In recent decades, climate projections have highlighted continuing increases in global average temperatures. Climate change impacts will be felt throughout the world but hazards and the severity of impacts will vary between regions. The Baltic Sea region can expect an increase in the occurrence of extreme weather events such as heavy precipitation events, windstorms, extreme temperatures (particularly heatwaves) and freezing rain events in northern areas.
Not all climate impacts will emerge in the same way: some will take place over time and others more abruptly. Multiple hazard events and other shocks could also take place at the same time. In addition, the interactions between social, ecological and technological systems often make the impact chains within these interlinked systems rather complicated. This brings new challenges and requires new methods of risk assessment to account for potential damage, while also highlighting the need to design appropriate responses that are capable of taking account of these cascading effects.
For example, the combined effects of the increased frequency of high-intensity storms, sea-level rise and more frequent storm tides will have compounding impacts on the capacity of individuals, governments and the private sector to adapt in time before loss and damage occur [3]. Cascading effects further intensify the impacts of natural hazards and can turn them into costlier and more deadly catastrophes. Cascading effects can have the same magnitude of impact within the region, or where the initial hazard trigger took place, as beyond. Consequently, accounting for the potential of cascading effects can strengthen the environmental, social and economic justifications for addressing risks [3]. Natural hazard events with cascading effects have already been experienced in the Baltic Sea region [3, 4]. Examples of cascading effects are provided in Table 3.1, 3.2, 3.3.
Table 3.1 Factors and Cascading Effects of Floods and Storm Surges
| Factors | Cascading Effects |
| Floods include can be categorised into flash flooding, coastal flooding and river flooding. Urban areas often have low levels of surface permeability that prevent precipitation from being absorbed into the ground, which makes them more susceptible to flooding events [5]. Apart from surface permeability, stormwater management and the location of assets are key factors in urban flooding and its impacts [5,6]. For example, buildings and residential areas closer to the sea or rivers are at higher risk of being damaged by storms, sea-level rise and floods [7]. | Many major cities in the Baltic Sea region are located around rivers. Flooding events in combination with storm surges are one of the costliest natural hazards. These cause major infrastructure damage and risk public safety. There is a strong economic argument in favour of addressing vulnerabilities to flooding.
The cascading effects of floods can affect the use of roads and railway lines, and prevent relief aid from reaching flood-affected areas. Damage to electricity grids can result in blackouts even in non-flooded areas. This can affect critical infrastructure such as hospitals, schools, trade and railways. Cascading effects can also include sewage overflows or chemical contamination of flood waters [8]. |
Table 3.2 Factors and Cascading effects of Droughts
| Factors | Cascading Effects |
| Climate change, together with other challenges such as urbanisation and economic development, can lead to increased demand for water [6]. Drought stems from a combination of factors such as increased temperatures, reduced cloud cover, reduced precipitation, more hours of sunshine and higher levels of evaporation. Drought has unique characteristics that make it different from other hazards. It affects regions differently and can even impact across vast geographic areas in various scales of land area [9].
Research projects increasing drought conditions across the Baltic Sea region towards the end of the 21st century. |
Droughts can trigger cascading risks even for cities in the Baltic Sea region. This could result in economic losses, as well as a decline in the quality of life, public health and ecosystems over time.
Reduced water availability affects hydroelectric power supplies, which can put critical infrastructure such as health services in danger at a time when societal groups such as the elderly would be increasingly in need of such services, e.g. during a heatwave. Among the industries directly affected by drought are agriculture, recreation, energy supply, tourism, timber and fisheries. Drought can also compress building foundations and have other effects on buildings and infrastructure such as water supply and delivery [9]. |
Table 3.3 Factors and Cascading effects of Extreme temperature and the Urban Heat Island Effect
| Factors | Cascading Effects |
| Extreme temperatures in urban areas have been observed since the mid-20th century. Incremental global warming is resulting in increases in the intensity and frequency of heat extremes, including heatwaves and changes in ecosystem functioning [10].
The Urban Heat Island (UHI) effect results from pavements and buildings radiating heat back into the air, leading to elevated temperatures. Increased exposure to both climate change and the UHI effect threatens urban settlements even in the Baltic Sea region. UHI effects have increased the number of people exposed to potentially health-threatening heat extremes in recent decades. |
Exposure to dangerously high temperatures endangers urban health and development, driving reductions in labour productivity and economic output, and increases in morbidity and mortality [11].
Extreme temperatures can trigger to intense tropical cyclones, damaging critical urban infrastructure [12]. Heatwaves can also result in loss of marine life, which can restructure entire marine ecosystems. |
Within urban settlements, these cascading effects affect different groups in society in different ways. The distribution of risks across society is highly unequal and the most severe impacts fall on the urban poor or other marginalised groups. Adaptation plans often fail to take account of high resolution risk distribution. Without such differentiated knowledge of exposure and vulnerability it is difficult to tailor adaptation measures [11, 12].
Green infrastructure can improve the adaptive capacity of lower income areas in cities [13]. Thus, climate hazards and risk assessments need to be seen in a local socio-economic context [14]. Risk assessment can also help to ensure that existing urban policies and practices related to landscape design, building construction, urban planning, stormwater management and land use management are applied in an integrated manner that is effective for climate adaptation. Green infrastructure should be seen as an important part of an inventory of solutions related to adaptation and resilience.
Cities are complex socio-ecological systems that consist of infrastructure, ecosystems, institutions and knowledge networks, all of which require cross-disciplinary and multistakeholder action to ensure sustainability and resilience [16]. Moving away from the more static notion of dealing with climate risks, urban managers and city leaders will need to adopt the dynamic concept of resilience to deal with urban challenges more broadly. At an urban scale, resilience refers to the ability of a city to ensure access to services and maintain essential functions in times of changing conditions or crisis. This includes putting in place structures that support the wellbeing of citizens and their ability to adapt and thrive in the face of continual change. The level of resilience depends on the ‘fragility’ of the urban system and its subsystems (social, economic, technical and environmental), as well as the capacity of its social agents (individuals, civil society, and the private and public sectors) to anticipate, adjust to and recover from stresses and shocks such as climate change [15].
Using green infrastructure and nature-based solutions is a promising approach to enhancing urban resilience through the promotion of ecosystems services. If planned correctly, this can also provide other benefits that promote sustainable development. It can be used to mitigate flooding risk and the UHI effect, improve air quality, reduce energy consumption in buildings, increase carbon storage, conserve wildlife habitats, and provide recreation and leisure amenities [16]. Here, long term, integrated approaches to urban planning and development are key to reducing risk and building urban resilience [14]. This requires work across sectors and disciplines, and at many levels of decision making.
The complex socio-ecological systems of a city comprise an unpredictable web of interdependencies [17]. The United Nations International Strategy for Disaster Risk Reduction (UNISDR) launched a campaign for local government in 2010 in the form of a 10-point checklist to reduce risk and build resilience in cities [18]. More recently, the Sendai Framework (2015–2030) adopted by the UN General Assembly is a global policy to address disaster risk reduction based on four principles [19]. For successful delivery of urban green infrastructure, we propose seven simplified principles of resilience that draw on these multiple available frameworks (see Table 3.2). Some additional essential principles related to flexibility, resourcefulness and safe failures have also been identified [16,17].
Table 3.2 Principles of Resilience
| Resilience Principle | Explanation |
| 1. Identifying risks | Urban planning policies and strategies focused on climate adaptation and disaster risk management should be based on an understanding of the different dimensions of climate risks. These dimensions are: exposure of persons and assets, capacity, hazard characteristics and the environment. Such knowledge can be leveraged for the purpose of risk assessment to establish priorities and mobilise resources [19]. |
| 2. Maintain diversity and flexibility | Cities with multiple connected and integrated components (species, actors, sources of information, infrastructure connections, etc.) are more resilient than those with only a few centralised components and pathways. Flexibility refers to the ability to perform essential tasks under a wide range of conditions, where parts of systems can be converted or modified to achieve the goal [15, 17]. |
| 3. Safe failure | The ability of a system to absorb or control shocks by either slowing down or avoiding a catastrophic response; or where failure in one structure does not result in failure in another, avoiding cascading impacts [15,17]. |
| 4. Resourcefulness | The capacity not only to identify the issue, but also to visualise, act, establish priorities and mobilise resources. Resourcefulness also refers to the related capacity to recognise and devise strategies that relate to the different incentives and operational models of different groups [15,17]. |
| 5. Encourage learning | The ability to engage in a continuous and collaborative learning process in which past experiences provide insight into new knowledge and alter strategies where necessary [15,17]. |
| 6. Promote collaboration and participation | Coordination across different government sectors as well active engagement and participation among relevant stakeholders is needed to build trust and create a shared vision. Well-connected governance structures deal with change swiftly and are fundamental to building resilience [17,19]. |
| 7. Investing in resilience | Public and private sector investment are essential to enhancing the economic, social, health and cultural resilience of people, communities, countries and their assets, as well as the environment. These investments can also drive further innovation, growth and job creation [18, 19]. |
Sources: [15-19]
Urban landscapes determine the context for and scale of green infrastructure in cities. Landscapes influence not only the functionality of public spaces, but also the scale of delivery of the ecosystem services that green infrastructure can provide. These include services such as maintaining biodiversity, water filtration, spaces for flood alleviation, public health, and recreational and educational opportunities.
In designing the urban landscape, planners need to factor in the various characteristics of different species of vegetation and open spaces to combat negative future climate impacts from urban heat island effect, flooding and wind. For example, xeriscaping uses native and adapted plant types that are well-suited for drought resilience while offering increased biodiversity, lower maintenance costs, and decreased energy and water use and also decreasing stormwater and irrigation runoff in cities. Other examples of smart and water efficient landscape designs include limiting turfed areas, and the use of efficient irrigation systems and watering schedules [20].
While urban nature-based solutions and green infrastructure aim to support multiple sustainability goals, questions around social equity and justice receive far less attention [21]. The trade-offs and unintended consequences of these interventions are often overlooked, particularly in terms of the equitable distribution of benefits [22, 23]. Previous research has concluded that green infrastructure solutions do not always benefit all segments of society [24]. Access to green spaces is still highly unequal and lower income, minority, older and female residents lose out. Ecological gentrification is one of the most common forms of unjust outcomes from the upgrading of urban green infrastructure. In such cases, the increase in or restoration of green spaces makes neighbourhoods unaffordable for current renters. The needs of more vulnerable communities that are also at risk from climate change and disaster losses should be put at the centre of sustainable land use practices and planning decisions in order to prioritise a justice-driven response to environmental and climate-related challenges [25]. This will also support city wide resilience building.
As noted above, strengthening a city’s resilience requires the identification and assessment of climate risk. This is seen as an essential component of climate adaptation and disaster risk management. Climate risk assessments identify the likelihood of future climate hazards, their location, the nature of the risks and their potential impacts on cities and communities. This is fundamental for informing the prioritisation of climate action and investment in adaptation in cities. It is therefore crucial to mainstream risk assessment and management in urban development, management and governance [14]. The risk assessment should cover hazards, as well as socio-economic and institutional contexts [15].
Table 3.4 Types of Climate risk assessment
| Type | Description |
| Hazard Impact Assessment | Identify type and intensity, and high-risk areas, as well as the losses resulting from climate hazards and climate change scenarios such as extreme temperatures and storm surges. For flood hazards, for example, criteria such as the intensity and frequency of floods, topography and drainage patterns need to mapped and assessed. |
| Socio-economic Assessment | Identify the populations most likely to be adversely affected, and investigate their adaptive capacity. For example, map the locations of populations vulnerable to hazards and understand the current and future population dynamics of the city. |
| Institutional Assessment | Understand whether there are agencies responsible for managing the risks arising from disasters and climate change, and whether they can deliver the desired outcomes. For example, carry out a financial capacity assessment of the institutional delivery of resilience building programmes. |
The collection, sharing and communication of hazard-related information is key to risk management and formulating further programmes to adapt to climate change. In a B.Green survey of urban planners in the Central Baltic region, urban planners emphasised the need for open data and data on flood risks, UHI effect, biodiversity, rainfall and drought, in that order. Among the commonly cited barriers to data availability were the absence of recognised standards and best practices related to data sharing, limited awareness, misaligned institutional incentives and lack of simple, affordable software tools. Integrated systems for data acquisition, management and sharing would help to overcome many of these challenges [15].
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