Analysis of the evolution, losses and gains of tidal wetlands in the Bohai Rim based on image data cube

Abstract

Under the influence of challenges posed by both human and natural factors, tidal wetlands in the Bohai Rim have been confronting severe threats. It is imperative to comprehend the evolution, as well as the losses and gains of tidal wetlands in the Bohai Rim, for effective coastal management and planning. However, the dynamic fluctuations in the losses and gains of tidal wetlands in this region are frequently overlooked. In this study, employing image data cubes and frequency method, we systematically monitored tidal wetlands in the Bohai Rim spanning the period from 1986 to 2022. Additionally, we performed an exhaustive analysis of the evolution, losses, and gains of tidal wetlands within the provinces and municipality surrounding the Bohai Rim, as well as a detailed analysis of typical areas. This study unveiled three key findings. Firstly, tidal wetlands in Liaoning, Hebei, Tianjin, and Shandong had experienced significant declines of 42%, 66.3%, 71.08% and 60.52% from 1986 to 2022, respectively; they had contracted spatially and changed from a contiguous complete distribution to a scattered fragmented distribution. Secondly, reclamation and erosion had led to the loss of tidal wetlands, while sedimentation had led to the gain of tidal wetlands. The loss area of tidal wetlands caused by reclamation and erosion, as well as the gain area of tidal wetlands caused by sedimentation, had exhibited fluctuating changes from 1986 to 2022. Finally, the area of tidal wetlands in the Liaohe River Delta, Tianjin Port, and Yellow River Delta had decreased by 46.48%, 74.96% and 22.36% from 1986 to 2022, respectively; and tidal wetlands in these three typical areas had spatially contracted. Our findings offer a fresh perspective and a solid scientific foundation for the effective management and strategic planning of tidal wetlands in the Bohai Rim region.