The article, New York Times: Thoreau Is Rediscovered as a Climatologist, describes how scientists are using Henry David Thoreau's notes on flora at Walden Pond to study changes that are occurring in vegetation and climate there. The article was written by Cornelia Dean and published on October 27, 2008.


PATTERNS: Studying the loss and change in plant species in Walden Pond. Photo by Rick Friedman for The New York Times

From the article:

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Thoreau died in 1862, when the industrial revolution was just beginning to pump climate-changing greenhouse gases into the atmosphere. In 1851, when he started recording when and where plants flowered in Concord, he was making notes for a book on the seasons.

Now, though, researchers at Boston University and Harvard are using those notes to discern patterns of plant abundance and decline in Concord — and by extension, New England — and to link those patterns to changing climate.

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On average, common species are flowering seven days earlier than they did in Thoreau’s day, Richard B. Primack, a conservation biologist at Boston University, and Abraham J. Miller-Rushing, then his graduate student, reported this year in the journal Ecology. Working with Charles C. Davis, an evolutionary biologist at Harvard and two of his graduate students, they determined that 27 percent of the species documented by Thoreau have vanished from Concord and 36 percent are present in such small numbers that they probably will not survive for long. Those findings appear in the current issue of the Proceedings of the National Academy of Sciences.

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Of the 21 species of orchids Thoreau observed in Concord, “we could only find 7,” Dr. Primack said.

From 1851 through 1858, Thoreau tracked the first flowerings of perhaps 500 species, Dr. Primack said. “He knew what he was doing, and he did it really systematically.”

Dr. Primack and Dr. Miller-Rushing did their own surveys in 2004, 2005 and 2006. They also consulted notes from Pennie Logemann, a landscape designer who tracked flowering times from 1963 to 1993 as an aid to planning Concord gardens. And they looked at contributions by members of area plant, insect and bird clubs and the work of additional participants in Concord’s long line of passionate amateur naturalists, some of whose records are preserved in the Free Public Library here.

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The study of the timing of recurring natural events is known as phenology. One of the important observations that has been made in this and other studies is that not all species respond to change in the same manner from a temporal perspective. A consequence of this is that when environmental change occurs, interaction between some species may become altered or eliminated. The graph below illustrates how the schedules of some species respond differentially to temperature changes:


Source of graph: How well do first flowering dates measure plant responses to climate change? by Abraham Miller- Rushing, David Inouye, and Richard Primack

A few more quotes from the New York Times article:

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Now the professors and their graduate students are on the trail of more data. For example, there is growing evidence that as birds change their migration patterns in response to climate change, they may no longer be in sync with the insect species they feed on. Elizabeth Bacon, another of Dr. Primack’s graduate students, is combing Thoreau’s notes on birds and the records of the Nuttall Ornithological Club, a local organization, to see what they can contribute.

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The scientists say their research demonstrates the importance of simply watching the landscape and recording what occurs in it. And it demonstrates the importance of old records and natural history collections, Dr. Davis said. But in general, he said, there is little interest in devoting money, time and space to their preservation.

“It’s hard to defend the space on major campuses,” Dr. Davis said. “Eaton could not have prepared his ‘Flora’ unless Harvard University had maintained herbarium specimens. Hosmer’s book was here in Concord for 100 years before anyone used it.”

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Source: New York Times: Thoreau Is Rediscovered as a Climatologist

See slide show The Warming of Walden


Photo from the slide show on the New York Times site, referenced above.

This phenomenon was also covered by National Public Radio (NPR) on October 28, 2008. See NPR: Climate Changing Walden Pond's Flowers.

In the interview with Charles Davis that is featured in the recording available as part of the story, Dr. Davis points out that some of the plants that are going out of sync with their pollinators include the orchids, buttercups, roses, asters, and lilies.

Additional Information

Walden Pond State Reservation
Wikipedia: Walden Pond
How well do first flowering dates measure plant responses to climate change? by Abraham Miller- Rushing, David Inouye, and Richard Primack
Wikipedia: Phenology
Wikipedia: Henry David Thoreau
Walden by Henry David Thoreau - 1854 (an annotated edition)
Stanford Encyclopedia of Philosophy: Transcendentalism

From the Google Earth Community Forums

Walden Pond overlay
Walking With Thoreau
Thoreau's Cabin

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