Abstract Body

The increasing of urbanization in already large cities leads to the continuous erosion of natural environments, and environmental issues as pollution or urban heat island. While this development entails significant consequences on biodiversity and human societies, roofs became more attractive over time to be used as production space (e.g. for energy or food) or vegetated roofs. The development of green roofs is expected to provide numerous key ecosystem services such as improving air quality, lowering water runoffs and increasing pollination.

Associating two uses on the same roof can lead to competition in a limited spatial context, but also potential complementarity. In this study, we combined photovoltaic panels and green roofs with different levels of plant diversity in a multifunctional approach. Our aim is to understand how the addition of photovoltaic panels on green roofs can positively or negatively influence the ecosystem services provided, such as water runoff, pollination, thermal comfort and electricity production. The interaction and feedbacks between these two elements can be equally complex and two-way: adding a solar panel on a vegetated roof can influence and change plant and pollinator populations and the evolution of substrate and water runoff volume and quality. Conversely, plant population, through evapotranspiration, can lower the temperature of panels and increase electrical production.

In order to study these hypotheses, we built a multicriteria system on 200 m² and composed of 28 experimental units. These replicated units include treatments with substrate only, substrate only with solar panels, and green roofs with or without solar panels at 2 levels of plant diversity/community compositions. This presentation will summarize and discuss the results comparing, between systems, the analyze of electric production, pollination, thermal comfort, plant diversity evolution and growth, substrate evolution in terms of physicochemistry, and the quantity and quality of runoff water.