11. Biodiversity and Health in the Face of Climate Change: Implications for Public Health

Public health is “the art and science of preventing disease, prolonging life and promoting health through the organised efforts of society” (Acheson 1988), and it focuses on the entire spectrum of health and well-being, not only the eradication of diseases. Public health activities can be targeted at both the population and the individual levels. Population-level interventions include those applied generally, such as a health campaign to increase knowledge and awareness of health risks or fluoridation of water supplies to reduce tooth decay, to those aiming to address the social, economic and environmental conditions that cause ill health, such as an urban regeneration project. Individual-level public health activities include personal services such as vaccinations, behavioural counselling and health advice. Non-medical interventions to individuals, which take place outside the clinical setting, and have a positive impact on health and well-being, also fall within the remit of public health. Such interventions include those promoting exposure to biodiverse environments.

Modern public health emphasises reducing avoidable differences in ill health between the most and least well-off in society (Acheson 1998; Marmot 2010). Morbidity and mortality rates are consistently and starkly higher among those with lower socio-economic status (SES) – typically 5–10 years’ reduced life expectancy compared to those who are relatively more affluent (Marmot 2013; Elo 2009). Individuals of lower SES tend to live and work in less healthy environments and have higher exposure to disease risk factors; these are “social determinants of health” (Marmot and Wilkinson 2005). Moreover, lower SES is independently associated with a further 2-year reduction in life expectancy even after accounting for other risk factors for mortality, such as cardiovascular risk factors (Stringhini et al. 2017). The traditional approach to preventing disease – that is, counselling to reduce unhealthy behaviours – does not effectively address this phenomenon, because social and physical environments and circumstances mitigate behaviour change. Such inequalities are high on the political agenda (Marmot 2010, 2013; Marmot et al. 2008; Stringhini et al. 2017), and addressing the social determinants of health is an important and emerging area of clinical and public health practice (Axelson et al. 2018; Andermann 2016).

Reducing unhealthy behaviours requires the construction of supportive environments that facilitate healthier lifestyles. A biodiverse natural environment is a health-promoting resource (Lovell et al. 2014). More fundamentally, biodiverse environments are a foundation for human well-being and health, helping to sustain ecosystems that provide human health benefits, including within nutrition and medicine. A number of suggested conceptual and practical frameworks have been described that link ecosystem health and biodiversity with human health and well-being (Keune et al. 2013; Tzoulas et al. 2007, Fig. 11.1).

Biological diversity (biodiversity) is “the variability among living organisms from all sources including, inter alia, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part; this includes diversity within species, between species and of ecosystems” (United Nations Convention on Biological Diversity 1992). Consequently, biodiversity can be categorised in many ways. Genetic diversity, although often not apparent visually, is arguably the fundamental level of biodiversity that underpins all the others. Where genetic variation is low, wildlife and agricultural populations tend to be less resilient to environmental changes including disease, pollution and the impacts of climate change. Within a single species, underlying genetic variation can be crucial in providing phenotypic (i.e. observable) differences. For example, the single species Canis lupus familiaris (domestic dog) provides a range of valuable attributes to benefit humans, including support for hearing, seeing, disease detection and companionship. Within species, there are less visible genetic differences; for example, individual street trees have differing levels of tolerance to pollution. Genetic diversity can also be important in providing sustainable crops and in moderating disease pathogens. For most people, morpho-species (organisms that look different from others) provide the basis for perceived species richness. The number, type and mixture of species (community structures) provide useful measures of richness at a fairly basic level.

At a broader level of diversity, organisms live in habitats that may form distinct entities, usually described in terms of their vegetation or physical characteristics (e.g. woodlands, grasslands, ponds, rivers). Habitats may be complex, featuring gradual horizontal transitions between different types (tall herbaceous vegetation merging into scrub and then becoming denser and taller woodland; open areas of water, becoming vegetated at the edges, merging into marshy areas and then wet grassland). Complexity is also increased by the vertical layers found within them (woodlands may feature ground vegetation, herbaceous layers, scrub, lower canopies of saplings, full canopies of mature trees and emergent trees that poke beyond the canopy).

Some ecosystem benefits in Fig. 11.1 rely on explicit exploitation of biodiversity (e.g. for food, medicine). There is abundant evidence that biodiversity is required for the basic needs of life (e.g. food, clean water). However, for ‘nature experience’, biodiversity could have an impact on human health via multiple pathways, and these could operate differently depending on whether the nature experience is ‘passive’ or ‘active’. A more biodiverse environment may offer greater opportunities for active participation, whereby the pathways to health outcomes could include physical activity and a reduction in social isolation. There are a number of theories proposed by which passive exposure to nature improves well-being, including Wilson’s (1984) Biophilia hypothesis, Ulrich et al.’s (1991) Stress Recovery Theory, and Kaplan and Kaplan’s (1989) Attention Restoration Theory (see Marselle Chap. 7, this volume, for further discussion of these theories). Specifically, greater biodiversity may offer greater scope for ‘soft fascination’ (passive interaction, entered into almost involuntarily, catching and holding one’s attention), a feature of Attention Restoration Theory. Greater biodiversity would also be more likely to trigger the innate response predicted by the Biophilia Hypothesis.

A given habitat can simultaneously provide multiple ecosystem (and therefore health) benefits. For example, tree canopies and open water provide shade and cooling in urban areas, providing physical benefits to human physiological systems, and can elicit aesthetic and spiritual benefits, thereby reducing stress, mental fatigue and exhaustion. Exposure to greenspace has been linked to a range of health benefits (Maas et al. 2006; Nieuwenhuijsen et al. 2017), and more naturalistic (and therefore possibly more biodiverse) environments have been postulated as being best suited to promoting such benefits (e.g. Tyrvainen et al. 2014). There is little empirical evidence that biodiversity specifically (rather than natural environments in general) contributes directly to human health and well-being. Lovell et al.’s (2014) systematic review identified only 17 studies that included an explicit consideration of biodiversity and a health outcome, ten of which suggested an association. In the wider literature, there is some expectation that habitats found to provide health and well-being benefits may also be biodiverse; for example, Park et al. (2011) reported mood changes, including in depression, when comparing forest to urban settings. One major work that does explicitly link human health with biodiversity in an urban context is Fuller et al. (2007), who found an increase in psychological well-being with exposure to sites of high biodiversity (species richness). Luck et al. (2011) also described associations between well-being and biodiversity (especially of vegetation). Much other research in this area provides evidence of (mainly positive) links between people’s perception of biodiversity and health and well-being benefits. From the wider literature, we can postulate some specific components of biodiversity that link to aspects of public health. Figure 11.2 presents a summary of our review of the links between levels of biodiversity (rows) and domains of public health (columns). The body of the table gives our assessment of the state of the evidence for links between the domains and levels of biodiversity. In general, the evidence for a direct link between biodiversity and health outcomes (the column on the right of Fig. 11.2) is less clear since the evidence of a causal relationship is less well established. However, there are plausible indirect links via the provision of the basic needs of life, which links to well-being and mental and physical health outcomes. There are also plausible (but unproven) direct relationships between exposure to biodiversity and mental and physical health outcomes. The following subheadings take each public health domain in turn and provide some selected examples to illustrate a public health viewpoint. A comprehensive review is beyond the scope of this chapter.

Human societies increasingly place species and natural habitats (especially biodiverse habitats) under considerable pressure (Lawton et al. 2010). Threats to biodiversity include urbanisation, intensive agriculture, increased pollution and impacts of climate change. Whilst the first three threats can be managed locally, regionally or nationally, climate change requires international cooperation. The role and responsibility of public health experts to campaign on climate change and other threats to biodiversity are given forcefully in the 2015 Lancet Commission on Health and Climate Change (Watts et al. 2015). It has become vital for health departments of governments not to operate in isolation; health professionals need to ensure that climate-health-related considerations are integrated into government-wide strategies. One example of cross-governmental working can be seen in the recent UK Environment Strategy, in which health features as a major section (DEFRA 2018). In addition to averting biodiversity loss (e.g. preventing deforestation), climate-related topics requiring cross-governmental thinking also impact directly on public health (e.g. phasing out coal as an energy source will protect cardiovascular and respiratory health). Initiatives to support lifestyles that are healthy for both humans and the environment will also help to provide resilience in the face of the health risks posed by climate change. See Keune et al. Chap 15, this volume, for further information on international and national nature-health initiatives.

Public health professionals need to ensure investment in health systems that can respond to climate change-induced threats to human health. For example, urban flooding can be a significant risk to human health both directly (through the risk of drowning) and through exposure to pathogenic microbes (Jørgensen et al. 2016). Similarly, changes in extreme temperatures in cities (including in Europe) are contributing to significant increases in heat-related mortality levels (Mitchell et al. 2016). Drought conditions can also exacerbate risks to health, for example, from microorganisms in the plumes from cooling towers (Pagnier et al. 2009), since water drawn from rivers containing municipal waste may become more concentrated during droughts.

The appropriate policy for maintaining and developing greenspaces of appropriate size and accessibility for public health has long been debated. In 1929, for London (UK), Unwin recommended 7 acres (2.83 ha) of greenspace be allocated per 1,000 people as playing fields (first report of the Greater London Regional Planning Committee in 1933, cited by Turner 1992). Later work for English Nature recommended an Accessible Natural Greenspace Standards model with (inter alia) at least 2 ha of natural greenspace within 300 m of all residents and at least 2 ha of Local Nature Reserve per 1,000 people (Harrison et al. 1995). It was recognised that such guidance was not being implemented by all local authorities and Pauleit et al. (2003) recommended the standards become flexible to address local contexts. Whilst greenspace standards may be appropriate to promote human health and well-being, these may need to be revised if greenspace is to mitigate the impacts of climate change on urban centres. For additional discussion about how human health is addressed in planning legislation, see Heiland et al. Chap. 20, this volume.

The International Convention on Biodiversity (2017) suggested that there is already sufficient evidence to justify several actions to protect human health, including integrating biodiverse greenspaces in urban development. It identified the need to address the drivers of ill health and biodiversity loss together (for further discussion on policies linking biodiversity, health and climate change, see Korn et al. Chap. 14, this volume). Governments should invest in research and monitoring, including quantifying the savings from reduced health-care costs and the enhanced productivity that would accompany climate change mitigation (Convention on Biodiversity 2017; Watts et al. 2015). Internationally, governments must support countries to become low carbon economies as a global endeavour (Watts et al. 2015), since consumption in wealthier countries drives carbon use in less wealthy countries. Public health professionals need to engage the public as well (Corner et al. 2014): framing climate change concerns around health and well-being may be more powerful than arguing to conserve the environment without an explicit link to human health (Myers et al. 2012).

Locally, a public health-informed system would encourage cities to support lifestyles that benefit both humans and the environment. Steps to achieve this include the development of highly energy-efficient sustainable housing; available low-cost active transportation; and increased access to greenspaces. These measures would promote more resilience in human health, whilst also reducing urban pollution, greenhouse gas emissions, rates of diseases associated with poor air quality (Watts et al. 2015) and diseases associated with a sedentary lifestyle (e.g. cardiovascular disease, cancer, obesity, diabetes). Whilst we acknowledge that all such actions are vital to the public health professional’s role, here we focus on access to biodiverse greenspaces.

Although cities are places where the benefits of nature have been historically disregarded in favour of clean and hygienic space (Keune et al. 2013), the concept of greenspace as a resource for public health is long-standing. Access to, and immersion with, nature was first championed in 1772 by the English politician, Joseph Addison and later by the founder of nursing, Florence Nightingale (1860). Many Victorian public parks were created as a public health resource (Wheater et al. 2007). Historically, the visual experiences of rural landscapes as a source of refreshment and renewal of physical, mental and spiritual health was thought to complement medical approaches, and this belief influenced the location of asylums in the 19th century (Hickman 2009). The tradition of therapeutic landscapes was suggested in 1992 by Wilbert Gesler (Bell et al. 2018), who described these as natural environments, which interact with the social environment, to provide spaces of healing.

A complex set of transactions between accessing greenspace and participating in greenspace led Bell et al. (2018) to develop “palettes of place” from macro-scale areas (countryside, coasts and seaside), through meso-scale (urban parks and riversides) to micro-scale palettes (hospitals, clinic gardens, woods and allotments). Pauleit et al. (2003) make the point that greenspace needs not only to be accessible, but also of good quality. Quality influences the way nature is perceived, and the extent to which people participate in and use nature (Kaplan and Kaplan 1989; Pretty et al. 2005). The modern shift to engage nature has emerged from an ambition to use biodiversity to nurture human health. Hence, the appetite to determine the effect of a mere view of nature has evoked research in a range of settings, populations and activities to illustrate the therapeutic influence of the landscape. For example, Ulrich’s (1984) seminal work exploring the restorative influence of views from windows on post-operative recovery of patients following cholecystectomy was one of the first influential studies to demonstrate the positive effects a view of nature can have on recovery. Ulrich reported that patients with a view of trees spent less time in hospital and required less analgesic than those without such views. It is worth noting that behaviour and cognition may also be moderated by naturalistic views: Kuo and Sullivan (2001) recorded reduced aggression associated with mental fatigue for residents in greener (nature-based) buildings, and Taylor et al. (2002) identified increased self-discipline (in girls at least) with increased natural views from home.

The ways in which exposure and engagement with nature for well-being has diffused into contemporary public health intervention strategies has been described in a series of models, which we have integrated and reformulated to incorporate the potential for biodiversity enhancement (Fig. 11.3). As a starting point, three distinct ways in which individuals engage with nature are described (Haubenhofer et al. 2010): (i) through outdoor activities such as walking as part of everyday life activities; (ii) through recreational activities such as the use of cycle paths and structured outdoor activities that could promote health; and (iii) nature being used as a therapeutic intervention within a ‘green-care’ context (left to right in Fig. 11.3). The latter includes, for example, those “nature-based therapy or treatment interventions — specifically designed, structured and facilitated for individuals with a defined need” (Bragg and Atkins 2016: 18). Hence the ‘nature, health and well-being sector’ is a term used to describe green care and health promotion services. The levels of nature and extent to which nature can be used to support well-being is depicted from top to bottom of Fig. 11.3 as earlier described by Pretty et al. (2005), who note that at one level (“viewing nature”), an individual is simply exposed to an environment through vistas; a second level (“being in the presence of nature”) involves greater participation in nature through activities such as walking or gardening (referred to as green exercise). The final level (“active participation in nature”) is based on a more prescribed approach where activities are considered as “therapies”, with an intention to treat, heal or alleviate through experiencing and interacting with nature. Since none of the existing models explicitly consider biodiversity, we have added consideration of how biodiversity links with each of the levels of engagement and how this may be enhanced to improve actual (as well as perceived) biodiversity. The intensity of the exposure to biodiversity varies depending on activity, and is likely to be higher when the participation is more active. For example, conservation volunteering may involve handling plant-life and soil, which brings people intimately in touch with biodiversity (soils can be extremely biodiverse even if they are not always perceived that way). Therapeutic gardens could be biodiverse, for example, through the variety in species required in the creation of a sensory garden. As per the Bragg and Leck (2017) extension to the existing models, well-being and the promotion of health are not static, and individuals often move across and within the nature, health and well-being sector (i.e. horizontally between health promotion and health therapy, and diagonally between different activities and therapies).

Box 11.1 is a case study that illustrates the variety of activities that can be supported in a community forest. This suggests multiple beneficial opportunities to access, engage with and, where prescribed, undertake as a therapy. Active participation probably has greater health benefits (Collins and O’Callaghan 2008), and more biodiverse environments can increase the therapeutic effects on humans (Annerstedt and Währborg 2011). Interventions that encourage people to support biodiversity, for example through choice of species when gardening, have the potential to simultaneously improve both human health and the health of the semi-natural environment (see Box 11.2).

Research over the last 20 years describes a range of nature-based activities that constitute green care and, crucially, the positive impact on health and well-being for people who may be vulnerable or socially excluded (Berget et al. 2012). The increased interest in such innovative approaches to well-being has led to a proliferation of terms used to denote nature-based work; consequently, the terms green care and nature-based interventions are often used interchangeably (Bragg and Atkins 2016). The spectrum of nature-based activities includes gardening, vistas and walking, food growing, community gardens, prescribed (for example, an imposed or recommended regimen) exposure to nature, nature-based activity or structured green care activities (Green Care Coalition 2017). Thus, social prescriptions using outdoor nature-based approaches, as available within the nature, health and well-being sectors, provide one way in which health professionals with a public health role might facilitate individuals to access biodiverse greenspace.

A major drawback in using greenspace to improve public health is that those who are socially disadvantaged are least likely to have access to good quality greenspace. The health benefits from biodiverse environments tend to be disproportionately experienced by the most advantaged sectors of society (Diaz et al. 2006). This is a social justice issue: the wealthy have less need of the health benefit; they tend to already possess greenspace by having the financial resources to live in greener areas and to own private greenspace; they may travel more extensively to areas of natural beauty; they are more likely to exercise/make use of the greenspace; and finally, they are more likely to displace less advantaged communities from newly greened, previously brownfield sites (i.e. in a process of gentrification).

Estimates of health impacts due to SES can be made at a geographical area level, where for a given area the average SES status is known and health data are available. At such geographical areas (carried out at the neighbourhood level, approximately 1,500 persons), it is also possible to measure aspects of the natural environment using geographical information system databases. These area-level analyses show that greenspace is positively associated with health, even after accounting for SES, e.g. in Holland (de Vries et al. 2003) and the UK (Mitchell and Popham 2008; Dennis et al. 2018). Indeed, the impact of greenspace on health is greater for those in the most deprived neighbourhoods (de Vries et al. 2003; Mitchell and Popham 2008). Specifically, Mitchell and Popham (2008) demonstrated that proximity to greenspace reduced health inequalities, and that this effect was stronger in the neighbourhoods with the lowest SES (Fig. 11.8).

Good access to greenspace in the local environment can disrupt the expected link between relative poverty and ill health (Mitchell et al. 2015). However, Wolch et al. (2014) warn that policies promoting greening of areas for those community areas most in need of such a disruption of health inequality may lead to gentrification and a displacement of the very people most in need. They advocate a balance of greening “just enough” to provide benefits without too great a disruption to planning and development. More research will be needed to determine whether this is appropriate, feasible and at what level it should be implemented.

Residing near to greenspace may not guarantee the full benefits of the natural environment, and in areas where greenspace is more fragmented a more targeted approach might be needed to bring people into contact with nature. This is where the nature, health and well-being sector could target those in socially-deprived neighbourhoods (by using social prescriptions for nature-based interventions) to fit within a public health strategy that aims to reduce inequalities in health.

Human health is intricately linked with the natural environment. Preservation of the variety of life on the planet is essential to maintain the complex interdependencies between ecosystems and human life. Biodiversity, because of its fundamental relationship with ecosystems services, helps to mitigate the effects of climate change, but is itself at risk of loss due to climate change. Arguably the single biggest priority for public health at a strategic international level is to work across governments and countries to protect biodiverse natural resources and introduce measures to stem climate change. Moreover, public support for such an endeavour is likely to be higher if the enormous impact on the health of the human population is emphasised as the outcome of a successful strategy to protect biodiversity and tackle climate change.

Public health professionals need to work on a large scale to support maintenance, enhancement and development of accessible, biodiverse greenspace. Public health leaders should work within governments to ensure that health considerations are incorporated into environment and sustainability strategies, and vice versa. Such strategies should be cognisant of the fact that populations that suffer from poverty and ill health are disproportionately more likely to also suffer from a lack of biodiverse natural environments. While these populations are a priority target for interventions to improve biodiversity, care should be taken that these efforts, by making the environment more pleasant, healthy and desirable, do not cause poorer populations to be displaced.

Public health practitioners are responsible for devising strategies to promote sustainable lifestyles and facilitate access to natural environments. Access to natural environments should be targeted at those most in need. There is an urgent need to embrace the fact that the natural environment is salutogenic, i.e. health giving. There is an equally urgent need to relax the usual positivistic standards of evidence of effectiveness required in medical intervention, and to utilise more suitable methods to evaluate nature-based solutions, for example, using quasi-experimental or mixed methodologies. This will allow more confident investment in schemes that prioritise access to nature over medical intervention. A significant driver for local decision-makers is the anticipated reduction in health-care costs, since improved outcomes will prevent costly use of doctors and hospitals. Such schemes, including nature-based social prescribing, give local commissioners of services the opportunity to target those from socio-economically deprived areas. Those with responsibility for social prescribing should be encouraged to use prescriptions that bring people into contact with nature, preferably where that engagement is active rather than passive. Further, it is likely that interventions resulting in exposure to environments with greater biodiversity will offer the greatest benefits for human health.

Whatever the scale, biodiversity has a fundamental role to play in human health and well-being. Public health professionals need to embrace biodiversity as a resource and be willing to fight to protect it. In so doing, they can target vulnerable populations and reduce inequalities in health between the richest and the poorest in our society.