Coupled Land‐Sea Warming Dominates the Net Land Carbon Uptake Variability in the Greater Bay Area of South China

Abstract

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.

China's conservation and restoration of coastal wetlands offset much of the reclamation‐induced blue carbon losses

“…Enhancing the carbon sequestration capacity of existing coastal wetlands needs further consideration in coastal wetland management, as our study found that 75.4% of SOC stocks were gained from unchanged coastal wetlands over the last three decades. However, the SOC stock in existing coastal wetlands would be exposed to threats of land‐sea warming (Fan & Li, 2022), Spartina alterniflora invasion (Xia et al., 2021), and sea‐level rise (Wang et al., 2019). The SOC stocks in mangroves and salt marshes might be substantially reduced after S. alterniflora invasion (Xu et al., 2022), and more efforts are suggested to focus on restoring native vegetation.…”

The risk of concurrent heatwaves and extreme sea levels along the global coastline is increasing

“…Coastal areas are the frontlines of climate change [1][2][3] . Both heatwaves over land and extreme sea levels pose a serious threat to coastal communities in the face of climate change [4][5][6][7] .…”