Urban landscape thresholds for bird diversity in China’s major cities

Cities face significant biodiversity loss, but the thresholds of urban landscape alterations causing this loss remain unclear. Bird diversity serves as a key indicator, yet its large-scale response to landscape changes requires further exploration. Bird diversity is affected by multi-dimensional landscape and environmental factors; however, it is still unclear which variables play a major role and under what threshold conditions different variables increase or decrease bird diversity. This study used public datasets and citizen science bird records to quantify bird diversity and landscape patterns across China’s 43 major cities. Generalized additive models (GAMs) were employed to analyze bird diversity responses to landscape metrics and identify landscape thresholds. Our findings show that high bird diversity is predominantly observed in low-latitude and eastern coastal cities, and 42 cities hosting threatened species. Urban bird diversity distribution is non-linearly influenced by landscape patterns, and the main driving factors are the aggregation and coverage of forests and water bodies. We identified nine landscape thresholds conducive to maintaining urban bird diversity, recommending the preservation of 6.4~17.9% of forest cover and more than 10.9% of water bodies in cities, alongside strategies to optimize the connectivity of both green and blue spaces. While the thresholds linking bird diversity indicators to urban landscape metrics are not fully generalizable, certain robust thresholds offer valuable insights for landscape management, presenting a novel approach to bird conservation amidst urbanization.