These days we would call him an entrepreneur. From the day he started writing books to his later years in manufacturing, Henry David Thoreau was ambitious and innovative. Not in the sense of building a company and an empire, but in the sense of making a living through excellence. At Walden Pond he set out to create a literary work of art, distilling two years of experience into one year for the ages. (In his day, writing well was a good way to make money.) Living on the Pond, he also made extensive observations of the natural world that scientists still use. When he eventually moved on to traditional commercial life in his family's factory, he designed what today we might call an innovative communication tool (then, an improved lead pencil and the machine to manufacture it). Read more in Robert Sullivan's illuminating book The Thoreau You Don't Know: The Father of Nature Writers on the Importance of Cities, Finance, and Fooling Around.
To read Thoreau's Walden; or, Life in the Woods is to discover the eloquence of nature and the beauty of a contemplative life. Yet, to understand it fully is to realize that in his day the Pond was a commercial site. A railroad ran next to the pond (it still does), and Thoreau built his cabin from the remains of a railroad worker's shanty along with other locally recycled materials. Companies made good use of the site: Ice Fort Cove, a few hundred yards from Thoreau's cabin, was named after a large commercial operation that, before refrigeration, cut blocks of ice from the pond and shipped them by rail and sea to places as far away as India. Also, near the Pond was the woodlot for the town of Concord, which is less than 2 miles away. To throw at this scene some modern interpretive jargon, we might say that life at Walden was embedded then as now in a broad set of human and ecological systems.
Of course, Thoreau never heard of global warming. Yet if he were with us today, I have no doubt that in his roles as innovator, entrepreneur, writer, citizen scientist, businessman, and respected family member, he would be doing everything in his power to stop it. And so should we.