Bird richness as a mediator between greenspace and mental health relationships

Neighborhood greenspaces are widely known to benefit bird diversity and human mental health. However, whether bird richness mediates the relationship between greenspace and mental health is unknown. We ascertain such mediation effects in 294 census tracts in Los Angeles City. We obtained greenspace data from one-meter resolution satellite imagery, bird species data from eBird citizen science datasets, and prevalence of poor mental health from the US Centers for Disease Control and Prevention. Mediation analysis combined with spatial error models was used to assess the mediating effects while controlling for geographic, demographic, and socio-economic factors. We found that the higher greenspace percentage was associated with increased bird richness (β = 0.188, p < 0.001), and such bird richness was associated with reduced prevalence of poor mental health (β =  − 0.020, p = 0.010). The bird richness partially mediated the relationship between the greenspace percentage and the prevalence of poor mental health, as evidenced by a decrease in coefficient efficiency from − 0.020 to − 0.017. Our findings underscore the need for public health policymakers, landscape architects, and greenspace managers to consider biodiversity-friendly strategies in the design of urban greenspaces to enhance both wildlife habitats and human mental health.