Restorative effects of urban biodiversity: a study based on age differences using multigroup structural equation modeling.

Rapid urbanisation has exacerbated public mental health burdens, and contact with urban green spaces is widely promoted as a low-cost restorative countermeasure. Yet the mechanistic pathways through which multisensory nature perception confers psychological benefit - and whether these pathways vary systematically across the human lifespan - remain poorly characterised. Here we report a quasi-experimental interventional field study conducted along three ecologically stratified walking trails in a large urban park in Fuzhou, China (N = 360; young adults, 18-35 yr.; middle-aged adults, 36-59 yr.; older adults, ≥60 yr). Using multi-group structural equation modelling (MG-SEM) restricted to the natural trail subsample (n = 240), we show that nature trails significantly elevated positive affect (p < 0.001), with visual plant complexity and birdsong emerging as the primary correlates of perceived restorativeness. Crucially, the indirect association linking perceived biodiversity to positive affect via PRS exhibited pronounced age-cohort variations, becoming prominent and highly significant specifically within the older adult cohort: young adults β = 0.052 (p = 0.138); middle-aged adults β = 0.219 (p = 0.051); older adults β = 0.574 (p < 0.001). These findings suggest that older individuals are more profoundly dependent on high-quality multisensory nature experiences to sustain psychological well-being - a pattern consistent with the cognitive resource depletion hypothesis of ageing. Our results provide actionable evidence for designing age-inclusive therapeutic landscapes and biodiversity-informed urban green infrastructure.