Description Sky Garden's biodiverse or 'brown roof' systems are the most eco-friendly system we offer. The idea of a biodiverse roof system is to mimic the surrounding environment that has been replaced by the building in order to reduce the ecological impact as much as possible. Often left to self-seed, the substrate is contoured to allow for a variety of native species to establish via seeds landing from the wind or native birds. Log piles, sand piles and boulders provide habitats for various species of insects, providing food sources for local wildlife and increasing the area's biodiversity.