Coastal wetlands are located in the ecotone of interaction between the land surface and sea, and anthropogenic activities extensively interfere with these wetlands through the reclamation of large tidal wetlands and destruction of the function of the ecosystems. In this study, we investigated the dynamic evolutionary characteristics of the Bohai Rim coastal area over the past 40 years using the Modified Normalized Difference Water Index, the fractal dimension, object-oriented classification, the land-use transfer trajectory, and regression analysis. Additionally, we quantified and monitored the evolution of reclamation and analyzed the correlation between reclamation and coastal wetlands based on 99 Landsat-2, -5, and -8 images (at 60 m and 30 m spatial resolution) over the period 1980–2019. The results showed that (1) the coastline of the Bohai Rim increased by 1 631.2 km from 1980 to 2019 with a zigzag variation. The artificial coastline increased by 2 946.1 km, whereas the natural coastline decreased by 90%. (2) The area of man-made wetlands increased by 3 736.9 km2, the area of construction land increased by 1 008.4 km2, and the natural wetland area decreased by 66%. The decrease of tidal flats is the main contributor to the decrease of natural wetland area (takes account for 91.1%). Coastal areas are affected by intense human disturbance, which was taken place across a large area of tidal flats and caused the landscape to fragment and be more heterogeneous. The coastal zone development activities were primarily concentrated in the southern Laizhou Bay, the Yellow River Delta, the Bohai Bay, the northern Liaodong Bay, and the Pulandian Bay. The solidified shorelines and increase in sea level have resulted in intertidal wetlands decreasing and impaired wetland ecology. (3) There is a good agreement between reclamation and the size of the coastal wetlands. Both land reclamation and the reduction in coastal wetland areas are significantly related to the population size, fishery output value, and urbanization rate. In summary, human activities, such as the construction of aquaculture ponds and salt pans, industrialization, and urbanization, are the primary forces that influence the environmental changes in the coastal region. This study is beneficial for establishing and improving the systems for the rational development and utilization of natural resources and provided theoretical references for restoring wetland ecology and managing future reclamation activities in other coastal zone-related areas.
Figure 1. Dynamics of the Bohai Rim coastal zone from 1980 to 2019 (red boxes show the hotspots of reclamation changes for the Laizhou Bay, the Yellow River Delta, the Bohai Bay, the Liaodong Bay, and the Pulandian Bay, respectively).
Figure 2. Spatial and temporal evolution atlas of land-use types in the Bohai Rim from 1980 to 2019 (the Overall Accuracy from 1980 to 2019 was 83%, 87%, 85%, 87%, 89%, 92%, 90%, 89%, and 93%).
Figure 3. Map of coastal wetlands structure transformation in the Bohai Rim from 1980 to 2019.
Figure 4. Changes in landscape indices in the Bohai Rim from 1980 to 2019.
Figure 5. Dynamic changes in the tidal flat reclamation in the Bohai Rim (the RMSE values from 1980 to 2019 was 28.2, 25.2, 23.5, 23.1, 22.5, 21.0, 19.4, 19.1, and 17.9).
Figure 6. Changes in the proportion of reclamation and the tidal flat in the Bohai Rim.
Figure 7. Significant change regions of reclamation in the Bohai Rim.
Figure 8. Correlation between reclamation and the tidal flat in the Bohai Rim.