Establish “green infrastructure” in urban areas
Overall effectiveness category Awaiting assessment
Number of studies: 1
Background information and definitions
Planting rooftops in urban areas, and growing plants up vertical structures such as walls and lamp-posts, often termed “green infrastructure”, is becoming increasingly popular, and is usually done with the aim of reducing pollution and run-off, or to improve building insulation (Dunnett & Kingsbury 2008). However, they may also be put in place to increase biodiversity, by providing habitat for a range of species (Oberndorfer et al. 2007), including nectar resources or egg-laying sites for butterflies and moths.
Dunnett N. & Kingsbury N. (2008) Planting green roofs and living walls. Timber, Portland, Oregon, USA. Second edition, ISBN: 0881929115.
Oberndorfer E., Lundholm J., Bass B., Coffman R.R., Doshi H., Dunnett N., Gaffin S., Kohler M., Liu K.K.Y. & Rowe B. (2007) Green roofs as urban ecosystems: ecological structures, functions and services. BioScience, 57, 823–833.
Supporting evidence from individual studies
A replicated, site comparison study in 2011–2012 on 11 green roofs in Taipei City, Taiwan (Lee & Lin 2015) found that green roofs had a lower abundance and species richness of butterflies than urban parks, but the abundance of butterflies was higher on older green roofs with more nectar plant species in a larger area. On green roofs, both the abundance (514 individuals) and species richness (12 species) of butterflies was lower than in urban parks (abundance: 3,141–8,882 butterflies; richness: 50–109 species). However, the abundance of butterflies was higher on green roofs established longer ago, and on roofs with more nectar plant species covering a larger area (data presented as model results). Eleven green roofs (95–590 m2, 7–34 m above ground), established 13–46 months before the study, contained a total of 34 butterfly nectar plant species (1–16 species/roof, covering 2–41 m2). Two urban parks (13–26 ha), established 18–25 years before the study, contained 20–45 nectar plant species. From August 2011–May 2012, butterflies were surveyed for four hours twice/month on each roof. From July 2008–June 2009, butterflies were surveyed in one urban park, and from March 2011–February 2012 they were surveyed in a second park (no further details provided).Study and other actions tested