Investigating the Legacy of Human Land Use in a Representative Salt Marsh System Using Sediment Cores and a Multi-Proxy Approach

The Northeast coast of what is now known as the United States has experienced significant environmental change, driven directly and indirectly by human land use, with implications for the geological and ecological processes governing salt marsh development and morphology. Present-day marshes preserve these changes in the sedimentary record. Proxy data allows us to observe these changes, as proxies stand in for direct measurements of past conditions. These proxies measure standard marsh processes (e.g., vertical accretion and organic matter deposition), characteristics (e.g., soil salinity and vegetation distribution), and historical land use changes (e.g., farming and land clearance). I use various physical and geochemical methods to analyze sediment cores (ranging from ~80 cm to ~150 cm) and a series of surface samples (5 cm) from a salt marsh system with a history of human land use spanning from approximately 1700 C.E. to 1900 C.E. (Cousins River Marsh, Freeport, ME). This thesis demonstrates how a multi-proxy can be used to understand natural and anthropogenic change in salt marshes, while also noting how episodic and hyper-local conditions can confound this approach. In particular, pollen data collected from a representative sediment core provided evidence of cattle grazing and upland agriculture, suggesting an age of onset for human activity in the marsh around ~1760 CE and addressing the legacy of farming in the Cousins River. The results of this study will inform how we interpret the stratigraphic record of salt marshes previously altered for and by human land use, provide new insights into how marshes respond to human perturbations, and discuss the implications for restoration and management strategies in marshes with similar legacies of human impacts.