Biological connectivity and its driving mechanisms in the Liaohe Delta wetland, China

Biological connectivity plays a cricial role in maintaining biodiversity and ecosystem function. However, it is poorly understood how to quantify biological connectivity and investigate its mechanisms in estuarine wetlands. In order to address this issue, this study aims to quantify biological connectivity in the Liaohe Delta wetland by utilizing three complementary approaches: the habitat quality simulation, the vegetation connectivity index, and the maximum entropy model. These approaches focused on habitat quality, vegetation, and bird species, respectively. The established criteria for assessing vegetation connectivity blockage and the jackknife method were utilized to identify the primary drivers of biological connectivity. The study found that (1) Habitat quality declined from 1976 to 2020, with a total decrease of 3.2 x 106. (2) Vegetation patches have more fragmented and less connected over the last 45 years. There was also a higher vegetation probability density of Phragmites australis than Suaeda salsa. The area of unchanged P. australis was concentrated within the nature reserve, while the area of unchanged S. salsa was 0, indicating that P. australis was more affected than S. salsa. The vegetation connectivity blockage was 33.16%, with human activities having a greater impact compared to natural suc-cession. (3) The area of suitable habitat for birds constituted 27.48% of the study area. Distance to S. salsa was the main driving factor, followed by the distance to intertidal muds, paddy fields, P. australis, and water sources. The results demonstrate that biological connectivity has generally declined over time, with human activities being a significant contributor. Our efforts to quantify biological connectivity provided clear spatial and tem-poral information on the trends and drivers of biological connectivity in the Liaohe Delta wetland. The results of this study can provide valuable information for conservation efforts aimed at preserving wetland biodiversity.