Developing urban green spaces for biodiversity: a review

Abstract

Urban green spaces, which are important for human and wildlife in the urban area, have changed into man-made spaces. Increased urbanisation has had and continues to have a negative impact on urban green spaces, and affects the urban microclimate as represented by ‘Urban Heat Island (UHI)’ phenomena. Especially, habitat fragmentation can be extreme within urban ecosystems, and fragments of natural vegetation may be too small or even too isolated to support some species. Therefore, the networks, which offer habitats and corridors that help conserve biodiversity, are also important to maintain the ecological services of a sustainable urban landscape, as well as total green area. However, there are rarely enough open spaces due to urban densification. This is why rooftops of buildings, which had not previously been regarded as spaces for planting for vegetation, have been utilised as a type of open space, and so green roofing has become one of the gradually developing fields of urban ecological engineering. This present paper aims to explore the potential of rooftops as habitats of urban wildlife comparing cases in Japan and UK, and pave the way for a preservation of urban biodiversity under restricted urban environmental conditions. As a result, it was suggested that Japanese green roof industries consider the concept of brown/biodiverse roofs instead of extensive roofs with sedum or lawn. At the same time, intensive roofs should be efficiently installed to provide ‘stepping stone’ in urban areas not having enough open space. If possible, however, to create habitats on the ground is more preferable than on the rooftop due to accessibility. Finally, if impervious spaces (e.g., concrete and asphalt) are replaced with pervious spaces (e.g., green area or brownfield), it is significant for not only urban biodiversity but also UHI.