Vries, S., de

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Nearby nature and human health: possible causal mechanisms and their implications

Vries, de, S.

NARCIS 

Wageningen Yield 

Nearby nature and human health:   
possible causal mechanisms and their implications 
 
Sjerp de Vries 
 
Alterra, Green World Research 
Wageningen University and Researchcenter (WUR) 
P.O. Box 47, 6700 AA Wageningen, The Netherlands 
 
 
Keywords: air quality, stress, physical activity. 
 
1. Introduction. 
Many people think of spending time in contact with nature as being good for their health. 
However, in the spatial planning of residential areas, the inclusion of green areas and 
elements to promote public health is not commonplace. There appear to be other, more 
pressing reasons leading to a preference for compact cities, densely populated, and 
with small amounts of greenery (Van den Berg et al, 2007). Why is the relationship 
between nature and health that so many of us assume exists, not more strongly 
reflected in health, spatial and nature policies? In this paper, we will look at the 
evidence base regarding the health effects of nearby nature in an urban context. The 
following two related questions will guide our evaluation: 
 
a. What exactly is the size of health benefits of having nearby nature in an urban 
context? 
b. What is the most efficient way to realise a health benefit of a certain size by 
making use of green space? 
 
2. Background. 
In the Netherlands, a relationship between the amount of nearby greenery and the 
perceived general health of residents has been observed (De Vries et al, 2003; Maas et 
al, 2006). The latter study showed that the proportion of people that reported having 
less than good health was about 1.5 times as high when only 10% of a 3-km circle 
around one’s residence consisted of green space than when this was 90%. Such 
studies give a rough idea about the possible dose-response relationships but due to 
their correlational nature, they offer little insight into the mechanism behind the 
observed relation. Moreover, it is not even clear to what extent the amount of green 
space plays a causal role at all. Although composition effects dealing with the socio-
economic status of the local population were statistically corrected to some degree, 
many alternative explanations remain possible. 
 
3. Possible causal explanations. 
The aforementioned studies were based on the premise that the amount of nearby 
nature would matter, because it would lead to more exposure to and/or contact with 
nature. The hypothesised importance of contact with nature was mainly based on 
theories and research on the restorative effects of such contacts (see e.g. Hartig et al, 
2003). Ideas about which type(s) of nature would be (more) relevant, were not very 
clearly developed, so all types were included: agricultural land, forests and nature 
areas, as well as urban parks. Finally, the 3-km radius was chosen somewhat arbitrarily 
(we also experimented with a 1-km radius, with more or less similar results). For 
practical purposes, it seems desirable to have more precise ideas as to why nearby 
nature would have a beneficial effect on human health and wellbeing and which 
conditions it should satisfy. Based on the literature, several possible mechanisms were 
identified. These range from green space improving micro-climate, to local greenery 
facilitating contact between neighbourhood members. We will briefly introduce what we 
consider are three of the most likely mechanisms, including their evidence base, 
namely, improving air quality by catching fine dust, reducing stress and/or restoring 
attentional capacity, and stimulating physical activity. Furthermore, we will discuss the 
implications the three mechanisms are likely to have for the spatial planning of greenery 
in an urban context. 
 
4. Discussion. 
It seems difficult for policy makers and practitioners to exploit the beneficial effects of 
nearby nature for human health, because it is not clear yet how much nature and of 
what type is needed to bring about a specific health effect. Space is a scarce 
commodity in an urban setting, and trade-offs have to be made; in politics, size matters. 
It also remains to be seen whether “all the good of green” can be realised by one and 
the same layout and type of greenery. Our preliminary analysis suggests that different 
mechanisms require different green structures and types of vegetation, and have 
different additional requirements. For example, to reduce fine dust levels, having lines of 
coniferous trees in the vicinity of (but not too close to) busy roads might be a good idea. 
But such areas may not be conducive to stress reduction (traffic noise) or physical 
activity (still poor air quality), therefore, focusing on one of the more prominent 
mechanisms might be a good idea. However, the relative importance of the different 
mechanisms is unclear. Even the optimal green structure per mechanism is not always 
clear, for example, greening building facades by using climbers and creepers requires 
very little space, however, its effectiveness in reducing stress has not yet been 
established. Perhaps offering nearby green oases of peace and tranquillity would have 
a much stronger effect. In other words: how important is the quality of the nature 
experience for it to have a restorative effect? More generally, are we able to move 
beyond showing the existence of significant effects in experimental settings, significant 
differences in cross-sectional studies, and significant relations in correlational studies, to 
assessing the long-term effect of the sizes of specific local greenery configurations in 
real-life settings? 
 
Key concluding points. 
• Within the Netherlands a positive relation between the amount of nearby green 
space and human health does exist, but … 
• The extent to which the amount of green space plays a causal role in this 
relationship is still unclear, and may be limited. 
• Three of the most likely mechanisms are: improving air quality, reducing stress 
and stimulating physical activity. 
• As far as we can tell, the above mechanisms differ considerably in their spatial 
implications: optimal green structures and types of greenery differ. 
• Research comparing different types of green space is scarce, even more so 
when it comes to long-term health effects in, for example, a residential setting. 
• In future research, a more functional look at urban green space seems desirable: 
what works how well for whom, and for what reason? 
• More specifically, mechanism-specific measures regarding the presence of the 
relevant type(s) of green space should be developed and tested. 
• Alternative explanations should not be overlooked, but actively researched 
(population density and cultural diversity, emission of air pollutants). 
 
References 
 
De Vries, S., et al (2003) ‘Natural environments - healthy environments? An exploratory analysis 
of the relation between nature and health’, in Environment & Planning A, 35, 1717-1731. 
 
Hartig T., et al (2003) ‘Tracking restoration in natural and urban field settings’, in Journal of 
Environmental Psychology, 23, 109-123. 
 
Maas J., et al (2006) ‘Green space, urbanity, and health: how strong is the relation?’, in Journal 
of Epidemiology and Community Health, 60, 587-592. 
 
Van den Berg, A., Hartig, T. and Staats, H. (2007) ‘Preference for nature in urbanized societies’, 
in Journal of Social Issues, 63(1), 79-96. 
 


et al (2006) ‘Green space, urbanity, and health: how strong is the relation?’,

Natural environments - healthy environments? An exploratory analysis of the relation between nature and health’,

Preference for nature in urbanized societies’,

Tracking restoration in natural and urban field settings’,

Nearby nature and human health: possible causal mechanisms and their implications

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