The annual rituals of nature — the date when the marsh marigold first unfurls its yellow petals or when the common alder pushes out its leaves — are among the most sensitive indicators of climate change.
And Concord, known more for its rebellious history and its illustrious writers, also contains a valuable cache of data, spanning more than 150 years, about the habits of plants and animals in town. Henry David Thoreau was one of the first chroniclers, filling an estimated 2,000 pages of his journals with detailed observations about the plants, animals, and seasons around him.
Other scientists and observers have continued the tradition, recording when birds return north and when plants come to life in the spring.
“As far as I know, there is more information about the effect of climate change in Concord than any other place in the United States,” said Richard Primack, a Boston University biologist who calls Concord a living lab for his research.
Primack has probably done more than anyone in modern times to extol Thoreau — best known as an author, philosopher, and Transcendentalist — in another role: as a scientist. Thoreau walked around Concord for hours each day in the decade before he died of tuberculosis at 44, observing and recording details about the plants he saw.
The writer also departed from the scientific practice of the day — shooting birds to identify them by their lifeless bodies — by buying a spyglass to see them better. Well over a century later, when Primack started searching for local historical data, he discovered Thoreau’s scientific journals.
Now a Concord Museum exhibit, “Early Spring: Henry Thoreau and Climate Change,” examines Thoreau as scientist. The exhibit, which opens April 12, also pays tribute to the unusually large number of Concord residents who have tracked minute details of the natural world around them, as well as Primack’s research.
“Thoreau’s records had been hiding in plain sight,” said David Wood, the museum’s curator. “They had been partially published, starting in 1935, but they tended to be left out because they’re not literary. They tended to be overlooked by the English majors who were studying these pages.”
The exhibit also includes some notebooks from Rosie Corey, now 81, who started recording details about the birds she saw on her daily walks in Concord in the early 1960s. Her notes became more elaborate over time, and Primack studied her data as part of his research.
Corey has noticed changes over her decades of observation.
“I look over my old lists and I see so many birds that I don’t see now,” she said.
Meadowlarks and warblers are harder to find, she said. She has not seen a field sparrow in years.
The exhibit includes photos from Corey’s niece, Cherrie Corey, who has been studying Concord’s natural history for decades. She often compares her observations to those of Thoreau.
“Most of the years of his life were spent finely combing the landscape of Concord,” she said. “Day after day, year after year, season after season. And no one else has done that anywhere else in the country.”
The exhibit at the Concord Museum, which has the world’s largest collection of objects related to Thoreau, will reunite Thoreau’s journals, mostly stored at the Morgan Library & Museum in New York, with the author’s simple desk, which has been on display at the museum.
The Concord Museum received a $141,000 federal grant for the exhibit, the first federal grant the museum has received in 20 years, according to Peggy Burke, executive director.
Primack, the exhibit’s guest scholar, has researched how climate change has affected the flowering times of plants, comparing modern data with the information Thoreau collected between 1852 and 1860. Primack and his lab found that for every 1 degree Celsius increase in mean spring temperature, plants bloom about three days earlier.
“We’re able to see that there’s a continuity of history from Thoreau’s time until the present time,” Primack said. “That’s why we’ve been able to do this work.”
Primack came to his work about a decade ago, when he decided to change the direction of his research. He had been studying the effects of climate change on plants and animals in southeast Asia and decided, instead, to focus on his home state.
But when he began searching for older records of plant flowering times in the United States, he came up short. Finally, after six months, someone told him about Thoreau’s journals.
“This was kind of a gold mine of data,” Primack said. “As soon as we saw it, we knew it was amazing.”
One afternoon, two weeks ago, Primack and his former graduate student Caroline Polgar drove to two snowy spots in Concord to collect tree branches for their next research project. They are now studying how winter temperatures affect the blooming of plants in the spring.
“They don’t care how warm it is,” Primack said. “They have to go through a long winter period.”
First Primack and Polgar collected alder branches at the edge of a meadow. Then they drove along the Sudbury River and followed a trail into the woods. They were searching for blueberry and huckleberry — but in the winter, when the plants are leafless, the shrubs are nearly identical.
“That’s blueberry, right?” Primack asked, pointing to a small bush.
“Yes,” Polgar said.
“We’re going to start collecting them,” Primack said, as he snipped off branches with pruning shears.
Primack and Polgar took 20 branches of each shrub back to Primack’s BU lab. They planned to place the branches in water, and see how long it takes them to bloom.
Not everyone in Concord agrees with Primack’s conclusions about climate change in Concord. Cherrie Corey said she has found many of the plants that Primack believed had disappeared from Concord. And although she agrees that temperatures have been more erratic, she believes Primack needs more years of his own data before he can draw conclusions about climate change.
Burke and Wood said science benefits from both academic research and data collection by local residents.
“People are deeply respectful of each other’s research,” Burke said. “We think it’s all very interesting and it all adds to the broader layer of information about the community.”