Compared to extreme drought, blistering heat, massive wildfires and tropical cyclones, the latest indicator of climate change is unexpectedly attractive: early spring flowers. Unusually warm spring weather in 2010 and 2012 at a pair of notable sites in the eastern U.S. led to the earliest spring flowering times on record—earlier than any other time in the last 161 years.
The researchers involved, from Boston University, the University of Wisconsin and Harvard, examined the flowers at two sites well-known for their roles in the early environmental movement: Walden Pond, where Henry David Thoreau started keeping flowering records back in 1852, and Dane County, Wisc., where Aldo Leopold first recorded flowering data in 1935.
“We were amazed that wildflowers in Concord flowered almost a month earlier in 2012 than they did in Thoreau’s time or any other recent year, and it turns out the same phenomenon was happening in Wisconsin where Aldo Leopold was recording flowering times,” lead author Elizabeth Ellwood of Boston University said in a statement. “Our data shows that plants keep shifting their flowering times ever earlier as the climate continues to warm.”
In Massachusetts, the team studied 32 native spring flowering plant species—such as wild columbine, marsh marigold and pink lady slipper—for which average flowering dates had been fairly well-documented between Thoreau’s time and our own. They found that the plants’ flowering dates had steadily moved earlier as temperatures increased—Thoreau saw them flower on May 15, while they flowered on April 25 and 24 in 2010 and 2012, respectively. In the two years studied, 27 of the 32 species had their earliest flowering date ever.
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