Global warming spurs early flowering: Study

Rising temperatures are causing flowers to bloom at their earliest dates in decades at two historic sites in US, according to new research.

Using the meticulous phenological records of two iconic American naturalists, Henry David Thoreau and Aldo Leopold, scientists have demonstrated that native plants in the eastern United States are flowering as much as a month earlier in response to a warming climate.

The study by researchers from Boston and Harvard Universities and the University of Wisconsin-Madison is important because it gives scientists a peek inside the black box of ecological change.

It may also help predict effects on important agricultural crops, which depend on flowering to produce fruit.

Compared to the timing of spring flowering in Thoreau’s day, native plants such as serviceberry and nodding trillium are blooming 11 days earlier, on average, in the area around Concord, where Thoreau famously lived and worked.

Nearly a thousand miles away in Wisconsin, where Leopold gathered his records of blooming plants like wild geranium and marsh marigold, the change is even more striking.

In 2012, the warmest spring on record for Wisconsin, plants bloomed on average nearly a month earlier than they did just 67 years earlier when Leopold made his last entry.

“These historical records provide a snapshot in time and a baseline of sorts against which we can compare more recent records from the period in which climate change has accelerated,” said researcher Stan Temple.

The new study, published in the journal PLoS One, is the first to suggest that the trend in flowering plants may continue beyond what has been observed in controlled studies.

The work thus has important implications for predicting plant responses to changing climate, essential for plants such as fruit trees, which are highly susceptible to the vagaries of climate and weather.

“We used relationships revealed in historical records to predict how 47 species of native plants would respond to unprecedented spring temperatures, but that has only been possible because naturalists, past and present, kept good records of what they observed in nature,” Temple said.

“Earlier blooming exposes plants to a greater risk of experiencing cold snaps that can damage blossoms and prevent fruiting,” said Temple in a statement.

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