Walden Pond and Global Warming

College professors continually go back to Henry David Thoreau's "Walden Pond" for lessons on self-reliance and Transcendentalism. But conservation biologist Richard Primack is using the 150-year-old work to study climate change.

Thanks to Thoreau's keen eye and meticulous record-keeping, the Boston University professor has used "Walden Pond" as a field guide to Massachusetts' past. Several times a week, Mr. Primack and his team of students trek to Concord, Mass., and wander the town's parks. They track when flowers bloom and when birds return from their winter vacations down south.

Comparing notes, Primack found that the signs of spring occur a week earlier than they did in the 1850s. Warmer average temperatures have accelerated the natural timetable, he says. Early blooms can throw off seasonal pollination and seeding, which might then further warp nature's schedule in future years. With Walden as his living laboratory, Primack hopes to suss out which flowers are most susceptible to the effects of global warming and find ways to protect those species.