Editing IPCC:AR6/WGII/Chapter-6 (section)

=== 6.2.4 Risks to Key Infrastructures ===

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Projected climatic changes, such as changing precipitation patterns, temperatures and sea levels, contribute to pressures on human well-being and the functioning of infrastructure systems ( ''high confidence'' ). Furthermore, risks evolve due to macro-scale drivers of change such as urbanisation, economic development, land use changes and other emergent factors (Adger, Brown and Surminski, 2018). Infrastructure networks are rapidly growing around the world (see Table 6.3). Since the quality and accessibility of infrastructure services are varied, it is important to understand how climate change poses different kinds of risk on them. Infrastructure can be broadly understood to include social infrastructure (housing, health, education, livelihoods and social safety nets, security, cultural heritage/institutions, disaster risk management and urban planning), ecological infrastructure (clean air, flood protection, urban agriculture, temperature, green corridors, watercourses and riverways) and physical infrastructure (energy, transport, communications [including digital], built form, water and sanitation and solid waste management) ( [[#Thacker--2019|Thacker et al., 2019]] ). This section focuses especially on physical infrastructure where the literature provides discrete risk and impact assessments. Physical infrastructure systems are often immobile, indivisible, involve high fixed costs and have longer lifecycles. Social and ecological infrastructure elements are rarely assessed alone and instead tend to be included in wider assessments of event impacts.

'''Table 6.3 |''' Selected indicators of global proliferation of infrastructure networks and their annual usage.

{| class="wikitable"
|-
! Infrastructure

! Scale

! Usage on annual basis

! Coverage/equity of access

! References

|-
| Electricity networks

| &gt; 20 million km of power lines in Europe and USA

| 25,721 TWh (2017)

| Global: 3130 kWh per person

Haiti: 39 kWh per person

Iceland: 53,832 kWh per person

| [[#IEA--2019|IEA (2019)]] ;

[[#World%20Bank--2019|World Bank (2019)]] ;

[[#ETSAP--2014|ETSAP (2014)]]

|-
| Gas and LPG pipelines

| Worldwide:

&gt; 2.5 million km w −1

| 40,531 TWh (2017)

| Global: 4.96 MWh per person (2015)

South Africa: 0.96 MWh per person (2015)

Saudi Arabia: 34.65 MWh per person (2015)

| [[#CIA--2015|CIA (2015)]] ;

[[#OWID--2020|OWID (2020)]]

|-
| Railways

| 2.69 million km

| 3835 billion passengers km −1 (2019)

9279.81 billion tonnes km −1 (2019)

| Switzerland: 0.7 m per person; 141 m km −2

Canada: 2.2 m per person; 8.6 m km −2

India: 0.06 m per person; 23 m km −2

| Koks et al. (2019);

[[#Statista--2020|Statista (2020)]]

|-
| Roads

| 63.46 million km

| 12,148 billion passengers km −1 private vehicles (2015)

5713 billion passengers km −1 public vehicles, e.g., buses (2015)

302.5 billion passenger km −1 active modes, e.g., walking and bicycles (2015)

| Belgium: 15 m per person; 5 km km −2

Malawi: 1 m per person; 164 m km −2

Canada: 31 m per person; 115 m km −2

| Koks et al. (2019);

[[#WorldByMap--2017|WorldByMap (2017)]] ;

[[#ITF--2019|ITF (2019)]]

|-
| Information and Communication Technology

| Worldwide:

91 million mobile phones in 1995;

8.2 billion in 2018 worldwide

| Worldwide:

43,000 PB in 2014

242,000 PB in 2018

(*1PB = 1 million GB)

| Europe: 85% of population are unique mobile subscribers; Asia Pacific: 66%; Sub-Saharan Africa: 45%

| [[#ITU--2019|ITU (2019)]] ;

[[#Vodafone--2019|Vodafone (2019)]] ;

[[#GSMA--2019|GSMA (2019)]]

|-
| Water

| 3.3 million km 2 land equipped for irrigation

The Global Reservoir and Dam Database (conservatively records) at least 7100 dams

| This irrigated land accounts for about 70% of total water withdrawals

These dams can retain over 7800 km 3 water.

| Sub-Saharan Africa: 24% coverage of safely managed drinking water services, 28% safely managed sanitation services,

Europe and North America: 94% and 78%, respectively.

| [[#Grigg--2019|Grigg (2019)]] ;

Lehner et al. (2011);

Lehner et al. (2019);

[[#UN%20Water--2018|UN Water (2018)]]

|}

Current climate variability is already causing impacts on infrastructure systems around the world ( ''high confidence'' ). For global physical infrastructure with a present value of USD 143 trillion, The [[#Economist%20Intelligence%20Unit--2015|Economist Intelligence Unit (2015)]] estimates present value losses of USD 4.2 trillion by 2100 under a 2°C scenario. This estimation rises to USD 13.8 trillion under a 6°C scenario. Extreme events are associated with disruption or complete loss of these infrastructure services, whilst gradual changes in mean conditions are altering physical infrastructure performance. Physical infrastructure is usually costly to repair and also have significant impacts on people’s health and well-being.

This section synthesises and assesses the emerging literature on climate change risks to key physical infrastructure domains as listed in Table 6.3: energy/electricity infrastructure, transportation infrastructure and information and communication technology (ICT) (water infrastructure is discussed in [[#6.2.2|Section 6.2.2]] ). It draws on evidence from around the world, but the specific risks to infrastructure in different contexts are explained in more detail in the regional chapters (especially [[IPCC:Wg2:Chapter:Chapter-9#9.8.4|Section 9.8.4.1]] for Africa, [[IPCC:Wg2:Chapter:Chapter-10#10.4.6.3.8|Section 10.4.6.3.8]] for Asia and [[IPCC:Wg2:Chapter:Chapter-13#13.6.1|Section 13.6.1]] for Europe). For cities and settlements, such risks are of particular concern owing to a lack of adaptive capacity across many economically important sectors and low levels of resource and capacity support to enhance adaptive capacity. Recent literature also illustrates the interconnected and interdependent nature of infrastructure systems (see Box 6.2), which lead to uncertainties over how risks in one sector lead to cascading, compounding or knock-on effects across other sectors ( [[#Zscheischler--2017|Zscheischler and Seneviratne, 2017]] ) (see [[#6.2.6|Section 6.2.6]] for elaboration). Therefore, adaptation options should address climate risks to infrastructure in an integrated and co-beneficial manner ( ''medium evidence'' , ''high confidence'' ) (see Sections 6.3 and 6.4).

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==== 6.2.4.1 Energy Infrastructure ====

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Energy infrastructure underpins modern economies and quality of life. Disruption to power or fuel supplies impacts upon all other infrastructure sectors, and affects businesses, industry, healthcare and other critical services both within and across jurisdictional boundaries ( [[#Groundstroem--2019|Groundstroem and Juhola, 2019]] ). The economic impacts of climate change risks are significant, for example in the EU, the expected annual damages to energy infrastructure, currently €0.5 billion yr −1 , are projected to increase 1612% by the 2080s ( [[#Forzieri--2018|Forzieri et al., 2018]] ). In China, 33.9% of the population are vulnerable to electricity supply disruptions from a flood or drought ( [[#Hu--2016|Hu et al., 2016]] ), whilst in the USA, higher temperatures are projected to increase power system costs by about USD 50 billion by the year 2050 ( [[#Jaglom--2014|Jaglom et al., 2014]] ). In a study of 11 Central and Eastern European countries, researchers found that energy poverty is exacerbated by existing infrastructure deficits and energy efficient building stock, as well as income inequality, which can lead to reduced economic productivity ( [[#Karpinska--2020|Karpinska and Śmiech, 2020]] ). Climate change is expected to alter energy demand ( [[#Viguié--2021|Viguié et al., 2021]] ), for example heatwaves increase spot market prices ( [[#Pechan--2014|Pechan and Eisenack, 2014]] ), with a disproportionate impact on the poorest and most vulnerable populations. Energy infrastructure are susceptible to a range of climate risks (Cronin, Anandarajah and Dessens, 2018), whilst issues pertaining to energy demand are considered by Working Group III.

Climate change can, for example, influence energy consumption patterns by changing how household and industrial consumers respond to short-term weather shocks, as well as how they adapt to long-term changes ( [[#Auffhammer--2014|Auffhammer and Mansur, 2014]] ). Recent studies from Stockholm, Sweden, show that future heating demand will decrease while cooling demand will increase (Nik and Sasic Kalagasidis, 2013). A study from the USA showed that climate change will impact buildings by affecting peak and annual building energy consumption ( [[#Fri--2014|Fri and Savitz, 2014]] ). From an infrastructure standpoint, the vulnerability of current hydropower and thermoelectric power generation systems may change due to changes in climate and water systems and projected reduction of usable capacities ( [[#van%20Vliet--2016|van Vliet et al., 2016]] ; [[#Byers--2016|Byers et al., 2016]] ). These examples show how energy infrastructure planning under climate change must take into account a greater number of scenarios and investigate impacts on particular energy segments ( [[#Sharifi--2016|Sharifi and Yamagata, 2016]] ).

'''Electricity generation.''' Electricity generation infrastructure can be directly damaged by floods, storm and other severe weather events. Furthermore, the performance of renewables (solar, hydro-electric, wind) is affected by changes in climate.

Most thermoelectric plants require water for cooling, many are therefore situated near rivers and coasts and thus vulnerable to flooding. Increases in water temperature or restrictions on cooling water availability affect hydroelectric and thermoelectric plants. A 1°C increase in the temperature of water used as coolant yields a decrease of 0.12–0.7% in power output ( [[#Mima--2015|Mima and Criqui, 2015]] ; Ibrahim, [[#Ibrahim--2014|Ibrahim and Attia, 2014]] ). Excess biological growth, accelerated by warmer water, increases risk of clogging water intakes ( [[#Cruz--2013|Cruz and Krausmann, 2013]] ). While some regions are expected to experience increased capacity under climate change (namely India and Russia), global annual thermal power plant capacity is ''likely'' to be reduced by between 7% in a mid-century RCP2.6 scenario and 12% in a mid-century RCP8.5 scenario ( [[#van%20Vliet--2016|van Vliet et al., 2016]] ). Worldwide, hydroelectric capacity reductions are projected at 0.4–6.1% ( [[#van%20Vliet--2016|van Vliet et al., 2016]] ). Analysis of the UK’s water for energy generation abstractions showed that an energy mix of high nuclear or carbon capture technologies could require as much as six times the current cooling water demands (Byers, Hall and Amezaga, 2014; [[#Byers--2016|Byers et al., 2016]] ).

Increasing temperatures improve the efficiency of solar heating but decrease the efficiency of photovoltaic panels, and deposition and abrasive effects of wind-blown sand and dust on solar energy plants can further reduce power output, and the need for cleaning (Patt, Pfenninger and Lilliestam, 2013). Projected changes in wind and solar potential are uncertain; the trends vary by region and season (Burnett, Barbour and Harrison, 2014; [[#Cradden--2015|Cradden et al., 2015]] ; Fant, Schlosser and Strzepek, 2016). In an RCP8.5 scenario, [[#Wild--2015|Wild et al. (2015)]] conservatively calculate a global reduction of 1% per decade between 2005 and 2049 for future solar power production changes due to changing solar resources as a result of global warming and decreasing all-sky radiation over the coming decades. However, positive trends are projected in large parts of Europe, the south-east of North America and the south-east of China.

'''Electricity Transmission and Distribution.''' Electricity transmission and distribution networks span large distances, with overhead power lines often traversing exposed areas. Power lines and other assets, such as substations, are often located near population centres, including those in floodplains. Structural damage to overhead distribution lines will increase in areas projected to see more ice or freezing rain (e.g., most of Canada), snowfall (e.g., Japan) or wildfires (e.g., California, USA) ( [[#Bompard--2013|Bompard et al., 2013]] ; [[#Mitchell--2013|Mitchell, 2013]] ; [[#Sathaye--2013|Sathaye et al., 2013]] ; [[#Jeong--2018|Jeong et al., 2018]] ; [[#Ohba--2020|Ohba and Sugimoto, 2020]] ). Electricity outages may last for prolonged periods of time and across vast areas, in addition to potentially disproportionately affecting poorer or more vulnerable communities. Increases in windstorm frequency and intensity increase the risk of direct damage to overhead lines and pylons, in many locations this is limited but [[#Tyusov--2017|Tyusov et al. (2017)]] calculate an increase as high as 30% in parts of Russia. Where the mode of failure is recorded, transmission pylons are seen to be more susceptible to wind damage, whilst distribution pylons are more ''likely'' to be affected by treefall and debris (Karagiannis et al., 2019). Increased temperatures can lead to the de-rating (lower performance) of power lines, whose resistance increases with temperature with efficiency reductions of 2–14% being projected by 2100 ( [[#Cradden--2013|Cradden and Harrison, 2013]] ; [[#Bartos--2016|Bartos et al., 2016]] ).

'''Fuels Extraction and Distribution.''' Non-electric energy infrastructure is susceptible to many of the same impacts as electric infrastructure. Extreme weather events impact extraction (onshore and offshore) and refining operations of petroleum, oil, coal, gas and biofuels. Disruption of road, rail and shipping routes (see [[#6.2.5|Section 6.2.5.2]] ) interrupts fuel supply chains. However, there are a number of risks that are specific to these sectors. Heat can lead to expansion in oil and gas pipes, increasing the risk of rupture ( [[#Sieber--2013|Sieber, 2013]] ), whilst heatwaves and droughts can reduce the availability of biofuel (Moiseyev et al., 2011; Schaeffer et al., 2012). Subsidence and shrinkage of soils damages underground assets such as pipes intakes ( [[#Cruz--2013|Cruz and Krausmann, 2013]] ), while additional human activity such as extractive drilling may induce earthquakes, as observed in the northern Dutch province of Groningen ( [[#Van%20der%20Voort--2015|Van der Voort and Vanclay, 2015]] ). In Alaska, USA, the thaw of permafrost and subsequent ground instability is estimated to lead to USD 33 million damages to fuel pipelines in an end-of-century RCP8.5 scenario (Melvin et al., 2017), with low-lying coastal deltas particularly vulnerable ( [[#Schmidt--2015|Schmidt, 2015]] ).

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<span id="transport"></span>
==== 6.2.4.2 Transport ====

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Since AR5, research has highlighted the implications for disruption to global supply chains (Becker et al., 2018; [[#Shughrue--2018|Shughrue and Seto, 2018]] ; [[#Pató--2015|Pató, 2015]] ), and has made advancements in quantifying costs of climate risks to transportation infrastructure. Climate risks to transport infrastructure (from heat- and cold waves, droughts, wildfires, river and coastal floods, and windstorms) in Europe could rise from €0.5 billion to over €10 billion by the 2080s (Forzieri et al., 2018). Across the Arctic, nearly four million people and 70% of all current infrastructure, including resource extraction and transportation routes, will be at risk by 2050 (Hjort et al., 2018), although the design of specific infrastructure may also affect the degree of infrastructure damage, depending on local geological and ecological conditions. Globally, [[#Koks--2019|Koks et al. (2019)]] calculated that approximately 7.5% of road and railway assets are exposed to a 1-in-100 year flood events, and total global expected annual damages (EAD) of USD 3.1–22 billion (mean USD 14.6 billion) due to direct damage from cyclone winds, surface and river flooding, and coastal flooding. The majority of this is caused by surface water and fluvial flooding (mean USD 10.7 billion). Although twice as much infrastructure is exposed to cyclone winds compared with flooding, a mean EAD of USD 0.5 billion is significantly less than for coastal flooding (USD 2.3 billion), as cyclone damages are largely limited to bridge damage and the cost of removing trees fallen on road carriageways and railway tracks. This is small relative to global gross domestic product (GDP; ~0.02%). However, in some countries EAD equates to 0.5–1% of GDP, which is the same order of magnitude as typical national transport infrastructure budgets, but especially significant for countries such as Fiji that already spend 30% of their government budget on transport (World Bank Group, 2017). [[#Koks--2019|Koks et al. (2019)]] did not assess future climate change impacts, but comparable studies calculating changes in EAD from flooding based upon land use show increases of 170–1370%, depending on global greenhouse gas emissions levels (Alfieri et al., 2017; Winsemius et al., 2015). Moreover, Schweikert et al., (2014) report that climate risks to transport infrastructure could cost as much as 5% of annual road infrastructure budgets by 2100, with disproportionate impacts in some low and lower middle-income countries.

Changes in rainfall and temperature patterns are expected to increase geotechnical failures of embankments and earthworks (Briggs, Loveridge and Glendinning, 2017; Tang et al., 2018; [[#Powrie--2018|Powrie and Smethurst, 2018]] ) from landslides, subsidence, sinkholes, desiccation and freeze-thaw action. For instance, Pk et al. (2018) show this could lead to a 30% reduction in the engineering factor of safety of earth embankments in Southern Ontario (Canada). Increased river flows in many catchments will also increase failures from bridge scours (Forzieri et al., 2018). [[#HR%20Wallingford--2014|HR Wallingford (2014)]] calculate that the projected 8% increase in scouring from high river flows in the UK will lead to 1 in 20 bridges being at high risk of failure by the 2080s, whilst in the USA the 129,000 bridges currently deficient could increase by 100,000 (Wright et al., 2012). With respect to temperature, analysis by [[#Forzieri--2018|Forzieri et al. (2018)]] concludes that heatwaves will be the most significant risk to EU transport infrastructure in the 2080s, as a result of buckling of roads and railways due to thermal expansion, melting of road asphalt and softening of pavement material. In the USA, over 50% more roads will require rehabilitation (Mallick et al., 2018), whilst USD 596 million will be required through 2050 to maintain and repair roads in Malawi, Mozambique and Zambia (Chinowsky, Price and Neumann, 2013).

In addition to direct damages from flooding and heatwaves, disruption caused by road blockages will be increased by more frequent flood events. For example, in the city of Newcastle upon Tyne (UK), road travel disruption across the city from a 1-in-50 year surface water flood event could increase by 66% by the 2080s (Pregnolato et al., 2017), whilst heatwaves could treble railway speed restrictions in parts of the UK (Palin et al., 2013). [[#Knott--2017|Knott et al. (2017)]] highlighted risks to coastal infrastructure where ~30 cm sea level rise sea level rise would also push up groundwater and reduce design life by 5–17% in New Hampshire (USA). Heavy rain and flooding can also inundate underground transport systems (Forero-Ortiz, Martínez-Gomariz and Canas Porcuna, 2020).

Many airports, and by their nature ports, are in the low elevation coastal zone, making them especially vulnerable to flooding and sea level rise. Under a 2 o C scenario, the number of airports at risk of storm surge flooding increases from 269 to 338 or as many as 572 in an RCP8.5 scenario; these airports are disproportionately busy and account for up to 20% of the world’s passenger routes ( [[#Yesudian--2021|Yesudian and Dawson, 2021]] ). Airport and port operations could be disrupted by icing of aircraft wings, vessels, decks, riggings and docks (Doll, Klug and Enei, 2014; Chhetri et al., 2015). Warming will increase microbiological corrosion of steel marine structures (Chaves et al., 2016). Fog, high winds and waves can disrupt port and airport activity, but changes are uncertain and with regional variation (Mosvold [[#Larsen--2015|Larsen, 2015]] ; Izaguirre et al., 2021; [[#Becker--2020|Becker, 2020]] ; León-Mateos et al., 2021; Taszarek, Kendzierski and Pilguj, 2020; Danielson, Zhang and Perrie, 2020; Kawai et al., 2016).

Waterways are still important transport routes for goods in many parts of the world, although they are mostly expected to benefit from reduced closure from ice (Jonkeren et al., 2014; [[#Schweighofer--2014|Schweighofer, 2014]] ), low flows will ''likely'' lead to reduced navigability and increased closures; [[#van%20Slobbe--2016|van Slobbe et al. (2016)]] estimate the Rhine may reach a turning point for waterway transportation between 2070–2095. Obstruction due to debris and fallen vegetation of roads and rails and to inland and marine shipping from high winds are expected to increase (Koks et al., 2019; Kawai et al., 2018; Karagiannis et al., 2019)..

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<span id="information-and-communication-technology"></span>
==== 6.2.4.3 Information and Communication Technology ====

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Information and communication technology (ICT) comprises the integrated networks, systems and components enabling the transmission, receipt, capture, storage and manipulation of information by users on and across electronic devices (Fu, Horrocks and Winne, 2016). ICT infrastructure faces a number of climate risks. Increased frequency of coastal, fluvial or pluvial flooding will damage key ICT assets such as cables, masts, pylons, data centres, telephone exchanges, base stations or switching centres (Fu, Horrocks and Winne, 2016). This leads to loss of voice communications, inability to process financial transactions and interruption to control and clock synchronisation signals. Insufficient information about the location and nature of many ICT assets limits detailed quantitative assessment of climate change risks.

Fixed-line ICT networks that sprawl over large areas are especially susceptible to increases in the frequency or intensity of storms that would increase the risk of wind, ice and snow damage to overhead cables and damage from wind-blown debris. More intense or longer droughts and heatwaves can cause ground shrinkage and damage underground ICT infrastructure (Fu, Horrocks and Winne, 2016). In mountain and northern permafrost regions, communications and other infrastructure networks are subject to subsidence because of warming of ice-rich permafrost (Shiklomanov et al., 2017; Li et al., 2016; Melvin et al., 2017).

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==== 6.2.4.4 Housing ====

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For the urban housing sector, climate impacts such as flooding, heat, fire and wind assessed in [[#6.2.3|Section 6.2.3]] will ''likely'' have detrimental effects on housing stock (including physical damage and loss of property value) and on residents exposed to climate risks ( ''robust evidence, high agreement'' ).

In the USA, for example, 15.4 million housing units fall within a 1-in-100-year floodplain (Wing et al., 2018). Assessment of the Miami-Dade area in Florida noted that coastal inundation caused by tidal flooding (and to a lesser extent sea level rise) resulted in over USD 465 million in lost real-estate market value between 2005 and 2016 ( [[#McAlpine--2018|McAlpine and Porter, 2018]] ), although property values have increased from high-end housing construction and climate adaptation measures ( [[#Kim--2020|Kim, 2020]] ). Emergent risk reflecting novel research include aggravated moisture problems in buildings from wind driven rain (Nik et al., 2015). Future risks from future sea level rise are elaborated in Section [https://www.ipcc.ch/chapter/6#CCP2.2 CCP2.2.1] . Housing infrastructure are also susceptible to extreme heat and wind events (Stewart et al., 2018). These risks are further elaborated on in [[#6.2.3|Section 6.2.3]] , although it is important to note that heat risks, in particular, tend to be concentrated within communities with a higher proportion of social housing (Mavrogianni et al., 2015; Sameni et al., 2015) or low-cost government-built houses and informal settlements.

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<span id="water-and-sanitation"></span>
==== 6.2.4.5 Water and Sanitation ====

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Apart from land subsidence from urbanisation (e.g., Case Study 6.2), substantial climate risks to urban sanitation arise from droughts, flooding and storm surges. Low flows from drought can lead to sedimentation, increase pollutant concentration and block sewer infrastructure networks ( [[#Campos--2015|Campos and Darch, 2015]] ). Flooding poses a greater risk for urban sanitation in low- and middle-income settings (Burgin et al., 2019) where onsite systems are more common. Floodwater may wash out pits and tanks, mobilising faecal sludges and other hazardous materials leading to both direct and indirect exposure via food and contaminated objects and surfaces, and pollute streams and waterbodies (Howard et al., 2016; [[#Braks--2013|Braks and de Roda Husman, 2013]] ; Bornemann et al., 2019). Floods also damage infrastructure; toilets, pits, tanks and treatment systems are all vulnerable (Sherpa et al., 2014; UNICEF and WHO 2019).

Sanitation systems coupled with floodwater management are at risk of damage and capacity exceedance from high rainfall (Thakali, Kalra and Ahmad, 2016; Kirshen et al., 2015; Dong, Guo and Zeng, 2017). In England, the number of water and wastewater treatment plants at risk of flooding is projected to increase by 33% under a 4 o C scenario (Sayers et al., 2015), but risks are generally increasing for both formal and informal urban sanitation systems (Howard et al., 2016).

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<span id="natural-and-ecological-infrastructure"></span>
==== 6.2.4.6 Natural and Ecological Infrastructure ====

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Urban ecological infrastructure includes green (i.e., vegetated), blue (i.e., water-based) and grey (i.e., non-living) components of urban ecosystems (Li et al., 2017). While land cover change from urbanisation directly reduces the extent of natural and ecological infrastructure (e.g., Lin, Meyers and Barnett, 2015), notable risks arise from climate drivers. Recent research particularly highlights future climate impacts on coastal natural infrastructure, including beaches, wetlands and mangroves, which cause significant economic losses from property damage and decreasing tourism income, as well as loss of natural capital and ecosystem services. Research on climate risks to urban trees and forests is comparatively limited. Instead, urban vegetation and green infrastructure are most often cast as adaptation strategies to reduce urban heat, mitigate drought and provide other ecosystem benefits (see [[#6.3.2|Section 6.3.2]] ).

Coastal natural infrastructure is exposed to sea level rise, wave action and inundation from increasing storm events (See also Section CCP 2.2.1). Beaches, in particular, are highly exposed to climate-induced coastal erosion (Toimil et al., 2018; Section CCP2). Research from settlements across coastal Southern California, USA, show that 67% of all beaches may completely erode by 2100 (Vitousek, Barnard and Limber, 2017). Coastal zones across Cancún, Mexico, are exposed to a combination of sea level rise and tropical hurricanes, further exacerbated by urban development patterns blocking natural sediment replenishment to beaches (Escudero-Castillo et al., 2018). In another case, beach erosion along the heavily urbanised Valparaíso Bay, Chile, is heightened by El Niño Southern Oscillation (ENSO) events, which in the past have caused an additional 15–20 cm in mean sea level rise (Martínez et al., 2018).

Wetlands, mangroves and estuaries, which tend to be heavily urbanised areas, are highly at risk from sea level rise and changing precipitation (Green et al., 2017; Feller et al., 2017; [[#Alongi--2015|Alongi, 2015]] ; Osland et al., 2017; [[#Chow--2018|Chow, 2018]] ; [[#Godoy--2015|Godoy and Lacerda, 2015]] ). Sea level rise is a concern for wetlands and mangroves across coastal urban Asia, the Mississippi Delta (US) and low lying small island states (Ward et al., 2016b). Research on the highly urbanised Yangtze River estuary in China shows that soil submersion and erosion from sea level rise, compounded by land conversation to agriculture and urban development, will cause all tidal flats to disappear by 2100 (Wu, Zhou and Tian, 2017). In another example, sea level rise and high rates of tidal inundation have increased overall salinity in the San Francisco Bay-Delta estuary, threatening the ecosystem’s ability to support biodiversity ( [[#Parker--2019|Parker and Boyer, 2019]] ).

Research on climate risks to urban trees and forests highlight direct impacts from extreme temperatures, precipitation, wind events and sea level rise, as well as exposure to other hazards such as air pollution, fires, invasive species and disease ( [[#Ordóñez--2014|Ordóñez and Duinker, 2014]] ). Since the 1960s, climate change has enabled growth of urban trees, supported by longer growing seasons, higher atmospheric CO 2 concentrations and reduced diurnal temperature range (Pretzsch et al., 2017), as well as increased fertilisation through urban-enhanced nitrogen deposition (Decina, Hutyra and Templer, 2020). However, these trends may change in the future as further warming and decreasing water supply may depress tree fitness, thus enabling more pests ( [[#Dale--2017|Dale and Frank, 2017]] ).

Climate risks to urban natural and ecosystem infrastructure entail significant economic costs. For example, in 2012, Hurricane Sandy led to total losses of up to USD 6.5 million to the New York City region’s low-lying salt marshes and beaches ( [[#Meixler--2017|Meixler, 2017]] ). Research from coastal settlements across Catalonia, Spain, shows significant levels of tourism loss (which contribute to 11.1% of the region’s GDP), infrastructure damage and natural capital loss attributed to inundation and erosion of beaches, which are projected to retreat by −0.7 m yr −1 given current sea level rise projections of 0.53–1.75 m by 2100 (Jiménez et al., 2017).

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<span id="health-systems-infrastructure"></span>
==== 6.2.4.7 Health Systems Infrastructure ====

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Healthcare facilities (hospitals, clinics, residential homes) will suffer increasing shocks and stresses related to climate variability and change (Corvalan et al., 2020). Some may be sudden shocks from extreme weather events, which both threaten the facility, staff and patients and increase the number of people seeking health care. There are extensive reports of health facilities being damaged after major floods and windstorms (e.g., 2010 floods in Pakistan, Hurricane Sandy in the USA) which can be further exacerbated by power and water supply failures (Powell, Hanfling and Gostin, 2012). Disruption to services may persist for many months because of damage to buildings, loss of drugs and equipment, and damaged transport infrastructure significantly increasing travel time for patients (Hierink et al., 2020). The impacts of climate change on the health of residents of ‘slum’ settlements will also compound the existing health burdens faced by these individuals, including infectious disease and other environmental public health concerns (Lilford et al., 2016; Mberu et al., 2016).

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'''Box 6.2 | Infrastructure Interdependencies'''
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Infrastructure networks are increasingly dependent on each other—for power, control (via ICT) and access for deliveries or servicing (Figure 6.2). Moreover, a range of other mechanisms can create interdependencies that impact upon climate risks by creating pathways for cascading failure (Undorf et al., 2020; [[#Barabási--2013|Barabási, 2013]] ). In the UK, for example, all infrastructures utilities identify failure of components in another utility as a risk to their systems (Dawson et al., 2018).

Key interdependencies include:

# The use of ICT for data transfer, remote control of other systems, and clock synchronisation. Pant et al. (2016) show that ICT is crucial for the successful operation of the UK’s rail infrastructure. The study shows that flooding of the ICT assets in the1-in-200 year floodplain would disrupt 46% of passenger journeys across the whole network.
# Water to generate hydroelectricity and for cooling thermal power stations. Reductions in usable capacity for 61–74% of the hydropower plants and 81–86% of the thermoelectric power plants worldwide for 2040–2069 (van Vliet et al., 2016), with some power generation technologies, including carbon capture and storage, requiring far higher volumes of water for cooling (Byers et al., 2016).
# Energy to power other infrastructure systems. Failure of urban energy supply disrupts other infrastructure services, with disproportionate impacts on the urban poor ( [[#Silver--2015|Silver, 2015]] ).
# Transport systems that ensure access for resources such as fuel, personnel and emergency response. [[#Pregnolato--2017|Pregnolato et al. (2017)]] show disruption across the city from a 1-in-10 year storm event could increase by 43% by the 2080s.
# Green infrastructure can provide multiple services, creating interdependencies between multiple physical infrastructure systems. For example, green space can support sustainable urban drainage, ''in situ'' wastewater treatment and urban cooling (Demuzere et al., 2014).
# Geographical proximity of assets leads to multiple infrastructures being simultaneously exposed to the same climate hazard. Disruption is disproportionately larger for interconnected networks (Fu et al., 2014).

There is usually limited information on the risks between infrastructure sectors. Without frameworks for collaboration, and coupled with commercial and security sensitivities, this remains a barrier to routine sharing and cooperation between operators. Despite this, methods to tackle interdependence in climate risk analysis are emerging ( [[#Dawson--2015|Dawson, 2015]] ). For example, [[#Thacker--2017|Thacker et al. (2017)]] analysed the criticality of the UK’s infrastructure networks by integrating data on infrastructure location, connectivity, interdependence and usage. The analysis showed that criticality hotspots are typically located around the periphery of urban areas where there are large facilities upon which many users depend or where several critical infrastructures are concentrated in one location. As infrastructure systems become increasingly interconnected, associated risks from climate change will increase and require a cross-sectoral approach to adaptation ( [[#Dawson--2018|Dawson et al., 2018]] ).

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