Biodiversity roofs are another form of extensive green roof (i.e. low maintenance) that makes use of recycled materials (e.g. crushed brick, crushed concrete etc.) in the growing medium.
This type of green roof is intended to create a natural wasteland and can be seeded initially with selected species to create some growth. However the basic design is to attract fauna and flora of all kinds. As the growing medium is not of high nutritional value, larger plants are not likely to survive and will die off creating further suitable habitat for invertebrates which in turn will attract other fauna.