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Why Boston's plants bloom earlier now than 100 years ago

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On a 100-acre farm in Middleborough, Mass., Betty Anderson has been taking notes for more than 50 years. "The first thing I do in the morning when I get up - besides getting myself a cup of coffee or tea - is look at the thermometer, and write down the temperature, the weather, and whatever interests me that day."

In countless "Daily Reminder" books, she has noted when the wood ducks return each spring and tracked the growth and flowering of plants in her garden.

Mrs. Anderson never dreamed that her notes would contribute to scientific research.

But Richard Primack, a biology professor at Boston University (BU), has used Anderson's records as part of a widespread effort to piece together the effects of climate change on the timing of springtime biological events, such as the return of birds and the flowering of plants.

His findings, corroborated by worldwide studies, show that plants and animals are adapting to higher annual temperatures.

Dr. Primack and his research team found that plants at Harvard University's Arnold Arboretum in Boston are flowering eight days earlier on average than they did 100 years ago. This change in flowering time parallels closely the rise in Boston's temperature - 1.5 degrees Celsius - over the same time period.

The results were presented this weekend at the annual meeting of the Society for Conservation Biology in New York.

While similar studies have been done, the arboretum study was unique in its use of herbarium specimens - clipped portions of plants, usually in flower, that are pressed, dried, mounted on paper, and dated. These specimens, in combination with data collected in 2003, enabled Primack's team to determine the trends of flowering times over more than 100 years.This "opens up a whole new way of looking at [the effects of] climate change on biological communities," Primack says, "because there are literally tens of millions of herbarium specimens from all over the world."In a year or two, scientists can use the specimens to track the effects of climate change over the course of a century.

Primack, together with Peter del Tredici, senior research scientist at the arboretum, combed the arboretum's database to find 229 species of flowering plants that were still living and for which they had herbarium specimens in full bloom. The oldest specimen, taken in 1885, was from a tree lilac still flowering today.


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