Urbanization as the main cause of ecological environment deterioration in cross-border coastal zones of northeast Asia

The coastal zone, as a transition zone connecting terrestrial and marine ecosystems, has a relatively unique ecological environment. It is also one of the regions with the most intense human activities, highly sensitive to global changes, and has a fragile ecological environment. Therefore, it is crucial to accurately and timely assess the spatial and temporal patterns of ecological risks in the context of global changes. This study systematically assessed the ecological risks in the transboundary coastal zone of Northeast Asia from 1990 to 2020. The results show that the ecological environment in the transboundary coastal zone of Northeast Asia improved significantly over the past 30 years, and the greatest improvement occurred between 2000 and 2010. Among the five risk levels, High and Low increased, while Medium declined. The areas of ecological risk at the High and Low levels increased by 2,979 km² and 4,554 km², respectively. The ecological quality was highest on the Chinese and Russian sides of the study area, while the Republic of Korea and Japanese sides are considered to be more disturbed, with urbanization being the main factor affecting the coastal ecological quality in this region. On the Democratic People’s Republic of Korea side, environmental protection policies effectively improved ecological quality between 2000 and 2010, with a 28% reduction in high ecological risk in 2010 compared to 2000. The results of this study provide a scientific basis for ecological protection and sustainable management in the Northeast Asia region.