URBAN GREEN INFRASTRUCTURE AND BIODIVERSITY: A META-ANALYSIS OF GLOBAL CITY TRENDS

Abstract

Urban green infrastructure (UGI) is now a source of environmental protection against the adverse impacts of urbanization and promotion of biodiversity in rapidly urbanized cities.  It is a meta-analysis of the findings of 80 peer-reviewed articles conducted to date at 25 sites in 31 cities across the world to understand the impact of various forms of green infrastructure, such as parks or green roofs and vegetated corridors, on urban biodiversity.  The parameters we considered were city governance quality, climate zone, policy integration at city level along with important biodiversity indicators such as species richness, Shannon index and Simpson index.  Basing on the results, UGI is found to be a substantial contributor to urban biodiversity with a pooled mean effect size (lnRR) of 0.42 (95% CI: 0.31-0.53), and therefore, it is found that it has moderate but consistent ecological advantages.  The most species richness was found in temperate cities with sound urban government and integrative policy structures.  Longitudinal study also depicted that gains in biodiversity increase with time particularly when researches take longer than 10 years.  Meta-regression uncovered that the quality of governance (p < 0.01) and green space connectivity (p < 0.05) produced strong evidence concerning the outcome of biodiversity.  Although such trends are positive, a large amount of variance existed between studies (I 2 = 57.3%). That happened largely due to differences in study design, climate and the scale of the green interventions.  Moreover, though 70 percent of the research discussions discussed the framework of urban policies, a small percentage of 45 percent discussed being fair and inclusive of all, indicating a substantial variation in implementation.  Funnel plots and the tests of Egger showed no publication bias at all hence giving the data further credibility.  Overall, the research demonstrates that properly planned and location-specific UGI assists cities in being more resilient to environmental changes and assists in achieving the Sustainable Development Goals (SDGs) associated with life on land, climate goals, and cities resistant to change.  In order to make the best of biodiversity, however, the governance inclusion, long term ecological monitoring, and socio-spatial justice will require to be at the top of the list in terms of green infrastructure arrangements in future cities.