"To be in company, even with the best, is soon wearisome and dissipating. I love to be alone." So wrote Henry David Thoreau at Walden Pond, the once bucolic site that provided his retreat from civilization. If Thoreau returned today, he would be appalled: last year some 350,000 visitors swarmed through the 400-acre state park near Concord, Mass., in an attempt to recapture the writer's sense of tranquillity.
The flood of tourists poses a dilemma. To keep the pond's sandy banks from crumbling under the heavy foot traffic, the Massachusetts Department of Environmental Management has begun reinforcing them with fieldstone and...