There is a growing consensus among environmental historians that there were forms of environmental activism in the late 19th and early 20th century. (dotearth.blogs.nytimes.com)
There is a fascinating book called Changes in the Land: Indians, Colonists, and the Ecology of New England by environmental historian William Cronon that traces the changing human impact on the New England landscape from the days when Native Americans burned the undergrowth to make hunting game easier to days of European farmers to more recent types of development. (dotearth.blogs.nytimes.com)
In hindsight, says environmental historian Wilko von Hardenberg of the Max Planck Institute for... (newscientist.com)