Seagrass, an ecologically and economically important coastal habitat, has experienced substantial declines worldwide due to anthropogenic stressors. Despite sustained management and restoration efforts, recovery has often fallen short of expectations. Although nutrient enrichment and declining water quality are widely recognized as key drivers of seagrass loss, it remains unclear whether these pressures can push ecosystems across critical thresholds, resulting in abrupt and potentially irreversible change, particularly at management-relevant scales. Here, we integrate 40 years of water-quality records and aerial monitoring data from the Chesapeake Bay, United States, to quantify the cascading effects of anthropogenic stressors on submersed aquatic vegetation (SAV) and to identify potential early-warning signals of shifts in SAV abundance. Using structural equation models, we evaluate how fertilizer use influences nutrient concentrations from subestuaries to the bay-wide scale. We further assess temporal changes in SAV dynamics to identify pressure-driven critical transitions. We found that bay-wide SAV abundance might have crossed a tipping point in 2010, while SAV dynamics exhibit distinct statistical signatures across salinity zones. This work will provide a framework linking human activities to ecosystem degradation and offer insights for identifying intervention points to improve the resilience and recovery of coastal ecosystems.