Last year, the New York Times ran a article about Henry David Thoreau called, "Thoreau is Rediscovered As a Climatologist". I recently found the article and was fascinated by its premise: Thoreau's keen observations of his surroundings now have a use in studying climate change.
With Thoreau's findings as a base, scientists have made startling discoveries such as, "...27 percent of the species documented by Thoreau have vanished from Concord and 36 percent are present in such small numbers that they probably will not survive for long." How sad is that?
Borrow A Week on the Concord and Merrimack Rivers [818 THO] and travel to Maine, Massachusetts, and New Hampshire as they existed in the 1840s. Plan a summer trip exploring some of the sites Thoreau visited and note how they have changed. Become a keen observer and record your observations and maybe a century from now someone will be studying your notes.