<p>Sea-level rise (SLR) and saltwater intrusion are driving large-scale ecosystem retreat along economically valuable coasts. However, it remains unclear how human interventions influence climate-driven processes, especially in rural areas. Sea-level-driven land use change is typically modelled as a binary response, where human-dominated uplands convert to wetlands instantaneously or else are protected indefinitely. Here we use 38 years of satellite observations across the mid-Atlantic SLR hotspot to show that marsh encroachment is nearly twice as fast, and 1.4–6.8 times more frequent, on agricultural land than forestland. Field measurements indicate that local interventions have slowed the loss of agricultural land on private property to rates far lower than SLR; however, our results suggest that, at the regional scale, agriculture accelerates the impacts of saltwater intrusion. These results imply a unique scale-dependent impact of humans on coastal management and extend our understanding of humans as principal agents of change, even in rural landscapes.</p>