The effect of urban green roof design on beetle biodiversity

Sydney Gonsalves,Olyssa Starry,Stephan Brenneisen,Alexander Szallies

doi:10.1007/s11252-021-01145-z

Sydney Gonsalves, Olyssa Starry + Show 2 more

Open Access

https://doi.org/10.1007/s11252-021-01145-z

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Abstract

The biodiversity conservation value of urban green spaces depends in part on design and management. The importance of habitat quality and complexity to species diversity has led to the suggestion that habitat design elements—varied substrate, greater plant diversity, logs or stones—would support invertebrate diversity on green roofs. To evaluate this possibility, we conducted pit-fall trap sampling on three green roofs of simple design (intended primarily for stormwater management), three habitat roofs, and five ground-level green spaces, in the Portland, Oregon metropolitan area. Beetles (Coleoptera) were sampled as representatives of total invertebrate diversity. Diversity was compared using sample coverage and Hill numbers to account for differences in sample intensity and fundamental differences in species diversity. Both habitat roofs and ground sites consisted of just over 20% native species, while stormwater roofs had about 5% native species, all of which were considered pests. We collected a greater abundance of beetles on the ground compared to roof sites like others have shown. However, when sample completeness is taken into account, habitat roofs had greater Shannon diversity compared to both ground and stormwater roof sites. Habitat roofs had the fewest dominant species representing 5% or more of total abundance, but also the lowest percent of species represented by singletons (27%). These results indicate that green roofs can support different beetle communities compared to those present at ground-level urban green spaces; our results also support previous findings that biodiverse design can reliably increase green roof diversity compared to more simply designed roofs.

Highlights

Urban areas represent one of earth’s few ecosystems that are increasing in extent while other types of habitat continue to be lost through degradation, fragmentation, and land-use conversion (Pickett et al 2011; Pataki 2015; UN 2016)
We found that green spaces on the ground have a richer beetle community with a greater number of both beetle species and individuals than green roofs, a finding consistent with other studies of insects on green roofs (MacIvor and Lundholm 2011; Tonietto et al 2011)
Our finding that habitat roofs had greater richness and Shannon diversity than the more designed stormwater roofs supports the habitat complexity hypothesis, since habitat roofs had more layers of vegetations, varied substrate depth, and elements such as logs and stones

Summary

Introduction

Urban areas represent one of earth’s few ecosystems that are increasing in extent while other types of habitat continue to be lost through degradation, fragmentation, and land-use conversion (Pickett et al 2011; Pataki 2015; UN 2016). This has resulted in species loss on every scale from large mammals to insects to microbes (Burkepile and Thurber 2019; Klink et al 2020). Small ground-level urban green spaces like gardens, lawns, parks, brownfields, and historic land cover remnants have been shown to be important refuges for native species (Croci et al 2008; Lorimer 2008; Pickett et al 2008; Goddard et al 2011). Independent of the differences between roof and ground locations, it could be shown, that green roofs can be permanently populated by stenoecious and Red Data Book listed species, which proves their possible suitability in principle as compensation habitats for urban biodiversity promotion and conservation aspects (Brenneisen 2003; Pétremand et al 2017; Pétremand et al 2018) in comparisons of green roofs to nearby ground-level urban green spaces, other studies found invertebrate species richness and abundance tended to be greater on the ground (MacIvor and Lundholm 2011; Tonietto et al 2011; Ksaizek et al 2012)

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