On July 4, 1845, Henry David Thoreau moved to a small cabin at Walden Pond, about a mile and a half from his hometown, Concord, Mass. “I went to the woods because I wished to live deliberately,” he explained, “to front only the essential facts of life.” For two years, two months and two days, he walked, observed, listened, wrote and read. The result was “Walden,” the book that made him one of the most beloved American writers, regarded by many as the country’s first environmentalist.
Yet today it’s another aspect of Thoreau’s work that’s proving vital, this time to ecological research. For the past decade, Richard Primack, a professor of biology at Boston University, has collaborated with colleagues at Harvard to use the observations in Thoreau’s journals as the basis for groundbreaking studies in climate change. From 1852 to 1861, Thoreau recorded the exact blooming and leafing-out dates of several hundred flowers, shrubs and trees in the Concord area, compiling charts and lists so meticulous that Primack and his associates — after the onerous task of deciphering Thoreau’s handwriting and matching 1850s plant names to their modern equivalents — have been able to compare them with present-­day observations at the same location.
In the nine years it took Thoreau to write and rewrite “Walden” — during which he struggled to align his passion (or, one might say, obsession) for detailed nature observation with his love for poetry — he walked the countryside, noting plant species and their growing seasons. He measured the depth of streams and ponds, took temperature readings, pressed samples of plants and recorded the arrival and departure of migrating birds. Instead of “calling on some scholar,” he marched miles through the woods for his appointments with plants. At times, he worried that “this habit of close observation” might harm his literary endeavors. One day, after a long boat trip, scribbling page after page of notes, he finished his journal entry by remarking that “every poet has trembled on the verge of science.”
During the years when Thoreau was redrafting “Walden,” he underwent a personal evolution — from a Transcendental poet who adored nature to one of America’s most influential nature writers. It was then that he began to use his journal as a precise record of his encounters with the natural world, developing a daily routine of serious study in the morning and evening, punctuated by a long afternoon walk. “I omit the unusual — the hurricanes and earthquakes — and describe the common,” he wrote in August 1851. “This has the greatest charm and is the true theme of poetry.” The journal entries, which had previously contained fragments and jottings, now became regular and chronological, documenting the seasons in all their intricacies. “This is my year of observation,” Thoreau proclaimed in July 1852. Armed with his hat as a “botany box” in which he kept plant specimens, a music book as his plant press and his walking stick as a measuring tape, he developed a deep appreciation of nature’s cycles and interrelationships.
All the great passages of “Walden” have their origin in Thoreau’s journals, engaging us on every level, from the grand sweep of the earth as “living poetry” to the humble frogs that “snore in the river” to the joy in bird songs heard in the early spring. His journal was “a book of the seasons,” “the record of my love” and of his “ecstasy” — some two million words altogether. Thoreau questioned whether anything he wrote would be better than his journal, comparing his words to flowers and wondering if they would look better artificially brought together in a bouquet (a book) or in the meadow where he had found them (his journal).
Andrea Wulf is the author of “Founding Gardeners: The Revolutionary Generation, Nature, and the Shaping of the American Nation.” She is an Eccles British Library writer in residence for 2013.