Assessing the Effectiveness of Large-Scale Ecological Restoration Measures in the Liaohe Estuary Using a Landscape Pattern Perspective

Abstract

In recent years, the Chinese government implemented many policies and actions to restore coastal wetlands. This study focused on assessing how these projects have influenced the landscape patterns of the Liaohe Estuary, an area of critical importance. By analyzing remote sensing images from 2009 to 2022, we determined the spatiotemporal changes in landscape pattern, fragmentation, and conversion. Results showed that (1) Reed (Phragmites australis) fields were the dominant landscape feature and covered 46.3–48.2% of the area; however, road was the serious factor in fragmenting these wetlands. Seepweed (Suaeda salsa) marshes, an iconic and characteristic wetland of the region, gradually expanded towards the estuary and coast over the study years. (2) Landscape fragmentation increased and seasonally changed during the study period and restoration measures actually resulted in more fragmentation of the landscape. (3) Ponds replaced 14.28 km2 natural landscape in the development stage and 40.93 km2 were restored to natural landscape during restoration and maintenance. (4) Active restoration projects caused landscape fragmentation to sharply increase initially, but then fragmentation declined as passive restoration continued in the maintenance stage. This study suggests that road construction should be carefully deliberated in ecologically sensitive areas and that ecological restoration (a combination of active and passive restoration) in the Liaohe Estuary region showed evidence of temporal lag and hysteresis that may be important for research in the future.