Green infrastructure: greenwashing or a tangible contribution to urban biodiversity?

What impact does green infrastructure really have on biodiversity in our cities? Associate Editor, Margaret Stanley looks at the recent synthesis and meta-analysis on this topic from Alessandro Filazzola and colleagues.

Swale - Margaret Stanley
Swale in a suburban subdivision. Photo by Margaret Stanley)

Given the impact of urbanisation on biodiversity, there’s been growing momentum around the world for putting green infrastructure into cities. It’s often designed to support ecosystem services, such as stormwater regulation, but with implied benefits for biodiversity. The question is, does green infrastructure actually benefit biodiversity? A recent Review by Filazzola et al examines the literature and analyses the evidence for green infrastructure providing biodiversity benefits.

The good news is that the authors found green infrastructure does enhance biodiversity more so than its conventional infrastructure equivalents. Not all green infrastructure is equal though in terms of biodiversity benefits. The study found that, while bioswales were better than conventional roadsides, and green roofs better than bare roofs, biodiversity on green walls was not different to that on building walls.

Likewise, not all species are the same. Vertebrates consistently did better on green, as opposed to conventional infrastructure, but results for invertebrates were inconsistent. This is likely due to taxa-specific responses to green infrastructure and potentially the ecological traps they may inadvertently create. The authors suggest functional traits might be a more useful means of assessing biodiversity responses to green infrastructure.

Green infrastructure research does have some ways to go to address the issue of biodiversity benefits. The authors had to exclude 91% of green infrastructure papers from their meta-analysis, simply because the papers did not include biodiversity measures, or the research neglected basic experimental design, including controls and replication. It seems that this field of applied ecology is ripe with opportunities for rigorous and novel research.

Read the full Review, The contribution of constructed green infrastructure to urban biodiversity: A synthesis and meta-analysis in issue 56:9 of Journal of Applied Ecology.

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