Key factors for biodiversity of urban water systems Kim Vermonden Key factors for biodiversity of urban water systems Vermonden, K., 2010. Key factors for biodiversity of urban water systems. PhD-thesis, Radboud University, Nijmegen. © 2010 K. Vermonden, all rights reserved. ISBN: 978-94-91066-01-6 Layout: A. M. Antheunisse Printed by: Ipskamp Drukkers BV, Enschede This project was financially supported by the Interreg IIIb North-West Europe programme Urban water and the municipalities of Nijmegen and Arnhem. Key factors for biodiversity of urban water systems Een wetenschappelijke proeve op het gebied van de Natuurwetenschappen, Wiskunde en Informatica PROEFSCHRIFT ter verkrijging van de graad van doctor aan de Radboud Universiteit Nijmegen op gezag van de rector magnificus prof. mr. S.C.J.J. Kortmann, volgens besluit van het college van decanen in het openbaar te verdedigen op donderdag 25 november 2010 om 10.30 uur precies door Kim Vermonden geboren op 20 november 1980 te Breda Promotores: Prof. dr. ir. A.J. Hendriks Prof. dr. J.G.M. Roelofs Copromotores: Dr. R.S.E.W. Leuven Dr. G. van der Velde Manuscriptcommissie: Prof. dr. H. Siepel (voorzitter) Prof. dr. A.J.M. Smits Dr. J. Borum (Kopenhagen Universiteit, Denemarken) Contents Chapter 1 Introduction 9 Chapter 2 Does upward seepage of river water and storm water runoff 19 determine water quality of urban drainage systems in lowland areas? A case study for the Rhine-Meuse delta (Hydrological Processes 23: 3110-3120) Chapter 3 Species pool versus site limitations of macrophytes in urban 39 waters (Aquatic Sciences 72: 379-389) Chapter 4 Urban drainage systems: An undervalued habitat for aquatic 59 macroinvertebrates (Biological Conservation 142: 1105-1115) Chapter 5 Key factors for chironomid diversity in urban waters 81 (submitted) Chapter 6 Environmental factors determining invasibility of urban 103 waters for exotic macroinvertebrates (submitted to Diversity and Distributions) Chapter 7 Synthesis 121 Summary 133 Samenvatting 137 Dankwoord 141 Curriculum vitae 145 Urban water system Nijmegen. Photo: Kim Vermonden Chapter 1 Introduction Kim Vermonden Chapter 1 Urbanization and urban water systems 10 Our world is rapidly urbanizing (Grimm et al., 2008). In the developed countries urban population already accounts for approximately 73% of the total population (United Nations, 2008). The number of mega-cities with more than 10 million inhabitants increased from two in 1950 to 20 in 2005. In the Netherlands approximately 83% of the population lives in urban areas and this percentage will probably increase to 92% by the year 2050. Cities are microcosms of global change and perfect to study ecosystem dynamics and responses of biodiversity to change (Grimm et al., 2008). Water systems play an important role in urban areas, providing vital services such as drinking water, irrigation, flood control, transportation, recreation and wildlife habitat (Postel & Carpenter, 1997). According to the European Water Framework Directive, three types of surface waters can be distinguished: natural, (heavily) modified and artificial water bodies (EU, 2000). Natural waters can be rivers, lakes, transitional or coastal waters. The second type refers to natural water systems that are (heavily) modified to fulfil human demands. The third type includes man-made water bodies that are especially constructed to provide services such as drainage of cities and towns. Urbanization often has negative effects on existing natural water systems, altering the morphology, hydrology, water chemistry, flora and fauna (Paul & Meyer, 2001, Walsh et al., 2005). Water systems in urban areas are often canalized and banks are frequently protected with wooden boards or paved with stones to avoid erosion. The area of impervious or hard surfaces, such as roofs and roads, is large, resulting in higher and more frequent peak discharges. Water quality is usually degraded with high nutrient and contaminant loadings. Native flora and fauna diversity generally declines, while tolerant, often exotic species become more abundant (Paul & Meyer, 2001, Walsh et al., 2005, McKinney, 2006). Nevertheless urban areas can also be an important habitat for flora and fauna. Urban woodlands in Rennes, France, accommodated more than 50% of the species present in peri-urban woodlands (Croci et al., 2008). Stewart et al. (2009) also found considerable plant diversity in urban woodlands, Christchurch City, New Zealand. Pryke & Samways (2009) showed that urban botanical gardens of indigenous plants had major invertebrate conservation value in South Africa. Langley et al. (1995) found that rotifer species richness was similar in urban ponds and reference sites. Collier et al. (2009) demonstrated that some urban streams can provide an important habitat for a range of native fish and macroinvertebrate species, including sensitive taxa. Le Viol et al. (2009) showed that macroinvertebrate family richness can be just as high in motorway storm water retention ponds, than in surrounding ponds in the wider landscape. Climate change is associated with increasing amounts of precipitation and more frequent heavy precipitation events in North Western Europe. This requires adaptation of cities and could offer opportunities to rehabilitate surface water systems. Rehabilitation of (heavily) modified water bodies and optimal design of artificial urban waters give opportunities to integrate vital ecosystem services and to create at the same time habitats for biodiversity in urban areas (Savard et al., 2000, Palmer et al., 2004, Kazemi et al., 2009). Recently, many local, regional, national and international initiatives have been taken for the optimization of the design and management of urban water systems (e.g. Arnhemse Waterpartners, 2003, Wang et al., 2006, Arghyam, 2007, Urban Water Project Partnership, 2008). Nowadays, urban water management projects also take Introduction into account the potential biodiversity value of urban waters (Bryant, 2006, Kazemi et al., 2009). Knowledge of the structure and functioning of urban surface water systems as habitat for flora and fauna species is needed to determine key factors for aquatic 11 biodiversity in urban areas, necessary to optimize their design and management for biological conservation. Biological assessment The ecological quality of water systems, including urban waters, can be assessed by measuring various biodiversity parameters (e.g., richness, Shannon index) at different scales (e.g., alpha, beta or gamma). The diversity of a system depends on many factors. This thesis focuses on the importance of biotic and abiotic conditions for biodiversity of urban surface water systems. Biodiversity in urban water systems is placed within the theoretical frameworks on productivity and disturbance, species pools and invasions as explained below. Relevance and indicators of biodiversity Biological diversity includes diversity within species, between species and of ecosystems (UNEP, 1992). In April 2002, the Parties to the Convention on Biological Diversity committed themselves to achieve a significant reduction of the current rate of biodiversity loss by 2010 at the global, regional and national level as a contribution to poverty alleviation and to the benefit of all life on Earth (COP, 2002). Biodiversity is the foundation upon which human civilization has been built. In addition to its intrinsic value, biodiversity provides goods and services that underpin sustainable development in many ways. The Curitiba Declaration on Cities and Biodiversity (2007) affirmed the importance to integrate biodiversity in urban planning and development, with a view on improving the lives of urban residents. Biodiversity can be measured at three different spatial scales: alpha, beta and gamma (Whittaker, 1972). Taxa richness within a community or area is expressed as alpha diversity. The difference between communities or areas is called beta diversity. Gamma diversity is the overall species diversity for the different communities or areas within for example a geographical region. Biodiversity can be expressed in many different ways. Species richness or the number of species in an area or a sample is the simplest form. Species evenness is usually calculated as the Shannon-index or Simpson-index using species and their abundances. More recent indices also incorporate other values, such as ecosystem values or economic values (Yoccoz et al., 2001). For example rare or endangered species could be weighted more heavily than common species. Single species, such as indicator species, flagships, umbrellas or keystones can also be used as the base of biological conservation, although it is difficult to prove if whole ecosystems profit from this approach (Simberloff, 1998). Biodiversity depends on many different factors, for example the regional species pool, geographical location, nutrient status, frequency and intensity of disturbances or invasion by exotic species. Intermediate disturbance theory Urban water systems are regularly disturbed by for example mowing of aquatic weeds, dredging of sediment and storm water peak flows. Theory and empirical evidence suggest that maximum species richness is reached at moderate frequencies or intensities Chapter 1 of disturbance, thus at intermediate disturbance (Hobbs & Heunneke, 1992). Disturbance creates possibilities for new species to colonize an area and species richness is hereby 12 increased when various successional stages coexist at intermediate disturbance levels (Connell, 1978). Severe