Green Roof Soils: New Prospects for Biodiversity.

Green roof technology is becoming popular worldwide for mitigating urban stormwater, heat islands, and conserving energy. Research at the Free University of Berlin beginning in the 1950’s pioneered the way for extensive green roofs in Germany, and later the lightweight engineered growing media developed in the 1980s and 1990’s. Typically comprised of expanded clay, shale, slate, sand, and low amounts of organic compost, the development of lightweight growing media greatly expanded the application of green roofs onto lightweight structures; however, it also resulted in low biotic diversity on green roofs. The German FLL Green Roof Guidelines were developed from 1975 onward and are a universal state-of-the-art guideline for the development of growing media for green roofs. Climates different from Central Europe are proving to be experimental for green roofs and are in need of new or revised guidelines for growing medias, but there is very little research and development to support these efforts. In North America for example, green roofs along the east coast need a greater capacity for drainage in growing media than provided in the FLL Guidelines. Plant pallets are also proving different across ecoregions as well. Several sites in Florida for example, are demonstrating that some Sedum spp. can’t tolerate the humidity and night time temperatures. With all such differences, there needs to be more research and development to support the industry. There are also emerging new uses for green roof technology that include growing food, treating industrial waste, sewage treatment, and wildlife habitat. The FLL Guidelines may outline provisions for extensive green roofs in Central Europe, but they fall short of addressing a diversity of applications elsewhere. New research by soil scientists is needed across diverse climates and cutting edge uses to support the development of reliable standards and guidelines. This presentation outlines recommendations for beginning green roof research in new areas.