Boston Globe: In the 1850s, a few years after he had gone to “live deliberately” in a cabin in the woods at Walden Pond, Henry David Thoreau began to compile detailed records on hundreds of species of plants in his beloved Concord. Those same data now are being used to measure the effect of climate change, and the news is not good, researchers said yesterday. Scientists from Boston University and Harvard reported that 27 percent of the species documented by Thoreau have disappeared, and another 36 …