Biodiversity is important to our quality of life, as the loss of valuable genes would have implications on available foods, fuels and medicines.
Species diversity is particularly low in urban areas, where hard surfaces dominate. Yet, according to DEFRA, almost 90% of the UK population is concentrated in such areas. Continued, unchecked development would further reduce urban greenery. According to NERC, the loss of habitats is the greatest threat to biodiversity.
Whilst not directly replacing ground-based habitats, green roofs provide food, shelter and nesting or resting places for creatures that may have been displaced by urban development (e.g. spiders, butterflies, birds and other invertebrates).
The interaction of birds, beetles and spiders with European green roofs has been studied by several researchers. Stephan Brenneisen (Basel University) concluded that birds (e.g. wheatears, skylarks, lapwings etc) are attracted to green roofs in search of food (insects and seeds) or for preening, cleaning, searching for nesting material, nesting and roosting. 60 different species of spider were also found on green roofs.
Green roofs should be viewed as complementary to the maintenance of 'green' corridors for flora and fauna within an urban setting, providing habitat stepping-stones for certain species that are at risk of becoming isolated.
The advantages of green roof habitats are:
- They are undisturbed;
- They are free of predators, notably the domestic cat; and
- They can be tailored specifically to attract a desirable species.
Specifying a Biodiverse Roof
The key to designing biodiverse roofs is to tailor the design to purposely attract the species targeted in the biodiversity action plan - there is no single best specification.
Plant Strategies can incorporate one, or a combination, of the following:
- Native plant species to replicate the pre-development building footprint or surrounding areas.
- Plant species that act as food sources (e.g. nectar for bees and butterflies) that in turn attract other wildlife (e.g. birds, spiders)
- Bare, non-vegetated areas to attract birds, such as pied wagtails
The substrate composition must be derived from the choice of planting - providing the air, water and nutrients that are appropriate to the plants' needs. However, substrate selection must also consider the implications for habitat. For example, research has highlighted how moisture retention properties can affect the density of population by beetles, whilst varying substrate depth is believed to encourage wildlife habitation.
Shelter stones and lying timber, amongst other additional features, can be carefully designed to encourage habitation by insects and to provide perching points and nesting habitat for birds.
Biodiversity by Blackdown
At Blackdown, we have extensive experience in tailoring our plants and components into a whole range of biodiverse roof schemes. Our Research & Development team has identified the most suitable habitat types, developed the appropriate plant mix and conducted rigorous trials to formulate effective biodiverse roof strategies.
Our Design Support Team will be happy to work with you to deliver your project's requirements. For further details, contact us.