Towards the design of biodiverse green roofs in Argentina: Assessing key elements for different functional groups of arthropods

Green roofs offer numerous environmental benefits, and thus their implementation is considered an initiative to create sustainable cities. However, the characteristics of green roofs that could enhance arthropod biodiversity and ecological functioning are poorly known, especially for South American countries. Here, we analyzed the influence of several characteristics of green roofs (plant species richness, vegetation cover of the roof, age, substrate depth, area, and isolation in terms of height and green cover in the landscape scale) on the abundance, richness (total and by functional feeding groups), and community composition of arthropods. To do that, we selected 30 green roofs located in different urbanization contexts, from small towns in semi-rural areas to Cordoba, the second-largest city of Argentina. Our results indicated a high diversity of arthropods, registering a total of 12,942 individuals corresponding to 505 species from 14 orders, being herbivores and parasitoids the dominant groups. The area of the green roofs was positively linked to total species richness, species richness of most functional feeding groups, and total abundance of arthropods. The community composition of arthropods on green roofs was also affected by their area, and by the green cover in the landscape. Moreover, green roofs with higher plant richness, mainly spontaneous, and less isolated (both vertically and horizontally) favored entomophagous arthropods. Other variables, such as age and vegetation cover of the green roofs, were also important for herbivores, predators, parasitoids and detritivores. Our study clearly demonstrates that green roof size is not all that matters for supporting arthropod biodiversity because promoting high plant diversity, allowing spontaneous ecosystem dynamics, and diminishing roof isolation foster entomophagous arthropod diversity. Our study is the first that considers multiple factors of roofs in South America and provides key knowledge for stakeholders interested in the development and management of this green infrastructure in semi-rural and urban landscapes.

Automated summary

Green roofs have a positive impact on arthropod diversity and ecological functioning, influenced mainly by roof area, vegetation cover, and plant species richness. Green roofs with high plant diversity and less isolation promote diversity of entomophagous arthropods.