Any green space is better for biodiversity and green roofs are will benefit wildlife more than traditional roofing methods.

However the question is always "which wildlife?"

Sedum Blanket/Mat Systems

Simple sedum blanket systems have been shown to have benefit for a limited range of invertebrate species and the sedums do provide a foraging source for bees in late June July.

Substrate based Biodiverse / Green / Brown roofs

Research demonstrates without doubt that the most productive approach from an ecological/wildlife perspective is to consider a substrate-based approach with a range of sedums and wildflowers. A range of wildflowers will provide foraging throughout the summer months and provide structural variation in the vegetation. This will allow a range of species to colonies the roofs.

Because of the nature of substrate based extensive green roofs it is not the quantity and the nearness to other green spaces that is important but the quality of the green roof design and implementation. Invertebrates associated with this type of roof can colonise the roof from quite considerable distances if the habitat is good.

This approach originally researched and promoted by the Swiss researcher Dr. Stephan Brenneisen has been promoted widely in the UK.

Dr. Gyongyver Kadas recently completed a long-term study of green roofs and invertebrate biodiversity with recommendations.

Further written papers on this subject by Dr. Brenneisen, Dr. Kadas and Dusty Gedge are available at:

http://www.urbanhabitats.org/v04n01/invertebrates_full.html http://www.urbanhabitats.org/v04n01/wildlife_full.html www.iob.org/userfiles/File/biologist_archive/Biol_52_3_Kadas.pdf

Calcareous flower rich habitat This work is focused on the provision of habitat for invertebrates associated with brownfield land. Many spiders, beetles and other invertebrates that are becoming increasing rare are often associated with brownfield land and well-designed green roofs.

Where green roofs are to be installed for reasons associated with biodiversity consideration should be given to the substrate and the type of flowers to be used [whether seed or plugs].

Many of the original German green roofs are good examples of central European dry calcareous flower rich habitat. In Switzerland this is still a common approach.

There is evidence from Europe that with good design green roofs can benefit a number of ground nesting birds including Skylark, Oystercatcher, Ringed & Little Ringed Plovers, Common Tern and Lapwings.

www.urbanhabitats.org/v04n01/birds_full.html

Semi intensive / Intensive green roofs

Although gardenesque in character such roofs can provide a significant resource for local biodiversity with good planting schemes. These should include some native and certainly include flowering plants that are of known foraging value for bees. Inclusion of water features, dead logs and nest boxes can increase the potential for such roofs to act as a resource for local wildlife.