Socioeconomic and spatial inequalities of street tree abundance, species diversity, and size structure in New York City

Abstract

Street trees are often unequally distributed in urban areas, and their physical and structural attributes, such as extent of canopy cover, species composition, and size distribution, are also spatially heterogeneous. Some studies report that inequalities are more prevalent in streetscapes than in private landscapes. Considering the existing inequality issues and public nature of street trees, street tree inequality studies warrant greater attention. However, most existing studies in this field focus heavily on the unequal distribution of tree canopy cover, while disregarding other tree attributes. In this study, seven street tree measures covering tree abundance, species diversity, and size structure were derived from high-resolution satellite images, Google Street View, and street tree census. We then applied the geographically weighted regression to these seven tree measures in New York City, United States, compared street tree inequalities among different socioeconomic groups, and identified inequality hotspots. Our results show that street tree inequalities are greatest with respect to tree abundance and species diversity. Furthermore, race-based and education-based inequalities are most notable, and age-, income-, and household characteristic-based inequalities were also detected based on tree abundance or species diversity. Socially vulnerable areas that suffer the most severe inequalities are clustered in Brooklyn and Queens. Disaggregated street tree inequalities, with explicit recognition of the differentiated distribution of limited tree resources among different social groups and across geographical areas, are critical for effective decision-making to alleviate environmental inequities.