Cities are human-dominated environments and as such, the presence and persistence of nature is dependent upon urban residents (Rees 1997). The human-nature relationship is symbiotic because urban nature is not just reliant on the residents of cities, but evidence suggests that human wellbeing is associated with the presence of nature. This symbiosis is rarely recognised by the governments, planning bodies and residents of cities. A large body of disparate (and unintegrated) research from climate scientists, urban ecologists, the public health professions, epidemiologists, psychologists, and urban sociologists demonstrates the associations between human wellbeing and nature in urban environments, but much of it is hidden by disciplinary silos or remains unintegrated and therefore ignored. With more than half of the world’s population now residing in cities, urban populations continue to grow (WHO 2010). The unplanned sprawl of many cities presents challenges for their governance. These challenges are compounded by a lack of awareness of how important it is for the most-populous environments in the world, cities, to have thriving and diverse natural elements throughout.

While urban environments present opportunities for residents, they also concentrate risks and adverse effects due to the dense population, such as air pollution, chronic non-communicable disease due to urban lifestyles, and the climate change-related impacts of extreme temperatures, rising sea levels, and the emergence and spread of infectious disease (WHO 2010). Some of these risks may be mitigated by the presence of nature. For example, heatwaves increase morbidity in urban areas due to heat stroke and heat exhaustion (McMichael 1993; United Nations 2005), whereas healthy greenspaces reduce the effect of heatwaves by reducing heat storage and nighttime re-radiation (Whitford et al. 2001; Onishi et al. 2010; O’Neill et al. 2009; Bowler et al. 2010a).

A disconnect between urban residents and nature can emerge in some cities: transport is planned for vehicular traffic rather than bicycles or pedestrians, built environments often focus on the indoors, and modern urban residents’ may be more inclined to spend recreational time with electronic media and television because their surrounds do not lend themselves to outdoor recreation (Dustin et al. 2010). The symptoms and effect of this disconnect for children has been popularized as a ‘Nature-deficit disorder’ (Louv 2005). As this disconnect progresses, the presence of nature in cities becomes less important to residents, and therefore governments and planning bodies. There is evidence of this occurring in Australia, for example, where policy has allowed modern residential development to have only a small proportion of open space, or back yard (Hall 2010). This has ecological impacts on the urban environment, impacting the biodiversity and microclimates in cities (Hall 2010).

Key features of urban design and planning that impact human wellbeing have been identified: walkable space, community space, and greenspace. The associations between walkable space, physical activity, transport and health in urban design are widely accepted (for example, Badland and Schofield 2005; Saelens et al. 2003; Jackson 2003), and community or shared space enhances health through social interaction, and social interaction (Mukerjee 2013). Greenspaces, or vegetated areas, have the potential to mitigate pollution, encourage physical activity and, therefore, support health, and mental wellbeing (de Vries et al. 2003; Bergeman 2012). Each feature is often researched as discrete, but the benefits derived from walkable, community and greenspaces overlap, bolstering human wellbeing by encouraging physical activity, social engagement, mitigating extreme climate events, and enhancing mental health (Matsuoka and Kaplan 2008).

In this paper we identify two additional features of urban environments that are critical to urban residents’ wellbeing: biodiversity and ecosystem functioning. Biodiversity and ecosystem function have been positively correlated (Benayas et al. 2009), with biodiversity contributing to ecosystem functioning through a range of ecological processes and biodiversity loss degrading ecosystem health and diminishing ecosystem function (Luck et al. 2003). However, the meaning of each term is distinct. Biodiversity is the diversity of organisms, while ecosystem functions, or ecosystem services, are the outcomes of the “functioning diversity” that support human existence (Folke et al. 1996).

Human wellbeing

The World Health Organization’s (WHO) definition of health has not changed since its inception in the constitution in 1947: “Health is a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity” (World Health Organization 1947). The WHO definition highlights the complexity of health, involving physical, mental and social aspects. This reflects the recent global trend recognizing the complexity of wellbeing, as evidenced by a proliferation of multidisciplinary reporting. For example, the Organization for Economic Cooperation and Development’s (OECD) 2011 Better Life Initiative includes ten categories in its index: housing, income, jobs, community, education, environment, civic engagement, health, life satisfaction, safety and work-life balance; the World Economic Forum’s 2012 Wellbeing and global success report outlines three related aspects of wellbeing: effective work, effective families, and effective communities; and the United Nations’ 2005 Millennium Ecosystem Assessment outlines the interdependence between human wellbeing and ecosystem stability and health.

In order to consider human wellbeing, the environmental context is critical. Contrary to the common assumption that humans are separate to their environment, this approach acknowledges that “people are an essential part of the environment; they are as real as trees, rocks or skyscrapers, and their interactions with each other and with places …influence their health and well-being” (Lindheim and Syme 1983). Human wellbeing, then, takes into account the multiple aspects of health as outlined by the WHO, and the environment in which humans live. With more than half of the global population living in urban areas (United Nations 2012), the wellbeing of urban residents is a significant consideration.

Established aspects of urban design that support human wellbeing

The three identified aspects of the urban environment that support residents’ wellbeing are often researched as discrete features. While they do overlap and some research acknowledges that, such as the work on green infrastructure (Tzoulas et al. 2007), it is useful to describe each aspect separately, as each makes some unique contribution to urban design.

Walkable space

Walkable space is space that affords easy walking, that is, safe, well-graded, spacious paths, pedestrian areas and parklands. Walkable spaces are important for urban residents for numerous reasons, but in particular are a catalyst for physical activity.

Physical exercise has been positively associated with health. It decreases the body’s reaction to stress by impacting stress hormones (Larzelere and Jones 2008) and is associated with reduced morbidity and cardiovascular condition (Weber 2010). Physical activity contributes to weight maintenance, which is significant in societies with an increased incidence of obesity, or “over-nutrition” (Pretty 2006; United Nations 2005). Benefits of physical activity are not limited to humans, but have been exhibited in domestic animals as well (for example, Alessio et al. 2005). Tree-lined footpaths along streets are a common example of a walkable space. The space should be easy to use for all kinds of people, including – for example – children and the elderly. Even the longevity and wellbeing of senior citizens have been found to be improved by the availability of walkable space in urban areas (Takano et al. 2002).

There is an overwhelming body of evidence that demonstrates that physical activity is beneficial for mental health (Tagles and Idrovo 2012), with additional benefits of physical activity in a natural environment such as an urban park or garden. Benefits of this ‘green exercise’ include positive influences on mental health, mood and self-esteem that are even greater for study participants in areas containing natural elements than those in built environments (Pretty et al. 2005; Barton and Pretty 2010). Benefits of a modest amount of ‘green exercise’ extend beyond people doing physical activity, including savings to health services by mitigating required treatment (Tzoulas et al. 2007).

In addition to the physical and mental health benefits, providing walkable space can encourage walking instead of driving. Walkable space provides cost-effective transport options that promote health and wellbeing of residents: a common objective of urban design policy (Badland and Schofield 2005).

Community space

Community space allows people to interact with other people, businesses, domestic pets and wildlife. Such spaces might include commons areas of apartments or businesses, parks, public sports grounds and pedestrian areas. For instance, social interactions contribute to mental wellbeing and mitigate depression (Miles et al. 2012).

Threats to mental health include depression and stressors (Matheson et al. 2006). Resilience against stressors is fostered when people are able to cope due to their good emotional health (Yancura and Aldwin 2008). Potential stressors include environmental stressors, ‘role strain’ (such as unemployment and poverty), extreme heat/cold, and psychosocial stressors (such as bereavement and relationship issues), particularly in older adults (Yancura and Aldwin 2008). In addition, emotional wellbeing is a strong predictor of good general health (Ostir et al. 2000). By providing community space where urban residents are likely to interact, they may discuss their lives or seek advice. This interaction performs a social support ‘coping mechanism’, a strategy that is linked with emotional wellbeing (Yancura and Aldwin 2008). Emotional distress, on the other hand, has been linked with disease due to increased susceptibility to physical illnesses, such as cardiovascular disease; impaired immune response; and potentially due to public health issues to do with health inequalities (Stewart-Brown 1998). Social interaction, then, is likely to foster emotional and mental wellbeing, which in turn supports physical health and overall wellbeing.

While providing community space to enable residents to socially interact, some people will interact with animals, whether wildlife or domestic pets, the latter having been found to significantly increase both neighbourhood interactions and a sense of community (Walsh 2009). There has been significant research on the impact of animals on mental health. Contact with animals has been reported to elevate psychological wellbeing (Tagles and Idrovo 2012). There has been a range of research to show that human-animal interaction has psychophysiological and psychosocial effects on humans, such as decreased cortisol levels, blood pressure, heart rate, pain, anxiety and depression, a buffered response to stress, and increased longevity and morale (Johnson 2010). Attachment relationships, while mostly between humans, have also been found between people and animals if those relationships create a sense of psychological safety (Peacock et al. 2012). People with companion animals tend to have a more positive perception of their situation and the progression or development of chronic disease can be reduced (Friedmann and Son 2009). Research involving a range of animals – domestic and otherwise – has also suggested that animal-human contact influences humans’ sense of self, for example, whether they are a ‘dog person’ or a ‘bird watcher’ or a ‘wildlife rescue volunteer’ (Clayton and Myers 2011). By encouraging people to utilise community space, pets are a catalyst for social interaction (Walsh 2009). Wildlife might also contribute to human health; feeding birds, a common activity in urban areas around the world, can benefit human wellbeing by giving providing an attachment relationship for people and ‘their’ birds (Jones 2011).

Social interactions are influenced by attributes of community space (Giles-Corti et al. 2005; Kazmierczak 2013). Community space in a public housing development is found to attract people outside to exercise and socially engage with neighbours (Kuo et al. 1998b). In particular, trees are associated with increased time spent outdoors (Coley et al. 1997). Residents in highly urbanised areas experience less aggression and violence when more green community spaces are present (Kuo and Sullivan 2001). The larger the space, the more attributes the space is likely to have – such as facilities for walking or running, children’s playgrounds, facilities for pet-exercise, spaces for picnicking – and thus the more attractive and well-used the community space will be (Giles-Corti et al. 2005; Kazmierczak 2013).

Greenspace

There are various types of natural space, or greenspace in urban areas, such as manicured parks, public and private gardens, graveyards, remnant vegetation, street trees, playing fields, and urban agricultural spaces. While often referred to as ‘greenspace’ in the literature, the presence of natural environments without vegetation, such as bodies of water and beaches, have also been found to benefit human wellbeing (Barton and Pretty 2010). Each of these types of natural space has different capability to impact the health of human and non-human inhabitants of cities. The urban environment is a matrix of natural and non-natural spaces, and the proportion of natural areas vary between cities and even parts of cities. It should be noted that access to natural areas, or greenspace, also varies throughout cities (Barbosa et al. 2007). Residents in the most urban areas of cities report more symptoms of ill-health than those with a greater proportion of local greenspace (de Vries et al. 2003). The groups of urban populations most at risk of ill-health in urban areas include low socioeconomic groups, the elderly, youth (Maas et al. 2006). A study of European cities found that greenspace provision is linked with the city size, not the density or number of urban inhabitants (Fuller and Gaston 2009), thus the management of greenspace for the health of urban inhabitants could be improved in the most-populous urban areas.

Benefits of public greenspaces often overlap with walkable and community spaces: a park may have the benefits associated with greenspace, afford easy walking and cycling through the park via walkable space, and - by adding benches or a child’s play equipment – creates community space that will encourage gatherings of people and facilitate interaction. All of these elements have benefits for human health and wellbeing (Nurse et al. 2010; Miles et al. 2012; Kuo et al. 1998b). For example, the urban heat island effect cause urban areas to be warmer than their surrounding areas (Frumkin 2002; Whitford et al. 2001), and extreme heat has negative impacts on urban residents, particularly those at risk of ill-health. Non-traffic-related air pollution, such as pollens, aeroallergens and toxins, may increase with urban warming, and this increase will affect the incidence of respiratory disease, asthma, allergies and mortality (Beggs 2004). Greenspace would help mitigate extreme temperatures in urban areas. Furthermore, walking or running through natural spaces has more benefits than the same physical activity in non-natural environments (Bowler et al. 2010b), so greenspace that is condusive to physical activity will benefit urban residents. Such studies investigating links between mortality and greenspace are often based in the United States or Europe, and as yet attempts to replicate them in New Zealand have failed (Richardson et al. 2010). This might be due to the greater abundance of greenspace in New Zealand (Richardson et al. 2010); nevertheless, further research in New Zealand and similar environments would elucidate.

Chronic diseases are the leading cause of death worldwide (World Health Organization 2013a). Chronic diseases progress due to noncommunicable aspects, such as lifestyle factors and environmental condition. The four kinds of chronic disease include respiratory diseases, such as asthma, diabetes, some cancers, and cardiovascular diseases such as stroke (World Health Organization 2013b). For example, some cancers, which are a leading cause of mortality worldwide, are preventable (World Health Organization 2008a). A small proportion (5–10 %) of cancer cases are attributed to genetic defects, while the remaining cancer cases are the result of environmental and lifestyle factors, such as tobacco (25–30 %), diet (15–20 %), infections, stress, physical (in) activity, environmental pollutants and radiation (Amamd et al. 2008). Urban design that incorporates elements that help to address environmental and lifestyle factors can help mitigate chronic disease for residents. By creating walkable and community space in parks that mitigate pollution and reduce stress, local governments could make real contributions to public health. For example, traffic-related air pollution is associated with cardiorespiratory deaths (Brunekreef and Holgate 2002). Air pollution, particularly related to increased traffic, is a physical health concern in urban areas; greenspace has the potential to mitigate air pollution (Whitford et al. 2001). Further, it is worth noting that “…our chances of being diagnosed with most chronic illnesses are determined not by the country we come from but by the country we migrate to” (Amamd et al. 2008), suggesting the worthwhile potential for improving the health of urban environments and residents at any time.

Greenspace is beneficial for mental health (Bergeman 2012). Time spent in greenspace has been found to reduce the effects of Attention-Deficit/Hyperactivity Disorder (Kuo and Faber Taylor 2004). Children have been reported to have more creative play, more access to adults and, in a separate study, better concentration and focus based on multiple measures of self-discipline when exposed to greenspace (Faber Taylor et al. 1998, 2002). Natural environments have been found to facilitate recovery from mental fatigue as measured by psychophysiological tests, and have the potential to create an ‘inoculation’ effect after the return to daily life experiences (Hartig et al. 1991, 2003). While many studies confirm that greenspace is beneficial, it is suggested that the presence of greenspace in neighbourhoods is beneficial for residents whether they use it or not (Miles et al. 2012).

Stress, common among urban inhabitants, involves any situation that places demands, whether real or perceived, on an organism that require it to change in order to survive or achieve homeostasis (Larzelere and Jones 2008). Stress impacts the wellbeing of all life, including humans, animals and vegetation (Kaplan 1995; Alessio et al. 2005) and can lead to disease (McEwen and Stellar 1993). Physical stress may be quantified, such as changes to the cardiovascular, endocrine, immune and nervous systems. Psychological stress is harder to define, however it has been thought to be a precursor to mental illness and has been associated with increased chance of relapse in psychiatric disorders and psychiatric morbidity (Larzelere and Jones 2008). There are multiple kinds of stressors, including pollution, crime, traffic, noise and economic strain. Stress from noise and financial strain has been associated with depression and other mental illnesses (Freeman 1984; Miles et al. 2012; Tagles and Idrovo 2012). Given the impact of stress on health, it may contribute to general ill-health and adverse health behaviors in humans, such as heavy drinking or smoking (Nielsen et al. 2008). For animals, pollution, having to adapt to a human-modified environment, noise and heat have been found to trigger stress (Ditchkoff et al. 2006; Martin et al. 2010; Partecke et al. 2006). Natural spaces are beneficial for stress recovery (Ulrich et al. 1991). Gardening has been found to reduce stress, as measured by self-reported mood and salivary cortisol levels (Ward Thompson et al. 2012; Van Den Berg and Custers 2011). Attention restoration theory (ART) (Kaplan 1995) attributes natural environments with holding involuntary attention, or ‘fascination’. While some sounds or lights in urban environments might be positive, the sheer amount of stimuli common in urban environments has the potential to overwhelm some residents with traffic and construction noise, lights and signs. ART suggests that exposure to nature can restore our cognition from stimuli overload (Kaplan 1995). Exposure to natural environments has been found to improve self-ratings of affective stress and a range of physiological measures for participants more quickly than those who were instead exposed to urban environments (Ulrich et al. 1991). Functional neuroanatomical research supports the different physiological responses people have to natural and heavily modified environments (Kim et al. 2010).

Human residents need not be in the midst of a park to reap benefits from greenspace (Han 2009; Kaplan 2001; Kaplan and Peterson 1993; Larsen et al. 1998; Leather et al. 1998; Moore 1981; Tennessen and Cimprich 1995; Ulrich 1984). A view of natural elements out a window has been reported to expedite recovery from surgery, where participants without a window and view recovered more slowly (Ulrich 1984), provide office workers with greater job satisfaction and wellbeing (Kaplan and Peterson 1993; Leather et al. 1998), improve college students’ attention (Tennessen and Cimprich 1995), contribute to apartment dwellers’ wellbeing and satisfaction with their neighbourhood (Kaplan 2001), and reduce prisoners’ need for health care facilities (Moore 1981). The presence of a humble pot plant has been found to have benefits for those in offices and classrooms (Han 2009; Larsen et al. 1998).

In general, being in the presence of natural elements helps people to feel good (Pretty 2004). Some organisations have made recommendations regarding the distance people should have from greenspace, such as the European Environment Agency, which states that people should be able to access greenspace with no more than a 15 min walk, and a UK Government agency, English Nature, recommends that urban residents should have greenspace less than 300 m from their homes (Barbosa et al. 2007).

Biodiversity and ecosystem function

In addition to the three established aspects of urban environments – walkable space, community space and greenspace –biodiversity and ecosystem services make significant contributions to human wellbeing. The provision of walkable and social spaces in cities is common. Green or natural spaces vary – from a small patch of lawn to an urban forest. The notion of nature in this regard is often undefined or simplistic – a park (that may comprise of lawn and a handful of trees), a garden (which may only include sparse plants), or an indoor plant. There is potential for this kind of nature to contribute very little to biodiversity or to the ecosystem functioning that support human existence. However, promoting biodiversity and ecosystem functioning has a purpose other than for doing it for its own sake.

Biodiversity

Human health and biodiversity are considered to be “inextricably linked” (Campbell et al. 2011), with recent reviews identifying how biodiversity is critical to biomedical research and human health (Chivian and Bernstein 2008). In addition to broad benefits to the persistence of humanity, such as for the development of drugs, biodiversity has potential benefits for urban residents at a local scale.

The biodiversity of natural areas has been found to be associated with human wellbeing, with participants across 15 parks reporting that they feel better in the environment with the greater species richness of plants and, to a lesser extent, birds and butterflies (Fuller et al. 2007). Participants were asked whether their visit to the park helped to clear their minds, think about personal matters, gain perspective and connect with nature. Participants were able to recognise and estimate the level of diversity in the park, demonstrating that the level of diversity is relevant to the public; this indicates that that not only do greenspaces provide measurable psychological and physical benefits to visitors, but that the biological complexity is significant for visitors’ psychological wellbeing (Fuller et al. 2007). While the same correlation between actual species richness and human wellbeing was not observed in other recent work, a positive association between wellbeing and perceived species richness was identified (Dallimer et al. 2012). The apparent lack of plant and animal identification skills and therefore actual recognition of biodiversity is relevant, as is the importance of perceived species richness and human wellbeing. Natural environments can be restorative for people experiencing attention fatigue (Kaplan 1995). One of the aspects of a restorative environment is that it must have ‘extent’, that is, it rich and coherent enough to be a convincingly natural environment (that is, with sufficient biodiversity to appear ‘natural’) and different from the usual environment that might be associated with stressors. If human visitors perceive an area to have greater biodiversity, then it may be more likely to impact their wellbeing due to the perceived extent. The perception of an environment is critical to how humans respond to it and thus how it will impact their wellbeing.

Direct impacts to human health, such as severe weather events, pollution, modified conditions for water-borne toxins, infectious-related illnesses, and animal vectors, are exacerbated in urban areas and may be mediated by biodiversity (Epstein 1995). Human-induced changes to the environment were associated with outbreaks of new infectious diseases in the 90s: the Hantavirus in the US and a novel variant of cholera in Bangladesh and India (Epstein 1995). Urban areas disrupt ecosystems, and climate change is likely to afford further ecological disruption and the introduction of vector species, such as rats, fleas and mosquitoes (Patz et al. 1996; Pongsiri et al. 2009). Instead of removing natural space in cities to eradicate animal vectors, attempts to increase the natural biodiversity may not only control the animal vector population, but will also be beneficial for human residents (Campbell et al. 2011). Wildlife might be falsely associated with pandemics (for example, bats and badgers for rabies and tuberculosis respectively), however anthropogenic change is more likely to be the cause (Campbell et al. 2011). Examples of mechanisms that control infectious disease, such as Lyme disease, include the presence of other vertebrates ‘diluting’ the disease, competition between the animal vector and other species, and predation to keep animal vector numbers low (Chivian and Bernstein 2004).

Encouraging biodiversity in densely-populated areas, such as cities, may cause human-animal conflict. Conflicts may be annoying – the presence of flies, spiders, or aggressive birds – or dangerous to humans – such as venomous snakes or large predators. Two approaches may assist the public perception of biodiversity in cities. A ‘one health’ approach aims to restrict zoonotic disease risks and encourage overall wellbeing of human and animals (Rabinowitz and Conti 2010). Maintenance is required around residential areas where wildlife exists, and policies introduced to ensure the ‘one health’ of humans and animals in communities. Examples of maintenance around homes include managing rubbish to prevent attracting animals, removing standing water that could be a breeding environment for mosquitoes, the prompt disposing of faeces, cleaning bird feeders and keeping firewood a certain distance from homes to prevent or distance rat and mice nests, and – where ticks are an issue – keeping grass cut short (Rabinowitz and Conti 2010). A second approach to address human-animal conflicts involves ecological education. Studies of Norwegian sheep farmers have found that famers in areas of high livestock loss were less negative about large carnivores than others, with the authors suggesting that this is due to a greater appreciation of the ecology of predation (Bjerke et al. 2000; Vitterso et al. 1998). Education about biodiversity and humans’ role in it is key to affecting the values that underlie human attitudes and behaviors.

While greenspace has been found to benefit human health and wellbeing in urban areas, there are other factors that impact human health (Verheij et al. 2008). Feelings of safety have been associated with increased trees, however it is not always the trees that affect perceptions of safety. A sense of social cohesion allows residents to ignore anti-social behaviors in favor of their local greenspace (Seaman et al. 2010). Where crime-rates are low in the immediate vicinity, residents are also more likely to spend time in the greenspace (Kazmierczak 2013). When trees and grass are well-maintained, there is a greater feeling of safety for residents (Kazmierczak 2013; Kuo et al. 1998a). It is therefore important for local governments to not only ensure that natural spaces in their cities are biodiverse, but that they are also maintained to ensure that residents experience maximum benefits by using those spaces.

In practice, there are various means of measuring biodiversity in cities. The percentage of greenspace, specifically trees, is positively associated with ecological performance (Whitford et al. 2001). There is a range of work measuring the species diversity of urban greenspace, such as increased avian diversity and spaces with larger patch sizes than other urban areas (Strohbach et al. 2013). Tree cavities are also important to provide habitats for wildlife, suggesting that mature and diverse trees are needed in order to support wildlife biodiversity (Strohbach et al. 2013). Natural areas – greenspace and bodies of water – might provide a range of benefits to local residents, however designing for biodiversity is more complex. An increase in species number may not result in more biodiversity that is native to the area, for example, in relation to introduced species. Whether the same benefits are realized from this modified biodiversity remains to be seen. Further research regarding the quality of greenspace, or the biodiversity in urban areas, continues to provide examples of how urban planners might design for biodiversity.

Ecosystem services

Human health and persistence is contingent on the health of the human environment and ecosystem functioning (Campbell et al. 2011; Jackson 2003). A range of ecosystem services, occur when ecosystems are healthy and functioning. The UN has framed ecosystem services in terms of benefits for humankind, including provisioning services (such as production of food, timber or other resources), regulating services (such as air quality or water regulation, pollination and storm protection), cultural services (such as natural assets for recreation and people to have a cultural identity), and supporting services (such as soil formation, biogeochemistry and primary productivity) (United Nations 2005). However ecosystem services exist independent from their benefits to humankind.

Considering an organism’s health or wellbeing in conjunction with the ecosystem it inhabits is common in ecology, and, after a recent report by the World Health Organization on outdoor air pollution, an emerging concern for the health professions. After reviewing the scientific literature, the WHO has concluded that outdoor air pollution, in addition to causing respiratory and heart diseases, is a key cause of lung and bladder cancers (2013). This range of illnesses could be reduced by ensuring ecosystem functioning. Ecosystem health is a simple concept, describing a state of “system organization, resilience and vigor, as well as the absence of signs of ecosystem distress” (Rapport et al. 1998). A healthy ecosystem is resilient to and/or free from degradation and stress, able to maintain its organization and productivity, and is likely to be biodiverse (Tzoulas et al. 2007; Rapport et al. 1998). Disruption to ecosystems, caused by habitat loss, air pollution, water quality, heavy metals, neurotoxicity and changes in climate, are likely to impact humans and animals, but also ecosystem function (Frumkin 2001). Residents of urban areas, where ecosystem services are compromised by development and therefore less biodiverse greenspace, vehicular air pollution and climate changes, are likely to be impacted by the degradation of their environment.

Outcomes of ecosystem services support the survival of humans and animals. The critical nature of ecosystem services in general cannot be emphasized enough to ensure human health and wellbeing. With the framing of ecosystem services as goods and services for humans, the Millennium Ecosystem Assessment (United Nations 2005) has influenced the concept of ecosystem services in policy (Ernstson 2013). Differences in how local governments manage ecosystems have the potential to create social injustice, or environmental injustice (Ernstson 2013). Maintaining a biodiverse greenspace or clearing it in favour of an enclosed, air-conditioned shopping center and car park will produce different outcomes for residents’ wellbeing. The inequitable distribution of resources, money and power, health outcomes are defined by the social situation in which people are born, grow, live, work and age (World Health Organization 2008b). Societies that experience inequality are less healthy (Gluckman and Thuotte 2008). For example, the life expectancy of men in Glasgow, Scotland, differs from 54 to 82 years depending on where they live and the kind of work they do (Hanlon, Walsh, and Whyte 2006). However, natural space is associated with high levels of wellbeing, including socioeconomic benefits and health equality (Whitford et al. 2001; Mitchell and Popham 2008). While an urban environment relies on its surrounds to provide the ecosystem services it requires, local ecosystem services such as air filtration and micro-climate regulation are important for urban residents at a smaller scale (Bolund and Hunhammar 1999). Because the maintenance of ecosystems and their functioning in and around urban areas is critical to all residents’ wellbeing, ecosystem services become a matter of social justice (Ernstson 2013; United Nations 2005). While there are legal cases that support this (for example, Lazarua and Houck 2005), the principle is far from settled. Further research is needed to ensure that ecosystems and ecosystem services are not compromised beyond a functioning threshold by anthropocentric activity, including urban design and planning, and that any ecosystem disservices or perceived disservices are addressed. Key to this research is evaluation of policy and urban design and planning options (Perrings et al. 2011). The outcomes of ecosystem functioning are not limited to conservation reserves, so the importance of maintaining ecosystem services should have widespread public awareness (Folke et al. 1996). Initiatives that raise residents’ awareness about the importance of ecosystem services are encouraged, as well as evaluation of their success (Hubacek and Kronenberg 2013).

Discussion

In order for the management of biodiversity and ecosystem functioning to become common in cities, it is important for urban planners and ecologists to realise that their work is associated with human wellbeing. This is obvious for policy development and the medical sciences, but not always so clear for other disciplines. Planning and designing urban environments to enhance residents’ wellbeing is critical to the growing human population. The key aspects already established – the walkable, community and greenspaces – are relevant. Without them, urban residents would be in a much worse state. However, green or natural spaces are so varied that their benefits to urban residents vary. In this respect, ensuring the provision of greenspace can be a simplistic interpretation of designing for wellbeing. In order to make a genuine impact on human wellbeing, urban ecosystems should have the ecological integrity required in order for them to function.

Ecologists have much to contribute to the design and planning of urban ecosystems. Urban ecology and the natural sciences have the capacity to study and advise on the state of biodiversity and its management, and study the changes to ecosystem functions, such as biochemical cycles, hydrologic systems and changes in climate (Grimm et al. 2008). The ecology of cities looks at the system of non-human life and human life in urban areas, acknowledging that the human influence is critical to the understanding of urban ecosystem functioning (Niemelä et al. 2009).

It is a goal of urban design to impact how residents engage their environment, but in conjunction with urban ecology and the medical sciences, urban design could make a more significant contribution to urban residents’ wellbeing (Jackson 2003). Biodiversity and ecosystem function should be considered during the design and planning process. Governments, whether local or national, have the ability to drive policy; for example, the European Environment Agency’s policy that urban residents have a maximum distance from their homes to accessible greenspace (Barbosa et al. 2007). In addition, governments can influence and educate the public through their policies and community engagement; for example, by providing recycling bins, regular collection and so on, governments can influence social norms and individual behaviors (Viscusi et al. 2011). It is important to realise that multiple disciplines should be involved in both the education and policy-development as well as in how the urban environment is built and managed. In order to transcend the established and potentially simplistic applications of urban design that affect human wellbeing, biodiversity maintenance is critical. As outlined above, biodiversity is essential to the integrity of natural spaces. A dual outcome of these cumulative influences should result in a functioning ecosystem, which would in turn ensure the flourishing of human residents and their wellbeing.

Concluding remarks

The most effective way to ensure human wellbeing in the most populous environments, cities, is to design, plan and maintain urban environments with key features in mind. Some of those key features are already established in urban design and planning, such as providing walkable and community spaces. In recent years, the benefits of greenspace in urban environments have become well known, with numerous links to the medical sciences, including physical and mental health, and micro-climate protection. Some greenspace, however, can be variable and potentially simplistic in its structure and therefore the benefits it might provide to local humans and animals. To avoid this risk and potential waste of resources in maintaining low-quality greenspace, promoting biodiversity is important. Biodiversity has been linked with human wellbeing, however there is still work to be done to identify the thresholds of influence that biodiversity has on surrounding spatial scales. Biodiversity is also integral to the healthy functioning of an ecosystem. Human wellbeing is contingent on ecosystem functioning – the air we breathe, the food we eat, the water we drink – all require functioning ecological integrity. A range of ecological work has demonstrated that ecosystems and biodiversity are affected by urbanisation, such as how different vegetation can support healthy soil (Edmondson, Davies, McCormack, Gaston, and Leake 2014) and reduce land surface temperature (Li, Zhou, Ouyang, Xu, and Zheng 2012). Multiple models of the links between human health and ecosystem services have been suggested (see Tzoulas et al. 2007 for a review), and some communities, cities and countries endorse them. However, there are multiple interpretations of how to achieve these links, for example the United States Environmental Protection Agency (EPA) and Natural England both support the development of green infrastructure, but the EPA has a focus on water management (Environmental Protection Agency 2014) and Natural England has a focus on green and blue spaces for recreation and food production (Natural England 2013). Different demographics are impacted in different ways, for example heatwaves are most likely to have negative effects on the elderly (United Nations 2005), and some of the areas most in need, such as dense urban populations in developing nations, experience some of the worst environmental degradation (United Nations 2005). On one hand, biodiversity and ecosystem function is critical to human health and wellbeing. However, on a policy and governance level, it is impractical to suggest a generic solution to supporting biodiversity and ecosystem functioning as solutions will vary between neighbourhoods, cities and countries. It may be that a series of principles, such as increasing biodiversity and supporting ecosystem function, may be more useful to guide policies, ecological monitoring and urban design to suit the needs of urban residents across various scales (such as, local or city-wide) (Jackson 2003).

By integrating multidisciplinary research, providing informed policy, educating key research to the public to influence social norms, and transcending the established management approaches of urban environments, human wellbeing can be enhanced. Ultimately, it is important for governments and disciplines to understand that the management of biodiversity and ecosystem functions is central to the maintenance of human wellbeing in cities. Ecologists and urban designers have enormous potential to contribute to the overall health of urban environments.