Coastal ecosystems represent a disproportionately large but vulnerable global carbon sink. Sea-level-driven tidal wetland degradation and upland forest mortality threaten coastal carbon pools, but responses of the broader coastal landscape to interacting facets of climate change remain poorly understood. Here, we use 36 years of satellite observations across the mid-Atlantic sea-level rise hotspot to show that climate change has actually increased the amount of carbon stored in the biomass of coastal ecosystems despite substantial areal loss. We find that sea-level-driven reductions in wetland and low-lying forest biomass were largely confined to areas less than 2 m above sea level, whereas the otherwise warmer and wetter climate led to an increase in the biomass of adjacent upland forests. Integrated across the entire coastal landscape, climate-driven upland greening offset sea-level-driven biomass losses, such that the net impact of climate change was to increase the amount of carbon stored in coastal vegetation. These results point to a fundamental decoupling between upland and wetland carbon trends that can only be understood by integrating observations across traditional ecosystem boundaries. This holistic approach may provide a template for quantifying carbon–climate feedbacks and other aspects of coastal change that extend beyond sea-level rise alone.

沿海生态系统是一个异常庞大但脆弱的全球碳汇。海平面驱动的潮汐湿地退化和高地森林死亡威胁着沿海碳库，但更广泛的沿海景观对气候变化相互作用方面的反应仍然知之甚少。在这里，我们使用大西洋中部海平面上升热点 36 年的卫星观测结果表明，尽管面积损失很大，但气候变化实际上增加了沿海生态系统生物量中储存的碳量。我们发现海平面驱动的湿地和低洼森林生物量减少主要局限于海拔不到 2 m 的地区，而其他温暖和潮湿的气候导致相邻高地森林的生物量增加。融入整个海岸景观，气候驱动的高地绿化抵消了海平面驱动的生物量损失，因此气候变化的净影响是增加沿海植被中储存的碳量。这些结果指出了高地和湿地碳趋势之间的根本脱钩，只有通过整合跨传统生态系统边界的观察才能理解这种趋势。这种整体方法可以为量化碳气候反馈和沿海变化的其他方面提供一个模板，这些变化不仅仅局限于海平面上升。这些结果指出了高地和湿地碳趋势之间的根本脱钩，只有通过整合跨传统生态系统边界的观察才能理解这种趋势。这种整体方法可以为量化碳气候反馈和沿海变化的其他方面提供一个模板，这些变化不仅仅局限于海平面上升。这些结果指出了高地和湿地碳趋势之间的根本脱钩，只有通过整合跨传统生态系统边界的观察才能理解这种趋势。这种整体方法可以为量化碳气候反馈和沿海变化的其他方面提供一个模板，这些变化不仅仅局限于海平面上升。