A leaf falls on Walden Pond in the autumn light

Book Review: Walden Warming by Richard B. Primack

Walden Warming: Climate Change Comes to Thoreau's WoodsWalden Warming: Climate Change Comes to Thoreau’s Woods by Richard B. Primack

My rating: 4 of 5 stars

The best part of this book is its founding idea. The author Richard Primack, a professor of Biology at Boston University, compared the information in Henry David Thoreau’s journals with his own modern day research to understand and measure how the climate and the plant and animal species of the area around Walden Pond in Concord MA have changed over the past 150 years.

Thoreau is introduced to geocaching

As an intermittent journal keeper, walker, biologist, and sometime admirer of Thoreau, I find that this research represents a kind of interdisciplinary, far-ranging, life of the mind that I have always admired. Primack’s work is an eloquent testimony to the best of Massachusetts where I lived for 17 years: its beauty, its history, its eccentricity, and its crazy weather.

The book itself, however, is a little scholarly, dry and understated. Its cover is a simple print–an artist’s conception of Thoreau’s cottage–and a few scientifically accurate black and white photographs adorn its pages. The writing is more lively and engaging than most scientific papers I’ve read, but it is also so detailed and thorough that it is unlikely the casual reader will persevere through the entire book. Trees, wildflowers, pond ice, weeds, migratory birds, bees, butterflies, fish, mosquitoes, amphibians, salamanders, and marathon runners all get their pages, sometimes entire chapters. I stopped reading myself a couple of times and might not have finished if I hadn’t been planning on writing this review.

By sifting through so much data, Primack and his team are able to conclude that the area around Boston, including Concord, is warming, and that this warming has consequences for the species that live there. The main conclusion is, in fact, that it is good for species to be flexible. The more flexible a species can be, the more likely it is to thrive. Primack is also conscientious enough to point out that the majority (about 2/3) of the warming since the 1850s that he currently observes in the Boston area is due to an “urban heat island effect”—the absorption of sunlight by dark paved surfaces such as roads, parking lots, and buildings—and only 1/3 is due to general global warming. His work therefore uses Concord area warming as a model for what could happen all over the earth when temperatures rise.

The book derives a great deal of its interest from Primack’s own story. His personal anecdotes about his wife’s fishing knowledge acquired while growing up in Malaysian Borneo, or with his children helping spotted salamanders across a golf course parking lot to their mating grounds, or running the Boston marathon as a true amateur in 1970, give the book a narrative structure and the lay reader a break from all the technical terminology. Perhaps unwittingly, the narrative also provides a birds-eye view of how a scientific career might be structured in the modern era. Primack devotes significant effort to explaining how and why he chose the research directions he did, and the obstacles he had to overcome to acquire data on various species in the first place. The reader is also party to the messiness inherent in drawing firm conclusions from data acquired in the field over many years.

IMG_6904A recurring theme in the observations made by Primack and his research team is diversity.
Many species were difficult to study at all due to scarcity, living habits, or appearance. And even when good records were available, only some species showed changes that seemed to correlate with warming temperatures. A set of wildflowers flowered earlier in years with warm spring temperatures and later in years with cold spring temperatures. When these species were considered together as a group, the researchers were able to calculate that these plants flowered on average two days earlier for each 1 degree Fahrenheit increase in temperature. By then comparing the abundance of the plants that could adapt their flowering times to temperature with those that did not, the researchers were able to conclude that the more flexible a plant could be with its flowering time, the more likely it was to have persisted or even flourished in today’s warmer climate.

I heard Primack speak at the Belmont MA library, about 2 years ago when the book first came out, and I think this material lends itself especially well to the seminar format, with slides: colorful flowers, trees, and butterflies, projected on the screen. Or better yet, perhaps, a walk in the woods oneself, accompanied by a naturalist.

Keeping this in mind, I turned to the section on Further Reading in the back of the book. This is a useful appendix that lists writings by and about Thoreau, field guides, resources about climate change, as well as links to original Primack Lab research articles and the lab’s blog (http://primacklab.blogspot.com/). This video does a great job of showing some of the plants they study in their natural habitat:


Primack also encourages readers to to start their own journals and get involved in citizen science. This is a great idea and it encouraged me to look up local organizations in my area of California. I would recommend this book to anyone interested in nature and the future of the planet.

Concord 2001
The author and daughter in Concord in 2001

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