The presence of an extensive range of plants (over 1,500 with more than 50 different species spread over 900 m²) on the green roof built at Di3A as part of the GIFLUID project (under the supervision of Prof. Giuseppe Cirelli) offers opportunities and resources to numerous living organisms, especially pollinating insects. The presence of pollinators not only has direct beneficial effects on the plants within the area but also indirect positive impacts on the surrounding urban environment by contributing to increased biodiversity.
A recent study carried out as part of the master’s thesis of Dr. Gioele Migliore, entitled “Plant–Pollinator Interaction in an Urban Context: The Green Roof of the Department of Agriculture, Food, and Environment (Di3A),” coordinated by Professors Gaetana Mazzeo and Daniela Romano, aimed to investigate pollinators and their relationships with the plants populating the green roof. Results revealed the presence of about forty species of pollinating insects, with a predominance of Hymenoptera (85% of the total), consisting not only of the honeybee but also of about twenty genera of wild bees, mainly Ceratina, Heriades, Hylaeus, Megachile, and Seladonia. The most frequently visited plant species were Cuphea hyssopifolia, Gazania nivea, Delosperma cooperi, and Verbena hybrida, which proved particularly attractive to Hymenoptera.
These findings provide valuable insights into urban biodiversity and the relationships between pollinators and plants. They also serve as a useful tool for selecting the most suitable plant species not only to meet the design needs of green roofs (reducing stormwater runoff volumes, mitigating hydraulic risks through water retention by plants and substrate, and improving the thermal insulation of buildings) but also to support the many insect species that inhabit non-natural environments. Moreover, the presence of pollinators allows plants to develop and reproduce more effectively.
Designing green roofs with the goal of improving pollinator attractiveness has the dual purpose of supporting the pollination of rooftop plants—thereby enhancing their survival prospects—and fostering the abundance of diverse pollinator communities in urban areas, with positive spillover effects on surrounding zones.
The Apidology Group of the Applied Entomology Section of the Department has continued monitoring flower-visiting insects (anthophilous insects) to assess the diversity of pollinators in this unique environment. Located in an urban context, the area consists of over 1,500 shrubs and herbaceous plants, selected to ensure high botanical diversity and a long flowering period.
Within the green area, artificial nests (“Bug Hotels”) were installed to facilitate the nesting of pollinating insects (Figure 1). To conduct a census of anthophilous insects during 2024, throughout the peak flowering season (from May to October), three surveys were carried out each month. On each survey day, observations were made at different times (morning, noon, and afternoon) using two different techniques:
i) Transect method – walking along a path among representative plants for 45 minutes, recording and/or capturing insects found on flowers;
ii) Observation plot – observing selected representative plants for a few minutes and recording the flower-visiting insects that landed on them (Figure 1).
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Figure 1: Bug Hotel installed on the green roof (top left); Observation plot (right); survey with net along the transect (bottom left).
