Red Oak (left), American Beech (center), Sweet Birch (right). These are fossil leaves removed from the Denlinger Mill study site. Image: Wilf Lab/Penn State
Buried leaves reveal precolonial eastern forests and guide stream restoration
UNIVERSITY PARK, Pa. — Sediment behind milldams in Pennsylvania preserved leaves deposited just before European contact that provide a glimpse of the ancient forests, according to a team of geoscientists, who note that neither the forests nor the streams were what they are today.
"Milldams were built from the late 1600s to the late 1800s in Pennsylvania and other parts of the east," said Peter Wilf, professor of geosciences, Penn State. "We can’t get information from historic records on what the area looked like before the dams because recording of natural history didn’t really begin until the 1730s and was not detailed."
U.S. census shows that by 1840, tens of thousands of milldams existed in the mid-Atlantic region. About 10,000 of these were in Pennsylvania. In Lancaster County, estimates were one dam for every mile of stream. The abundance of dams in the area altered the landscape dramatically, according to the researchers.
"I see a potential modern day benefit for this research," said Sara J. Elliott, recent Penn State master’s degree recipient, currently a research scientist associate at University of Texas Austin, Bureau of Economic Geology. "Attempts to restore precontact environments have been unsuccessful when the effects of milldams were not considered. Understanding the past forest makeup may provide a way to help get a successful and useful reconstruction.”
Three-hundred year old fossils discovered in Pennsylvania are helping expand our understanding of what the forests of the United States looked like before colonization by Europeans. European settlers dramatically reshaped the landscape by clearing forests, damming rivers, and razing topographical features.
This is as true for the five boroughs of New York City as it was for much of the Eastern Seaboard. Our 50-acre Thain Family Forest is a living remnant of the forests that once covered New York City, but it is not an exact replica of those long ago times. Changes in climate, imported diseases and invasive species, and the natural progression of a forest’s life have changed the makeup of this remarkable plot of land. Forests are living, breathing things, so even though we talk about our Forest as a remnant of a long ago time, discoveries like this one help us understand what it really did look like 300 years ago, without all the guesswork. ~AR