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Blooms in Boston: Clues About Our Climate

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Feb 10, 2006 10:19 am US/Eastern

Blooms in Boston: Clues About Our Climate

(WBZ)

Click to enlarge 1 of 1: Abe (left) and Dr. Primack (right) record a Rhododendron vaseyi in bloom.

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Richard Primack & Abraham Miller-Rushing, Plant Ecologists, Boston University

The debate over global warming has only heated up due to destructive storms like Hurricanes Katrina, Rita and Wilma. While scientists ponder the impacts a warmer climate may have on these large scale weather events, subtle changes in our growing season right here in Boston shed light on a changing world. Careful observers may have already noticed local plants blooming earlier in the spring than in the past. Our research confirms that the growing season in Boston is in fact longer than it was just 100 years ago.

Nestled in Jamaica Plain, not far from the heart of the city, the Arnold Arboretum is an oasis of green space and botanical gardens run by Harvard University. Besides living species, the Arboretum is home to thousands of preserved plant specimens that have been carefully documented and cataloged for over a century. These herbarium specimens, taken directly from the property, are dried, pressed and dated, providing a clear record of past flowering times when Boston was cooler on average than it is today.

To investigate changes in Boston's growing season, we examined 229 herbarium specimens collected over the last 120 years from trees and shrubs still living on the grounds of the Arboretum. During the spring and summer of 2003, we tracked the flowering times of these plants. Using the available historical data, we compared recent flowering dates to flowering times in the past. Based on our study, over the last 25 years, plants have flowered about 8 days earlier than they did just 100 years ago. We believe these earlier flowering times are due to a warmer Boston. In fact, weather records show the temperature in Boston has increased by roughly 2ºC during this period. So on average, plants are responding about 4 days earlier for each 1ºC increase in average spring (February May) temperature.

While big storms may provide fuel for the global warming discussion, you don't need to look any further than your own backyard to witness the impact warmer weather is having on our lives.

Dr. Primack is a Professor of Plant Ecology and has been studying flowering times since 1978. Dr. Primack and his graduate student, Abe Miller-Rushing, are now using historical data sets and their own current observations to study the effects of climate change on flowering times at Walden Pond.