Do green roofs provide habitat for bats in urban areas ?

As the world population continues to increase, with more than 50 percent of people now residing within cities, remaining natural and semi-natural habitats within urban areas play an increasingly important role for people and wildlife (Mortberg and Wallentinus, 2000; Benedict and McMahon, 2002; Jim, 2004; Town and Country Planning Association, 2004; Bierwagen, 2007; Gill et al., 2007; Tratalos et al., 2007). Urban development has been shown to be a direct threat to biodiversity, by causing and continuing to cause habitat destruction and degradation (McNeely and Mainka, 2005). Green roofs are a technology that seeks to lessen the impacts of urbanisation on people and wildlife. A green roof is the roof of a building that has been deliberately (partially or completely) covered with vegetation and a growing medium. They can be broadly categorised into ‘intensive’ and ‘extensive’ type roofs according to their depth of substrate and management requirements. Intensive roofs are the equivalent of parks or gardens on roofs with trees and shrubs included within their design. They have a deep substrate (200–400 mm) and require investments in plant care and irrigation. Conversely, extensive roofs have shallower substrates (20–200 mm, but usually about 35–75 mm) and require less maintenance. In general, they comprise ‘sedum roofs’ that support low growing succulent plants, or ‘biodiverse roofs’ which are planted with and/or have become colonised by a variety of wildflowers, herbs, sedums, mosses and grasses. Green roofs provide ecosystem services such as a reduction in the urban heat island (Kumar and Kaushik, 2005; Jim and Hongming, 2010), alleviation of the impact of flash floods following summer storms (Mentens et al., 2006; Carter and Jackson, 2007; Stovin, 2010), improved thermal and energy performance of buildings (Okeil, 2010; Teemusk and Mander, 2010) and improved air quality (Clark et al., 2008), as well as urban green space that offers amenity and wildlife value (Cle mants et al., 2006; English Nature, 2006; Dunnett and Kingsbury, 2008; Acta Chiropterologica, 14(2): 469–478, 2012 PL ISSN 1508-1109 © Museum and Institute of Zoology PAS doi: 10.3161/150811012X661774