Create new ecosystems through nature-based methods: the case of Mediterranean green roofs

Abstract

The creation of new ecosystems is a complement to conservation and restoration to fight against biodiversity erosion. In urban areas, roofs are an opportunity to test it. Nevertheless, techniques must be guided by ecologically related natural habitats. Botanical surveys were conducted in southeastern France which allowed us to identify hundreds of plant species that can be used on roofs in a Mediterranean climate. Of these, 80% are still not commercially used, especially the annual species. A screening process was then developed based on the use of functional traits accessible in databases. Thirty-four species have obtained the best scores possible. Eighteen were tested as their seeds were easily available. End of 2012, experimental green roofs were built in Avignon and Heverlee (Belgium) which vary in the depth of the substrate and exposure. After a two-year survey, the situations with the thickest substrate and shading position showed the most important plant cover and species-richness. However, in all cases a persistence of the newly created plant communities was measured after the summer and winter periods, thanks to the regenerative abilities of annual plants, which allows to predict their sustainability on the long term.