If you build it, they will come: invertebrates on green roofs

Abstract

Since the industrial revolution, urban expansion has leapt forward and shows no sign of slowing (Horák et al., 2022; Shafique et al., 2018; Wang et al., 2022). This development has led to extensive loss and fracturing of habitat (Cameron et al., 2012; Horák et al., 2022; Parker & Zingoni de Baro, 2019). Retention of remnant vegetation is known to support functional urban ecosystems (Kabisch et al., 2017), therefore, the creation of new green spaces in cities could better support urban biodiversity (Cameron et al., 2012; Kabisch et al., 2017; Mathey et al., 2015; Parker & Zingoni de Baro, 2019). In addition to the ecological benefits that this brings, urban greenery has been seen to improve the mental and physical health of urban residents (Burley, 2018; Kabisch et al., 2017; Suppakittpaisarn et al., 2017; Tzoulas et al., 2007), but also provide community areas for recreation and exercise (Jim & Chen, 2006; Shafique et al., 2018). Where ground-level space is unavailable or costly, green roofs can provide a unique solution to introducing greenery into urban areas (Cameron et al., 2012; Horák et al., 2022). While the concept of growing plants on roofs has a long history, the modern practice of installing green roofs has existed for less than 100 years (Wang et al., 2022). Here ‘green roof’ is used as a broad definition encompassing all forms of elevated vegetation built on the roofs of residential, industrial, or administrative buildings. Within the world of green roofs, they can be categorized many ways, such as by substrate depth, vegetation composition, or intended purpose (Chell et al., 2022; Dusza et al., 2020; Jacobs et al., 2022; Rumble et al., 2018; Schrader & Böning, 2006). Green roofs as ecosystems have received little emphasis in the literature, as most research is focused on the design and construction aspects of green roofs (Dvorak & Volder, 2010; Scolaro & Ghisi, 2022; Shuraik et al., 2022). Other ecosystem contexts such as arid and tropical climates, and the paucity of research available, present an exciting prospect for developing a deeper understanding of how these built green environments can support urban biodiversity, and in particular invertebrates. A diverse array of invertebrates could provide myriad ecosystem services to green roofs (Braaker et al., 2017; Fabián et al., 2021; Gonsalves et al., 2022; Mathey et al., 2015; Shafique et al., 2018). Detritivore invertebrates like earthworms and beetles can catalyse soil nutrient cycles, increasing soil quality and subsequently plant health (Ganault et al., 2022; Santonja et al., 2018). Nectivorous and pollinator invertebrates like bees and butterflies can promote flower blooming and increase aesthetic value of a space (Katumo et al., 2022). Predatory invertebrates such as spiders and ladybeetles can control the populations of pest species (Fabián et al., 2021). In addition, these invertebrate communities can also form part of higher order ecological food chains, in particular insectivorous birds and microbats (Partridge & Clark, 2018). The lack of green roof specific research in urban invertebrate ecology is a gap in the literature, and it is important to know exactly where the major gaps are before further investigation can take place. Therefore, we completed a systematic quantitative literature review (SQLR) to identify these gaps, while simultaneously highlighting patterns and common findings in the current research.