Seite - 162 - in Biodiversity and Health in the Face of Climate Change

162 Thus, one may question whether the level of biodiversity, especially that in terms of functional species diversity, is a relevant factor with regard to the mental health benefits that a certain amount of nature or a natural area may generate. Given that nature conservation and mental health promotion are two separate goals, an appro- priate first question might be whether successful nature conservation and efficient application of nature to promote mental health can go hand in hand. Are the require- ments that nature conservation imposes compatible with those that the promotion of mental health imposes? Such a question fits in the context of multi-functional use of space, something that is particularly relevant in the urban domain. And yes, perhaps there are synergy benefits to be had by using the same area to accomplish both goals. But it is also possible that trade-offs have to be made. Some ecologically desirable species of animals or plants may be either considered too dangerous to expose people to, or too vulnerable to human presence or certain types of human activity in their habitat to allow people to access the area. 8.1.2 Mental Health and  Well-Being Although the focus of this chapter is on biodiversity, this is in the context of biodi- versity  – mental health research. Therefore, we discuss the concepts of mental health and mental well-being as well, although less extensively. Mental health is defined by the WHO as a state of well-being in which an individual realises his or her own abilities, can cope with the normal stresses of life, can work productively, and is able to make a contribution to his or her community (World Health Organization 2016). Although the WHO does not provide a definition of well-being, mental health is clearly not merely about the absence of mental disorders. For a defi- nition of mental well-being, in this book the description proposed by Linton et  al. (2016) is suggested: dimensions linked to the theme of mental well-being assess the psychological, cognitive and emotional quality of a person’s life. This includes the thoughts and feelings that individuals have about the state of their life, and a per- son’s experience of happiness. A first comment regarding these definitions of mental health and mental well- being is that it is difficult to say where the one ends and the other begins. Furthermore, although the WHO definition of mental health talks about a state, this is not a very transient or momentary state. Mental health usually is not thought of as fluctuating over the course of a day. The time dimension of mental well-being is less clear. Happiness can be used to describe a very momentary state of affairs or be inter- preted more in terms of life satisfaction: satisfaction with one’s life when looking back over a longer period of time (Eid and Diener 2004). Linton et  al. (2016) seem to focus on the latter, given their use of the term ‘state of their life’. Furthermore, both life satisfaction and happiness may be thought of as having both a hedonistic (pleasurable) and a eudaimonic (meaningful/fulfilling) component (Ryan and Deci 2001). In the remainder of this chapter, when we use the term ‘mental health’, men- tal well-being is implied. S. de  Vries and R. Snep