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Conservators Annual Dinner Meeting
May 27, 2009

Climate Change Comes to Thoreau's Concord

  Also at the dinner ...  

Climate change means species loss. And the evidence is here, in Concord, according to Richard Primack, who addressed the Newton Conservators at their 2009 annual dinner. Henry David Thoreau was a close observer of nature. A hundred and fifty years ago, Thoreau recorded in detail the date for the first spring appearance of various animal and plant species near Walden Pond. By comparing data from Thoreau and new data from a study by their Boston University research team, Primack and Abraham Miller-Rushing have found much earlier blooming dates or arrival dates for certain migrating species, resulting in mis-synchronization of natural cycles. The result, says Primack, is a dramatic decline in biodiversity from the agrarian Concord of Thoreau to the present, with most of the decline occurring in the past 50 years.

Primack gave a wonderful presentation that covered his laboratory research efforts over the past decade on plant flowering activities. His laboratory group does research on conservation biology and plant ecology, including tropical ecology and climate change biology. He presented his research showing that many plants in the area where Henry David Thoreau once lived are now blooming earlier than at the time of Thoreau’s record. The current climate shows a temperature increase of more than two degrees Centigrade. Dr. Primack concludes that this is due to climate change and urbanization.

His laboratory group has been investigating the flora in the Concord area for over five years and has found significant differences in the flowering times of some plant species. In a recent publication (Ecology 89(2), 2008, pp. 332-341), he reported that these plants are now flowering, on average, a week earlier than reported by the botanical records by Thoreau and others. He found that plant flowering times are most correlated with mean temperatures in the months before flowering. Many plant species are no longer found in the area; this likely is due to the change in climate. His laboratory group is investigating whether or not the missing species are primarily plants that flower with a particular day length time period instead of plants that are strictly temperature dependent. He also discussed studies that found insects hatching earlier, a trend similar to that for temperature sensitive plants.

Problems arise with the migration of birds from South America that have their own photoperiod schedule and may arrive too late to effectively start their offspring, as their insect food base has moved to a new life cycle stage. Among the other observations by Primack and his team are these:

  • plants flowering eight days earlier than they did 150 years ago
  • wood ducks arriving six weeks earlier
  • birds from the southeast U.S. arriving earlier, but not birds from South America
  • 27% of species observed by Thoreau now extinct
  • 36% now rare in Concord
  • 21 orchid species in Thoreau’s time, versus seven now
  • 75% of species native 150 years ago, versus 61% now
  • 84 new species
  • 243 missing species

Most of Concord in Thoreau’s time was cleared land used for agriculture. Rare species in Concord are found in high concentrations at disturbed areas, including the former town dump, rather than at re-forested locations. Primack advocates active management of open spaces to create clearings where species that are now rare can flourish. He also advocates that we assist nature in re-locating species that may be endangered, moving species that historically have made a home in New Jersey or points south to our community and re-locating species from here to points north.

Professor Primack’s presentation was particularly well received by the Conservators, who gave him numerous questions to field. It was an exciting evening that was capped by a very moving presentation on the effects of global warming. You can learn more about Professor Primack’s research on his website at Boston University .

- William Hagar and Eric Reenstierna


Editor's note: Primack's book, Walden Warming: Climate Change Comes to Thoreau's Woods, was published by the University of Chicago Press in 2014.

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