Monitoring Coastal Blue Carbon Ecosystems by Combing Satellite and UAV Remote Sensing Data in Southern China

Coastal blue carbon ecosystems are among the most productive, vulnerable and threatened ecosystems in the world. They play important roles in marine biodiversity maintenance, water purification, nutrient recycling, carbon sequestration and storage. Remote sensing methods have become complementary to conventional surveying methods due to their rapidity, large area coverage, and repeatability of observations. The persistent cloud cover, tidal inundation, variable water turbidity near the coastlines make it necessary to monitor coastal blue carbon ecosystems by combing satellite and Unmanned Aerial Vehicle (UAV) remote sensing data. Here, we presented two examples, which integrate satellite, UAV and field survey data to monitor mangroves, salt marshes, and seagrass beds in Southern China. With multi-source Chinese Earth observation satellite imagery as well as UAV data in 2019 and 2022, we monitored the distribution changes of mangroves and salt marshes in Guangdong province, Guangxi Zhuang Autonomous Region and Hainan province. The mangrove areas increased dramatically, mainly due to the Special Action Plan for Mangrove Protection and Restoration (2020–2025) which aims to increase China’s mangrove area by 70% by 2025. The salt marsh area in Guangxi decreased, partly due to the controlling measurements of the invasive species Spartina alterniflora by the local government. Based on high-spatial resolution satellite, UAV and field data, we showed the spatial distribution map of seagrass beds (Halophila beccarii) near an estuary in Shantou city, Guangdong province in 2020, demonstrating the potential of combing satellite and UAV imagery to monitor seagrass beds on the local scale. With more remote sensing data accumulated due to the frequent satellite overpasses and UAV surveys, further research is required for continued improvements in multi-source remote sensing data fusion techniques designed specifically for blue carbon ecosystem monitoring.