PA Aquatic Resource Restoration Conference 2026: Past, Present and Future

In Rambunctious Garden: Saving Nature in a Post-Wild World (2013), nature writer Emma Marris challenged conventional ecological restoration by asking readers to imagine a stream. She then noted that the typical mental image—a single-thread, meandering channel with high banks — is often a human construct rather than a historical reality. While high-energy, meandering streams are ubiquitous today, the geologic record indicates they did not exist in the mid-Atlantic region prior to land-use changes associated with colonial settlement. By analyzing valley-bottom strata and extensive backhoe trenches at dozens of sites in Pennsylvania and Maryland, we reconstructed the region’s landscape evolution from the Last Full Glacial Maximum to the present. Following a late Pleistocene period of cold, dry tundra conditions and deeply frozen ground south of the continental ice sheet margin from ~30,000 to 11,500 years ago, warming at the onset of the Holocene Epoch triggered permafrost thaw and the initiation of widespread wetlands within several millennia. Hundreds of radiocarbon dates, thousands of extracted seeds and other macrofossils, numerous pollen studies, and the presence of beaver DNA in sediments reveal that spring-fed wetlands featured multiple small, shallow, anabranching channels and ponds throughout the Holocene. These wetland floodplains accumulated carbon-rich soils at rates of ~1 to 2 cm per century (although rates might have changed with time), producing an average of 1 meter of Holocene wetland soils. In essence, pre-colonial mid-Atlantic valley bottoms were not characterized by meandering streams that carried high sediment loads and built migrating gravel bars, but rather “wonderfully messy” low-energy wetlands that retained organic matter and fine sediment rather than transported it.