Page - 115 - in Biodiversity and Health in the Face of Climate Change

115 regularly and are satisfied with its quality, the same (or similar) outdoor space is not supporting the needs of young to middle-aged adults. The authors showed that judgements about the quality aspects of urban green space vary across age groups, but place more importance on utilising green space than either on the size of green space or on proximity. Understanding how all these attributes interact and translate into health outcomes is one direction for future research. Interestingly, results of only two studies were based on objective health mea- surements (Michael et  al. 2014 through clinical examination for detecting obesity; Richardson et  al. 2017a using accelerometry for detecting physical activity). All other studies under review  used secondary data from official statistics or data from health questionnaires where respondents reported their health status themselves, mostly through well-developed Likert scale measurements for perceived health. In the two studies using objective measures, no consistent association between health and urban green space was identified. One could argue that objectively measured health is the most reliable because it might be less biased by indirect indicators or perceptions. There are, however, other studies that use objective measures to assess potential links between stress levels and urban green space, e.g. through cortisol levels or electroencephalography (Ward Thompson et  al. 2012; Aspinall et  al. 2013). In these studies, stress levels were found to decrease in greener environ- ments. Stress levels, however, always depend on many different aspects that may lead to an increase or decrease in stress levels. A combination of both subjective and objective measurements is an important field for future research. Focus on the method of measurement is worth discussing here. All studies used and produced quantitative data and conducted statistical analyses. The review showed that important results were produced from this approach. No study in this review used qualitative research methods, such as an ethnographic approach that includes assessments of observing free behaviour. For children of a particular age group, Chawla (2015) pointed out that ethnographic approaches show how green space can contribute to the development of children’s capabilities and to their “complete physical, mental and social well-being”. Echoing Chawla (2015), future research should combine qualitative and quantitative approaches that include eth- nographic assessment (see Kabisch and Haase 2014; Low 2013 for further details), but also experimental and correlational methods that, when used together, may increase the understanding of health and the environment. The selection of particular search terms for the review has, of course, produced somewhat narrow results. Using other search terms may have contributed to a larger evidence base on the urban green space-health outcome association, e.g. through increasing the scope to other types of nature, such as trees. However, the focus of this review was to look at potential confounding factors that may explain health- outcome results, and to urban green spaces as a broad group of urban nature. Further, by limiting the review to recent studies, older studies are omitted, although they certainly are as important to review and discuss, especially as they relate to confounding variables. 5 The Influence of  Socio-economic and  Socio-demographic Factors in  the  Association…