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date: 27 March 2023

Climate Change Impacts on Cities in the Baltic Sea Regionfree

Climate Change Impacts on Cities in the Baltic Sea Regionfree

  • Sonja DeppischSonja DeppischAtelier for Resilience and Transformation

Summary

While not all projected climate change impacts are affecting especially and directly at all the cities of the Baltic Sea region (bsr), including its basin, those cities expect very different direct as well as indirect impacts of climate change. The impacts are also a matter of location, if the city with its built structures and concentration of population is located in the northern or southern part of this basin, or more inland or directly at the coast. As there are many different definitions in use trying to determine what a city is, also in the different national contexts of the bsr, here it is cities in the sense of being human-dominated densely populated areas, which are also characterized by higher concentrations of built-up areas, infrastructure, and soil-sealing as well as socioeconomic roles than rural settlements are. Those characteristics render cities also especially vulnerable to climate change impacts while there are some opportunities arising too.

There are many studies on climate change impacts on the Baltic Sea itself as well as on the various ecosystems, but the studies on the observed as well as potential future impacts of climate change on cities are disperse, many are also of a national character or concentrating on a small number of cases, leaving some cities not well studied at all. This renders an all-encompassing picture on the cities within the bsr difficult and even more complicated as every city provides a mix of built-up and open structures, of socioeconomic structure and role in a region, nation-state, or even on an international level, and further characteristics. Their urban development is dependent on manifold various interdependencies as well as climatic and nonclimatic drivers, such as, to name just a few diverse examples, urban to international governance processes, or topography and location, or also different socioeconomic vulnerabilities within the Baltic Sea basin. Accordingly every urban society and structure provides specific exposure, vulnerabilities, and adaptive capacity. Generally, the cities of the bsr have to deal with the impacts of temperature rise, natural hazards, and extreme events, and, depending on location and topography, with sea-level rise. With reference to temperature rise and the increase of heat waves, it is important to consider that cities of a certain size within the Baltic Sea basin contribute to their own urban climatic conditions and provide already urban heat islands. Also, urban planning and building facilitated by local political decisions contribute to the extent of urban floods as well as their damage, as these are regulating, for example, the sealing of soils or new built-up areas in flood-prone zones.

Keywords

Subjects

  • Climate Impact: Extreme Events
  • Climate Impact: Sea Level Rise
  • Climate of the Baltic Sea Region

Multidisciplinary Research on Climate Change Impacts on Cities in the Baltic Sea Basin

Cities are very different due to their individual urban development processes influenced by different socioeconomic interdependencies across different levels and their specific attributed roles as well as further drivers of their development. Even the definition of what a city basically is differs in very different contexts (UN HABITAT, 2020), be they academic or political, even within a political European macro region such as the Baltic Sea region (bsr), which has the same name as used here (but differently written), but is not completely congruent to the Baltic Sea basin or catchment area, as the name Baltic Sea region (bsr) is used here and in other contexts, too (see, e.g., Rutgersson et al., 2022). Cities are understood here as human-dominated, densely populated areas, which are also characterized by higher concentrations of built-up areas, infrastructure, and soil sealing, as well as socioeconomic roles, than rural settlements. Due to their specific characteristics, cities experience the impacts of climate change differently, providing different aspects of vulnerability, exposure, and adaptive capacities. However, from a more generalized bird’s-eye view on cities in a specific region such as the bsr, which is here broadly understood as the whole Baltic Sea catchment area, it is interesting to try to summarize findings on observed and potential future climate change impacts on cities in a specific region. This holds true if the variety and diversity of available studies on climate change impacts on cities in such a region are considered; often these studies are in national contexts or with a small number of cases. Also, many different disciplines providing expert knowledge on different fields such as urban climate, architecture and construction, health of the urban population, or urban economic development are essential to consult. Not all these studies results are published in English; rather, they appear in national languages represented in the bsr such as Polish, Latvian, or German. Altogether, these realities render researching climate change on cities in the bsr very difficult while cross-cutting through all the relevant material appears nearly impossible. However, a glimpse of different disciplinary studies and different aspects of climate change impacts on cities in the Baltic Sea basin covering different national and biogeographical contexts is given.

It is important to collect those different insights and provide a generalized overview on observed and potential future climate change impacts on the cities of the Baltic Sea catchment; this can be a starting point for a long journey that provides more locally and regionally based insights that are systematically collected or even steered for a European Union–related macro region such as the bsr. A first step was taken by the BACC II process, the “Second Assessment of Climate Change for the Baltic Sea Basin” (the BACC II Author Team, 2015), which added a chapter of climate change impacts on urban complexes (Deppisch et al., 2015) in comparison to its first assessment BACC (BACC Author Team, 2008), where the issue of climate change impacts on cities was not considered.

Relating to this overview, the second part of current scientific findings is structured in a similar way along the observed as well as potential future climate change impacts on cities of the Baltic Sea catchment area. This catchment area is considered according to the older climate change assessments of the Baltic Sea basin (BACC and BACC II) as well as to the latest update (Meier et al., 2022). This term refers to the political bsr to a certain extent and has a huge amount of overlapping areas, but the bsr and the Baltic Sea catchment area (or the Baltic Sea basin, here, this term is identically used to the catchment area) do not provide identical borders. Within this text, as in many others, too (e.g., Rutgersson et al., 2022), the understanding of the Baltic Sea region (bsr) comprises the catchment. Consequently, it entails not only the coastal cities of the Baltic Sea, among which are some European national capitals such as Stockholm, Copenhagen, and Helsinki, but also cities located more inland and still part of the catchment, for example Vilnius, the capital of Lithuania. As there are many possible ways to delineate the bsr, and the results differ because of the disciplinary context and aim of the delineation, in order to avoid confusion, here it refers to the physio-geographic definition of the Baltic Sea catchment area and not a specific alternative of the straits (Klemeshev et al., 2017). This catchment area comprises the territory of whole nation-states such as Estonia, Latvia, and Lithuania; almost the whole territory of Poland, Finland, and Sweden; a distinct portion of Denmark and of Belarus; as well as smaller parts of Germany and Russia; and, finally, very small parts of Norway, Ukraine, and the Czech Republic (Klemeshev et al., 2017, pp. 6–8), with the latter not being considered here. For a visual overview of this catchment area please see also Inácio et al. (2020).

Some light is also shed on adaptation issues., but it is not the focus of this article.

The first and subsequent sections focus on the “Development of the Topic” as such and are chronologically structured, while the second section displays the current state of research on different climate change impacts—first in a nutshell and then in respective details.

Development of the Topic

As a variety of very different disciplines spanning from natural to engineering to the social sciences work on the topic of climate change impacts on cities of the Baltic Sea basin, it is difficult to determine when exactly the topic appeared in this dispersed field, which is also characterized by studies and research works published in many different languages. Therefore, in the following paragraphs, some main lines of development are sketched without claiming completeness or the detection of its origin.

To start with the global perspective, the first impacts assessment of the established Intergovernmental Panel on Climate Change (IPCC) tackled the potential impacts of climate change on human settlements in general, not explicitly on cities, and mixed with impacts on further sectors such as energy or transport (Hashimoto et al., 1990). But this report, already, mentioned a potential rise of the urban heat island (UHI) effect as an impact of climate change, especially for cities (Hashimoto et al., 1990, p. 5-3).

The second IPPC report put more emphasis on cities, which it differed from rural settlements (Scott et al., 1995), and it stressed that through climate change impacts large investments in cities were at risk (Goldemberg et al., 1995, p. 23), the salinity of surface water supply for low-lying coastal cities could increase, and it scenarized threats to the urban infrastructure (Pearce et al., 1995, p. 195) as well as health impacts on populations with more summer deaths and less winter deaths due to warming (Pearce et al., 1995, p. 198). Also, the role of nonclimatic drivers on the development of human settlements was highlighted, for example, urbanization, explicitly the concentration of populations in coastal zones, above all in the so-called developed world (Scott et al., 1995, pp. 403–404). The report also discussed direct climate change impacts such as the requirement of cooling buildings because of higher temperatures (Scott et al., 1995, pp. 407–408), the increase in air pollution (Scott et al., 1995, p. 409), and problems for and damages to the urban infrastructure (Scott et al., 1995, pp. 409–411). The Regional Assessment on Europe stressed impacts of climate change as an increase in the urban heat island (UHI) effect, growing demand of energy for cooling in summers, especially as a new demand in northern Europe with a decreasing demand for heating during winter (Beniston et al., 1998, p. 174), yet, the Baltic Sea basin as a European region was not explicitly mentioned (Pearce et al., 1995, p. 198).

In 1998, the third IPCC report contained more available studies, more quantitative studies, more details about impacts, and more studies on adaptation to the latter (Scott et al., 2001, pp. 387–388). Sea-level rise, working together with other impacts of climate change, was summarized as a particular threat to coastal settlements, stressing several examples and potentially most affected regions globally; although the report did not refer to cities of the Baltic Sea coast, for the first time, the chapter on Europe emphasized the specifics of the Baltic Sea and named it, together with the Mediterranean Sea, as the most prone for sea-level rise due to a low tidal range (Kundzewicz et al., 2001, pp. 659–660). As a central climate change impact the authors of the settlement chapter highlighted an increase in urban floods, which were considered a climate change impact for cities all over the world, especially ones providing less or insufficient drainage and sewage as well as water supply capacity (Scott et al., 2001, p. 395).

The fourth report restrengthened the role of nonclimatic drivers on sustainable development issues (Wilbanks et al., 2007, p. 359). The exposure and vulnerability of settlements in risk-prone areas such as low-lying coastal zones was stressed, and for the first time in the settlements chapter, low-lying areas along the long Baltic Sea coastline and explicitly Estonia were highlighted as threatened by sea-level rise (Wilbanks et al., 2007, p. 372). And it was shown that adaptation within human settlements can make a decisive difference than with no adaptation (Wilbanks et al., 2007, p. 381).

The fifth report finally provided an explicit chapter on urban areas with deep insights about the climate change impacts on different urban sectors (Revi et al., 2014). There, under the impression of an urbanizing world, the strong impacts on urban complexes were highlighted as well as the need for urban adaptation and the explicit role of cities therein. Finally, the topic of climate change impacts on cities was broadly settled in this fifth report and took broad space, too.

More specifically for Europe, the European Environment Agency published for the observed period at the beginning of the 21st century up to the year 2017 many relevant reports on climate change impacts in Europe and on urban adaptation. Four reports presented outcomes of indicator-based assessments of climate change impacts on Europe as of 2004, 2008, 2012 and 2016. The second report of 2012 did not entail a specific chapter on climate change impacts on urban settlements, but it had a chapter on urban vulnerability and provided an overview of cities’ vulnerabilities to different climate change impacts. While the text does not go into the details besides some examples, for instance the Copenhagen floodings in 2011 (European Environment Agency [EEA], 2012, p. 223), still, from the various maps on factors determining vulnerability on specific climate change impacts, it can be specifically drawn on the different cities in the Baltic Sea basin and their prospective vulnerability, for example on their vulnerability on urban floods (EEA, 2012, p. 227).

The third report (EEA, 2017) considered more explicitly the European macro regions, among which the bsr is one, and reported on the results of the vulnerabilities of urban settlements in Europe.

Especially for the Baltic Sea basin, the BACC process performed and published two assessments of the state of knowledge on climate change in the Baltic Sea catchment area (BACC Author Team, 2008; BACC II Author Team, 2015). While the first assessment did not focus on climate change impacts on cities, the second BACC assessment, within its fifth part on socioeconomic impacts of climate change, entailed a chapter titled “Socio-economic Impacts—Urban Complexes” (Deppisch et al., 2015, p. 411). This chapter presented the results of the assessment of, until then, available published publications, mainly in English but also in some other languages used in the Baltic Sea basin. The authors presented knowledge on climate change impacts on cities along with impacts on different urban services and technical infrastructure, such as waste water management, drinking water supply, transportation, and buildings (Deppisch et al., 2015, pp. 412–415); and on the urban socioeconomic structure (Deppisch et al., 2015, pp. 415–417); on the urban population (Deppisch et al., 2015, pp. 417–418); and it also shed some light on adaptation issues (Deppisch et al., 2015, pp. 418–419).

The topic of adaptation appeared at different times in the Baltic Sea basin with implemented adaptation strategies at the political level, but in 2007 there were just a few national initiatives (Hilpert et al., 2007, p. 5). But the initiatives, which were developed, were cross-cutting adaptation strategies at the locals level, such as in Malmö and in national capitals such as Copenhagen, Helsinki, and Stockholm (City of Malmö, 2011; Committee of the Regions, 2011).

Also for the European Union funding policy related macro region bsr as a whole, an adaptation strategy and a related action plan were developed and published, already in 2013. This so-called Baltadapt Strategy is a strategy for adaptation to the impacts of climate change in the bsr as a whole and does not focus explicitly on cities, but it entails many relevant issues such as adaptation of buildings or public transport, as well as cross-level coordination (Andersson, 2013).

Current State of Research

This second section provides insight on climate change impacts on cities explicitly of the Baltic Sea basin from the early 21st century until the year 2022. The relevant state of research on the past, current, and projected future climate change developments in this bsr can be found in studies from the years 2021 and 2022 (Meier et al., 2022). They can be derived from more general overviews such as the finalized report of Working Group I of the Intergovernmental Panel on Climate Change (IPCC; Arias et al., 2021), and they are stated in a very brief overview version also in the regional fact sheet on Europe, where the bsr is part of northern Europe, one of the four differentiated European greater regions (Intergovernmental Panel on Climate Change [IPCC], n.d.).

Overview: Current and Potential Future Climate Change Impacts on Cities (of the Baltic Sea Basin) in a Nutshell

Working Group II of the IPCC stated in its early relevant reports that the expression of the climate change impacts depends on the location of the human settlement as well as on further nonclimatic impacts and their complex interaction. This result persists and is acknowledged in the current state of research on climate change impacts, for example on European urban settlements (Kaźmierczak et al., 2020).

As the bsr is made up of different biogeographical regions with different key impacts of climate change relevant to cities (Kaźmierczak et al., 2020, pp. 17, 21), a brief common overview on general climate change impacts on those cities and their potential vulnerabilities is given before the details and further specifications across the bsr are provided in subsequent chapters. Those are mainly informed by single studies that do not focus on all cities of the Baltic Sea basin, but they do concentrate on cities within a national context or in specific locations, such as on or near coasts or are single study or few cases studies.

The main adverse climate change impacts on urban settlements in the Baltic Sea are extreme weather events such as heat waves, heavy precipitation events, sea-level rise, and storm surges for the cities located in the coastal zones of the Baltic Sea as well as urban floodings.

The increase in heat waves and the number of heat days as a future climate change impact is specifically severe for urban settlements, as in some cases those conditions are meeting already existing urban heat islands (UHIs), and the urban vulnerability might be augmented due to a lack of cool, open, and green spaces in the cities. At the same time, in the northern parts of the bsr, the average rise in temperature in winter will reduce the number of cold-related threats (Kaźmierczak et al., 2020).

While droughts are a more obvious topic to the southern parts of Europe, still, the northern part of Europe has some singular cities with a higher vulnerability to be impacted by droughts that are located in Germany, Latvia, and Lithuania (Tapia et al., 2017, pp. 149–151).

Due to their specific location, to sealed soils, and further nonclimatic factors determining their vulnerability, such as urban drainage or sewage systems, flooding is an important climate change impact on cities in the bsr, too, be it pluvial, river, or coastal flooding (Tapia et al., 2017, pp. 149–151).

Sea-level rise and its impacts on coastal cities are relevant and will cause damages in the future, for instance in the Scandinavian capitals Helsinki, Copenhagen, and Stockholm (Kaźmierczak et al., 2020, p. 40).

The next paragraphs on the state of research on specific climate change impacts on the cities of the Baltic Sea basin will shed light on more details of the specific climate change impacts and provide more details on exemplary single cities.

State of Research on Specific Climate Change Impacts on the Cities of the Baltic Sea Basin

Sea-Level Rise, Storm Surges, and Floods

The consequences of future sea-level rise are an expected climate change impact on several cities in the considered region, characterized by different exposure, also with reference to time and different vulnerabilities as well as to the specific state of implemented adaptation measures. Especially together with storm surges and floods it is considered a threat to the urban settlements of the Baltic Sea basin. Currently and in the near past, parts of the Baltic Sea coastal cities already experienced sea floods with urban damages, for example, St. Petersburg in Russia or in the Gulf of Finland (Särkä et al., 2017, p. 299). For the future scenario, it is expected that the coastal cities of the Baltic Sea basin will experience losses due to coastal floods with an expected future increase of exposed inhabitants (Rutgersson et al., 2022, p. 283).

Kalbarczyk and Kalbarczyk (2020) state sea-level rise as a projected future impact of importance for all Polish coastal cities. Sanders et al. (2021) confirm this generally for the Polish coast, which they consider highly vulnerable. More detailed and specific study results exist for impacts of sea-level rise on the Polish coastal city of Gdansk (Sanders et al., 2021), for which the authors see existing adaptation plans but not a sufficient implementation of adaptation measures yet. Further specific results published in English also exist for the Polish city Szczecin (Bradecki & Konsek, 2020), which is not located directly on the coastline but at the Oder River, mouthing in the Szczecin lagoon. Parts of the city of Szczecin are threatened by sea-level rise, especially in combination with floodings (Bradecki & Konsek, 2020).

For Lithuania, a study on the city of Klaipeda states that under a high-emission scenario and projected for the long term, a sea-level rise of 100 cm will increase the risk of floodings of the local river Danė and the Klaipeda strait significantly and affect three times more of the city area, and it will increase the occurrence of before rare, severe, and so called 100-year flood events (Cepiene et al., 2022, pp. 8–14, 17).

Also for the cities on the German coasts, future sea-level rise is a threat for their inhabitants, but the German coastal infrastructure is judged as protected until the middle of the 21st century due to coastal protection measures, but an increase of those measure will be needed later on (Umweltbundesamt, 2021b).

In Scandinavia, due to the land-uplift (Särkkä et al., 2017, p. 304), the impacts are partly expected later than in other parts of the bsr but still are cited as one of the main climate change impacts for coastal cities and especially for the Scandinavian capitals Helsinki, Copenhagen, and Stockholm (Kaźmierczak et al., 2020). In Helsinki, for instance, due to the specific local tidal circumstances, land-uplift and mean sea-level have leveled out in the years 1982–2011 (Särkkä et al., 2017, p. 307), but this differs along the Finish coast (Särkkä et al., 2017, p. 304), and it cannot therefore be assumed true for other Finish cities—sea-level rise will become a severe event earlier than expected.

But urban flooding is not only relevant to coastal cities but also to many other cities, likewise evoked by extreme weather events, as will be shown in the next paragraphs.

Heavy Precipitation Events and Urban Floods

Even if the literature on current and projected future developments of climate change in the Baltic Sea basin are substantially and widely described, it has to be acknowledged that for extreme events the uncertainty level of these data and scenarios is higher (Rutgersson et al., 2022).

However, Rutgersson et al. (2022, p. 280) highlight the potential strong impacts of heavy precipitation events in urban regions, especially if this is linked with a warmer climate. The northern part of the bsr expects a strong increase in heavy precipitation events as a key climate change impact (Kaźmierczak et al., 2020, p. 21). Swedenanticipates heavy precipitation events with strong impacts on its cities as well as on road infrastructures, with consequences for urban transport (Kalantari & Folkeson, 2013; Storbjörk & Uggla, 2015).

In the southern part of the Baltic Sea basin, as for instance in Gdansk, at the Polish Baltic Sea coast, currently an increase in heavy precipitation events has been found (Szpakowski & Szydłowski, 2018, pp. 178–179). The impacts of these events on the specific location depend not only on topography but also on drainage and sewage systems and other characteristics. Gdansk is an example where the topography renders the city highly vulnerable to heavy precipitation events, especially with the expected increase of number and extent of those events with a further changing climate in the future; as a consequence, Gdansk needs a better urban drainage system (Szpakowski & Szydłowski, 2018, pp. 181–182).

Also the German part of the Baltic Sea basin awaits a strong increase in heavy precipitation events (Umweltbundesamt, 2021a).

Next to or interlinking with heavy precipitation events or further extreme events, rivers flooding are important in some of the cities of the bsr, depending on their location in relation to a river. Floods are expected to vary seasonally, as experienced already with a decrease of floods during spring, and an increase during autumn and winter; the scenarios project a similar development in the future (Rutgersson et al., 2022, p. 282).

Heat Waves and Days of Extreme Heat Meeting the UHI Effect

Heat waves, especially, will increase in their intensity, frequency, and duration due to climate change in the bsr, and its inhabitants are not adapted to those temperatures, which will then increase the need for cooling buildings to prevent severe health impacts (Rutgersson et al., 2022, p. 260). Heat waves are a problem for several cities in the bsr. Especially in Denmark, Estonia, and Lithuania, they impact cities with a higher vulnerability; and several cities in Finland, Latvia, Poland, and Sweden and one German city with a high vulnerability can be found (Tapia et al., 2017, pp. 149–151).

A study of Latvia showed that the increase in the number of days of extreme heat will be a challenge for the major Latvian cities and that adaptation measures were essential to prevent negative impacts on health and mortality of the urban residents, while a positive effect is gained through the decrease in the number of extreme cold days and their effect on human health (Avotniece et al., 2012). Martinez et al. (2018, pp. 389–391) observed for Vilnius (the capital of Lithuania) that while cold-related deaths are higher in their number than heat-related deaths, for the observed period 2009–2015, the mortality in Vilnius due to heat increased. For the near future around 2030 and subsequent years, the authors project a further decrease in cold-related mortality and an increase in heat-related deaths, which will double the amount of the cold-related victims.

At the beginning of the 21st century, heat waves are and will occur in the future. The UHI effect will happen in many cities of the Baltic Sea basin, for example, the medium-sized German city of Rostock, Stockholm, and major Polish cities (Degórska & Degórski, 2015; Richter, 2016; Richter et al., 2013). The UHI effect is also a problem for medium-sized and coastal cities assuming, before concrete study results became available, to be not affected due to the coastal breeze. But also urbanization processes in the bsr do foster the UHI, as was shown in St. Petersburg (Jones & Lister, 2002) or Stockholm (Moberg et al., 2002). Miles and Esau (2020, pp. 9–10) could even proof the UHI for smaller and medium-sized cities for the very northern part of the bsr. Nevertheless, in this northern part of Europe, the cities are starting from a lower average temperature than in the southern European parts, having potentially less heat-induced mortality cases of vulnerable persons in consequence (Kaźmierczak et al., 2020, p. 28).

Heat waves meeting the UHI is a climate change impact that renders living conditions in those UHIs difficult for vulnerable persons and the thermal stress puts human health in the cities at risk (Degórska & Degórski, 2015; Kundzewicz et al., 2018), what is not only projected for the future but also stated as a current impact leading to health problems as well as to an increase in water consumption is, for example, the German city of Rostock (Bender et al., 2019). Kolendowicz et al. (2018) showed current data for some chosen cities of the southern Baltic Sea coast such as Rostock, Klaipeda, Świnoujście, Kołobrzeg, and Hel (as well as nonurban locations) by referring to universal thermal climate index values that the bioclimatic conditions with strong heat and cold stress mainly depend on high-pressure systems. It is helpful for human well-being to use biometeorological indices that indicate thermal comfort according to multiple variables and can signal days with cold or heat stress for urban inhabitants. Apart from heat waves especially, for instance Kažys and Malūnavičiūtė (2015) showed in their study focusing on beach conditions that the thermal temperature in general will be comfortable at the Baltic Sea coast (in contrast to, e.g., the Mediterranean coast), with warmer developments in the southern part. This can have economic positive effects for the coastal cities as it might increase tourism.

Potential Further Climate Change Impacts Such as Droughts, Wind Storms, and Changes in Air Quality

No clear signals are available on if and how the issue of droughts during summer periods will play a decisive role in the cities of the bsr regarding their ground water and drinking water supply. Some as Riga, the capital of Latvia, and the German city Rostock expect problems caused by droughts, such as for the drinking water supply (Kudryavtseva et al., 2021) or, for example, sandstorms affecting transportation. This also depends on the system of drinking water and further land use and land cover in the surrounding areas of the cities.

With respect to climate change impacts on the air quality in the cities of the region, it depends on the scenario used. Generally, an increase in ozone because of warmer temperatures is expected. But, for instance, in Helsinki, a study showed that even if temperatures will rise, it is not expected that the threat of ozone for urban dwellers will rise too (San José et al., 2016). That is different than in other European cities. There are also studies stating, that generally, even if air quality in the cities of the bsr has improved during the last decades (Meier et al., 2022), still, ozone might become a problem with climate change (Meier et al., 2022).

Wind and especially windstorms can cause severe damages in cities, too (He et al., 2021, p. 2), but it is a difficult issue to be generalized, as those wind-related developments are heavily dependent on local conditions, which are in cities especially the built and unbuilt urban and peri-urban structure and theland-use. Coastal cities are increasingly at risk due to climate change (He et al., 2021, p. 26). Rutgersson et al. (2022, p. 257) state no clear picture in climate change projections of the impact cyclones will have on the Baltic Sea basin, but they stress that wind gusts that accompany storms can lead to severe damage, with the caveat that the knowledge base on wind gusts does not present a clear picture. Although they are short-term phenomena, those wind- and windstorm-related events as well as cyclones, and their further interlinked impacts, can cause severe damages to infrastructure and can cause human losses (Rutgersson et al., 2022, pp. 280–281).

Consequences for the Urban Fabric and Economy

The specific climate change impacts on the cities of the bsr as well as general warming will have diverse impacts on the built as well as unbuilt environment of those cities.

The effects floodings have on the urban infrastructure, for example on the transportation infrastructures, water sewage as well as drinking water supply structures were mentioned in more detail in the section “Heavy Precipitation Events and Urban Floods” and can be found in several studies for specific single or also for several cities of the bsr. A study for the transportation infrastructure of Lithuania gives a detailed insight (Nemaniūtė-Gužienė & Kažys, 2017).

Sea-level rise and the expected increase of storm surges will require more coastal protection measures (Andersson, 2013). For the tourist sector this can decrease attractiveness of the Baltic Sea coast, especially near cities that require even more protection of their built environment and the inhabitants. Also the tourist infrastructure in the cities can be negatively impacted and has to be protected to keep up with its services (Umweltbundesamt, 2021b). A risk of sea-level rise is direct damage in the cities. Copenhagen and Gdansk are two out of the four European cities most at risk of this threat, and they are both located on the Baltic Sea coastline (Abadie et al., 2019).

A warmer climate is expected to reduce the energy demand for heating in winter, especially in the northern parts, as was, for instance, shown for Kaunas in Lithuania (Øygarden et al., 2014), but it will increase energy demand in the summer due to the costs of air-conditioning and cooling. Even if concrete calculations of those future demands are difficult and depend on specific local conditions, studies of Finland and Lithuania expect that, until the end of this century, the decrease in energy demand for heating will slightly exceed the increase needed for cooling (Jylhä et al., 2015; Sabunas & Kanapickas, 2017). In comparison to other European countries, it is the Scandinavian countries that will explicitly gain through a decreased energy demand as a positive climate change impact (Damm et al., 2017). Another economic sector relevant to the development of the cities of the bsr is tourism, which is also expected to profit from warming as the tourist season will extend and the weather during summer warmer and eventually more stable (Andersson, 2013).

But while having advantages, a warmer climate as well as extreme events can impact the open green spaces of the cities in the bsr, too. With extreme events, such as droughts and storms as well as heat, urban trees are at risk (Burley et al., 2019). This is important to account for as those green spaces can deliver services to the urban societies that are even more relevant due to the impacts of climate change on urban dwellers. For instance, urban green parks and their vegetation, through their thermal effects, can regulate the climate and temperature and protect urban inhabitants by producing shade, with the cooling effect increasing with the size of the park (Venhari et al., 2017) as was also stated in a study on mortality rates due to selected heat waves in the 1990s as well as in the beginning of the 21st century in the Polish 10-largest cities (Graczyk et al., 2019). This is relevant to how cities can adapt to a changing climate.

Climate Change Impacts and Urban Adaptation

The extent of the negative impacts and damage caused by climate change will depend on the implementation of adaptation strategies and measures in the cities of the Baltic Sea basin, be they inland or coastal cities.

As Kaszmierzak et al. (2020, p. 9) put it for European cities in general, having the current as well as potential future climate change impacts in view, many European local authorities have acknowledged the need for adaptation, mainly at the policy level. This is a strong advancement. But as those strategies and awareness-rising actions develop, implementation in cost-intensive physical measures is very slow (Kaszmierzak et al., 2020, p. 9).

Nevertheless, the cities of the Baltic Sea basin advanced in their adaptation policies, and it is not only the capitals but also many more cities of different sizes progressing on the path of adaptation. Stockholm, the Swedish capital, started its initiatives on climate change in 2007 with a so-called action program on climate change, and it developed a plan for adaptation for the whole Stockholm region by 2010 (Deppisch et al., 2011, p. 220). Also in 2010, Copenhagen, the Danish capital, published its climate plan and addressed five main adaptation initiatives, focusing on surface water drainage, additional green open spaces, cooling buildings, and protection against rising sea-levels and floods (Deppisch et al., 2011, p. 223); it finally published its adaptation strategy in 2011 (City of Copenhagen, 2011). And also for the Finish capital and the peri-urban region, the greater Helsinki region, an adaptation strategy with mainly short-term activities for the period of 2012–2020 was issued in 2012 (Clar & Steurer, 2019; Deppisch et al., 2015, p. 419). More cities in the bsr followed with adaptation activities. The Union of Baltic Cities, a political union of cities from 10 countries, in 2019 published a general resolution on the necessity of adaptation and disaster risk reduction (Union of Baltic Cities, 2019). Barriers to municipal adaptation were stated, too, for instance for Swedish municipalities (Carlsson-Kanyama et al., 2013) or small towns in Denmark and Finland; while it was emphasized, that those towns can profit from participating in European projects on urban adaptation (Fitton et al., 2021). In addition, adaptive capacity varies among the different Baltic countries not only at the local, but already at the regional level (Juhola et al., 2012). Cities of the bsr can also gather further support by joining initiatives for adaptation and resilience; for instance, the Covenant of Mayors, C40, or 100 Resilient Cities, as well as more knowledge exchange and learning how to implement adaptation projects (Kaźmierczak et al., 2020). Adaptation is not the main topic here, but it will influence the extent of climate change impacts, an exemplary glimpse in some details shows that the cities progressed in their adaptation efforts. Within the cities themselves, better urban planning and building, including green infrastructure in the cities as a whole and especially in the UHIs, is considered an effective and necessary adaptation measure for current conditions and under global warming (Bender et al., 2019; Richter, 2016; Saaroni et al., 2018), which can also decrease the increased demand for cooling during summer. Vegetation was even considered to be the most effective UHI-mitigation method, a study on the effect of urban parks on the UHI showed for Wroclaw, a medium-sized inland Polish city of the bsr (Blachowski & Hajnrych, 2021). Stysiak et al. (2016) propose in their study a further afforestation in the wider Copenhagen metropolitan region as an effective adaptation measure to prevent the negative impacts of heat waves in the Danish capital. In the cities directly, as was shown in a study for Swedish cities (next to other European cases), urban green infrastructure can mitigate the UHI under a changing climate through forests, larger parks, and street trees, but this is ambivalent in its effect for the analyzed Swedish cases, as during northern winter periods the shade has an adverse effect on the population, and it can increase heating requirements (Saaroni et al., 2018).

But nature-based solutions in the meaning of using the services and functions of healthy or restored ecosystems (Veerkamp et al., 2021, p. 10) can also be implemented to adapt to further climate change impacts in the cities of the Baltic Sea basin. For instance against floods, the Copenhagen Cloud Outburst Management Plan is an example on how this can be applied (Veerkamp et al., 2021, p. 38). With reference to adapted building, Bradecki and Konsek (2020) suggest for the Polish city of Szczecin, threatened by sea-level rise and floods, floating houses as a method of adaptation, but this is not widely acknowledged in Poland yet. For Klaipeda in Latvia, Cepiene et al. (2022, p. 17) suggest in view of the anticipated floodings of buildings in the town and the threats to the inhabitants, not to build next to the river.

Location Matters and the Different Expected Impacts Force Cities to Implement Adaptation Measures

The Baltic Sea region (bsr) is a very large area within Europe comprising the boreal biogeographical region almost as a whole and parts of the continental biogeographical region and several (whole or in parts) nation-states. The focus on cities is not decreasing this issue of diversity, but it shows that there are cities of different sizes and number of inhabitants, of socioeconomic importance, and of different vulnerabilities as well as different exposures due to specific settings of infrastructure, people, buildings, and so on in specific topographic conditions.

But some general lines can be drawn on the main climate change impacts bsr’s cities have to deal with, even though there are many studies concentrating on one or some cases only.

While there are climate change impacts on the cities of the bsr expected to cause damages to infrastructure and services in the cities as well as negative impacts on human health, there are also some positive impacts expected, such as an extended tourism season with positive socioeconomic effects or less energy demand for heating during the winter.

The future costs and extent of climate change impacts on the cities will depend on the implementation of tangible adaptation measures, not only in the capitals and big cities of the bsr but also in affected medium-sized and small cities, be they coastal or inland cities.

Further Reading

References