Effects of residential garden features on biodiversity: A systematic review

In the urban mosaic of habitats, residential gardens can sustain high levels of biodiversity. Although many gardeners are interested in biodiversity-friendly designs, they lack a clear overview of the available evidence to guide their choices, as the scientific knowledge about it remains dispersed. Here, we present a comprehensive synthesis of peer-reviewed articles investigating the relationship between residential garden features and biodiversity. Through a systematic search of Web of Science and Scopus, we identified 3,872 articles and retained 31 after a three-stage screening process and critical appraisal. These articles report the effects of 16 garden features on the richness and abundance of 62 taxonomic groups. Evidence was generally sparse and uneven across garden features and taxa, with many results supported by a few studies. Arthropods were highly documented, contrary to bats, amphibians, or reptiles. Index of garden heterogeneity was the most documented feature and often showed positive effects on birds, bumblebees, and butterflies. However, many studies reported non-significant or contradictory results, limiting broad generalizations. Floral resources showed the most consistent positive effects on pollinators, regardless of their nativness. Lawn area did not show clear effects. Shrub area and tree number and cover were generally beneficial for beetles, birds, earthworms, and wasps, although many other taxa appeared unaffected. Future studies should propose new protocols to study a wider range of garden features, beyond their presence and area, and provide independent replication for poorly documented taxa. Explore the tensions between garden use and biodiversity-oriented design options is also a promising line for future research.