Satellite reveals severe disturbance of the native invasive species Derris trifoliata on the mangrove forests in the Beibu Gulf, China

Mangroves provide essential ecological functions and services but face increasing external disturbances, leading to degradation and even mortality. While most studies focus on external drivers of mangrove decline, the role of internal factors remains underexplored. Derris trifoliata, a native climbing vine associated with mangroves, has been reported to cause localized degradation and mortality in recent years. However, the lack of spatial distribution data on D. trifoliata hinders comprehensive mangrove health assessments and management efforts. Here, we developed a multi-level automated classification method integrating spectral characteristics and phenological information to detect D. trifoliata using time-series Sentinel-2 imagery on the Google Earth Engine platform. Focusing on the Beibu Gulf mangrove wetlands, we found that D. trifoliata exhibits distinct seasonal greenness variations and unique spectral reflectance, enabling its effective identification and differentiation from invaded mangrove patches, terrestrial vegetation, and salt marshes. This approach achieved an overall classification accuracy of 93.7 % in the Beibu Gulf region. In 2023, the total D. trifoliata coverage in the coastal zone was 220.49 ha, with 83.14 % (183.33 ha) concentrated in Beihai City and 73.29 % (161.59 ha) distributed in the Lianzhou Bay estuarine delta. D. trifoliata primarily invaded true mangrove communities, especially Aegiceras corniculatum stands, covering 155.51 ha (70.53 % of total invaded area).These results demonstrate the effectiveness of satellite remote sensing in detecting such ecological disturbances and quantify the considerable impact of D. trifoliata on Beibu Gulf mangroves, highlighting the need to prioritize monitoring of its threat to specific mangrove communities (e.g., A. corniculatum).