Even though he died 150 years ago, Henry David Thoreau is now providing additional evidence to substantiate climate change. By examining records that Thoreau, the renowned American author and philosopher who showed us how to live more simply in “Walden” and taught us a thing or two about “Civil Disobedience,” used to keep, scientists have found that not only has the average temperature risen, but also that plant life cycles are changing.
While scientists overwhelmingly believe global warming to be a legitimate threat, the topic is still divisive in the political realm. Therefore, a pair of researchers, Richard Primack and Abraham Miller-Rushing, thought it would be useful to compare climate records from long ago to today to identify and demonstrate what kind of change has occurred. However, they encountered a problem in tracking down relevant detailed data from the past. Fortunately, they learned of the extensive plant records Thoreau maintained over a period of several years that have done just the trick.
From the years 1851 to 1858, Thoreau kept diligent tabs on the nature around him. Tracking more than 500 species of wildflowers, he charted biological details including which days they first flowered. Though these documents have previously gone unpublished, scholars have preserved these journals that might otherwise be discarded as mundane details because of Thoreau’s legacy.
Even with all of this information laid out, the research process was not that easy. Evidently, Thoreau’s messy handwriting makes for a difficult read. Moreover, because plant names have changed over the past century and a half, a lengthy research process was necessary to ensure that they were studying the same plants.
In comparing the biological conditions in Concord, Massachusetts today to those that Thoreau noted 155 years ago, Primack and Miller-Rushing made some interesting findings. After a few years of literal “fieldwork,” they learned that 27% of the species no longer existed in Concord, while an additional 36% of plants that used to be common in the area were now considered rare to the region. This decrease in species population indicates environmental changes.
More tellingly, the researchers discovered that the plants that still thrive in Concord are flowering an average of 10 days earlier than they were in the 1850s. Since the time plants bloom is known to be sensitive to the temperature, this progression strongly suggests a significant change in climate, as well. Using the various biological indicators, the researchers estimate that the average temperature in Concord has risen by 2.4 degrees Celsius.
Although the researchers’ initial study focused on Thoreau’s wildflower data, they say they also intend to use the information he collected on the days local trees “leaf-out.” While they have yet to investigate thoroughly, they say that it’s apparent that Concord trees are blooming earlier now, too.
“Thoreau was also an activist, and perhaps he would also be involved in the movement to reduce the greenhouse gases that are linked to climate change,” said Primack. Given Thoreau’s declaration, “We can never have enough of nature,” Primack’s theory does not seem like much of a stretch. Global warming may not have even been a concept in Thoreau’s time, but it is a credit to his affinity for nature that he left behind evidence that may help society to address contemporary environmental issues.
A full text version of Primack and Miller-Rushing’s study is available at BioScience.
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