Biodiversity in residential gardens: a review of the evidence base

Abstract

Residential gardens are a principal component of urban green infrastructure throughout the world and their potential positive contributions to biodiversity are increasingly recognised. But the characteristics of gardens reflect the needs, values and interests of individual households. The present review summarises evidence from studies of garden biodiversity published in the scientific literature, describes major themes and identifies important knowledge gaps. A search of the Web of Science database identified 408 published articles on the biodiversity of residential gardens (1981–2022), with numbers increasing over time and a strong bias towards Europe (32.1%) and North America (23.8%). Plants and invertebrates were most frequently studied, and species diversity was often correlated with garden size and habitat complexity. Botanic composition and vegetation cover were often positively associated with the diversity and abundance of fauna. Non-native plants contributed substantially to garden plant diversity and evidence from some studies indicated benefits to other species linked to their functional attributes. Intensive management including frequent lawn mowing, fertiliser and pesticide application, and a more formal, ‘neater’ garden appearance were often associated with reduced biodiversity. However, results varied amongst studies, for example in relation to the impacts of mowing frequency on lawn diversity. There was a general paucity of experimental evidence on the impacts of different management regimes on garden biodiversity and few replicated experimental tests of recommended ‘wildlife-friendly practices’. Several studies identified the importance of connectivity amongst gardens and with other green infra-structure for species dispersal and ecosystem functioning. Emerging threats to garden biodiversity include their replacement by development, conversion to hard surfaces and declining plot sizes. Managing these challenges and maximising the biodiversity value of residential gardens requires greater engagement from policymakers and planners, and partnerships between public bodies and private households to co-ordinate local initiatives.

Vegetation density is the main driver of insect species richness and diversity in small private urban front gardens

“…Some efforts have been made to understand the relationships between garden size and biodiversity in the urban setting (Majewska & Altizer, 2018). A recent extensive review of the literature showed that several studies especially link garden size to positive effects for plants biodiversity (Delahay et al, 2023). Garden size being important to insect diversity has also been confirmed by a meta-anlysis, yet importantly only includes studies on larger gardens (Majewska and Altizer, 2020; 6.1m 2 – 70 000m 2 ).…”

Bridging biodiversity and gardening: Unravelling the interplay of socio-demographic factors, garden practices, and garden characteristics

“…The first studies aiming to detect the biodiversity of gardens in Western Europe and North America were conducted at the beginning of the 1990s (Delahay et al, 2023). Interest in the role of urban and suburban gardens in the preservation and support of urban ecosystems has increasingly gained interest since then (Delahay et al, 2023) and showed that even small, but resource-rich, garden habitats can significantly increase insect diversity (Griffiths-Lee et al, 2022) and support ecological services such as pollination, biological pest control or climate regulation (Andersson et al, 2007; Cavan et al, 2021). Gardens can function as ecological corridors or stepping stones for a multitude of organisms in the otherwise barren and often hostile urban landscape and, particularly when they have favourable habitat features (e.g.…”