The new study gives scientists a peek inside the black box of ecological change in response to a warming world.
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 naturalist Henry David Thoreau's day, native plants such as serviceberry and nodding trillium are blooming 11 days earlier, on average, in the area around Concord, Massachussetts, where Thoreau famously lived and worked, the journal Public Library of Science One reported.
Nearly a thousand miles away in Wisconsin, where naturalist Aldo 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," explained Stan Temple, study co-author and professor of wildlife ecology at the University of Wisconsin-Madison (UWM).
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, according to a university statement.
"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 added.
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