While Henry David is most famed for Walden and Civil Disobedience, his painstaking work as a naturalist is turning out to have a rather significant legacy of its own. The author detailed the first flowerings of 500 species of plants in Concord, Massachusetts, between 1851 (a few years after returning from Walden Pond) and 1858. His tables have recently been pored over to see what it reveals about the changing climate.
After deciphering Thoreau's "notoriously bad" handwriting, and spending "a large amount of time" matching the names used for plants in the 1850s with their modern equivalents, (the research scientists) compared Thoreau's data on flowering dates, coupled with research from 19th-century local botanist Alfred Hosmer, with modern data of their own. Looking at 43 common Concord plant species, they found "unambiguously" that these plants, on average, "are now flowering 10 days earlier than they were in Thoreau's time," they write in an article for the journal BioScience.
Over the 155 intervening years, the average temperature in Concord increased by 2.4 Celsius, they estimate.
Researchers also learned that quite a lot of plant species that Thoreau observed -- a full 27 percent -- are no longer growing in Concord, and another 36 percent are now very rare. The scientists are now turning to Thoreau's meticulous notes on the dates when trees in Concord leafed-out for further comparison.
For the record (so to speak), Thoreau didn't leave his natural history observations to these tables. He worked as a land surveyor, and drew from his remarkably detailed journal to write essays like Wild Apples, which examines the history of the apple tree in both our landscape and our literature. He tried his hand at travel literature that takes a distinctly ecological bent; see, for example, The Maine Woods and A Week on the Concord and Merrimack Rivers. One of those books was the first of his career; the other published posthumously.
The New England icon visited the geographies of Detroit, Mackinac Island, Chicago, Milwaukee, St. Paul, and Ontario in the last year of his life, seeking a cure for the tuberculosis that would eventually kill him at age 44 in 1862. What I would give to see the Great Lakes country through the eyes of Thoreau.
Ah, but I can.