. Since the 1960s, the mean temperatures for January, February and March–important months for spring flowering plants–have increased by 1.8 degrees Fahrenheit. If global temperatures continue to increase (some predictions for future warming are more than six degrees Fahrenheit), more dramatic changes could lie ahead.

The earlier bloom affects more than just the date when a garden will burst into color, the scientists report. Because some species are changing but others are not, plants may be forced into competition with unfamiliar foes. Moreover, the development of new hybrid species could be curtailed. The violet species Viola odorata and Viola hirta, for example, used to flower simultaneously. But because the former now flowers a month sooner than the latter, they are less likely to hybridize in the future. The authors conclude that the changes they have recorded, together with alterations to species’ geographical range that often accompany climate change, will have “profound ecosystem and evolutionary consequences.”