Walden Pond; or, How Global Warming and Invasive Species Can Change Everything

Andrew Wetzler, NRDC, Chicago
Posted on Thursday 11th February 2010

"A man is rich in proportion to the number of things which he can afford to let alone."


-- Henry David Thoreau, Walden; on, Life in the Woods


John Platt has a terrific piece up at Extinction Countdown about the changes that global warming and invasive species have brought Walden Pond, made famous by the transcendentalist Henry David Thoreau, whose thought was profoundly influential on America’s environmental movement.


Thoreau famously documented his “experiment” of living sparsely in a small cabin by a pond in Walden.  “To be awake is to be alive" he wrote.  Thoreau was a keen observer of nature and took detailed notes of the species he observed in the area and their behaviors.  This “Concord data set” was begun by Thoreau in 1851 and naturalists have continued to add to it until the present day.  In recent years, scientists have used Thoreau’s data to document changes to his little Pond.  They ain’t pretty.


  • Over the last 150 years the mean annual temperature in the Walden area has increased by 2.4°C;
  • This climate shift has allowed non-native (invasive) species of plants to out-compete their native rivals by flowering earlier;
  • As a result of the combination of climate change and competition from invasive species, 27 percent of the plant species Thoreau recorded are now locally extinct;


As we’ve discussed here at Switchboard many times, invasive species are a nasty business.  Unfortunately, climate change often seems to make it worse.


This post originally appeared on NRDC's Switchboard.


Andrew Wetzler serves as Director of NRDC's Endangered Species Project in Chicago. NRDC is a non-profit organization dedicated to protecting the environment, people and animals. NRDC was founded in 1970 and is comprised of more than 300 lawyers, scientists and policy experts, with more than one million members and e-activists.

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