Healthy planet, healthy people

Climate change is now recognised as one of today’s dominating threats to human health [1]. Alterations in infectious, parasitic and zoonotic diseases, heat- and cold related mortality, and consequences of extreme events provide overt examples of expected health impacts [2, 3]. Insidious, chronic effects of climate change are less well recognised, but may be very significant and will most probably increase over time. Such include for example secondary impacts, like impaired fresh water flow, and tertiary impacts, like health risks associated to escalating resource conflicts [4].

The latest report from the World Health Organization (WHO) concludes that climate change is expected to cause approximately 250 000 additional, unequally distributed deaths annually between 2030 and 2050 [5]. Yet, these figures probably represent underestimations as longer term secondary and tertiary impacts are not accounted for.

The health sector and the public are waking up at last

Climate change has, by convention, been considered a topic to be dealt with by ecologists and other environmentally related disciplines, and has been underestimated as a serious health issue. The awareness among both health professionals and the public has consequently been insufficient. The direct link to human behaviour has neither been acknowledged. This has resulted in insufficient investments in preparing for climate change impacts on health and an unawareness of the urgent necessity of interactive collaborations between the environmental, behavioural and health sector.

However, as immediate health consequences of climate change are now emerging the topic is gaining increased attention amidst the health sector and in policies [1]. A few studies have also investigated the knowledge of health impact of climate change among the general public, showing that although awareness of health impacts exist the salience is lacking [6]. This demonstrates the value of communicating the health risks that our unsustainable behaviour results in and it has been called for reframing climate change as a public health issue for a better understanding of our dependence on healthy ecosystems [7–9].

More must be done and novel ideas must be explored

Studies and reports from medicine and public health are increasingly addressing the issue of health impacts from climate change [1, 2, 10–12]. However, much more research is needed, particularly in low-income countries, often the most vulnerable to health effects of climate change [4].

Environmental threats do not fall into individual risk factor categories (in the way that tobacco consumption can be readily studied by, for example, epidemiological methods) but are inherently more complex and elude causality studies and efficient interventions at individual or family levels. In spite of some efforts of interdisciplinary research projects, we do not yet have sufficient knowledge to predict which interventions are most appropriate for particular environmental threats. This obstructs the development of efficient policies and actions for facing and managing current and future environmental challenges in the public health sector.

Many of today’s health care approaches regarding the health impacts of climate change are of a downstream character, based on preparing for what to do when extreme events occur, rather than working upstream to hold disasters at bay. An upstream approach by the health sector to reducing climate change would involve mitigating strategies with possibly much larger and cost-efficient health and environmental benefits.

Engineering and economic system changes for reducing GHG emissions and revert the rapid speed of climate change are promising, but insufficient to meet the climate stabilisation targets of the Sustainable Development Goals (SDGs). Individual and household behaviour changes are also necessary and this is an area for the health sector to urgently start exploring and implying. Dietz et al. [13] showed that environmentally aware household actions could substantially reduce carbon emissions, with little or no impact on general wellbeing.

In a recent editorial on climate change and human survival in the British Medical Journal, McCoy et al. write that health professionals “should each use whatever influence we have to change the minds and behaviour of others” [14]. This is an ethical call for the health sector to adopt a novel model for achieving sustainable health, and resisting and mitigating the severe consequences of climate change. We must learn how to adopt such a model and what ethical tools to use for changing “the minds and behaviour of others”, and not the least ourselves.

What is the desired behaviour?

Pro-environmental behaviour (PEB) is a behaviour that can have major impact on preserving ecosystems and mitigating climate change [13]. It can be defined as the propensity to take actions and decisions with pro-environmental impact and is commonly understood to be a consequence of attitudes and concerns related to ecosystem destruction, climate change, and other adverse ecological impacts of human activity [15]. PEB is exemplified by behaviours such as decreased use of motorised transport, adopting of recycling, choosing environmentally labelled products, or changing eating habits to more vegetarian food. It can be measured using, for instance, the General Ecological Behaviour (GEB) scale, a reliable and validated measure determining the function of environmental values and intentions, and responsibility feelings [16].

Incorporating efforts towards PEB into public health research and actions, and also explore how such behaviours may be induced, would be one way to reply to the call for health professionals to change human behaviour and actively embrace climate change as part of the medical curriculum.

How can behaviour be changed?

Behaviour change for the environment has been approached on a societal level through, for example, provision of information, policies, legislations, or enforcements, often with limited success in terms of desired behavioural outcomes and particularly sustained behaviour change is rarely achieved [17]. Although public awareness about climate change is relatively high the behavioural response is small, referred to as the so called “attitude-behaviour” or “value-action” gap [18].

Theories, with more or less empirical support, concerning factors that influence PEB, include the Theory of Planned Behaviour [19], the Value-Belief-Norm [20], and the Theory of Normative Conduct [21]. In research on motivational factors, concepts like “warm glow” or “helper’s high” [22, 23] have been suggested, which link evolutionary adaptive traits of humans (by doing good to others your chance for survival increases and is therefore an inherited quality) to biological development, as the brain reacts on us “doing good” by releasing ‘feel-good’ neurotransmitters, like oxytocin [24]. These concepts have mostly been applied in relation to pro-social behaviour, but links have also been drawn to PEB [25].

Behaviour change from a biological perspective

Physiological reactions are evoked by internal or external stimuli. These reactions, steered by the brain, result in particular behaviours that are beyond our control of will. For example, stress stimuli automatically induce less cognitively influenced behaviours, by impeding or suppressing activity in the prefrontal cortex (PFC) of the brain [26]. PFC is in charge of higher order cognitive functions, memory, and decision making and stressful stimuli may therefore induce less rationally based behaviours as consequence [27]. Thus, depending on type of stimuli our decision making is unconsciously directed in various ways.

Research in psychology and neuroscience has shown that individual decision-making and subsequent behaviours depend on both rational and non-deliberative, automatic thinking [28, 29]. The rational system is controlled and deductive, while the automatic is uncontrolled, associative and environmentally determined [30]. External stimuli, affecting the automatic system, activates various parts of the brain, determining physiological reactions which in turn guide our behaviour [31].

Most research on human automatic processes has examined social stimuli and social behaviour [25].

Two major neuro-cognitive systems have been proposed as being responsible for socialising behaviour; the mirror neuron system [32] and the mentalizing system [32, 33], especially the mirror neuron system believed to occur automatically [29].

Other studies in the field of social psychology have looked at inducing commitment [16], but to date no consistent solution has been proposed. More importantly, the potential consequences of the theories and changes in behaviour are seldom taken into account in public health policies and activities.

Environmental stimuli and behaviour change

Compared to social factors or motivators, less research has considered physical environmental stimuli and subsequent automatically induced processes with behavioural impacts. Some studies looking at effects of enriched environments in rat models have revealed that stimulating environments increase levels of neurotrophic factors with consequences for behaviour, rats becoming more socially interactive [34]. This demonstrates how environments with positive cues induce certain behaviours, which might provide a first insight into what environments may be particularly important for automatically changing also human behaviour. However, the underlying mechanisms are unknown and comparable human studies have not been performed.

Other studies on environment and behaviour, defined within the scope of place-based determinants of life-style behaviour, have suggested that physical activity levels can increase by access to healthy environments [35].

Research on concepts like “choice architecture” or “nudging”, have also touched on the idea of how more or less disguised modifications of environmental features influence life-style behaviour [36, 37]. However, far less attention has been devoted to study health effects of behaviours other than those that are directly life-style related.

Recent research, examining behavioural differences along an urban-rural scale has opened a window of understanding on how environments influence neural processing and behaviour. Epidemiological and neuroscientific studies have demonstrated that urban (as compared to rural) dwellers have a higher risk of developing mental disorders [38, 39] and also differ in their capacity to cope with stress as indicated by changes in brain structure and function [40]. There is reason to suspect, therefore, that environmental cues may affect behaviour through automatic reactions initiated by the brain’s responses to the environment, but the area is insufficiently explored and it is unclear which environments might evoke particular behaviours. As urban environments seem to have a specific effect on brain function and behaviour it may be interesting to look into what is known about its counterpart - the natural environment, including urban green spaces.

Natural environments and automatic behaviour

Natural environments, such as woodlands or urban green spaces, are recognised for their positive effects on stress relief, health, and wellbeing, partly mediated by automatic physiological and neurophysiological reactions [41, 42]. Nature also seems to have an impact on our cognitive function [43]. Even brief encounters with nature and passive exposure may result in immediate effects [44, 45]. A recent brain-imaging study showed that exposure to nature decreases rumination resulting in a reduced risk for depression [46]. The evidence on improved human health and wellbeing by green and natural environments is increasing, showing effects on mental health [47, 48], physical condition with effects on for example cardiovascular health [49], pregnancy outcomes [50], and cognitive and behavioural development [51, 52]. As part of WHO’s environment and health programme, an urban green space indicator has been developed as a proxy for a city’s public health potential [53].

Drawing on these studies, one may suspect that exposure to natural environments can have an immediate, spontaneous behavioural impact through automatic neuro-physiological reaction (see Fig. 1). That this behavioural impact would be in a pro-environmental direction is supported by a recently published study that actually demonstrated that nature exposure may promote environmentally sustainable behaviour, at least in a laboratory setting [54]. However, long-term effects and mechanisms remain to be explored.

Other studies have shown that aesthetically pleasing nature leads to prosocial behaviour [55], which in turn is connected to PEB [56]. Another study revealed that increased concern about marine sustainability was engendered by “nature exposure” through visiting an aquarium [57]. It has also been suggested that feelings of connectedness to, and restoration from nature are linked to PEB [58, 59]. Even childhood experiences in nature appear to enhance adult environmentalism [60] a perturbing fact as children of today spend less and less time outdoors [61].

Much of the research on natural environments’ impact on human beings sets itself within theoretical frameworks referring to humans’ evolutionary development in nature and how this might make us prone to wellbeing and automatically induced stress recovery [62, 63]. Other theories focus on how attention restoration in nature reduces mental fatigue and improves cognitive functioning [64, 65]. Altogether, these theories point in the same direction as suggested above – that nature may indeed induce immediate unconscious and automatic responses. An evolutionary fundament to potential effects on PEB by nature would suggest that the effect could also be retained over time.