A Melbourne study assessing bat, bird, and insect presence in urban habitats found that increasing volume of understory vegetation and percentage of native vegetation had positive effects on populations. A 30%-120% higher occupancy by bats, native birds, beetles, and bugs was observed with an increase in understory volume from 10% to 30%. The study also found 10%-140% higher occupancy across all native taxa with an increase in proportion of native vegetation from 10% to 30%.
Threlfall, Caragh G., Luis Mata, Jessica A. Mackie, Amy K. Hahs, Nigel E. Stork, Nicholas S. G. Williams, and Stephen J. Livesley. Increasing biodiversity in urban green spaces through simple vegetation interventions. Journal of Applied Ecology, 54 (2017): 1874-1883. https://doi.org/10.1111/1365-2664.12876.