The Plum Island Ecosystems (PIE) LTER is developing a predictive understanding of the response of a linked watershed-marsh-estuarine system in northeastern Massachusetts to rapid environmental change. Over the last 30 years, surface sea water temperatures in the adjacent Gulf of Maine have risen at 3 times the global average, rates of sea-level rise have accelerated, and precipitation has increased. Coupled with these changes in climate and sea level are substantial changes within the rapidly urbanizing watersheds that influence water, sediment, and nutrient delivery to the marsh and estuary. In PIE IV our focus is on: Dynamics of coastal ecosystems in a region of rapid climate change, sea-level rise, and human impacts.