Socioeconomics and biodiversity in cities: moving beyond patterns to mechanisms.

Socioeconomic status-biodiversity associations are widely reported in cities. However, most studies remain correlational and cannot distinguish whether socioeconomic status drives biodiversity change, biodiversity shapes socioeconomic outcomes, or whether observed patterns reflect biodiversity gains versus losses. We propose a unifying framework organizing established mechanisms from diverse urban research into four hypothesized causal pathways: (A) investment-driven biodiversity enhancement, (B) disinvestment-driven biodiversity degradation, (C) biodiversity-driven socioeconomic improvement, and (D) biodiversity loss reinforcing socioeconomic decline. This framework supports pathway-specific study designs and helps practitioners anticipate whether biodiversity interventions will reduce or exacerbate inequality. Shifting from pattern description to mechanism identification is essential for credible inference and for informing urban planning and governance interventions aimed at reducing environmental inequality.