Unequal Land and Water Changes Between Nations Driven by International Boundary Rivers: Mapping and Temporal Analysis of Shared Borders Between China and Its Neighbors

Abstract

International Boundary Rivers (IBRs), as natural political frontiers, constitute one-third of China's land borders. However, a lack of systematic monitoring has led to a limited understanding of the distribution of these politically significant rivers and the potential risks posed by their dynamic nature. Here, we present the first comprehensive inventory and dynamic analysis of over one hundred IBRs (totaling ∼7,500 km) between China and 10 neighboring countries, quantifying the unequal changes they induced between nations over the past 36 years. Our findings reveal that although China's IBRs are numerous, their water distribution and dynamics are predominantly controlled by large northeastern systems, such as the Amur River. Over the last 36 years, these rivers have undergone widespread morphological changes and migration, with maximum channel shifts exceeding 1 km. Most IBRs are dominated by the Permanent-to-Seasonal transition, indicating a general decline in stability. Critically, the asymmetric nature of river migration has subjected riparian nations to unequal erosion and deposition, resulting in physical land gains and losses. This pattern is particularly pronounced along the large IBRs bordering Russia and North Korea, significantly affecting water resource allocation and land use. Furthermore, while bilateral treaties stipulate national borders remain fixed irrespective of river changes, the incessant movement of IBRs has led to the emergence and disappearance of over a hundred river islands. These sensitive changes create potential territorial risks. We argue that IBRs are geopolitical water bodies demanding urgent attention, and this study underscores the urgency of collaborative efforts among nations to maintain their stability.