GREEN ROOFS IN GENEVA: POTENTIAL REFUGE FOR PLANTS AND BRYOPHYTES?

Presentation at the 1st European Green Urban Infrastructure Conference, Vienna, Nov. 2015

by Marianne Hédont

 

 

 

 

 

What about biodiversity on Geneva green roofs ?
Because of the high diversity of green roofs existing in a city and their level of maintenance, their potential to host threatened plant species can be different from a city to another. In order to better regulate the implementation of green roofs in the Canton of Geneva, it is crucial to better know what plant communities are found on green roofs and if they are important for the conservation of native species.

A two-year survey for a picture of the situation
This study was part of a larger two-year project for monitoring green roof ecosystem services in Geneva. The survey of vascular plant and bryophyte communities was realized on 30 green roofs, belonging to « extensive » and « intensive » classes. All established species were inventoried and their relative abundance were recorded on each roof.

Diversity of plants and bryophytes
Half of the 298 species observed were wild colonizing species with 65% of native and 14% of protected species in Geneva. Only 51% of the planted species are native. For bryophytes, 43 species were identified, representing 12% of the bryoflora of Geneva. One moss is critically endangered (IUCN Red List). Invasive species observed: 7 vascular plants and 1 moss.

 

Recommendations
Using seed mixtures with specific native communities should increase the conservation value of extensive green roofs and create roofs sustainable functionnal ecosystems. Also a better recognition of invasive species by maintenance responsibles should limit their development on green roofs.

Perspectives:
Developing ans testing new native seed mixtures with specific communities of dry calcareous grasslands, is one of the goals of the ongoing applied project SEED (SEminum on Edifices Downtown) - contact : patrice.prunier@hesge.ch.

 

 

 

 

 

FOCUS
Observed on 30 green roofs :

- 298 vascular plant species
- 175 native species (58%)
- 32 protected species in Geneva (10%)
- 43 species of mosses and liverworts
- 5 threatened species

Reseach done together with Julie Steffen, Patrice Prunier, University of Applied Sciences and Arts of Western Switzerland (HES-SO), rue de La Prairie 4, 1202 Geneva, Switzerland

3 photos of inventoried green roofs. Image credit : hepia