Drivers of individual tree mortality across the US coasts

Coastal forests are carbon-dense ecosystems providing critical services, including storm protection, water filtration, timber, and fisheries, to millions of people living in vulnerable low-lying regions. Increasing evidence suggests that tree mortality is accelerating across these habitats, driven by rising water tables (leading to anoxia), salinization, and extreme weather events such as droughts and storms. These stressors are triggering rapid shifts in coastal forest structure, function, and carbon balance. Yet, the spatial extent of coastal tree mortality remains poorly mapped due to the heterogeneity of coastal landscapes. Consequently, it becomes challenging to elucidate the pace and mechanisms behind such die-off patterns, particularly in areas beyond sea-level rise hotspots. Here, we present a deep learning–based approach for tracking individual tree mortality biennially between 2010 and 2023 using sub-meter aerial imagery across the coastal United States, spanning the Atlantic, Gulf, and Pacific coasts, as well as the Great Lakes region. By tracking over 200 million individual tree mortalities over the past decade, we captured signals of canopy stress and decline across at-risk forests, which enabled us to elucidate the underlying mortality drivers. We identified many mortality hotspots not captured by traditional remote sensing approaches or surveys. This approach offers a scalable framework for identifying emerging mortality hotspots and understanding how climate and hydrological stressors are reshaping forest resilience. Such insight is crucial for informing adaptive coastal management and anticipating ecosystem transformation under accelerating climate change.