Seite - 285 - in Biodiversity and Health in the Face of Climate Change

285 Ksiazek 2015; Salisbury et  al. 2015), the use of horticultural cultivars has been linked to a reduction in the forage value of planting for pollinators in general (Bates et  al. 2011; Salisbury et  al. 2015). Moreover, the spread of alien invasive species from gardens and parks is another significant issue in many parts of the world (Reichard and White 2001; Russo et  al. 2017). The conservation value of green spaces that are popular with people can also be limited by significant levels of dis- turbance and degradation, which prevent native species from colonising and persist- ing (Brown and Grant 2005), and result in assemblages dominated by adaptable generalists (Kowarik 2011) and the homogenisation of urban biodiversity (McKinney 2006). Even for human-nature interactions that people perceive as being good for wildlife, such as the supplementary feeding of wild birds, we have little evidence as to whether they deliver  biodiversity conservation  benefits (Fuller et  al. 2008; Robb et  al. 2008; Jones 2018). Despite this, suitable habitat within urban areas can support threatened and spe- cialist species, and warrant conservation attention (Baldock et  al. 2015; Ives et  al. 2016). In developed regions, where intensive use of the wider landscape, particu- larly through agriculture, has resulted in species declines, urban areas have become important for sustaining regional abundances of some species. Substantial propor- tions of the populations of some previously widespread and common species now occur in urban green spaces (e.g. Beebee 1997; Gregory and Baillie 1998; Mason 2000; Bland et  al. 2004; Peach et  al. 2004; Speak et  al. 2015; Ives et  al. 2016; Tryjanowski et  al. 2017). For instance, over 600 species have been recorded in Weißensee Jewish Cemetery in Berlin. It supports 25 plants, five bats and nine birds that are species of conservation concern, and one of the lichens (Aloxyria ochro- cheila) present on the site is considered very rare across the wider region. The cem- etery therefore acts as an unintended refuge for a wide range of taxa (Buchholz et  al. 2016). 12.2 Green Spaces Managed Primarily for  Biodiversity At the other end of the green space continuum are formal protected areas, now inter- preted as a global conservation network, where the objective is to maintain and enhance biodiversity (see MacKinnon et  al. Chap. 16, this volume). Currently, there are more than 200,000 protected areas globally, after a huge expansion of the net- work over the past few decades (Watson et  al. 2014, Butchart et  al. 2015). Some of the earliest protected areas were preferentially designated in  locations used heavily for recreation (Pressey 1994), and some protected areas are still managed with access and use by people as a primary management goal, such as many of the National Parks in the UK (Smith 2013). However, this is usually the exception rather than the rule for three inter-related reasons. First, protected areas have overwhelmingly been established in areas not needed for economic activity (Pressey 1994), so they are often sited at higher elevations, on 12 Biodiversity and  Health: Implications for  Conservation