Urban Aquatic Ecosystems: the good, the bad and the ugly

Urbanisation has had a profound impact on the natural environment (Pickett et al. 2001, Grimm et al. 2008), with a growing proportion of the global population living in urban areas (United Nations 2010). Historically, urban centres were typically located close to waterbodies due to the ecosystem services that they provided to society such as the provision of water, food, power and transport (Everard & Moggridge 2012, Chester & Robson 2013). In contemporary towns and cities waterfronts remain the focus for many economic and recreational activities (Francis 2012, Mansfield et al. 2014) and have been the focal points for regeneration and restoration activities. Urban waterbodies have been subject to significant degradation as a result of urbanisation, leading to reductions in floral and faunal biodiversity and compromising their ability to deliver the services for which the original urban centre developed (Grimm et al. 2008).Attitudes towards urban waterbodies are changing as part of wider reformation in the way in which the environment is viewed (Findlay & Taylor 2006). Urban waterbodies are no longer simply viewed as degraded systems of little value, but as novel ecosystems with an intrinsic value in their own right (Francis 2014, Moyle, in press), that make significant contributions to both local and regional biodiversity and conservation activities (Hassall 2014, Kowarik 2011). Despite extensive degradation, urban water bodies retain some functionality acting as natural retention (sediment or water) features (Briers 2014), ‘biohighways’ (Francis 2014), refugia (Chester & Robson 2013) and facilitating species migration and connectivity between isolated habitats and populations (Findlay & Taylor 2006). The role of urban waterbodies in providing important regulating and cultural ecosystem services (in addition to the provisioning services identified above) is also increasingly recognised.