Wealth and Altitude Explain Urban Plant Diversity in Residential Areas of Hainan, China

Rapid urbanization worldwide poses significant challenges to biodiversity, as urban habitat fragmentation coexists with diverse landscape forms. Residential areas, a critical component of urban ecology, are essential for understanding the mechanisms that drive biodiversity conservation and the harmonious coexistence of humans and nature. Additionally, the gradient distribution of biodiversity remains a focal point in ecological research, aiding in the comprehension of fundamental species–environment interactions. In this study, we sampled 269 residential areas across fifteen counties and municipal districts on Hainan Island to investigate biodiversity alongside residential characteristics, as well as socio-economic and environmental variables. Utilizing the Generalized Linear Model (GLM), we analyzed the differences and commonalities of plant driving factors through horizontal and vertical two-dimensional gradient models with box plots, Principal Component Analysis (PCA), Principal Coordinate Analysis (PCoA), and path models to examine the existence, distribution, and nature of these gradients. Our findings indicate the following: different plant types are driven by distinct mechanisms; cultivated plants are primarily valued for ornamental purposes, whereas in rural areas, their edible value is emphasized. Urban residential plant diversity was primarily influenced by altitude and fundamentally affected by economic factors. Our analyses identified distinct differences in the driving factors influencing various plant types and established two primary gradients of plant diversity distribution within residential areas: a horizontal gradient influenced by housing prices and a vertical gradient corresponding to changes in elevation. Both gradient models were found to be outcomes of socio-economic factors, highlighting the significant role of economic development in shaping urban biodiversity.