The contribution of constructed green infrastructure to urban biodiversity: a synthesis and meta-analysis.
The development of buildings and other infrastructure in cities is viewed as a threat to local biodiversity and ecosystem functioning because natural habitat is replaced. However, there is momentum for implementing green infrastructure (GI), such as green roofs, wetland detention basins and community gardens, that partially offset these impacts and that benefit human health. GI is often designed to explicitly support ecosystem services, including implied benefits to biodiversity. The effects of GI on biodiversity have been rarely quantified, but research on this topic has increased exponentially in the last decade and a synthesis of the literature is needed. Here, we examined 1,883 published manuscripts and conducted a meta-analysis on 33 studies that were relevant. We determined whether GI provides additional benefits to biodiversity over conventional infrastructure or natural counterparts. We also highlighted research gaps and identified opportunities to improve future applications. We determined that GI significantly improves biodiversity over conventional infrastructure equivalents, and that in some cases GI had comparable measures of biodiversity to natural counterparts. Many studies were omitted from these analyses because we found GI research has generally neglected conventional experimental design frameworks, including controls, replication or adequate sampling effort. Synthesis and applications. Our synthesis identified that taxa specificity is an important consideration for green infrastructure (GI) design relative to the more common measurements at the community level. We also identified that ignoring multi-trophic interactions and landscape-level patterns can limit our understanding of GI effects on biodiversity. We recommend further examination of species-specific differences among infrastructures (i.e. green, conventional or natural equivalents) or using functional traits to improve the efficacy of GI implementation on urban biodiversity. Furthermore, we encourage policy makers and practitioners to improve the design of GI to benefit urban ecosystems because of the potential benefits for both humans and global biodiversity.