Climate Changing Walden Pond's Flowers

Henry David Thoreau is perhaps best known for his book Walden, about living a simple life in harmony with nature. But Thoreau didn't just love nature — he studied it and kept meticulous notes. Now, scientists are using Thoreau's records to look at how the landscape has changed during the past 150 years.

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STEVE INSKEEP, host:

It's hard to find the right word to describe Henry David Thoreau. Writer.

RENEE MONTAGNE, host:

Philosopher.

INSKEEP: Iconoclast.

MONTAGNE: He's a rebel.

INSKEEP: Hermit. None of them are quite right. But Thoreau's own precise descriptions are paying dividends. He wrote "Walden," a famous book about living a simple life in harmony with nature. He also studied nature and kept meticulous notes.

MONTAGNE: Now scientists are using Thoreau's records to look at how the landscape has changed over the last 150 years. NPR's Nell Greenfieldboyce has more.

NELL GREENFIELDBOYCE: Charles Davis is a biologist at Harvard University who has to admit that he's never actually read "Walden."

Mr. CHARLES DAVIS (Assistant Professor of Organismic & Evolutionary Biology, Harvard University): Bits and pieces. But I'm kind of embarrassed to say that I've actually never read thoroughly through the seminal work. So I'll have to plead my ignorance there.

GREENFIELDBOYCE: He got intrigued with Henry David Thoreau for a different reason. He says a couple years ago he heard a talk about research by two scientists at Boston University, Richard Primack and Abraham Miller-Rushing. They had been pouring over the notes that Thoreau kept as he explored the area around Concord, Massachusetts. For years, Thoreau walked through fields, woods, and wetlands jotting down exactly when each flower bloomed, when birds came and left. Davis says he really was an amazing naturalist.

Mr. DAVIS: So there's a tremendous body of data that for the most part had been un-mined. And that was basically the efforts of the Boston University researchers that were involved with the project.

GREENFIELDBOYCE: And the Boston scientists were also able to look at the current state of Thoreau's old stomping grounds. Davis says even though modern-day Concord has shopping malls and highways, around half the land hasn't been developed.

Mr. DAVIS: It's been very well-protected over the last 150 years. So it really is sort of a living laboratory.

GREENFIELDBOYCE: And there have been dramatic changes in that living lab.

Mr. DAVIS: Something like 25 percent of the species that Thoreau saw, you can no longer see in the Concord area today.

GREENFIELDBOYCE: And Davis says another 36 percent are now so rare that scientists think they're on the way out, too. In the current issue of the Proceedings of the National Academy of Sciences, Davis and his colleagues say it looks like the plants that are declining can't adapt to a changing climate. Weather records show that around Concord the average yearly temperature has gone up a few degrees Fahrenheit over the last century. And the researchers found an interesting pattern. The plants that are declining seem to be the plant families that can't change their blooming times in response to changing temperatures.

Mr. DAVIS: So those include things like, you know, the orchid lineage, the buttercups and some of their relatives, roses, some of the aster groups, lilies and their relatives.

GREENFIELDBOYCE: He says, if plants always flower at the same time of year, they may go out of sync with pollinators that are responding to climate changes. David Inouye is a conservation biologist at the University of Maryland. He says biologists have data going back centuries for some individual species, like cherry trees in Japan. But what's unusual about this study in Massachusetts is that it looks at how different members of an entire plant community respond to changing conditions.

Dr. DAVID INOUYE (Professor and Director, Conservation Biology Program, University of Maryland): Thoreau would probably be both pleased that his data have had such enduring value and perhaps pleased that people are learning enough about these problems to be able to think about how we may be able to help prevent not just local extinctions, but global extinctions from occurring.

GREENFIELDBOYCE: But Thoreau might not be pleased to learn what's been lost from the woods around Walden Pond. Nell Greenfieldboyce, NPR News.

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