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A stream of new ideas keeps this Friends teacher on the move by H e i di Bl a l oc k
F
or Bill Hilgartner, science is an action word, something to do, not just study. Since joining the Friends faculty in 1983, the low-key science teacher and paleoecologist has spent his summers indulging his passion for field research and sharing his findings with others through articles in such peer-review journals as The Holocene and The Journal of the Torrey Botanical Society. His efforts have paid off not only in terms of his own professional development, but also on behalf of the scientific community. Hilgartner, who earned a doctorate in geography and environmental engineering in 1995 from Johns Hopkins University and serves on the faculties of the university’s Whiting School of Engineering and Maryland Institute College of Art (MICA), has teamed up with Franklin and Marshall College geologists Dorothy Merritts and Robert Walter on a controversial project that’s shaping the debate on stream restoration. “Dorothy and Bob published a paper that’s created a paradigm shift in geomorphology,” explains Hilgartner. It started some years back when the couple (they are husband and wife) began dissecting the banks of several rivers in Lancaster County, Pa., to determine the age and composition of the sediment layers. They concluded the sediment had come from a series of dams constructed in the 1700s. Hilgartner explains, “Settlers would move into these marshy valleys and build dams — you might find 10
to 15 of them in some of the longer rivers. At the same time, Colonial inhabitants were cutting down the forests and hillsides to create agricultural lands, all of which creates a huge amount of erosion.” The eroded materials filled the reservoirs behind the dams. Eventually they broke and the contents spilled out, cutting channels through the sediment. “The settlers basically buried the old wetlands that used to be there,” Hilgartner concludes. This discovery led to another question for the geologists: If the sediment is only 300 years old, then how old are the wetlands? Enter Hilgartner. “Dorothy was interested in the fact that I could identify fossil seeds,” he says. From a core sample taken from Little Falls in northern Baltimore County, Hilgartner identified the seeds of several species of sedge, including tussock sedge. “We got carbon-14 dates of 5,000 years at the bottom and 300 years at the top,” he adds. The findings were dramatic and far-reaching. “We used to think that the rivers you see today in the Piedmont river valleys of central Maryland and southeastern Pennsylvania were shifting around for thousands of years. We now know the river channels in the upper reaches are only 300 years old. Before that there was this very different wet, marshy valley,” says Hilgartner. “That’s pretty neat.” The discovery has practical applications. “Stream restoration is big
The settlers basically buried the old wetlands that used to be there.
Bill Hilgartner, pictured at a sandstone quarry in Washington County, Md., is using his expertise in fossil seeds to help shape the stream restoration debate.
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