Influence of garden composition and gardening practices on the biodiversity of residential garden: a systematic map

Urban residential gardens are important for urban biodiversity, as they provide resources and habitats for different species, and exhibit comparable species richness and abundance to abandoned urban sites or parks. Although landscape and local parameters shape biodiversity in residential gardens, only local parameters such as garden composition and gardening practices are modifiable by gardeners. However, the knowledge on this topic is not clearly described, which limits the possibility of summarising the results. To fill this gap, we systematically mapped the peer-reviewed articles exploring the effects of garden composition and gardening practices on the species richness and abundance of residential gardens. Using two databases, we collected 3,872 articles. After three-stage screening and critical appraisal, we retained 52 of them. The articles provided 755 instances, with 54% of them presented in just two articles. Apart from these two articles, arthropods are mostly studied, with a focus on butterflies, bees, and spiders. Garden composition is more documented than gardening practices. For garden composition, vegetation surface and richness, garden heterogeneity, and floral resources are the most frequently studied. For gardening practices, the use of pesticides, insecticides and herbicides are often investigated. One knowledge cluster of 14 instances was identified, focusing on the effect of floral resources on bees. This systematic map underlines that despite a growing interest in the biodiversity of urban gardens in general, knowledge about the modifiable parameters that shape residential gardens' biodiversity is still scarce, thus limiting our ability to give relevant advice to the general public on this issue.