Dynamic Changes in Landscape Pattern of Mangrove Wetland in Estuary Area Driven by Rapid Urbanization and Ecological Restoration: A Case Study of Luoyangjiang River Estuary in Fujian Province, China

Coastal wetlands are natural complexes situated between terrestrial and marine ecosystems and are one of the most productive ecosystems in terms of global biomass production. However, under the influence of intensive human activity, global coastal wetlands have undergone rapid degradation. In this study, RS technology, landscape ecology, and object-oriented methods were used to interpret remote sensing images from different periods and analyze the dynamic changes in landscape patterns and their driving mechanisms in coastal wetlands in the Luoyangjiang River estuary from 1983 to 2021 by considering changes in the landscape pattern index. The results show that the patch areas of all the types of wetland landscapes in the Luoyangjiang River estuary changed, and the patch areas of mangroves and Spartina alterniflora increased. The patch density of the coastal wetlands increased significantly, the index of mangrove aggregation increased, and the index of separation decreased. From the perspective of the overall characteristic value of the landscape pattern, the landscape diversity index and the evenness index of the study area gradually increased, and the difference in the proportion of different types of landscape was reduced. Additionally, the patch number and patch diversity significantly increased, the maximum patch index and the spread index decreased, and the landscape separation index significantly increased. Rapid urbanization and the implementation of many ecological restoration projects were shown to be the main factors driving changes in the landscape indices of coastal wetlands in the Luoyangjiang River estuary. In the study period, rapid urbanization significantly reduced the area of coastal wetlands, and the implementation of ecological restoration projects increased the fragmentation, heterogeneity, and dispersion of wetland landscapes in the study area and decreased the aggregation of wetland landscapes. Moreover, the distribution of all the types of landscapes gradually became more uniform.