Abstract: Background & Aims: Habitat degradation and loss caused by human activities pose a major threat to wildlife worldwide. This study focuses on the coastal waters of Southeast China. Through the integration of multi-temporal Landsat satellite remote sensing data with socioeconomic indicators, we systematically reveal the spatial patterns and driving factors of coastal reclamation activities over the past three decades (1990-2020). Furthermore, the method of minimum convex polygon (MCP) is employed to analyze the impacts of these reclamation activities on the habitats of Chinese white dolphin (Sousa chinensis), a representative cetacean species in coastal ecosystems. These findings provide scientific support for optimizing China’s marine ecological redlines and formulating conservation strategies for endangered marine species. Results: We revealed that driven primarily by regional population density (r = 0.638, P < 0.001) and per capita regional GDP (r = 0.635, P < 0.001), the cumulative coastal reclamation area in the study region reached 1,683.20 km² with an annual average reclamation intensity of 0.30 hm²·a⁻¹·km⁻¹ over the past three decades, exhibiting a distinct spatial pattern characterized by "higher intensity in the north, lower intensity in the south, and significant clustering in estuarine zones." The extensive coastal reclamation activities have caused varying degrees of impact on local populations of Chinese white dolphin: the Xiamen Bay population exhibited the highest proportion of habitat loss (9.03%), with a coastal reclamation intensity of 0.46 hm²·a⁻¹·km⁻¹ in its habitat, followed by the Pearl River Estuary population (4.63%, 0.43 hm²·a⁻¹·km⁻¹), while the southwest waters of Hainan showed the lowest loss proportion (0.06 %, 0.02 hm²·a⁻¹·km⁻¹). Notably, only 8.25% (818.94 km²) of the existing coastal habitats for Chinese white dolphin are located within protected areas, revealing significant conservation gaps. Conclusion & Recommendation: There are urgent actions required to: (1) establish an integrated land-sea conservation framework to protect the existing habitats and enhance connectivity; (2) develop a population dynamics monitoring system based on individual identification; and (3) construct an adaptive management system encompassing "monitoring-assessment-regulation" workflows.

Key words: Remote sensing imagery, MNDWI, coastal reclamation intensity, habitat, conservation gaps