The woods surrounding Walden Pond in Concord, Massachusetts have changed a lot since the time when Henry David Thoreau traversed their landscape. There’s a parking lot by the pond, throngs of people now gather where he once lived in isolation — and there are numerous monuments to Thoreau’s greatness.
I walk my dog through these woods nearly every morning. Like Thoreau, I watch for seasonal changes. Lady slippers, for example, are a sure sign of spring. Each year, I await their appearance with bated breath, and year after year they have come back to amaze me with their delicate beauty.
Unlike Thoreau, I don’t take detailed notes, though it has been hard not to note how the recent freakishly warm weather has hastened the appearance of local bloomers. According to a recent study, lady slippers and other local flowers appeared three weeks earlier in Massachusetts in 2012 than they did in Thoreau’s time.
Thoreau would most likely be shocked by the changes to his woods since his death, and he’d be horrified to learn the implications of global warming. Yet, he also would be heartened to know that data he began gathering in his flower journal in 1852 provides valuable insights for today’s biologists as they study the impact of climate change on native plants.
“Record-Breaking Early Flowering in the Eastern United States” uses data collected by Thoreau in Concord, Massachusetts, and by author and scientist, Aldo Leopold from 1935 to 1945 in Dane and Sauk counties, Wisconsin. It serves as a baseline for understanding and predicting how warmer temperatures during record-breaking years, such as we experienced in 2012, will continue to impact the flowering times of local plants like the lady slipper.
According to the study’s authors,
“… historical phenological data, such as those initiated by Thoreau and Leopold, are critical to understanding plant responses to current and future warming, and to test whether increasing temperatures may result in continued earlier flowering.”
Their analyses of this data shows plants have responded to global warming by blooming earlier and earlier each year with record breaking spring temperatures — such as those experienced in Massachusetts and Wisconsin in 2012 — resulting in the earliest flowering times in recorded history.
While these plants seem to be adapting to climate change so far, the study’s authors posit that they cannot continue to adjust their cycles indefinitely.
As Harvard Professor Charles Davis, the study’s co-author, recently told the New York Times,
“If species don’t receive the proper chilling requirements, then they may not be able to set their flowering for spring. Once that point is met, it’s likely to be a very bad thing for plant species experiencing that problem.”
What is bad for plants is bad for all life on earth. Thoreau once said,
“Though I do not believe that a plant will spring up where no seed has
been, I have great faith in a seed. Convince me that you have a seed
there, and I am prepared to expect wonders.”
Let’s do all we can to protect these wonders so that our grandchildren can expect them just as Thoreau once did.
Photos: Judith A. Ross