Achievements, flaws, and future goals of scientific research on green roofs in Mediterranean cities: first feedback from ongoing meta-analysis

Current scientific research points out the low number of papers focused on the environmental patterns in Mediterranean urban areas, where green infrastructure is still strongly underrated by scientists as well as by politicians, planners and decision-makers. In this paper, the results of a simple meta-analysis on the topics treated in scientific literature about the Mediterranean green roofs (MGRs) are presented. Our review pointed out the strikingly higher attention paid to building materials, energy efficiency and hydraulics with respect to life sciences (including basic ecology, horticulture, soil, plant and animal sciences) in the target paper selection. In fact, despite the availability of plentiful information about the Mediterranean vascular flora and vegetation, this is not so informing the selection of plants for roof greening purposes. The role of soil-based substrates in local bio-geochemical cycles, plant and animal communities and their dynamics have also been poorly studied so far. Social and perceptive aspects are completely underrated too, whilst the management strategies and the dominant economic approach are informed more by energy-saving than by the finding innovative and sustainable materials and techniques. More investments are needed to: 1) diversify the techniques and materials for roof construction, respecting local ecoregional features and circular economy; 2) sustain the use of native plants, well adapted to stand environmental stress and anthropogenic disturbance; 3) avoid potentially invasive alien plants; 4) implement the cost-benefit effectiveness of MGRs in the medium- and long-term.