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

Abstract

AbstractUrbanisation changes the natural ecosystems and vegetation to urban green spaces, and causes insect communities to experience novel challenges for survival. New evidence suggests that urban green spaces, no matter how small, can provide meaningful habitats for insects. Information on design and management of small gardens (<10m2) in dense urban areas is still scarce. In particular, it is hardly known which garden designs provide most benefits to insects. We surveyed 65 small private urban front gardens (μ=1.7m2) in Amsterdam and The Hague in The Netherlands and measured a series of garden attributes thought to be relevant for general, flower-visiting and herbivorous insect species richness and diversity. Plant coverage and richness were the strongest predictors for insect biodiversity and species richness. We found no support for associations with native vs. exotic plants or garden size.Synthesis and applicationsTo strengthen insect biodiversity in the urban environment, we recommend future design of urban green spaces to focus on maximising coverage and richness of vegetation, potentially even using exotic species to fill in the gaps where native plant species cannot survive.HighlightsSmall urban gardens hold large potential for supporting urban insect communitiesTotal vegetation cover was the strongest predictor for insect diversity and richnessPlant richness was the second strongest predictor, but not for herbivorous insectsGarden size had no effect on insect diversity or richnessNative vegetation did not impact insect diversity or richnessAbstract FigureGraphical abstract. Shown are either plus or minus signs indicating a positive or negative trends from the models that predict species richness and Shannon biodiversity of insects, pollinators or herbivores by the design of small urban gardens.*indicates a statistically significant trend at p-value < 0.05. A plus or minus sign without*means a visible statistically non-significant trend. A greyed out square indicates exclusion of the term in the model. A white square indicates non-significant and non-visible trend.