Perceived biodiversity of public greenspace and mental well-being.

Biodiversity is known to promote the mental well-being of urban residents. However, few studies have examined the perceived and empirically measured biodiversity and their potential pathways related to mental health. This study constructed a composite biodiversity index (bio index) using multiple NDVI metrics through Principal Component Analysis (PCA) and validated its effectiveness through a validation experiment. Relying on a survey in two major cities in China (N = 5,895), this study explored how perceived and empirically measured biodiversity are associate with mental well-being (CESD-10 score) through people's perceived psychological restoration, physiological restoration, and satisfaction with greenspace. Pathway analyses were conducted using PLS-SEM to examine the complex interplay of these variables. The results showed that perceived biodiversity was significantly and positively associated with mental health, potentially mediated by perceived psychological restoration, physiological restoration, and satisfaction with greenspace. The total effect of perceived biodiversity on mental health was stronger in Shanghai than in Beijing, with specific mechanisms differing regionally. Empirically measured biodiversity showed an insignificant relationship with mental health. Our finding recommends the importance of integrating perceived biodiversity into urban greening practice to promote mental well-being.