Landscape pattern evolution and ecological risk assessment of the Yellow River Basin based on optimal scale

Rapid urbanization is a global phenomenon that has altered many ecosystems and created ecological risks. Landscape ecological risk (LER) reflects the extent to which ecosystems are threatened by human activities and environmental change. LER can be also employed to effectively monitor and assess environmental quality. A large number of studies have been conducted to explore the LER in the basin from the perspective of Land Use and Land Cover (LUCC). Ecological environmental issues such as land degradation have seriously hindered the sustainable development of the Yellow River Basin (YRB). Based on the LUCC data of the YRB in the four periods of 1990, 2000, 2010 and 2020, this study aims to determine the most suitable spatial analysis scale using the coefficient of variation and semi-variogram, and analyzes the landscape pattern and LER of the YRB. We found that the landscape pattern of the YRB exhibits obvious scale dependence, and the analysis effect is most effective at the scale of 90 km x 90 km. Throughout the study period, the landscape pattern exhibited increasing frag-mentation, a decrease in the degree of aggregation and an increase in the heterogeneity of distribution. In terms of LER, it is in a better state as most of the LER levels have shifted from higher to lower levels, and the proportion of lower and lowest risk is constantly increasing. This study improves the precision of spatial scale investigations and offers valuable insights for future studies on landscape pattern and LER in the basin.