Cities dominated by impervious artificial surfaces can experience a multitude of negative environmental impacts. Restoration of green infrastructure has been identified as a mechanism for increasing urban resilience, enabling cities to transition towards sustainable futures in the face of climate-driven change. Building rooftops represent a viable space for integrating new green infrastructure into high-density urban areas. Urban rooftops also provide prime locations for photovoltaic (PV) systems. There is an increasing recognition that these two technologies can be combined to deliver reciprocal benefits in terms of energy efficiency and biodiversity targets. Scarcity of scientific evaluation of the interaction between PVs and green roofs means that the potential benefits are currently poorly understood. This study documents evidence from a biodiversity monitoring study of a substantial biosolar roof installed in the Queen Elizabeth Olympic Park. Vegetation and invertebrate communities were sampled and habitat structure measured in relation to habitat niches on the roof, including PV panels. Ninety-two plant species were recorded on the roof and variation in vegetation structure associated with proximity to PV panels was identified. Almost 50% of target invertebrate species collected were designated of conservation importance. Arthropod distribution varied in relation to habitat niches on the roof. The overall aim of the Main Press Centre building green roof design was to create a mosaic of habitats to enhance biodiversity, and the results of the study suggest that PV panels can contribute to niche diversity on a green roof. Further detailed study is required to fully characterise the effects of PV panel density on biodiversity.
C. Nash, J. Clough, D. Gedge, R. Lindsay, D. Newport, M.A. Ciupala and S. Connop
Leon Blaustein, Gyongyver J. Kadas and Jessica Gurevitch
Green roofs can provide environmental benefits that include increased building insulation, mitigating urban heat islands, providing aesthetic value, reducing runoff and storm water flooding in urban environments, improving air quality by sequestering pollutants, cooling photovoltaic panels to improve their function, and providing habitat for fauna and flora. Until very recently, improvements of green-roof environmental services had been achieved largely by horticulturalists, engineers, and architects. In recent years, ecologists have increased their participation, implementing ecological theory for enhancing biodiversity, and selecting specific plant assemblages for other environmental services such as carbon sequestration and for providing cooler roofs. Moreover, ecologists can use green roofs as relatively novel habitats for testing and developing ecological theory. This special issue is devoted to fostering input from ecologists for advancing the environmental and ecosystem services of green roofs. A wide range of ecologists can explore the topic of the ecological aspects of green roof design and implementation including island biogeography theory, niche theory and null models, the role of environmental heterogeneity, invasion ecology, and plant selection. They can contribute ecological methodology and study design for strong inference.
Bracha Y. Schindler, Lior Blank, Shay Levy, Gyongyver Kadas, David Pearlmutter and Leon Blaustein
The integration of photovoltaic (PV) panels and green roofs has the potential to improve panel efficiency to produce electricity and enhance green roof species diversity and productivity. In this review, we provide an overview of research on the effects of green roofs on PV panel electricity production, and predict the expected effects of the PV panel on green roof plant communities. Previous studies suggest that PV panels are more efficient above a green roof than above several types of conventional roofs due to the cooling effect of green roofs on the temperature-sensitive PV cells. Some ecological studies on shade suggest that shade imposed by panels may enhance the biotic productivity of green roofs. Shade is often shown to be important for seedling survival, particularly in arid environments – so the effect of shade on plants may depend on climate and irrigation. Previous studies also suggest that shade variations over the roof area may enhance plant diversity, as such heterogeneity creates niches of light and moisture levels that are appropriate for a diversity of plants. These positive effects on plant diversity may lead to increased arthropod diversity as well. Additional replicated studies are needed to test the reciprocal effects of green roofs and PV, as past studies lacked replication. Future directions for research that could guide the design of green roof–PV integration include the effects of irrigation, plant diversity, and green area-to-panel ratio on the roof.
Amiel Vasl and Amy Heim
The growing phenomenon of green roofs throughout the world mostly results in the establishment of extensive green roofs with low species diversity. However, research from the last few decades has shown that several advantages can accrue from diverse ecological systems, such as increased faunal diversity, storm water retention, thermal stability, pollution mitigation, and visual appeal. The maintenance of diversity on extensive green roofs has not been closely examined and few studies incorporate methods to ensure long-term coexistence into green roof design. Theoretical work has placed much focus on the niche and neutral theories that attempt to explain diversity as a result of the existence of different habitats or of demographic and dispersal patterns, respectively. These theories have resulted in several theoretical and practical recommendations for the maintenance of diversity in ecological systems and could suggest additional practices that would support biodiverse green roofs. We hereby review and discuss relevant theory and supporting research to provide suggestions regarding future research in the field as well as practical green roof construction recommendations and species selection.
Jeremy T. Lundholm
Green roofs and other constructed environments represent novel ecosystems, yet have potential to contribute to biodiversity conservation goals. Constructed ecosystems are intentionally managed to produce specific services, and thus could be viewed as highly artificial or controlled. Yet all constructed ecosystems exhibit spontaneous dynamics, as community structure changes due to internal or external ecological processes. While all green roofs have some element of design and human control over ecological trajectories, the level of ongoing management can vary greatly. I discuss “wildness” as a characteristic of green roofs in response to their spontaneous dynamics after initial setup, and their potential to provide ecosystem services related to human psychological well-being, aesthetics and habitat for biodiversity. This approach suggests new design possibilities in interaction with spontaneous ecosystem dynamics and highlights a need for greater ecological understanding of green roof systems.