By Alan Harman
Exceptionally warm spring weather in 2010 and 2012 resulted in the earliest flowering times known in 161 years of recorded history at two sites in the eastern United States.
Many plants need a long winter break to undergo physiological changes that make them bloom in the spring.
But Boston University researcher Elizabeth Ellwood says this blooming is occurring earlier than before due to warmer springs caused by climate change.
It’s still not known what affects this will have on plant productivity, pollinators such as bees and ecosystems in general.
Ellwood and her team from Harvard University and the University of Wisconsin report in the journal PLOS ONE that they compared flowering times now with those recorded near Walden Pond in Massachusetts by Henry David Thoreau beginning in 1852 and Aldo Leopold's records of spring flowering in Wisconsin beginning in 1935.
They found many plants flower up to 4.1 days earlier for every degree Celsius rise in mean spring temperatures, but this relationship is linear from Thoreau's time to the present day.
In other words, long-term observations could be used to predict plant response to weather extremes outside of the historical range. The authors explain that though spring rising temperatures are causing record earlier flowering, temperatures have likely not yet reached a point where plants are not able to respond in terms of their flowering times.
“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” Ellwood says.
“Our data shows that plants keep shifting their flowering times ever earlier as the climate continues to warm.”
Harvard Professor of Organismic and Evolutionary Biology Charles Davis says the data shows that the two warmest years on record – 2010 and 2012 – also featured record breaking early spring flowering.
“It appears that many spring plants keep pushing things earlier and earlier,” Davis says.
“The striking finding is that we see the same pattern in Wisconsin as we see in Massachusetts. It's amazing that these areas are so far apart and yet we're seeing the same things–it speaks to a larger phenomenon taking place in the eastern United States.”
Davis says the study provides a tangible example of the potential consequences of climate change.
“The problem of climate change is so massive, the temptation is for people to tune out,” he says. “But I think being aware that this is indeed happening is one step in the right direction of good stewardship of our planet.
“When we talk about future climate change, it can be difficult to grasp. Humans may weather these changes reasonably well in the short-term, but many organisms in the tree of life will not fare nearly as well.”