Spatial pattern of critical wetland patches and its influencing factors in a coastal area, North China

Knowing the spatial pattern of critical wetland patches has an important significance for the restoration and protection of wetland ecosystems. However, the spatial pattern of critical wetland patches in coastal areas is not well understood, and its influencing factors are also unclear, especially in coastal areas. In this study, landscape indices were used to study the spatial pattern of the wetlands in the Hebei-Tianjin coastal area, North China. Correlation analysis, analysis of variance, and structural equation modeling were used to study the influences of environmental and human factors. The results revealed that a total of 211 important wetland patches were located in the Hebei-Tianjin coastal area. The average area of these patches was 182.38 ha, the largest patch was 15,173.32 ha, and the smallest patch was 1.10 ha. The coefficient of variation of the patch area was 6.11, indicating a strong variation. The landscape indices that reflect the distribution characteristics (Distribution-Indices) had higher values in the south than in the north, while the landscape indices that reflect the shape characteristics (Shape-Indices) had lower values in the south than in the north. This indicates that the critical patches in the south were more aggregated, but their shapes were simpler than those in the north. The soil type and temperature were two important environmental factors, and the population density, gross domestic product, and aquaculture were important human factors that influenced the landscape pattern of the wetland patches. Both the environmental factors and human factors influenced the Distribution-Indices more than the Shape-Indices. The environmental factors mainly exerted direct effects on the Shape-Indices, while they had both direct and indirect effects on the Distribution-Indices. The human factor exerted a significantly higher effect on the distribution indices compared to the environmental factors, while their effects were similar for the shape index. The results of this study suggest that human disturbances should be controlled, especially in protecting the distribution of wetlands.