Impact of global urban expansion on the terrestrial vegetation carbon sequestration capacity

Continuous urban expansion has a negative impact on the potential of terrestrial vegetation. Till now, the mechanism of such impact remains unclear, and there have been no systematic investigations. In this study, we design a theoretical framework by laterally bridging urban boundaries to explain the distress of regional disparities and longitudinally quantify the impacts of urban expansion on net ecosystem productivity (NEP). The findings demonstrate that global urban expanded by 37.60 x 104 km2 during 1990-2017, which is one of the causes of vegetation carbon loss. Meanwhile, certain climatic changes (e.g., rising temperature, rising CO2, and nitrogen deposition) caused by urban expansion indirectly boosted vegetation carbon sequestration potential through photosynthetic enhancement. The direct decrease in NEP due to the urban expansion (occupying 0.25 % of the Earth's land area) offsets the 1.79 % increase due to the indirect impact. Our findings contribute to a better understanding of the uncertainty associated with urban expansion towards carbon neutrality and provide a scientific reference for sustainable urban development worldwide.

Automated summary

Urban expansion has a negative impact on terrestrial vegetation, and its mechanism remains unclear with no systematic investigations. This study designs a theoretical framework to explain regional disparities and quantify the impacts of urban expansion on net ecosystem productivity (NEP). The findings show that global urban expanded by 37.60 x 104 km2 during 1990-2017, contributing to vegetation carbon loss. However, certain climatic changes caused by urban expansion indirectly enhance vegetation carbon sequestration potential. The direct decrease in NEP due to urban expansion offsets the indirect increase, providing insights for carbon neutrality and sustainable urban development.