As Earth's warming is driven by anthropogenic activities (e.g., urbanization), land and ocean warming significantly affect the net carbon uptake (NCU) of global ecosystems. However, the driving mechanism of coupled land‐sea warming on the NCU under rapid urbanization in coastal areas remains poorly understood. Here, we used long‐term remote sensing and meteorological observation data combined with spatial analysis and multivariate statistical methods to study the impact of coupled land‐sea warming and urbanization on land net primary productivity (LNPP, a proxy of the net land carbon uptake) in the Guangdong‐Hong Kong‐Macao Greater Bay Area (GBA), a rapidly urbanizing and climatically vulnerable area of South China. We found that the total LNPP decreased by 0.40 TgC from 1985 to 2015 and declined suddenly after 2003, driven by the reduced relative humidity and increased vapor pressure deficit (VPD). The increased VPD was caused by coupled land‐sea warming, and the indirect effect (γ = −0.51, p < 0.001) of coupled land‐sea warming on LNPP variability was much stronger than the direct effect (γ = −0.16, p < 0.05). In addition to the severe decline in the LNPP (0.20 TgC) induced by coupled land‐sea warming, urbanization caused a large loss in LNPP (0.16 TgC), which accounted for 40% of the total LNPP loss. Our findings can support future predictions of regional carbon uptake and inform future climate change mitigation strategies to implement carbon peak and neutrality goals.

Mangrove wetlands are rapidly being lost due to anthropogenic disturbances and natural processes, such as sea-level rise (SLR), but are also recovering as a result of conservation efforts. Accurate and contemporary mangrove maps to detect their distribution and changes are urgently needed to understand how mangroves respond to global change and develop effective conservation projects. Here, we developed a new change detection algorithm called temporal consistency checking combining annual classification and spectral time series (TCC-CS) for tracking mangrove losses and gains. Specifically, mangrove change events were determined by measuring the deviation of greenness and wetness of candidate change segments from automatically collected mangrove reference samples. By applying to the world’s largest mangrove patches, we monitored the 35-year mangrove trajectory in the Sundarbans from 1988 to 2022 using all available Landsat images on the Google Earth Engine platform. In the Sundarbans, 18,501.89 ha of mangroves have been gained, but these have been offset by losses of 27,009.79 ha, leading to a net mangrove loss of 1.42% (8507.9 ha) in the past 35 years. We further mapped the pixel-level change agents and found that SLR-induced erosion and degradation, instead of human activities, were the major drivers of losses in the Sundarbans. Trend analysis on loss agents indicates that mangrove losses caused by human activities, such as the expansion of croplands and aquaculture ponds, have declined, but SLR is still a persistent threat to mangrove wetlands in this iconic mangrove area. Our study provides a computationally efficient methodology for examining large-scale mangrove changes, and the resultant annual mangrove maps provide strong support for mangrove conservation in the Sundarbans.

Human activities and climate change have profound effects on marine ecosystems, leading to changes in ecosystem functionality and even reduced resilience. Hence, a systematic assessment of the marine ecosystem resilience and the drivers of resilience is needed. This study provides an approach to help measure the resilience of reduction marine ecosystems by calculating early warning signs of marine net primary productivity, while introducing fishing activities and environmental data in the study area to evaluate the factors affecting marine ecosystem resilience. The results showed that in 36.29% of the Chinese exclusive economic zone, resilience was likely to be significantly decreased. There was a non-linear relationship between fishing activities and indicators of resilience reduction, with pixels with high-intensity fishing activities being more susceptible to resilience reduction. Fishing regulations are urgently needed in areas where marine ecosystem resilience may be reducing. Effective management and protection of marine ecosystems require assessment of the spatial overlap between marine ecosystems states and human activities. This study provides a scientific basis for sustainable management of social-ecological systems by comparing high-precision fishing data to marine environmental data, thereby analysing marine ecosystem resilience through the use of early warning indicators.