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Urban Nature: A Public Health Resource
Terry Hartig, PhD, MPH, Docent in Psychology
Institute for Housing and Urban Research
and
Department of Psychology
Uppsala University, Sweden
Paper presented at the conference "Naturen – En tillgång i Stockholmsregionen," April 3, 2003,
Stockholm, Sweden.
Introduction
I want to begin by thanking the organizers of this conference for the opportunity to present to you
today on the topic of "Urban Nature: A Public Health Resource."
How are we justified in thinking of urban nature as a public health resource?
I want to argue here that the widely shared concern for psychological stress as a major public health
problem adequately motivates our interest in urban nature as a public health resource.
Researchers ordinarily think of stress as a process, a process set in motion when a person perceives
that they cannot manage the demands they face.
When a person feels that it all has become too much – the noisy neighbors, heavy traffic, impossible
deadlines, the 80 email messages waiting in the inbox – then stress arises. We may see this in how
the person feels (perhaps tense and easily irritated), in how she behaves (perhaps more smoking or
drinking to ease tension), and in physiological changes (as with elevated levels of blood pressure,
muscle tension, and some hormones).
When stress becomes chronic, when it continues over a long period, then we may see an increased
susceptibility to a variety of illnesses. Research has over the past decades given us an increasingly
nuanced picture of the complex immune, hormonal and other physiological processes that play a
role in a person becoming "sick from stress."
Research over the past decades has also helped us to understand how widespread environmental
conditions like noise, or a heavy workload in combination with little control over the work, may
have negative health effects that we can see in populations, such as a higher incidence of heart
disease.
If chronic stress is a public health problem, then how does that make urban nature a public health
resource?
I frame it like this: Urban nature can serve the health of urban populations by providing people with
easily accessible opportunities to regularly interrupt the stress process and renew the psychological
and physiological resources they need to go on with their everyday lives.
Two mutually reinforcing aspects of the experience afforded by urban nature seem particularly
important in this.
1. One is gaining psychological distance from the demands and routines of everyday life. This
allows or permits stress recovery.
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2. The other is being able to appreciate natural scenery. This advances or promotes stress recovery.
To date, we lack solid epidemiological evidence that connects the recreational use of urban nature
with the incidence of illnesses in which stress might play a causal role.
However, we do have a small but growing body of experimental evidence that concerns an
intermediate step – how people exposed to acute stressors show different patterns of stress recovery
in natural versus urban environments.
In the brief time I have, I want to present for you some of this experimental evidence. I will
mention results from some of my laboratory and field experiments on the stress-reducing effects of
natural environments and natural features for people living in cities.
The natural – urban comparison in each of these experiments is practically important: We have to
consider what other settings urban residents would find when in search of restoration, if they did not
have access to parks and other relatively natural environments.
Study 1: Umeå experiment
With the first two experiments, I want to make the point that even a very brief period of passively
looking at pictures of a natural environment can help a person feel better following a stressful
experience, in comparison to an urban condition that might otherwise be available for stress
reduction.
In each of these experiments, groups of university students viewed a long series of slides that
simulated a walk either through a forest – Gamlia in Umeå – or through downtown Stockholm.
In the first experiment, students at Umeå university (N = 34) viewed the slides for about 14 minutes
immediately after performing a set of rapid-paced, attentionally demanding tasks for 50 minutes.
They then completed a questionnaire that asked them to describe how cheerful, affectionate, warmhearted and so forth they felt at just that moment.
Here we see their results (Figure 1). Those students who viewed the forest scenes show more
positive affect – that is, essentially, more positive emotion – than those students who viewed the
Stockholm scenes.
Note that the scale ranges from 1 for not at all to 5 for very much. A higher score indicates more
positive affect.
Study 2: Göteborg experiment
In a second experiment, students at Göteborg university (N = 36) viewed the same slides for about
14 minutes immediately after attending a lecture for 3 hours. They then completed a questionnaire
on which they rated words like "friendly" and "playful" on how appropriately they described how
they felt just then.
Note that the scale ranges from 1 for not at all appropriate to 5 for completely appropriate. A higher
score indicates more positive affect.
Here again, we see that the groups differ in positive affect, this time for measures grouped as
"Hedonic Tone" and "Relaxation" (Figure 2).
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These may look like small differences, but in relation to the degree of variation in the scores, they
are fairly substantial, and the effects are statistically reliable.
Also, bear in mind, this is quite a mild intervention; they only looked at pictures of one or the other
environment for 14 or so minutes.
Study 3: Orange County experiment
I want to emphasize that this is not just a matter of people saying that they feel happier. In this next
experiment, we also looked at physiological aspects of stress recovery that might occur as a person
actually walks in an urban forest. I completed this experiment in Orange County, California, part of
the large Los Angeles-Orange County metropolitan area.
In this experiment, we first randomly assigned equal numbers of men and women to two
environmental conditions, one involving a walk in a nature preserve, and the other involving a walk
in an area of medium-density retail and office development with substantial car traffic (the urban
environment).
The subjects were healthy, young university students. After going through initial preparations at a
central location, they drove to the assigned field site. The routes to the two sites were carefully
matched in terms of distance and the number of potential stops. The subjects made the trip during a
low-traffic period of the day, so the traffic faced on the different routes would be similar.
An important part of the measurement procedure involved an ambulatory blood pressure monitor.
Each subject wore such a device throughout the course of the experiment. We had programmed the
device to take readings at 10-minute intervals, from the time of the initial preparations, during the
drive, and during the walk. During the initial preparations we collected a set of measures while the
subject sat quietly. Thus, we could look at how much blood pressure increased or decreased at
different points in the experiment, relative to a baseline value obtained while the subject rested.
We could establish from the blood pressure measures collected during the drive to the field site that
on average the drive itself caused a significant increase in blood pressure over the baseline value.
Thus, the drive functioned as a stressor, and to an equal degree for both groups. This established the
possibility for stress recovery to occur directly after the drive.
Complicating matters somewhat, half of the subjects assigned to each environment completed a
lengthy series of attentionally demanding tasks after arriving at the field site. We added this into
the experimental design as a means to test competing theories about the restorative effects of
environments. This is not the place to go into detail on this issue; what is important here is that
performing the tasks also elevated blood pressure, and to a level similar to that seen after the drive.
At the field site the participants took a long walk. Let's look now at the blood pressure results from
the walk (Figure 3). Two features of these results are important here. First, in agreement with our
expectations, during the initial half of the walk systolic blood pressure declined among the subjects
in the nature preserve, while it increased among those in the urban environment. By 20 minutes into
the walk, systolic blood pressure had declined to the baseline level, despite the fact that the subjects
were standing rather than seated.
Secondly, we see that the trends reversed sometime after the measure obtained at 20 minutes into
the walk. We think that this has to do with the fact that the subjects turned back to the field lab after
walking for 25 minutes. We can then interpret the change as a reflection of negative anticipation;
the subjects in the nature reserve understood that they would soon leave it.
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In addition to change over time in blood pressure, we measured change over time in the subject's
emotions. Before they made the drive to the field site, and then again just after they finished the
walk, they filled out a short form indicating the degree to which they experienced a variety of
emotions. Some of these, like being affectionate or cheerful, we could group together as a measure
of positive affect, or positive emotion.
As in the first experiment, the scale ranges from 1 for not at all to 5 for very much. A higher score
indicates more positive affect.
As we can see (Figure 4), having walked in the nature reserve increased positive emotion, while
having walked in the urban environment reduced it.
Notice that the blood pressure and emotion data speak to both the positive impact of walking in the
natural environment and to the way in which the urban environment hindered these subjects'
recovery from stress.
Conclusion
What do these studies imply for professionals who are concerned about (1) promoting health and
preventing disease in urban populations and (2) managing the demands of varying groups for urban
land?
I return to my earlier point: Urban nature can serve the health of urban populations by providing
people with easily accessible opportunities to regularly interrupt the stress process and renew the
psychological and physiological resources they need to go on with their everyday lives.
To the extent that we do not make natural settings available to people living in cities, we have to ask
whether the land is otherwise going to uses that might also serve restoration – or to uses that instead
increase the level of psychological demands that residents will have to face in their everyday lives –
more crowding, more traffic noise, more air pollution, and so forth.
Note. For further details on the studies mentioned here, see the following articles:
Hartig, T., Böök, A., Garvill, J., Olsson, T., & Gärling, T. (1996). Environmental influences on
psychological restoration. Scandinavian Journal of Psychology, 37, 378-393.
Hartig, T., Evans, G. W., Jamner, L. D., Davis, D. S., & Gärling, T. (2003). Tracking restoration in
natural and urban field settings. Journal of Environmental Psychology, 23, 109-123.
For additional reading on restorative values of natural environments, see the following:
Bodin, M., & Hartig, T. (2003). Does the outdoor environment matter for psychological restoration
gained through running? Psychology of Sport and Exercise, 4, 141-153.
Hartig, T. (1993). Nature experience in transactional perspective. Landscape and Urban Planning,
25, 17-36.
Hartig, T., & Evans, G.W. (1993). Psychological foundations of nature experience. In T. Gärling &
R.G. Golledge (Eds.), Advances in psychology: Vol. 96: Behavior and environment: Psychological
and geographical approaches (pp. 427-457). Amsterdam: North-Holland.
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Hartig, T., Kaiser, F. G., & Bowler, P. A. (2001). Psychological restoration in nature as a positive
motivation for ecological behavior. Environment and Behavior, 33, 590-607.
Hartig, T., Mang, M., & Evans, G. W. (1991). Restorative effects of natural environment
experiences. Environment and Behavior, 23, 3-26.
Korpela, K., & Hartig, T. (1996). Restorative qualities of favorite places. Journal of Environmental
Psychology, 16, 221-233.
Korpela, K. M., Hartig, T., Kaiser, F. G., & Fuhrer, U. (2001). Restorative experience and selfregulation in favorite places. Environment and Behavior, 33, 572-589.
Staats, H., Kieviet, A., & Hartig, T. (2003). Where to recover from attentional fatigue: An
expectancy-value analysis of environmental preference. Journal of Environmental Psychology, 23,
147-157.