Seite - 440 - in Biodiversity and Health in the Face of Climate Change

440 ume), plants with thorns and toxic parts (especially near playgrounds for children), or meadows managed for wildlife, rather than closely mown lawns, which could increase the risk of tick infestation (WHO 2016; Müller et  al. Chap. 4, this volume). In conclusion, two points must be emphasised: Firstly, one single green space will not usually include all recommended features and elements, as this is unlikely to be possible in a limited space and as individual elements and uses can be in con- flict with each other. Secondly, all points described in this section exclusively refer to health aspects, not to other requirements green spaces should fulfill, e.g. in terms of biodiversity and nature conservation or climate adaptation. Of course, in land- scape planning these other demands have to be considered as well, and sound deci- sions have to be made in favour of one of them if conflicts cannot be avoided or minimised. 19.5.2 Green Space Systems Especially in urban areas, it is not individual green spaces which determine the ‘green quality’ of a city, but the entire system of green spaces, which is unique to every city. Relevant questions for human health regarding this are as follows: How are different green spaces distributed within a city (and its surrounding regions)? Is there a spatial concentration of green spaces or are they evenly distributed across the city? How many inhabitants have easy access to these spaces and are they close to their homes? Do different green spaces offer possibilities for different uses and requirements, so that the whole green space system enables a good variety of uses and offers possibilities for many different user preferences? Are the green spaces interlinked (for example by smaller ‘greenways’) that allow for walking, hiking or cycling in a green environment for a longer distance? Only after  these questions are answered, can the potential health effects of ‘local green’ be assessed for an entire municipality or city. To ensure a minimum supply of public green spaces to their inhabitants, different cities have come up with standard values on recommended accessibility standards for green space per inhabitant. Some consider a minimum size of green space that should be available within a maximum distance from every inhabitant’s home, e.g. Natural England’s 2010 recommendation (by no means always met) of a minimum of 2  ha of green space within 300  m (5  minutes’ walk) of home. Others consider a minimum of green space per inhabitant. In Berlin, for example, 6  m2 per inhabitant are considered necessary, even if this standard is not fulfilled in all parts of the city (Umweltatlas Berlin 2017). Beyond this, distinctions are made between different types of green spaces regarding their proximity to housing areas (Rittel et  al. 2016, 56f; WHO 2016). Furthermore, the spatial network of all green spaces and green- ways of a city is crucial. Beyond supporting walking or hiking during leisure time (e.g. ‘20 green main routes’ in Berlin, the Highline Park in New  York), this should encourage daily physical activity as an integral part of people’s life, which is, S. Heiland et al.