I have just posted a new video in which Darwin speculates on primeval forests. He begins by reciting, from imperfect memory, the beginning of Henry Wadsworth Longfellow’s poem Evangeline: something like “This is the forest primeval. The murmuring pines and the hemlocks, in garments green, indistinct in the twilight, stand like druids of eld…” Evangeline begins in Acadia. Well, Longfellow might have thought that the Acadian forest had always been there, but by the time Longfellow published the poem in 1847 geologists had already begun to understand that the entire northern part of the North American landscape had been covered by glaciers until about ten thousand years ago. The Acadian forest was less than ten thousand years old.
Another place many tourists visit is Walden Pond, where Henry David Thoreau lived in nature (actually only a couple of years, and in a forest profoundly altered by human activity). Many may think that the forest at Walden has always been there, but Thoreau would have been the first to tell you that the forest was always changing, especially as hardwoods grew up underneath pines in the process of ecological succession. He studied tree rings and could give you the evidence that the forest was always changing.
Darwin speaks to you in this video from a forest in Alsace in northeastern France. It looks like an ancient forest. The forest itself may look not too different from when the Empress Josephine saw it in the nineteenth century on the way to her mansion in Strasbourg. But none of the trees were there when Josephine saw them.
We know this because the oldest trees are about a century old. When a big old tree dies and falls over, it frequently blocks hiking paths. Municipal workers (the forest belongs to the town of Bischheim) cut away the trunks and move them off the path. The radial cuts reveal tree rings, one ring for each year of growth. The oldest ones on which I have counted the rings were about a hundred years old when they fell.
This means they started growing about the time of World War I. At this time, most of Alsace was a devastated landscape, in which almost all the trees were dead. (World War II did not have such a severe effect on Alsace.) A few lucky seedlings survived near a ballast mining pit (which is now Lake Balastière) and lived until they fell down and I saw them a century later. The forest looks impressive—lots of big beech, linden, and maple trees—but the whole forest grew in a century.
Every forest is in constant flux—old trees dying, young trees taking their place, sometimes trees of the same species, sometimes of a different species. There is perhaps no primeval forest anywhere. Sorry, Longfellow.



