Space-time cube reveals escalating light pollution in China's national parks: impact of boundary geometry and human activities (1992–2021)

Light pollution has become a significant threat to global biodiversity and ecological health. With the increase of urbanization, protected areas such as national parks are increasingly affected by light pollution. Using the space-time cube model, the spatiotemporal patterns of light pollution and its correlation with multiple factors in five major national parks in China (Panda, Northeast Tiger and Leopard, Hainan Tropical Rainforest, Sanjiangyuan, and Wuyi Mountain) were analyzed from 1992 to 2021. The results show a significant upward trend in the light pollution indices across all five parks. The total nighttime lighting index (TNLI) experienced a 52.2-fold increase, while the mean nighttime lighting index (MNLI) rose by a factor of 1.1, the maximum nighttime lighting index (MANLI) by 0.6, and the total nighttime light area (TNLA) by 39-fold. Light pollution is influenced by park shape complexity and is mainly concentrated in boundary zones, window areas, settlements, and roads. The impact of building areas and human activities within park and outside the 1 km buffer zone on light pollution levels is significant, especially outside the park. These findings provide critical references for light pollution control in national parks, emphasizing the need for differentiated management strategies, optimizing park boundary shapes, setting up external buffer zones, and controlling light pollution both within and outside the parks to effectively protect biodiversity and ecological health.