Effects of anthropogenic disturbances on the carbon sink function of Yangtze River estuary wetlands: A review of performance, process, and mechanism

Abstract

Estuarine wetlands are an important part of coastal blue carbon and play an essential role in mitigating climate change. However, their geographical location typically exposes them to numerous anthropogenic disturbances. The responses of carbon sink function to changes in ecological factors induced by these disturbances still lack a systematic and comprehensive compendium. To fill this knowledge gap, we selected the Yangtze River estuary, a representative estuary in China, and reviewed the potential effects of anthropogenic disturbances on the carbon sink function of wetlands, with emphasis on the key processes of carbon turnover (including plant carbon fixation and soil respiration) and the microbial mechanisms involved. Most of the reviewed anthropogenic disturbances negatively affected carbon sequestration in the Yangtze River estuary wetlands, either by inhibiting plant growth (e.g., reclamation, siltation of high tidal flats, and hydraulic engineering projects) or by promoting organic carbon decomposition (e.g., reclamation, invasion of Spartina alterniflora, livestock grazing, tidal organic matter input, and eutrophication). By integrating the carbon input and output processes, we argue that reclamation, tidal organic matter input, and eutrophication weaken the carbon sink function of the Yangtze River estuary wetlands, and that some wetlands conservation measures are necessary considering the dual carbon target proposed by China in 2020.

Keywords

• Yangtze River estuary wetlands
• Anthropogenic disturbances
• Carbon sink
• Plant carbon fixation
• Soil respiration