[Spatio-temporal Analysis of Carbon Sequestration of Wetlands in Guangdong-Hong Kong-Macao Greater Bay Area Based on the InVEST model].

Abstract

The carbon sequestration capacity of wetland ecosystems is of great significance for achieving the "carbon peaking and carbon neutrality" goals. Spatio-temporal changes in wetlands and the carbon sequestration capacity of the wetland ecosystem in the Guangdong-Hong Kong-Macao Greater Bay Area （GBA） during 1990 and 2020 were investigated based on long-term series and refined wetlands classification datasets. The results showed that： First, the area of wetlands in the GBA increased from 1990 to 2000 and then decreased from 2000 to 2020. The total wetland area increased by 181.08 km² during the study period, with river channel and reservoirs/ponds as the main growth categories. Wetlands in the GBA were mainly distributed along the banks of the Pearl River and its tributaries, as well as in three coastal areas namely Huangmao Bay, Qi'ao Island, and Shenzhen Bay. Second, the carbon storage changing characteristics of the wetland ecosystem were similar to that of the area, which showed a similar pattern of an initial increased and subsequent decrease during the study period. The carbon storage of the wetlands decreased by 0.12×10⁶ t in the past 30 years. The order of the average carbon storage proportions of the wetland types were reservoir/pond, river channel, coastal beach, inland beach, mangrove, wetland, and lake. Third, the wetland area in the GBA increased, while the carbon storage showed a decreasing trend during the study period. The average carbon storage per unit area of wetlands continued to decrease during the study period, which indicates a continuous decline in the carbon sequestration capacity and quality of the wetland ecosystem, which could be attributed to the encroachment of human activities, such as rice cultivation and aquaculture on a large number of wetlands, leading to a continuous decline in coastal beaches with high carbon sequestration capacity. Although the area of mangrove increased rapidly, yet its area and proportion were too small to offset the carbon sequestration capacity loss induced by the mass disappearance of mudflat, floodplain, and swamp. These findings provide decision-making support for protecting wetlands and enhancing the carbon sink capacity of wetland ecosystems in the GBA.