Urban biodiversity by design: A multi-taxa, causal evaluation of targeted habitat interventions and ecological ecosystem across major Chinese cities

Rapid urbanization in China fragments habitats and simplifies green space structure, but cities are increasingly piloting compact “ecological micro-interventions” whose cross-taxa benefits remain weakly quantified. This study causally evaluates five scalable interventions native flower strips, seasonal unmown refugia, hygiene-protocol bee hotels, bird/bat nest boxes, and shaded riparian “dark corridors”—on plants, soil microbiota, pollinators, birds, and bats across 12 major Chinese cities (Beijing, Shanghai, Guangzhou, Shenzhen, Chongqing, Chengdu, Wuhan, Nanjing, Hangzhou, Xi'an, Tianjin, and Suzhou) during 2012–2024. We integrate 13,962 site-years of observations (vegetation plots, soil eDNA/metabarcoding, pan-trap & transect pollinators, standardized bird point counts, full-spectrum bat acoustics) with annual remote-sensing covariates (NDVI, NDBI, and summertime land-surface temperature). A hierarchical Bayesian multi-taxa occupancy–abundance model links interventions to guild-level responses; a city-block matched difference-in-differences design identifies causal effects; and structural equation modeling partitions direct habitat effects from microbiome-mediated pathways. Results indicate that (i) connected dark corridors reduce nocturnal illuminance by 0.8–2.1 lx and increase bat activity by 21% (95% CI: 12–30%), strongest along restored riverfronts in Wuhan and Chengdu; (ii) unmown refugia extend season-long floral continuity and raise pollinator richness by 25% (16–34%), with bird insectivory indices up 11% via prey spillovers; (iii) bee-hotel hygiene (≤6 mm apertures; 36-month cleaning) cuts parasite load by 39% (27–51%) and lifts cavity-nester occupancy by 23% (13–32%); (iv) native flower strips increase plant α-diversity by 0.35 Shannon units and boost arbuscular mycorrhizal fungal abundance by 20% (11–29%); and (v) nest boxes placed <8 m within multilayer vegetation improve passerine breeding success by 14% (5–23%), particularly in Shenzhen and Hangzhou where shrub layers are intact. Networked micro-interventions, paired with microbiome-aware management and low-light riparian design, deliver measurable, multi-trophic biodiversity gains in dense Chinese cities and provide an actionable template for municipal biodiversity net-gain policies. • Multi-taxa framework enhances urban biodiversity across Chinese cities. • PRISMA-based synthesis integrates 184 studies from 2012 to 2024. • Ecological connectivity boosts multi-trophic richness by over 20%. • Native vegetation and soil microbiota improve ecosystem functionality. • Governance and citizen engagement strengthen biodiversity outcomes.