sustainability Review Biodiversity Impact of Green Roofs and Constructed Wetlands as Progressive Eco-Technologies in Urban Areas Sonja Knapp 1,2 , Sebastian Schmauck 3 and Andreas Zehnsdorf 4,* 1 Current address: Helmholtz Centre for Environmental Research—UFZ, Department Community Ecology, Theodor-Lieser-Str. 4, 06120 Halle (Saale), Germany;
[email protected] 2 Department of Ecology, Technische Universität Berlin, Rothenburgstr. 12, 12165 Berlin, Germany 3 Federal Agency for Nature Conservation, Karl-Liebknecht-Str. 143, 04277 Leipzig, Germany;
[email protected] 4 Helmholtz Centre for Environmental Research—UFZ, Centre for Environmental Biotechnology, Permoserstraße 15, 04318 Leipzig, Germany * Correspondence:
[email protected] Received: 3 September 2019; Accepted: 15 October 2019; Published: 21 October 2019 Abstract: The total amount of sealed surfaces is increasing in many urban areas, which presents a challenge for sewerage systems and wastewater treatment plants when extreme rainfall events occur. One promising solution approach is the application of decentralized eco-technologies for water management such as green roofs and constructed wetlands, which also have the potential to improve urban biodiversity. We review the effects of these two eco-technologies on species richness, abundance and other facets of biodiversity (e.g., functional diversity). We find that while green roofs support fewer species than ground-level habitats and thus are not a substitute for the latter, the increase in green roof structural diversity supports species richness. Species abundance benefits from improved roof conditions (e.g., increased substrate depth). Few studies have investigated the functional diversity of green roofs so far, but the typical traits of green roof species have been identified.