food, water or other services (Roy et al. 2018). Meanwhile, urban planning processes may ignore the valuable role of natural environments as providers of livelihood resources for poorer urban residents (Roy et al. 2018). Poorer populations may therefore be adversely affected both by development, which destroys natural resources such as the infilling of ponds, and conversely by the designation of protected areas, which limit access to people who use them to supplement their income or food supply (see chapter 2).
There are, however, cases in which biodiversity can also be harmful to urban dwellers’ health, for example zoonotic diseases like Ebola, Middle East Respiratory Syndrome, West Nile Fever and COVID-19, which jump between animals and humans (UNEP 2020). Urban development, environmental degradation, climate change and increased demand for meat in diets are bringing humans and animals closer together in cities, facilitating the emergence of zoonotic diseases. Paying more attention to the integrated treatment of human, animal and environmental health can help prevent and reduce the risk of the development and spread of zoonotic diseases (UNEP 2020).
Urban biodiversity has been shown to have positive impacts on physical and mental health and well-being (Brown and Grant 2005; Fuller et al. 2007; Tzoulas et al. 2007; Jorgensen and Gobster 2010; Romanelli et al. 2015). Biodiversity loss may affect biocultural diversity (biological resources that are particularly culturally valued) (Maffi 2005; Maffi 2018) and the persistence of traditional ecological knowledge (Maffi 2005; Raymond et al. 2010), as well as social-ecological memory (Barthel, Folke and Colding 2010). Further declines in biodiversity could also result in urban dwellers having less contact with nature, a decrease in environmental literacy and an “extinction of experience”, with the potential for negative impacts on health and well-being (Louv 2008; Soga and Gaston 2016). This may result in a desire for people to reconnect with nature (Folke et al. 2011; Andersson et al. 2014). However, it may also allow for new experiences of nature in cities as “novel ecosystems” (Hobbs et al. 2006; Kowarik 2011).
Access to sufficient clean freshwater is essential for human well-being (SDG 6). Sustainable water management requires a balance between competing goals and trade-offs to ensure sufficient and safe water for human well-being, food, energy and nature (minimum environmental flows). These challenges are aggravated by infrastructure and institutional structures that were often not designed to cope with multiple stressors (Friend and Thinphanga 2018). Surface and groundwater overuse and contamination is increasing water insecurity, reducing the volume of water available, affecting its quality and driving up costs. In rapidly developing and urbanizing nations that have not yet implemented comprehensive measures to control and treat pollution at source, pollution levels are relatively high (Wen, Schoups and Van De Giesen 2017). Globally, four out of five people in urban areas use piped water supplies (WHO and UNICEF 2017), although this does not guarantee water quality and reliability. Just 39 per cent of the global population (2.9 billion people) use a safely managed sanitation service, and three out of five of them live in urban areas (WHO and UNICEF 2017).
58 GEO for Cities
While access in urban areas is higher than in rural ones, residents of informal urban and peri-urban settlements and other vulnerable groups are particularly likely to have precarious access to drinking water and sanitation. Access in urban areas may be overestimated in some cases, since informal settlements are not always counted in the data and also due to differing levels of access (Mitlin et al. 2019). Residents of informal settlements often obtain water from communal sources or private vendors at a much higher cost and without quality guarantees, since water is not delivered from a public supply network (United Nations Water 2017; Mguni et al. 2020). The lack of a stable water supply can lead communities to store water in open containers, inadvertently providing a vector breeding for dengue, malaria and other waterborne diseases. Poor sanitation leads to the pollution of waterways and coastlines and affects urban dwellers’ health (for example, through waterborne diseases) and well-being, especially women and girls who depend on inadequate public sanitation facilities (UNEP 2019). The COVID-19 outbreak has highlighted how the difficulty of good handwashing hygiene in marginalized urban areas disproportionately exposes these groups to infectious diseases (WHO 2020b; Van Belle et al. 2020).
In the Global North, shrinking cities means less demand for water, leading to water stagnation and increasing the risk of bacterial growth and microbial contamination in pipes (Naumann and Bernt 2009). Water quality also is also affected by ageing or inadequate infrastructure (for example, lead pipes), a lack of regional planning (Morckel 2017) and a lack of regulatory compliance (Allaire, Wu and Lall 2018).
Many people live in coastal areas, where impacts such as rising sea levels, coastal erosion, storm surges and coastal pollution have direct and indirect effects on the health and well-being. For example, coastal flooding, which is the most common natural hazard and is exacerbated by poor urban planning and inadequate drainage, can cause loss of life and injuries, as well as the contamination of water and food supplies. Because the impacts can be so severe, urban residents affected by floods may experience long- term mental health issues, including stress and anxiety (Fernandez et al. 2015; Waite et al. 2017). Other impacts include salinity intrusion in groundwater, which can also affect health.
Cities are major sources of pollution for coastal zones. This can impact both residents of cities and people beyond their boundaries. The economic and social costs of marine litter and chemical pollution on cities include indirect costs, such as making them less attractive, disrupting tourism and causing the decline of coastal fisheries and aquaculture. People whose livelihoods rely on coastal and marine ecosystems may be disproportionately impacted. Microplastics and associated contaminants from marine litter can affect the marine food web and potentially, human health through seafood consumption, although the transfer of microplastics from seafood to humans and the implications for human health are still not fully understood (Carbery, O’Connor and Palanisami 2018).
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