Adaptation and Mitigation Strategies Against the Urban Heat Island Effect a Comparative Study on Amsterdam and Rotterdam

Adaptation and mitigation strategies against the urban heat island effect A comparative study on Amsterdam and Rotterdam

Author: Marijn Fennema ([email protected]) Student no. 11054670 Word count: 17301 Course name: Bachelor Scriptieproject Sociale Geografie en Planologie Bachelor Thesis Project Human Geography and Urban Planning Course no.: 734301500Y Coordinator: Drs. J. K. Maiyo Second reader: Dhr. J.V. Rothuizen Date: June 25, 2018.

Acknowledgements First of all, I would like to thank Drs. Josh Maiyo, my bachelor’s thesis supervisor for guiding me through the process of writing my thesis and doing research as a human geographer. He has also given me insight about what doing academic research is really like, which made me realize that although I will soon have my bachelor’s degree, I still have a lot to learn.

Secondly, I would like to thank all the interviewees for helping me with my thesis by interviewing them, sharing information I would not have obtained otherwise. More specifically, I would like to thank Alexander Wandl and Jeroen Kluck for sharing their knowledge and insights about heat stress in the Netherlands. Besides that, I want to thank the people interviewed at the municipalities, municipal health services housing corporations for sharing their current views on the urban heat island effect as well as their strategies to cope with it. I would also like to thank De Groene Stad (the green city) for sharing their vision.

Finally, I would like to thank my family, and my friends in particular for their support and positivity during the thesis writing process.

Abstract Background. Human interference with the climate system is occurring, which leads to changes in human and natural systems. These changes have caused impacts on natural and human systems around the globe in the past and will continue to do so in the future. One of these effects is the urban heat island effect, which is a phenomenon that occurs in urban areas, where the air temperature is usually higher than in the surrounding countryside. This is caused by three phenomena. The first being urbanization, population growth and urban sprawl, the second being more manufactured materials and the third being an increase in heating and cooling needs. The Netherlands has experienced negative effect from the urban heat island effect. The 2006 head wave for instance led to an estimated 1000+ fatalities in the Netherlands, for a large part those living in urban areas. Research goal. This research is aimed to find out the current situation of heat stress in the Netherlands, and Amsterdam and Rotterdam in particular. This study also looks into how Amsterdam and Rotterdam are trying to cope with heat stress and implementing adaptation and mitigation strategies. Research Methods. The urban heat island adaptation and mitigation strategies in Amsterdam and Rotterdam are researched by analyzing existing scientific literature as well as in-depth interviews with people that are linked to heat stress and the urban heat island.

Results. Although heat stress does not receive the attention it deserves, heat awareness in both cities is rising at an institutional level, which could eventually lead to the implementation of more adaptation and mitigation strategies specifically aimed at reducing heat in cities. The public, on the other hand, does not seem to be aware of heat stress. Adaptation strategies against heat stress include the use of air conditioning and acting according to the national heat plan. Vegetation is the primary mitigation strategy in both cities in the outdoor space as well as applied on the built environment (mainly via green roofs). Many adaptation and mitigation strategies are applied through co-benefits strategies, are often (but not always) top-down and applied generically.

Conclusion. When comparing the two municipalities in heat awareness, it seems that Rotterdam is more aware of the urban heat island and its implications than Amsterdam. This is on the levels of heat awareness, as well as heat-oriented adaptation and mitigation strategies. The key difference in adaptation and mitigation strategies is that Amsterdam is overall a greener city, and Rotterdam is applying more adaptation and mitigation strategies that are aimed at the urban heat island effect. The reason for this might be that in Rotterdam, there is more need for heat-specific adaptation strategies, because it can become warmer in summers due to Amsterdam being a much greener city

Recommendations. This study recommends making more use of the polycentric approach in order to become resilient against the urban heat island effect, or resilient cities in general. Similar future research should include interviews with urban planners, urban architects and urban engineers, as well as interviewing or surveying residents to investigate public heat awareness.

Table of contents 1 Introduction 5 1.1 Research topic 5 1.2 Scientific relevance 6 1.3 Research questions 6

2 Theoretical framework 7 2.1 The urban heat island effect 7 2.2 Causes of the urban heat island effect 7 2.3 Adaptation and mitigation strategies 9 2.4 A polycentric approach to the urban heat island effect. 9 2.5 Urban Resilience 10

3 Operationalization 13 3.1 Heat awareness 13 3.2 Adaptation and mitigation strategies 13 3.3 Implementation of adaptation and mitigation strategies 14

4 Background 16

5 Study area 18 5.1 The Netherlands 18 5.2 Amsterdam 18 5.3 Rotterdam 20

6 Methodology 22 6.1 Research design 22 6.2 Data collection methods 22 6.3 Reliability and validity 23 6.4 Ethical considerations 23 6.5 Data analysis 24 6.6 Limitations 24

7 Results: heat awareness 25 7.1 Institutional awareness 25 7.2 Public awareness 27 7.3 Concluding remarks 28

8 Results: adaptation and mitigation strategies 29 8.1 Adaptation strategies 29 8.2 Mitigation strategies 33 8.3 Concluding remarks 36

9 Results: implementation of adaptation and mitigation strategies 37 9.1 Heat stress adaptation and mitigation as primary or secondary objective? 37 9.2 Policy: top-down or bottom-up? 38 9.3 Area-oriented or generic adaptation and mitigation? 39 9.4 Concluding remarks 39

10 Discussion 40 10.1 Co-benefits, the only way to adapt? 40 10.2 Rising heat awareness 40 10.3 Differences in adaptation and mitigation between Amsterdam and Rotterdam 41 10.4 A polycentric approach to the urban heat island effect? 42

11 Conclusion 43

12 References 45

13 Appendix 52 13.1 The heat stress framework by Hatvani-Kovacs et al. (2018) 52 13.2 Screenshots of the Extrema Rotterdam weather app 53 13.3 Infographic municipality of Amsterdam 54 13.4 Positions of the interviewees 55

1 Introduction 1.1 Research topic Urbanization is a rapidly growing form of land use change that is mainly driven by the population and the economy in a country (Ma et al., 2005). Although it is considered as an emerging phenomenon that can lead to many environmental problems in developing countries nowadays, urbanization has played a big role in the economic development of the now “developed” countries in the 20th century (Davis & Keating, 2015).

One of the countries that has experienced rapid urbanization in the 20th century is the Netherlands. The number of urban inhabitants in the Netherlands has grown substantially over the past decades, with 59,8% living in urban areas in 1960 and 76,8% living in urban areas in 1990 (United Nations, 2014). According to the United Nations World Urbanization Prospects report (2014), the Netherlands is currently one of the world’s most urbanized countries, with 90,5% of its inhabitants living in urban areas (United Nations, 2014). This trend of urbanization is expected to continue until at least 2050, where an estimated 96,4% of the inhabitants in the Netherlands will live in urban areas, which will make the Netherlands the 13th most urbanized country in the world (United Nations, 2014). Almost one sixth of the Dutch population resides in Amsterdam and Rotterdam, the two largest cities in the Netherlands, with 1,1 and 0,9 million inhabitants living in both urban agglomerations respectively (United Nations, 2014).

Urbanization can lead to various effects. These effects range from an increase in air pollution (Barbera et al., 2010) to an increase in surface temperature and a decrease in humidity (Wang et al. 2013). In the Netherlands, many cities have experienced expansion in the 20th century, which in many cases has led to urbanization-induced temperature increase (Koopmans et al., 2015). One of the most significant effects caused by urbanization closely related to urbanization- induced temperature increase is the urban heat island effect, which means that urban areas experience higher temperatures than rural areas (Peng et al., 2012). The urban heat island effect leads to higher surface temperatures due to mainly an increase of impervious surfaces, which is one of the effects of urbanization (Yao et al., 2017). The urban heat island effect is considered as a threat because of its many negative effects, the most substantial negative effect being the influence on human life by increasing the risk of exposure to health threatening heat (Zhou et al., 2015). This has led to an increase in mortality rates (Tan et al., 2010). The urban heat island effect is not a problem that only occurs in tropical climates. In fact, it also occurs in countries with a cooler climate like the Netherlands. Here, cities such as Rotterdam can experience an urban-rural temperature difference of 7 oC in the summer (Keuning, 2009).

Although the urban heat island effect can lead to threatening situations for humans, there are many strategies that help to adapt or mitigate the urban heat island effect. This includes strategies such as increasing green areas and open spaces (Rushayati et al., 2016) or increasing the albedo (surface reflectivity) with the usage of reflective pavements (Synnefa et al., 2011). In this thesis, I will compare the adaptation and mitigation strategies against the urban heat island between Amsterdam and Rotterdam.

1.2 Scientific relevance Some research has already been done on the urban heat island effect in Amsterdam, Rotterdam and the Netherlands in general (Van der Hoeven & Wandl, 2013; 2015; Koomen et al., 2013, Heusinkveld et al., 2014). Most research that has been done regarding the urban heat island is remote sensing research on mapping the urban heat island. Many of these researches do mention some adaptation and mitigation strategies, such as that tree capacity mitigates the urban heat island (Rafiee et al, 2016). However, most of the reports do not mention the possibilities and opportunities for mitigating the urban heat island. Other reports mention urban and regional heat island adaptation measures in cities in the Netherlands (Icaza, 2017) but do not compare these cities with each other directly. This is why this research will be scientifically relevant, because according to available knowledge, a research study that compares the current state of adaptation and mitigation measures against the urban heat island effect in the two largest cities of the Netherlands has yet to be done.

1.3 Research questions The Netherlands is one of the world’s most urbanized countries, and notwithstanding its flattening population rate, it is still expected that the Netherlands is becoming even more urbanized. This urbanization can have various climatic side effects that need to be adapted or mitigated. In this research, I am going to compare the effectiveness of adaptation and mitigation strategies against the urban heat island effect due to urbanization in Amsterdam and Rotterdam. Hence the following research question:

How do Amsterdam and Rotterdam apply adaptation and mitigation strategies against the urban heat island effect?

This will be examined through the following sub-questions:

How aware are Amsterdam and Rotterdam of the urban heat island effect?

What are the main adaptation and mitigation strategies against the urban heat island in Amsterdam and Rotterdam?

How are adaptation and mitigation strategies for the urban heat island effect implemented in Amsterdam and Rotterdam?

In the literature review, I will examine the urban heat island effect in Amsterdam and Rotterdam, and the municipal reports that mention heat stress or the urban heat island effect.

2 Theoretical framework 2.1 The urban heat island effect Although this study focuses on urban heat island adaptation and mitigation, the urban heat island effect itself should be described before elaborating on the adaptation and mitigation strategies.

There is not much debate about the exact definition of the urban heat island effect. Oke (1987) describes the urban heat island effect as a phenomenon that occurs in urban areas, where the air temperature is usually higher than in the surrounding countryside (Oke, 1987). This definition has been used in many different reports related to the urban heat island effect (Kleerekoper et al., 2012; Taleghani, 2018; Ketterer & Matzarakis, 2014). Although this concept has been well researched and documented, the understanding of the topic was quite limited (Mohajerani et al., (2017); Yow, 2007). This has changed in the past decade due to the greater focus on global warming and climate effects, the greater prevalence of hotter cities, and changes in technology for measurement and analysis (Mohajerani et al., 2017).

The urban heat island effect is not the same as the surface heat island effect. Whereas the urban heat island effect is about the temperature of the atmosphere (Oke, 1987), the surface heat island effect is about land surface temperature (Li et al., 2017). These concepts are related, however, because a high land surface temperature has a direct influence on the urban heat island effect (Li et al., 2017).

The urban heat island can lead to various negative side effects, such as heat stress. Heat stress can be described as a leading cause of weather-related human mortality, with the high-risk groups being the elderly, the very young and individuals with health problems (Oleson et al., 2015). Although heat stress is a common natural phenomenon, it is expected that global warming will lead to more population fractions experiencing heat stress (Sherwood & Huber, 2010). It is expected that next to global warming, the urban heat island effect will exacerbate extreme heat in urban areas, leading to even more heat stress (Stone, 2012). Extreme heat temperatures are most known for the health risks it leads to, but extreme heat also affects water quality, outdoor spaces (fire hazard), livability (urban comfort) and networks (increasing need for electricity) (Kluck et al., 2017).

2.2 Causes of the urban heat island effect According to Mohajerani et al. (2017), the urban heat island has three main causes. The first being urbanization, population growth and urban sprawl, the second being more manufactured materials and the third being an increase in heating and cooling needs (Mohajerani et al., 2017). Urbanization, the most significant cause of the urban heat island, has many different factors contributing to the urban heat island effect. These effects range from increasing absorption of solar radiation due to high density building (Santamouris et al., 2011) to increasing city density due to urban growth (Doulos et al., 2004) to a decrease in vegetation (Akbari et al. 2001) Increasing population growth leads to many global environmental changes, including deforestation and biodiversity loss (Grimmond, 2007), which contribute to the urban heat island effect because they lead to a decrease in surface and air temperature. An increasing population often leads to an increase in anthropogenic heat release (Mohajerani et al., 2017).

There is still some debate if sprawl, the decentralization and geographical expansion of cities over large areas (Stone et al. 2010) leads to an increase of the urban heat island effect. Previous studies have shown different results about the effect of sprawl on the urban heat island effect (Kohler et al, 2017; Stone et al. 2010).

Manufactured materials often have a lower albedo and greater heat storage compared to regions with native vegetation, which is a major influence on the development of the urban heat island effect (Golden & Kaloush, 2006). The changing materials can lead to new surfaces and atmospheric conditions, altering the airflow, as well as an exchange of energy and water (Mohajerani et al., 2017).

An increase in heating and cooling needs, as well as many other technological developments in society, contribute to the urban heat island effect (Mohajerani et al., 2017). An increase in temperature in cities leads to an increasing demand for cooling techniques such as air conditioning. Although air conditioning provides cooling for human comfort, air conditioning services itself generate more heat, which has an effect on the nearby, local-scale external climate (Grimmond, 2007). An increasing outside temperature thus leads to an intensification in energy consumption for cooling mechanisms (Santamouris et al., 2015), which leads to a hotter outside temperature due to the heat generated by air conditioning.

Another influencing factor on the urban heat island effect is surface water. Rivers, lakes, fountains and other bodies of water experience evaporation during warm periods, which leads to cooling its surrounding area. However, due to its low albedo rate, water absorbs heat, which contributes to the nocturnal heat island effect (Van der Hoeven & Wandl, 2015).

Figure 1 adequately visualizes the causes of the urban heat island effect.

Figure 1: How the urban heat island effect occurs (Yamamoto, 2006).

2.3 Adaptation and mitigation strategies In order to defend society against the negative effects of environmental issues, measures need to be taken. These measures can range from building dykes to prevent floods due to sea level rise, installing solar panels to one’s roof to reduce the use of fossil fuels or installing particulate filters on diesel cars to reduce air pollution. These kinds of strategies can be classified among two categories: adaptation and mitigation strategies.

Adaptation strategies include avoiding hazardous locations and taking measures to counteract or reduce the dangers of environmental phenomena (Dietz et al., 2008). The IPCC distinguishes adaptation in human systems from adaptation in natural systems. In human systems, adaptation strategies seek to moderate or avoid harm or exploit beneficial opportunities, whilst in some natural systems, human intervention may facilitate to expected climate and its effects (IPCC, 2014b). An example of an adaptation strategy is building dykes in order to prevent flooding in the Netherlands (Keessen et al., 2013). This is as a prime example of an adaptation strategy because dykes reduce the chance of flooding, but the cause of flooding is not tackled.

Whereas adaptation strategies are more about preventing or controlling the outcomes of environmental problems, mitigation strategies are more focused on combatting the causes of the environmental problem (Dietz et al., 2008). In other words, mitigation strategies strive to tackle the source of the problem, instead of reducing its consequences (IPCC, 2014a). Using sustainable energy sources instead of non-sustainable energy sources are considered mitigation strategies, because these strategies reduce CO2 emissions by using energy sources such as hydrogen, that do not emit fossil fuels (Wang & Naterer, 2014), thus tackling the source of the problem instead of reducing its consequences.

Instead of focusing solely on one strategy while neglecting the other, the future of climate policy will have to consider a combination of adaptation and mitigation strategies (Brasseur & Granier, 2013). Because mitigation strategies tackle the source of the problem instead of its consequences, one might think that mitigation strategies are always preferred over adaptation strategies. This is confirmed in the article of Brasseur and Granier, who claim that mitigation should be the first objective of international agreement, but that adaptation will probably become necessary (Brasseur & Granier, 2013). However, sometimes it is not possible to carry out both adaptation and mitigation strategies at the same time, which can happen due to constraints (Klein et al., 2007: 749). These constraints include financial constraints, political constraints, environmental constraints and so on. When these constraints occur, tradeoffs between adaptation and mitigation strategies have to be made (Klein et al., 2007).

Although adaptation strategies tend to be near-term and mitigation strategies tend to be viewed as more long-term solutions, there is a direct overlap between these strategies. This is because in reality, both adaptation and mitigation strategies will interact with each other for the duration they are implemented, regardless of the level they are initiated (Moser, 2012). This is why in this research report, both adaptation and mitigation strategies will be considered in order to create a clear image of the current situation in Amsterdam and Rotterdam.

2.4 A polycentric approach to the urban heat island effect. The urban heat island effect is not the same in each urban area. Instead, the urban heat island is dependent on the regional atmospheric and geographic conditions. The location, climatic conditions and seasonal variations all should be considered while analyzing the urban heat island effect in a particular city (Mohajerani et al., 2017).

The intensity of the urban heat island effect is also affected by the built environment of an urban area. As mentioned before, urban sprawl is linked to the urban heat island effect, which might suggest that cities with more urban sprawl have a stronger urban heat island effect than denser cities (Stone et al., 2010; Mohajerani et al., 2017). The urban heat island effect is affected by other factors as well, and urban heat is present in both sprawled as dense cities (Debbage and Shepherd, 2015). This suggests that the urban heat island is an irregular phenomenon, and an issue that is best tackled with localized research and mitigation efforts, and mitigation strategies need to be tailored to individual cities (Mohajerani et al., 2017, Debbage and Shepherd, 2015).

This suggests that regarding the urban heat island, there is no one-size-fits-all strategy, which is a common phenomenon within environmental science. This is best explained by Hansen & Bi (2017): “adaptive capacity varies greatly between different populations, communities, and individuals, depending on levels of vulnerability, resilience, and available resources” (Hansen & Di, 2017:353). Approaching adaptation strategies from a collectivist viewpoint fails to acknowledge such differences. Instead, adaptation strategies must be considered through local decision makers because there is no one-size-fits-all (Hansen & Bi, 2017).

I also support an approach that is more focused on local knowledge. Ostrom (2010) introduced the polycentric approach for coping with collective action and global environmental change. According to Ostrom, “polycentric systems are characterized by multiple governing authorities at differing scales rather than a monocentric unit” (Ostrom, 2010:552). An advantage of a polycentric system is that participants can use local knowledge, which is often not considered in monocentric systems. Furthermore, the polycentric approach has considerable advantages due to the mechanisms for mutual monitoring, learning, and adaptation of better strategies over time (Ostrom, 2010).

In relation to the urban heat island effect the polycentric approach can be beneficial because of the different actors involved, as well as local knowledge. A polycentric approach can possibly prevent large top-down strategies that do not take local situations into account. It also supports collaborative planning, which could lead to adaptation and mitigation strategies that are more local-oriented.

2.5 Urban Resilience A subject that is gaining increasing prominence across many studies on cities and climate change is (urban) resilience. Urban resilience emphasizes the idea that cities, urban systems, and urban constituencies need to be able to quickly bounce back from climate related shocks and stresses (Leichenko, 2011). Although there are some literary disagreements on resilience, there is a broad consensus that cities must become resilient to a wide range of shocks and stresses, and efforts to foster climate change resilience must be bundled with efforts to promote urban development and sustainability (Leichenko, 2011). The urban heat island effect falls within this ‘wide range of shocks and stresses’ in order to prepare for climate change, as many studies show the relation between addressing the urban heat island effect and resilience (Emmanuel & Krüger, 2012; Shafique & Kim, 2017; Leal Filho et al., 2018)

In order to become resilient, cities should not aim to maintain stability. Instead, cities, or systems in general, should aim for flexibility (Nelson et al., 2007). A resilience approach recognizes that vulnerabilities are an inherent part of any system. This means that resilient systems should identify acceptable levels of vulnerability and respond when vulnerable areas are disturbed instead of trying to eliminate vulnerability (Nelson et al., 2007).

For this research, the heat stress resilience framework by Hatvani-Kovacs et al. (2018) will be taken into account (figure 2). In this framework, four sectors related to urban heat stress are considered: public health services, the building and construction industry, urban planning and infrastructure services and utilities (Hatvani-Kovacs et al., 2018).

Social and ecological systems need to be understood as related, coupled systems instead of apart from each other (Nelson et al., 2007). This is the case in the heat stress resilience framework, which consists of strategies aimed at social systems (increasing the accuracy of health alerts), strategies aimed at ecological systems (green space ratio) and strategies aimed at both systems (building cool public spaces) (Hatvani-Kovacs et al., 2018).

The heat stress framework includes some factors that are irrelevant for this research. This is because the heat stress framework is based on heat stress in Australia, whereas this research analyzes heat stress in the Netherlands, which has completely different atmospheric and geographic conditions. Although I have stressed the importance that the urban heat island is best tackled with localized research and mitigation efforts, I still believe that the heat stress framework is also applicable on the Netherlands to a large extent. There are some suggestions that are solely focused on Australia, but overall, the framework addresses many aspects of heat stress risk and resilience that are applicable in the Netherlands as well.

The entire heat stress framework can be found in the appendix.

Figure 2: The policy framework to increase urban heat stress resilience (Hatvani-Kovacs et al., 2018).

3 Operationalization 3.1 Heat awareness The first concept that will be researched is heat awareness. As mentioned earlier, heat awareness could lead to making the necessary step to adapt to heat stress (Klok & Kluck, 2018). For this research, heat awareness will be divided into two types of heat awareness: institutional and public awareness.

Institutional awareness will be analyzed at the municipalities, municipal health services and housing corporations. In addition to that, the experts on the urban heat island effect will also be asked about their thoughts on institutional heat awareness. Some strategies, such as heat warning systems, are specifically aimed at informing the public about heat stress. Study shows that although municipalities can be aware of heat stress and even make substantial efforts to prevent heat-related morbidity and mortality, it could still be that the public might be unaware of the dangers of hot weather in urban areas (Lane et al., 2014). The “public” will not be interviewed for this research. Instead, the interviewees will be asked about their experience with public heat awareness. For instance, the municipal health services will be asked about their experiences with public heat awareness.

3.2 Adaptation and mitigation strategies There are different kinds of adaptation and mitigation strategies against the urban heat island effect. These strategies range from applying vegetation in the open space to constructing green roofs to warning the public via television. Adaptation and mitigation strategies will be covered separately. First, I will look into the adaptation strategies that are applied in both cities, followed by the mitigation strategies in both cities.

Adaptation and mitigation strategies will be divided into three types of strategies: outdoor space, built environment and social adaptation. Many scientific reports analyzing heat stress distinguish strategies aimed at reducing outdoor temperatures from those reducing indoor temperatures (Franck et al., 2013, Ashtiani et al., 2014). This does not mean that these strategies are not interrelated. In fact, there are many adaptation strategies applied in the outdoor space that influence the indoor space and vice versa. For instance, applying vegetation can lower the outdoor air temperature (Taleghani, 2018), which directly affects the indoor temperature (Franck et al., 2013). However, the indoor temperature is dependent on more factors than solely the outdoor temperature, such as the urban structure. Adaptation and mitigations strategies that are applied in the outdoor space include planting trees and increasing the albedo (Taleghani, 2018). In addition, impervious surfaces increase the urban heat island effect. By removing impervious surfaces, the urban heat island effect could reduce (Van der Hoeven & Wandl, 2013).

There are some strategies applied on or in buildings that affect the indoor temperature as well as the outdoor temperature, such as green roofs and green façades (Taleghani, 2018). Although both of these strategies influence both the indoor and the outdoor environment, they will be covered by “built environment” because these strategies are applied on or in the built environment. Other adaptation strategies, such as the use of air conditioning, cool the temperature inside buildings and thus reduce mortality rates, but can on the other hand lead to an increase in the outdoor temperature (Tremeac et al., 2012).

Adaptation and mitigation strategies that are applied on the built environment include air conditioning, green roofs and green façades. Isolation will also be considered. Although well- isolated buildings tend to warm up slower, thus staying cool for a longer period of time, well- isolated buildings also tend to retain heat for a longer period of time, thus giving the building less opportunity to cool down (Van der Hoeven & Wandl, 2013; Parag, 2008). Rising building temperatures often lead to more use of air conditioning (Yamamoto, 2006).

Next to strategies that are applied in the outdoor space and the built environment, there are adaptation strategies that are not covered by these categories but are still considered adaptation strategies against the urban heat island effect. Strategies such as heat wave warning systems (Kim et al., 2014) and drinking water (Lane et al., 2014) help people adapt to heat stress, even though these strategies do not have implications for the indoor and outdoor temperature. Other social adaptation strategies, or behavioral adaptation strategies, are adapting sleeping habits to reduce sleep time exposure to intense heat (Hendel et al., 2017).

The heat stress framework by Hatvani-Kovacs et al. (2018) is divided into four sectors related to the urban heat stress; public health services, the building and construction industry, urban planning and infrastructure services and utilities. These sectors will be sorted into the three subgroups stated above; Social and behavioral adaptation will include the public health services, the built environment will include the building and construction industry and the outdoor space will include urban planning as well as infrastructure services and utilities.

3.3 Implementation of adaptation and mitigation strategies “Implementation of adaptation and mitigation strategies” will be analyzed separately from “adaptation and mitigation strategies”. This is because these concepts are approached differently. The latter looks into what is implemented, whereas the former looks into its decision-making context. The three main topics within the decision-making context are heat as primary or secondary objective, top-down or bottom up approaches and area-oriented or generic approaches.

Climate change adaptation is place and context-specific (IPCC, 2014a), which means that not only that some strategies are more effective in one place than in another, some climatic problems are more present in one place than in another as well. In order to analyze if the urban heat island is considered a primary or secondary objective, I will investigate if both cities have heat-specific adaptation reports. If heat-specific strategies have yet to be implemented, it could still be that the urban heat island effect is combatted through co-benefit strategies. This means that strategies can include actions with co-benefits for other objectives (IPCC, 2014a). Green roofs, for example, have multiple benefits, including the reduction of greenhouse gases, prevent water runoff during peak precipitation and reducing the surface temperature of roofs (Moghbel & Erfanian Salim, 2017).

According to the IPCC (2014a), all adaptation and mitigation strategies can be sorted into two broad categories: top-down and bottom-up approaches. Both approaches can be understood from a development studies perspective: “In most cases, resettlement planning is based on this kind of top-down centre outwards approach to planning. Planners assume that their expertise allows them to ‘understand and manage the interests of the farmers better than the farmers do for themselves” (Lightfoot 1979, p. 30 in Adams, 2009, p. 312). The bottom-up approach suggests

14 that “for success, developments must be not only innovative and research based, but locally conceived and initiated, flexible, participatory and based on a clear understanding of local economics and politics” (Adams, 2009, p. 328). Translated to environmental studies, these approaches stay more or less the same, and revolve around the level of involvement of the public. Top-down, the public is lesser involved than in bottom-up. Examples of bottom-up approaches are citizen participation and neighborhood initiatives (Niederer & Priester, 2016). Top-down strategies can range from the public having hardly any influence on the project to the public being consulted by the strategy-implementing party (Skarp et al., 2017). Previous studies have shown that the urban heat island effect is not equally dispersed over both cities, but that some neighborhoods experiences higher temperatures than others during hot periods (Van der Hoeven & Wandl, 2013; 2015). The IPCC also mentioned that adaptation is place- and context-specific, and there is no single approach for reducing risks appropriate across all settings (IPCC, 2014a). Hence, I will analyze if Amsterdam and Rotterdam use more area- oriented strategies, or more generic adaptation and mitigation strategies. This will be done by asking the interviewees if the strategies are implemented generically or area-oriented, as well as looking into policy reports.

Concept Dimensions Indicators Heat awareness Institutional awareness Heat awareness and risk perception at the municipalities (Runhaar et al., 2012). Public awareness Experiences with public heat awareness. Questions from the public at municipal health services. Adaptation strategies Outdoor space Creating shading (Runhaar et al., 2012). Built environment Air conditioning (Tremeac et al., 2012). Sun Screens, creating shading (Runhaar et al., 2012). Social/ behavioral Warning systems (Kim et al., 2014), adapting adaptation sleeping habits (Hendel et al., 2017), drinking water (Lane et al., 2014). Mitigation strategies Outdoor space Applying vegetation, increasing the albedo (Taleghani, 2018). Removing impervious surfaces (Van der Hoeven & Wandl, 2013). Built environment Green façades, green roofs, increasing the albedo (Taleghani, 2018). Strategy implementation Primary objective Reports aimed at adapting or mitigating to the urban heat island effect or heat stress. Secondary objective Co-benefits strategies (IPCC, 2014a), no reports aimed at combating to urban heat. Top-down approaches Lack of citizen participation and neighborhood initiatives (Niederer & Priester, 2016), Consultation (Skarp et al., 2017) Bottom-up approaches Citizen participation, Neighborhood initiatives (Niederer & Priester, 2016). Area-oriented strategies Specific strategies on city-district or neighborhood level. Generic strategies No specific strategies on city-district or neighborhood level. Table 1: Operationalization table.

4 Background Human interference with the climate system is occurring, which leads to changes in human and natural systems. These changes have caused impacts on natural and human systems around the globe in the past and will continue to do so in the future (IPCC, 2014b). One of these effects is temperature rise. The average temperature in the Netherlands is expected to rise between 1,3 oC and 3,7 oC by 2085, depending on the climate scenario. In addition to that, more extreme weather events are more likely to occur (KNMI, 2015). In urban areas, climate change will lead to increased frequency, intensity and/ or duration of extreme weather events such as heavy rainfall, warm spells and heat events, drought and intense storm surges (IPCC 2014a).

There are many examples of urban areas experiencing such extreme weather events. An example closely related to this research is the Paris heat wave in 2003. In August 2003, France, and Paris in particular, experienced a devastating heat wave, which killed nearly fifteen thousand, mostly elderly, people in France, and over a thousand in Paris alone (Keller, 2013). After this disaster, heat awareness raised. France developed a national “Plan Canicule” (heat wave plan), which resolved around responsibility, prevention and solidarity during heat waves, with measures such as count at-risk persons, cooled rooms and support emergency medical services and personnel (Poumadère et al., 2005). The “Plan Canicule” is still relevant and updated regularly.

Although mostly known for its effects on the residents of Paris, the Netherlands also experienced negative effects from the 2003 heat wave, with an estimated 1700 deaths (Van der Hoeven & Wandl, 2013). The Netherlands experienced its second heat wave of the decade in 2006, which led to an estimated 1000+ fatalities in the Netherlands (Statistics Netherlands, 2006). The 2006 heat wave led to the highest temperature ever recorded in Rotterdam (27,8 oC). In addition, the 2006 heat wave led to the highest death ratio among people over 75, with 385 fatalities. This means 75 extra deaths among people over 75 in July compared to the average amount of deaths in July in Rotterdam (Van der Hoeven & Wandl, 2015). Although the amount of extra fatalities is unknown for Amsterdam, the land surface temperature of Amsterdam was 10 to 20 oC warmer than its rural surroundings. (Van der Hoeven & Wandl, 2013).

It was not until 2006 that the Netherlands was developing national adaptation strategies against heat stress. In 2007, the first Dutch heat wave plan, the “Nationaal Hitteplan” was released due to the 2006 heat wave (RIVM, 2014). This late development of heat plans in comparison to Paris can be explained from the fact that the water-related issues instead of heat stress is seen as the predominant climate-related issues (Van der Hoeven & Wandl, 2013) as well as the position of the Netherlands in a mild maritime climate zone close to the sea in which high temperatures have not been a concern for a long time (Van Hove et al., 2011).

Heat plans like the “Nationaal Hitteplan” mainly revolve around social adaptation, being vigilant as the government and warning the people on time. This is one of many forms of heat adaptation and should not be the only form to adapt to heat. Other examples are cool roofs that due to reflectivity keep roofs, and thus the indoor temperature cooler in Athens (Synnefa et al., 2012), pavement-watering to reduce maximum outdoor daily heat stress in Paris (Hendel et al., 2016) and constructing parks as well as tree planting in cities have a cooling effect on its urban surroundings (Yang et al., 2016).

Urban heat can lead to many negative effects. Increased temperatures lead to damaged ecosystems, more pollutants in the air, can lead to deaths by heat stress and will likely cost tremendous amounts of money for both residents and governments (Susca & Pomponi, 2018). As mentioned above, there is enough knowledge about adaptation strategies that can be implemented against the urban heat island. However, it is a mixed picture when it comes to taking these steps and implementing these adaptation strategies in order to prevent or reduce urban heat (Susca & Pomponi, 2018). In this research, I will try to find out the current situation of heat stress in the Netherlands, and Amsterdam and Rotterdam in particular. I will also look into how Amsterdam and Rotterdam are trying to cope with heat stress and implementing adaptation and mitigation strategies.

5 Study area

5.1 The Netherlands Situated in a temperate maritime climate zone, the climate of the Netherlands is characterized by mild summers, cool (but not cold) winters and overall high precipitation (KNMI, 2015). The average temperature in the summer months is 17 oC, and the average winter temperature is 3,4 oC (KNMI, 2015). There are many different climate scenarios for the Netherlands in the 21st century, in which there are many differences. There are some general predictions for the Netherlands that are likely going to occur no matter the climate scenario, such as rising temperature in both summer and winter and more high-intensity precipitation (KNMI, 2015). In particular the temperature rises will be of great importance for this research, because temperature rise and climate change in general influence the urban heat island intensity (Corburn, 2009).

One of the most important city regions in the Netherlands is the Randstad area, which is a megapolis with a population of 7,1 million inhabitants consisting of the four largest cities in the Netherlands; Amsterdam, Rotterdam, The Hague and Utrecht and their surrounding areas. In this research, I am going to compare the two largest cities in the Randstad areas; Amsterdam and Rotterdam.

5.2 Amsterdam Amsterdam has a population of approximately 811.000 and an urban agglomeration of 1,1 million inhabitants, which makes Amsterdam is the largest city in the Netherlands (Municipality of Amsterdam, 2017a; United Nations, 2014). As the capital of the Netherlands, Amsterdam is of great global importance in many areas. Schiphol airport is the third airport in Europe in terms of market share and is one of the most visited tourist destinations in Europe (Schiphol, 2018; Rawding, 2000). Amsterdam is also home to many headquarters of large companies, and the port of Rotterdam is the fourth largest port in Europe (Port of Amsterdam, 2013). Although these factors are good economically, there are many downsides to these factors when linked to climate change. It has been proven scientifically that tourism affects climate change (Amelung & Moreno, 2012). Amsterdam Schiphol Airport is responsible for noise, air and odor pollution, as well as greenhouse gas emissions (Staatsen et al. 1994). Shipping in Amsterdam also leads to severe air pollution of nitrogen dioxide, sulfur dioxide and fine particles (Van Zoelen, 2017). In other words, the activities that are of great importance for Amsterdam economically can lead to many climatic downsides that could be linked to temperature rise and the urban heat island effect.

Not the entire metropolitan area of Amsterdam will be investigated in this research. Instead, this research will focus on the following city districts in Amsterdam: Amsterdam city center (Centrum), Noord, Oost, Zuid, West, Nieuw-west and Zuidoost. The Westpoort port area of Amsterdam will be excluded in this research, because with 192 inhabitants (OIS, 2017), this area has barely any residents that will be affected by the urban heat island. The research area of Amsterdam is shown in figure 3.

The urban heat island in Amsterdam Overall, the urban heat island is present in Amsterdam, especially in the summer months. In the summer, the urban heat island effect in Amsterdam when compared to its surrounding countryside can lead to an increase of over 3 oC on moderately warm summer days with a daytime maximum temperature of 20 oC, and up to 5 oC on hot summer days (Koomen & Diogo, 2017). On these summer days, the temperature differences between urban Amsterdam and its surrounding rural areas increases by 0,15 oC for each degree increase in maximum daytime temperature (Koomen et al, 2013). This temperature difference is much of a problem on moderately warm summer days. On hot summer days and during heat waves however, the Figure 3: The research area in Amsterdam (the Westpoort Area will not be urban heat island can lead to risks. investigated in this research). Source: OIS Amsterdam (2016) and ESRI Nederland (2018), map made by the author. In the past, Amsterdam has experienced some heat waves, with the heat wave in 2006 being the most significant. Heat waves can lead to health risks such as fatigue and headaches, and even fatalities in extreme cases (RIVM, 2012). During heat waves, the urban heat island in Amsterdam can be quite substantial. The land surface temperature in residential areas with impervious surfaces can be 10-20 oC higher than its surrounding rural areas by day during heat waves (Van der Hoeven & Wandl, 2013). During the night, the urban heat island effect in Amsterdam is not only 7-9 oC warmer than its surrounding rural areas, Amsterdam also cools down to a lesser extent than its surrounding rural areas (Van der Hoeven & Wandl, 2013). By analyzing these heat waves, it seems that the urban heat island effect in Amsterdam is in the upper range of what could be expected in European cities (Van der Hoeven & Wandl, 2013).

The urban heat island effect affects every city district in Amsterdam. Nevertheless, the urban heat island differs between, and even within each city district. The urban heat island effect affects the entire city of Amsterdam, but Amsterdam West and the city center in particular (Rombouts & Van Zoelen, 2015). This is because of the lower quality of life of the neighborhood and the poorer energy efficiency of the buildings (Van der Hoeven & Wandl, 2013). Amsterdam Noord, Zuid and Zuidoost (with the exception of the Amstel III/ Bullewijk district) are relatively cool when compared to the rest of Amsterdam (Van der Hoeven & Wandl, 2013). The urban heat island effect strikes Amsterdam the hardest on the most urbanized locations, most of these locations lying around the city center. The areas where the urban heat island has the least significant effect are Waterland (Noord), Lutkemeer/Ookmeer (Nieuw-West) and Nellestein and Driemond (Zuidoost).

5.3 Rotterdam Although less important economically and globally than Amsterdam, Rotterdam is still one of the most important cities of the Netherlands. With a population of around 618.000 (Municipality of Amsterdam, 2017) and an urban agglomeration of 0,9 million inhabitants (United Nations, 2014), Rotterdam is the second-largest city in the Netherlands. The Port of Rotterdam is Europe’s largest port and industrial complex (Port of Rotterdam, 2017). In corporation with The Hague, Rotterdam is also linked to the Rotterdam The Hague Airport, which is a small airport compared to Schiphol. Although having less of a business climate in comparison to Amsterdam, Rotterdam is also home to some headquarters and branches of domestic and international. Like in Amsterdam, these generally positive economic factors do have some negative downsides that are related to climate change and the environment.

Some regions in the municipality of Rotterdam will be excluded for this research. This applies for the following city districts: Hoek van Holland, Rozenburg, Pernis, Hoogvliet and the port and industrial areas. This is because most of these areas are too far away from the city center, or do not have a significant number of inhabitants in order to be investigated properly. The areas that will be examined in this research are: Rotterdam city center (Centrum), Delfshaven, Overschie, Noord, Figure 4: The city districts that will be investigated in this research in Rotterdam. Hillegersberg-Schiebroek, Source: Statistics Netherlands (2016) and ESRI Nederland (2018), map made by the Kralingen-Crooswijk, Prins author. Alexander, Feijenoord, IJsselmonde and Charlois (figure 4).

Regarding sustainability, Rotterdam is known for its movable storm surge barrier, the Maeslantkering. Since its opening in 1997, the Maeslantkering has closed twice, during storms in 2007 (Volkskrant, 2007) and 2018 (NU.nl, 2018), which has led to the prevention of possible floods. Rotterdam is also part of the Rockefeller 100 resilient cities program, which is set up by the Rockefeller foundation to help more cities build resilience to the physical, social and economic challenges that are a growing part of the 21st century (Rockefeller foundation, 2018).

The urban heat island in Rotterdam Like Amsterdam, the urban heat island effect in Rotterdam is the most significant in the summer. On windless summer days with a temperature of over 30 oC, the maximum urban heat island intensity can lead to a temperature difference of over 8 oC in comparison to the surrounding countryside in the densest city areas of Rotterdam (KVK, 2011). Studies have shown that the pre-war districts in Rotterdam (North, South and West) are warmer and thus more vulnerable to the urban heat island effect in comparison to the other areas of Rotterdam, mainly the low-rise districts with many green spots (Van der Hoeven & Wandl, 2015; Municipality of Rotterdam, 2013). More specifically, the areas with a high surface temperature due to the urban heat island effect in Rotterdam are mostly highly urbanized areas with impervious surfaces that are located near industrial activities.

During the day, Delfshaven, Feijenoord and IJsselmonde are affected the most by the urban heat island effect. During the night, the harbor and industrial areas of Rotterdam, as well as Pernis, are most affected by the urban heat island effect. The areas that are affected the least by the urban heat island effect are districts with many low-rise buildings such as Kralingen. The city center itself, including the Kop van Zuid area, is also greatly affected by the urban heat island effect (KVK, 2011).

6 Methodology 6.1 Research design This study’s research design will be the comparative design, where two (or more) cases are studied by using the same methods (Bryman, 2012). In this research, the two cases that will be compared are the built-up areas of Amsterdam and Rotterdam. A comparative research can be either quantitative or qualitative, depending on the context and the methods used. This research will be using mainly qualitative data, making it a qualitative comparative study. Although this research is mostly about the urban heat island as a natural phenomenon, the social factors that influence and are influenced by the urban heat island effect will also be examined. The epistemological approach in this research is the interpretive theory, or interpretivism, in which the subject matter of social sciences is treated as fundamentally different from that of the social sciences (Bryman, 2012). This research will be based on the inductive theory. With an inductive approach, a theory will be formed as the outcome of the research and its findings (Bryman, 2012). Hypotheses are not needed in order to implement an inductive research. This is the opposite of a deductive approach, where hypotheses are formed before collecting data and analyzing results (Bryman, 2012). The research question will be answered by taking interviews and analyzing existing scientific literature regarding the urban heat island effect in Amsterdam and Rotterdam. 6.2 Data collection methods The research methods in this research will be a combination of a literature review and interviews with people that are linked to the heat stress.

Scientific literature that has already been written will be the base for this research. From the literature, I will use the data for examining the existing situation for both cases. Existing data has also been used for constructing the theoretical framework. Some scientific research has already been done regarding urbanization, the urban heat island effect and adaptation and mitigation strategies in Amsterdam, Rotterdam and the Netherlands in general. In addition, I have also made use of scientific articles that revolve concepts related to urban heat island adaptation and mitigation, mainly urban resilience.

For this research, I have done in-depth interviews with people that are linked to heat stress in one way or another. The interviewees for this research are sampled through purposive sampling. This means that the research participants are not chosen on a random basis, but strategically with the research goal in mind (Bryman, 2012). The samples are chosen from establishing criteria concerning the kinds of cases that need to be addressed for the research questions, which Bryman describes as the generic purposive sampling approach (Bryman, 2012). The units of analysis for this research are adaptation and mitigation strategies.

The criterium used for deciding the research group are that they have to be somewhat linked to urban heat island adaptation and mitigation, preferably in Amsterdam and Rotterdam. I have tried to interview people that are active in one of the four subgroups related to urban heat stress by Hatvani-Kovacs et al. (2018). The people interviewed at municipal health services fall within the public health services, the housing corporations are included in the building and construction industry, and the municipalities include urban planning and infrastructure services and utilities.

Parties linked to urban heat island adaptation and mitigation include municipalities, housing corporations and municipal health services. From each of the previously mentioned parties, I have interviewed someone who is linked to heat stress in some form. Besides that, I have interviewed two experts that have done research on the urban heat island effect in the Netherlands. I have also interviewed an employee at De Groene Stad (The Green City), a company that aims to inform and stimulate the interest with authorities, organizations and companies which are professionally involved in planning and developing the urban area, ensuring green will be applied appropriately (De Groene stad, 2018). I have tried to make the interviews as balanced as possible, which means that I have tried to interview the same amount of people in Amsterdam as in Rotterdam. There is some sampling error in this research. This is because I have interviewed three people who work at the municipality of Rotterdam, and just one employee from the municipality of Amsterdam. The other interviews are without any sampling error.

Each interview held is a semi-structured interview, which means that I have set up a list of questions or topics for each interview beforehand, but I have had a great deal of leeway in how to reply (Bryman, 2012). In each interview, I have asked questions that were not set up beforehand in order to get more information from the interviewees on specific topics.

6.3 Reliability and validity This study has taken place in Amsterdam and Rotterdam. Only a small sample of people involved in the urban heat island effect in both cities have been interviewed. One housing corporation per city, one employee per municipal health service, a few employees from both municipalities, two researchers and one external company are interviewed. However, only a small amount of people in both cities that are invloved in the urban heat island effect is also quite low. The external validity, the degree to which findings can be generalized across social settings (Bryman, 2012) is low. This study gives insight and possibly develops theoretical ideas regarding urban heat island adaptation and mitigation across various parties. This means that it is not possible to generalize the results in both cities, but that the internal validity is high in this research.

The external reliability, the degree to which a study can be replicated (Bryman, 2012) is also low for this research. Both the urban heat island effect as well as the adaptation and mitigation strategies against it can change over time, which will likely lead to different results than the results of this study.

6.4 Ethical considerations All interviewees have been informed about the aim of this study before each interview in order to avoid misconceptions. The respondents agreed for recording their interview for transcribing reasons. A week before handing in the thesis, I sent each respondent their quotes as well as other information related to them or their organization. This is again done in order to avoid misconceptions.

I have asked each respondent for their permission to use their identity. I have only used the identity of the respondents that agreed with using their identity. The respondents who preferred to be anonymous or from whom I have not received an answer will remain anonymous. The anonymous respondents are referred to as abbreviations of their function and city they live in. For instance, AM1 means Amsterdam Municipality 1, RHS1 means Rotterdam Health Service 1. The list of interviewees can be found in the appendix.

6.5 Data analysis The interviews have been coded manually. The interviews have been coded directly after transcribing each interview. Quotes were sorted into different themes (some of the quotes in multiple themes) such as heat awareness, adaptation strategies and strategy implementation. I have used the Grounded Theory in order to come to conclusions from the collected data. This means that the theory is derived from data and is systematically gathered and analyzed through the research process (Bryman, 2012).

6.6 Limitations This study has some limitations. I could only interview 11 participants related to the urban heat island effect. I wished to have interviewed more people related to the urban heat island effect, but this was not possible due to time limitations. I have not interviewed the residents in both cities. This means that public awareness is solely based on the experiences of the interviewees, which could be misleading. I also have not interviewed urban designers and architects in both cities. This is a limitation, because urban designers and architects might have more knowledge on urban heat island adaptation and mitigation in the outdoor space as well as the built environment. As mentioned earlier, only one housing corporation in each city has been interviewed. Although the housing corporations interviewed have a relatively large housing stock, they still cover a small amount of the total housing stock in each city. Finally, this research is done from a social-scientific perspective. I have analyzed the different measures that are currently used in both cities, but I have not measured the how the adaptation and mitigation strategies affect the urban heat island effect in both cities.

7 Results: heat awareness The urban heat island effect is considered in many countries as one of the top climate-change related threats in urban areas. In the Netherlands, however, water-related issues such as an increase in precipitation, flooding and sea level rise are considered as the predominant issues caused by climate change (Van der Hoeven & Wandl, 2013). This combined with the fact that the Netherlands is situated in a mild maritime climate zone close to the sea is the reason that high temperatures have not been a concern in the Netherlands for a long time, and why the urban heat island effect is often not considered when analyzing climate scenarios for the Netherlands (Van Hove et al., 2011).

7.1 Institutional awareness The Dutch ministry of Rijkswaterstaat (part of the Dutch Ministry of Infrastructure and water management and responsible for the design, construction, management and maintenance of the main infrastructure facilities in the Netherlands (Rijkswaterstaat, 2018)) acknowledges that the negative health effects of heat stress, especially in urban areas, must be addressed. This is why heat stress is included in the Dutch National Adaptation Strategy for 2018-2019 (NAS, 2018). The NAS focuses on three components: the implementation of local heat plans in municipalities, doing research on heat and smog during events, which leads to advice on how to handle during such circumstances and the development on heat vulnerability maps (NAS, 2018). In June 2018 “Congres Hittestress”, the first national heat stress congress will take place. This congress resolves around how the Netherlands will cope with a warmer climate and focuses on raising awareness around heat scenarios in the Netherlands (Congres Hittestress, 2018; NAS, 2018).

Within the institutions interviewed, heat stress is not considered a priority climate-wise. Both municipalities primarily focus on water stress, municipal health services prioritize issues such as air quality over heat stress and housing corporations focus on making houses more sustainable, mainly by isolating them. According to Alexander Wandl, the institutions do not put heat stress on a more primary position due to the lack of awareness.

“I think there is not enough awareness on the level of the developers. So, it may be in the municipal plans and so on, but if you are talking about the real implementation, that tends to disappear, because you cannot make a lot of money” (Alexander Wandl).

This is substantiated further in the article by Runhaar et al. (2012). Although heat stress is not a new phenomenon in the Netherlands, urban planners do not seem to be aware of it, or even perceive it as a problem. This might be because of the rather abstract knowledge on heat stress due to the limited information on local heat stress projections (Runhaar et al., 2012). The lack of heat awareness in the Netherlands is mainly takes place on a local level (Klok & Kluck, 2018). The article by Runhaar et al. shows that there is a substantial difference between the municipalities of Amsterdam and Rotterdam regarding heat stress awareness. Amsterdam did not expect heat stress to occur due to the low building density and the presence of much open space and open water. Rotterdam, on the other hand, was one of the few municipalities that was active in the area of heat stress in 2012, and the only municipality that had made estimations about the health impacts of heat stress (Runhaar et al., 2012).

Amsterdam: institutional awareness Amsterdam does not have a specific heat policy. This does not mean however, that there is no heat awareness in Amsterdam. In fact, AM1 mentioned that heat is the next thing they want to address in Amsterdam. The municipal health service in Amsterdam has more adaptation strategies against heat stress compared to the municipality. This is in order to prevent health issues in risk groups that will be affected by heat stress. Mainly the elderly, the chronically ill and people who work outside, but also children and event visitors can experience health issues due to heat stress, according to Ben Rozema. However, if you look at the priority of heat within the municipal health service of Amsterdam, heat is not at the top. Other issues, mainly aerial pollution get the priority over heat. Eigen Haard, one of the largest housing corporations in Amsterdam, is not focusing on heat stress in particular, but more on general climate adaption strategies that make houses more energy-efficient, according to Wim de Waard.

Rotterdam: institutional awareness The municipality of Rotterdam acknowledges that Rotterdam will experience more and longer warmer periods (in 2050, Rotterdam will experience twice as many hot days compared to 2010). This in combination with a city that is getting more compact, will probably lead to a drastic increase in the urban heat island effect (KVK, 2011). This is why the municipality of Rotterdam has included heat as one of the main subjects in the adaptation strategy of Rotterdam (Municipality of Rotterdam, 2013). In the adaptation strategy the consequences of heat waves, such as health issues, thermal comfort, infrastructural issues and consequences for flora and fauna are taken into account (Municipality of Rotterdam, 2013). This will be further elaborated upon in the adaptation and mitigation chapter. The interviews as well as well as climate adaptation reports have shown that the municipality of Rotterdam is currently more aware of the consequences of urban heat compared to Amsterdam. Heat stress and its effects are included in the national adaptation strategy of Rotterdam, and according to RM2, heat is an important theme within the adaptation strategy of Rotterdam. Considering health services, the attitude of the municipal health service Rotterdam is comparable to Amsterdam. “Heat stress has a relatively low priority. This is partly because we have programs such as the national heat plan, which national and local media cover once it is activated. This gives the image that heat stress is covered” (RHS1).

Within housing corporation Woonstad Rotterdam, the urban heat island is an upcoming issue. For the past decade, Woonstad Rotterdam mainly focused on making its housing stock more energy efficient. Besides that, Woonstad has recently recruited a sustainability specialist who mainly focuses on circularity and climate adaptation. The two main subjects within climate adaptation are water nuisance and heat stress.

7.2 Public awareness For this research, no surveys or interviews have been taken to investigate the public awareness. The results in this section are retrieved from interviews, when asked about their experience with public heat awareness.

The experts have the opinion that there is hardly any public awareness at all concerning heat stress. According to Jeroen Kluck, heat stress is not considered a threat by many people in comparison to water stress. When elderly people were asked about heat stress, a common answer was that they would not think they would experience negative effects from heat. Some people even see hotter cities as a beneficial effect.

“What you hear a lot among citizens is: we will get the temperature of Marseille, that would be great” (Jeroen Kluck).

Hot weather is indeed seen as something positive among citizens, as RM2 points out:

“People are used to a rainy climate. When the sun shines, people go to terraces and drink beer because we are glad the sun is finally shining again. This is actually the worst thing to do” (RM2).

Because of the lack of public awareness, the implementation of adaptation and mitigation strategies can be delayed. Alexander Wandl argues as well that due to the lack of public awareness, it is more difficult to “get things through” and implement heat-focused strategies.

Amsterdam: Public awareness The fact that people do not consider heat stress as a threat is confirmed by both municipal health services. According to Ben Rozema, the municipal health service in Amsterdam receives relatively few questions and reports on heat stress. The municipal health service does receive questions from schools that want to organize school trips and events such as marathons or dance festivals. Ben Rozema also states that heat measures are generally known. “The heat measures are generally known because of the previous campaigns that were held. Most people know that you have to drink more water, prevent that the sun does not shine inward and to ventilate in the evening” (Ben Rozema).

Wim de Waard mentions that most of the tenants at Eigen Haard care about other issues than climate change or the urban heat island effect. However, it seems that the tenants care about the indoor temperature.

“Simply said, our tenants do not care much about sustainability ideals such as carbon neutrality. At first, the tenants notice factors such as the temperature, it should not be too hot or cold. Also, the presence of mold. Secondly, they care about the energy bills. The residents care about other issues than carbon neutrality and climate change” (Wim de Waard).

Rotterdam: Public awareness The municipal health services of Rotterdam seems to have the same views on public heat awareness compared to Amsterdam. “Within our discipline, we have the image that people worry a lot about low-risk issues and hardly worry about high-risk issues. I expect that heat stress is generally seen as a low-risk issue, but heat stress actually has many risks” (RHS1).

Woonstad Rotterdam has a large housing stock that is used for social housing. These houses have affordable rent and are intended for people from lower income groups. According to Hanneke van der Heijden, many of the tenants at Woonstad Rotterdam do not prioritize climate-related issues, and often do not have the knowledge of these issues.

“For many tenants, sustainability is not a priority in their lives. It already takes a lot of effort to increase awareness about tenants’ behavior in energy use. A topic like heat stress is even more difficult to relate to since the effects are less obvious in peoples’ daily lives. Where the energy bill drops when you are saving energy, this direct benefit is lacking in terms of climate adaption strategies like coping with heat stress.” (Hanneke van der Heijden).

7.3 Concluding remarks Although heat stress does not receive the attention it should get, heat awareness is rising, which could eventually lead to the implementation of more adaptation and mitigation strategies specifically aimed at reducing heat in cities. Rotterdam has started to include heat stress in its policies more than Amsterdam, but even in Amsterdam, the expectations are that heat will be one of the next things that will be addressed. Considering both housing corporations, Eigen Haard has yet to implement heat-specific strategies, whereas Woonstad Rotterdam recently is putting in some work in order to do more about climate adaptation, including heat stress.

It seems that the public is not very aware of heat stress in both cities. The municipal health services hardly receive questions from citizens about heat stress, and experts on heat stress also agree that most citizens are unaware of the dangerous effects of heat waves. The same goes for housing corporations in both cities, where it seems that most of the tenants care more about other issues than heat stress.

8 Results: adaptation and mitigation strategies

8.1 Adaptation strategies

8.1.1 Outdoor space Most strategies applied in the outdoor space are mitigation strategies. There are some exceptions, however. Water tapping points are scattered over both cities, which means that people have the possibility to stay hydrated without spending money during warm summer days. In addition, both municipal health services encourage events such as dance festivals and marathons to implement heat-stress reducing strategies. Strategies include handing out free or low-priced water bottles at events during summer in order to prevent visitors from dehydration.

8.1.2 Built environment

Isolation Every housing corporation in the Netherlands is working on becoming more sustainable. Housing corporation Eigen Haard focuses specifically on becoming carbon neutral in 2050. In order to become carbon neutral in 2050, measures need to be taken, with isolation being one of the most important measures. Improving isolation in houses is the most used strategy in order to become sustainable at housing corporation Eigen Haard. This is done through façade isolation, roof isolation and insulated glazing. However, if you isolate a house, you also have to improve its ventilation, Wim de Waard notices.

Woonstad Rotterdam also has worked on making the houses more energy efficient for the past couple of years.

“In order to become more sustainable, some interventions have to be prioritized. (…) A couple of years ago, Woonstad made their portfolio more energy efficient by decreasing energy loss (by improving isolation) and generating sustainable energy, mainly solar energy” (Hanneke van der Heijden).

The experts on urban heat also agree that making buildings more energy efficient needs to be done in combination with good ventilation, and not only isolation.

“With proper isolation, it will take a while before a building is warmed up. But once a building is warmed up, it will stay warm for a longer period of time. Concerning heat stress, ventilation is much more important than isolation” (Jeroen Kluck).

“It is important how you make buildings more energy efficient. Don’t look only at isolation. Because if you follow only the aim of energy efficiency through insulation, the result is that buildings become and stay very hot inside” (Alexander Wandl). Furthermore, becoming energy-efficient is one of the biggest tasks of the 21st century, and isolation buildings is one of the most effective adaptation strategies. However, especially during summer months, isolated buildings will get hotter. Hence, ventilation systems are needed.

Air conditioning When considering ways for ventilating a building, the consideration between air conditioning systems and natural ventilation often is made. Using air conditioning systems is one of the most commonly used ways of ventilation. However, although air conditioning leads to a cooler temperature inside buildings, due to its energy use, it will heat the public space (Grimmond, 2007).

“By adapting to the urban heat island effect, especially with elderly people, using air conditioning sounds as a logical solution. However, it can be the most disastrous solution. It uses enormous amounts of energy. It has a cooling effect indoors, but it will lead to an even hotter outdoors environment. The electricity networks will also not be able to manage all the air conditioning systems. Using air conditioning can lead to all kinds of unwanted repercussions” (Roland van der Heijden).

On the other hand, applying air conditioning systems use as an effective adaptation strategy against the people that are more vulnerable to heat stress. This is why at both municipal health services, air conditioning is seen as a mainly positive solutions that help the more vulnerable population groups.

“If you look at the outcome of less fatalities during heat stress due to air conditioning, you should look at how you can apply air conditioning, but under certain conditions, for instance linking them to solar panels or to only use them during heat periods” (Ben Rozema).

“For the people that do not have the possibility to search for cool places elsewhere, air conditioning is a good solution, because it limits the negative effects of overheating, such as dehydration, headaches, nausea and even extra fatalities. So, from a healthcare perspective, I have no issues with air conditioning, but I understand the argument that it is not a proper solution, and we only make the city warmer by using air conditioning” (RHS1).

There are more sustainable ventilation alternatives in comparison to air conditioning. This is called natural ventilation. Examples of natural ventilation are heat/ cold pumps, but also constructing houses in such a way that you can control the wind coming into your house on specific moments.

When asked about applying natural ventilation instead of air conditioning, most of the respondents replied that air conditioning is the main ventilation system that is applied in both cities. Although the respondents from both municipalities were aware of the negative impacts of air conditioning, air conditioning is still the dominant ventilation system, and natural ventilation systems have yet to be constructed on a large scale.

Housing corporation Eigen Haard does not use air conditioning, but both natural and carbon- driven ventilation. Air conditioning is not used because it is not sustainable and leads to higher energy bills.

“We are such a large municipality, we are active with sustainability, reducing energy, and make use of energy that is as green as possible. Natural ventilation is needed for that” (AM1).

Although the respondents from the municipality of Rotterdam indicate that they want natural ventilation to be applied in the city, carbon-driven ventilation is also the most dominant form of ventilation in Rotterdam.

“I indicate that I want more natural ventilation systems in the city, because with our current plans, we make use of electricity, which uses energy. Natural ventilation is more favorable. It is something we want to develop, because using air conditioning isn’t everything” (RM2).

“It is something we have in picture and we want to develop, but we have yet to come up with a specific policy” (RM1).

Woonstad Rotterdam does not own many houses with air conditioning. Most houses are ventilated via mechanical suction, heat recovery ventilation or natural ventilation. There are some examples of housing blocks owned by Woonstad Rotterdam that have heat pumps, but the maintenance of these heat pumps is not the responsibility of the housing corporation.

8.1.3 Social/ behavioral adaptation

National heat plan As mentioned in the background chapter, the Dutch National Institute for Public Health and the Environment (RIVM) developed a national heat plan “Nationaal Hitteplan” in 2007 because of the 2006 heat wave. This heat plan aims to alert the country on time to take measures in order to reduce and prevent heat stress (RIVM, 2014). The national heat plan tries to communicate on time to the risks groups such as elderly people, obese people, small children and homeless people, but also healthcare providers (RIVM, 2014). In order for the national heat plan to operate as adequate as possible, the RIVM has collaborated with parties such as the Dutch ministry of public health, well-being and sport (VWS), the Royal Dutch Meteorological Institute (KNMI), municipal health services, healthcare institutions and the media. The Nationaal Hitteplan makes agreements with event organizations in order to make events during summer heat-proof and inform the parties linked to the Nationaal Hitteplan.

The national heat plan has three phases. The first phase is the watchful phase, which runs from June 1 to September 1. Before this phase, organizations have to prepare themselves for a period of persistent heat and its risks (RIVM, 2014). The second phase is the pre-warning phase, which occurs when there is a small chance of 4 consecutive days with a maximum temperature above 27 oC. During this phase, organizations are informed about the possible chance of a heat wave, which rises awareness. Residents are not informed, because the risk of a possible heat wave is too small. Besides that, if the public is warned too often, the credibility of the warning will decrease (RIVM, 2014). The warning phase, which is the third phase occurs when there is a high chance of 4 consecutive days with a maximum temperature above 27 oC. When this phase starts, the RIVM sends a warning mail with informative content and up-to-date weather information to organizations such as the municipal health service. These organizations have the task to communicate this information to their regional contacts and followers. The Dutch residents will be informed by press releases from the RIVM. Organizations that have set measures in the watchful phase can perform these measures during the warning phase (RIVM. 2014).

Extrema Rotterdam heat stress app In June, the municipality of Rotterdam in collaboration with the municipal health service Rotterdam will launch a mobile app in which they record the experiences within the city regarding the weather. By filling in your personal information, the app will calculate the risk group you are in regarding heat stress.

By collecting satellite data in combination with your personal information, the app gives you advice about adapting to heat, such as drinking enough water and showing the water tapping spots in Rotterdam, but also showing where the coolest spot in a radius of 500 meters is. This way, people who have downloaded this app can always seek out to cooler spots and prevent heat stress. The app also allows users to create extra profiles for others, which can be beneficial for caregivers who help the elderly.

According to Jeroen Kluck, the cool spots in the city could be the solution to coping with heat stress in a city.

“I do not know if we will succeed, but if we are smart enough, we should invest in enough cool spots in the city where one can stay. This way, the city will get more pleasant due to the cooling” (Jeroen Kluck).

Screenshots from the Extrema app can be found in the appendix. Infographic Amsterdam does not have an app that helps people adapt to heat stress. However, Amsterdam has created an infographic that informs vulnerable groups to heat stress about measures they should make.

“One of our spin-offs is a project on our department in collaboration with the Red Cross, we have developed an infographic in which the vulnerable groups are mentioned, the phenomena of heat stress and how you can prevent heat stress” (Ben Rozema). The heat stress infographic can be found in the appendix.

8.2 Mitigation strategies

8.2.1 Outdoor space

Vegetation When the experts were asked about most effective strategies against heat, they seemed to agree that applying vegetation is the most important strategy in the open space. Alexander Wandl argued that in the public space, green is the most dominant strategy. Jeroen Kluck agrees with this.

“Greening is the most effective. Wind is also effective, but wind is not always present. Shading is very important. It does not matter if it is shading by trees or buildings. But there are large differences between temperature in shadow spots and in spots where no shadow is present” (Jeroen Kluck).

The two experts on the urban heat island both mention that making the city greener is the most effective adaptation strategy in the public space. According to Alexander Wandl: “ “In the public space, it is all about green, green, green. Less impervious and more pervious surfaces and more vegetation.” (Alexander Wandl).

Amsterdam profiles itself as a city of trees. It is estimated that there are a million trees in Amsterdam (from which there are 270.000 street trees), which is quite special (Municipality of Amsterdam, 2018). The municipality is applying green and vegetation in various forms. One of the most prominent forms is just by planting trees, but the municipality is also applying vegetation on school playgrounds, tramlines, small parks and gardens (AM1). The municipality is also investing in “postzegelparkjes” which are

“small parks, often in collaboration with residents from a specific neighborhood, in which also trees are present” (AM1).

In addition to that, Amsterdam is investing in a green network, which are recreative cycling and walking routes that go in and out the city that are as green as possible (AM1). In these strategies, the greening of school yards in particular, tiles are being removed, which leads to less impervious surface.

With 160.000 trees in the city and 450.000 trees in its surrounding green areas and forests, Rotterdam has significantly less trees than Amsterdam (Municipality of Rotterdam, 2018). The municipality of Rotterdam is trying to make the outdoor spaces of the city greener:

“Rotterdam is applying vegetation in the city. This is primarily for other reasons, but it does address the urban heat island” (Roland van der Heijden).

According to Livien van de Ven, vegetation has benefits in many sectors, including biodiversity, climate, economy social cohesion and health. Instead of looking for adaptation strategies that reduce heat stress, she sees applying vegetation as the strategy that has the most benefits, including reducing heat stress.

“Climate change leads to negative effects such as water stress and more precipitation. Last week, you saw a lot of water nuisance in South-Limburg. Partly by planting trees, the water storage capacity gets bigger. Concerning heat stress, more vegetation leads to temperature decrease in urban municipalities” (Livien van de Ven)

Other strategies in the outdoor space It seems that applying vegetation is the only mitigation strategy that is implemented in the outdoor space. Although this is the primary strategy to reduce urban heat, removing impervious surfaces is also an important strategy. According to Alexander Wandl, large parts of the outdoor space is private land, which is often tiled. Both cities do not have programs that encourage to remove impervious surfaces in backyards. Eigen Haard and Woonstad Rotterdam have discussed this with other parties but have yet to start such programs.

8.2.2: Built environment

Green roofs Both cities have green roof plans. According to AM1, Amsterdam has a total of 300.000 square meters of green rooftop surfaces, based on aerial photographs, which is around 2600 buildings with a green roof. When compared to the total of 12 square kilometers in Amsterdam, 300.000 (2,5%). This does not seem as much. However, the construction of green roofs is a phenomenon of the past decade.

“The past 3 years, 40.000 square meters of green rooftop surface has been constructed. Most of the green rooftop surface has been constructed in the past 10 years” (AM1).

In addition to that, Amsterdam has been giving out subsidies for eight years to people who construct green roofs, partially to make the indoor climate more heat-proof. Housing corporation Eigen Haard does help with the construction of green roofs occasionally, but this is definitely not the norm. Woonstad Rotterdam is in the process of starting a pilot green roofs program. If this pilot works out well, the program could be extended.

Rotterdam mentions that applying green roofs, green façades and more reflective materials will help making the built environment more heat resilient (Municipality of Rotterdam, 2013). Rotterdam has a high number of flat roofs, and many of these roofs are unused. From the 14,5 km2 of flat roof surface in Rotterdam, 220.000 m2 is used as a green roof (Rotterdam Climate Initiative, 2018). Rotterdam is encouraging its citizens to construct green roofs with a subsidy program (Kleerekoper et al. 2012). The subsidy is currently €20 per square meter but will decrease to €15 per square meter of green roof (Rotterdam Climate Initiative, 2018). The municipality of Rotterdam has been actively greening flat rooftop surfaces since 2007, primarily out of water measures, according to RM2. “In 2007, the goal was set to have 160.000 square meters of green roof top surface in 2014, and a long- term goal to have 800.000 square meters of green rooftop surface in 2030, and more than half of the real estate owned by the municipality” (RM2). The municipality is also giving out subsidies per square meter of green rooftop surface. However, the contribution per square meter has been decreased slightly since 2018.

Furthermore, the development of green roof surface in both Amsterdam and Rotterdam is an upcoming trend. Most of the green roofs in both cities have been developed for the past decade, and it seems that both cities will continue the construction of green roofs. However, this does not mean that green roofs are always mitigating heat. “In order for it to function as a mitigation measure against the urban heat island effect, a green roof needs to be irrigated, so that the evapotranspiration is functioning. That is important. It doesn’t help if you have a green roof, and that everything is brown when it’s hot. It needs to stay green, wet, evapotranspiration needs to function. Otherwise it doesn’t have a cooling effect.” (Alexander Wandl). Moreover, if you have a green roof that dries out during hot, dry summer periods, it will not have any cooling effect. This is why the irrigation of green roofs has to be stimulated. Fact sheets from organizations that commit to greener cities, such as “De Groene Stad” (the green city) mention that green needs to be irrigated. Otherwise, it will dry out, and will have less effect. The quality of green roofs in both cities is unknown. In the case of Amsterdam, AM1 said the following:

“We have 300.000 square meters of green rooftop surface, but we do not know its quality. Hence, we do not know how many square meters are functioning adequately and how many square meters are not” (AM1). The green roofs program in Rotterdam is derived from sewage charge and is currently more focused on reducing water stress and prevent the flooding of streets, not on reducing heat stress. Both RM1 and RM2 argue that the green roofs have to be focused on reducing both heat stress and water stress, and not only focusing on water.

Both cities are currently experimenting with new types of green roofs as well. This is mostly out of water stress issues, but this can improve the city’s resilience during heat waves as well. According to RM2, most green roofs in Rotterdam have a water storing capacity of 15 liters per square meter. To make investing in green roofs more interesting for market operators, green roofs need additional functions, RM1 states. To promote this, the Rotterdam roof program focuses on four colors: blue (water storage), green (vegetation), red (recreation) and yellow (energy). For example, placing a coffee bar or café on a green roof makes it worthwhile to invest. The municipality of Rotterdam is also trying to improve the water storing capacity, which is done from a collective perspective to reduce water stress. Smart roofs and polder roofs are examples of roofs that are interesting for investors, but there are many different types of green roofs in Rotterdam.

“Smart roofs have a water storage capacity that is 7 times higher than a traditional sedum roof. There are also sensors that can deflate the roof if heavy rainfall is predicted” (RM2).

“There is also the polder roof system in Amsterdam, in which the stored water is directly used for the irrigation of plants, which leads to more possibilities” (AM1).

These two types of green roofs are much better adaptation strategies against the urban heat island, because the roofs stay wet for a longer period of time, which is needed in order for it to function against heat stress. However, there are not many of these roofs in both cities. Concerning smart roofs, there is only one smart roof in each city. The shift towards polder roofs

35 is gradually happening, but the vast majority of green roofs that are being constructed are sedum roofs. Green façades According to AM1, there are thousands of green façades in Amsterdam. Amsterdam has a green façade program and is also giving out subsidies to residents who are constructing green façades and façade gardens on their house. Most of the green façades in Amsterdam are grounded. Amsterdam also has some non-grounded green façades that are irrigated via a particular system. However, there are only around 10 non-grounded green façades in Amsterdam, because these façades cost a lot of maintenance. Most of the green façades in Amsterdam can be found within the city ring.

“We subsidize green façades, and although this is not always the case, green façades regularly provide shadows and cooling” (AM1).

Unlike Amsterdam, Rotterdam does not have a green façade program. Hence, green façades in Rotterdam are not eligible for subsidies. Rotterdam does have a few green façades, but it is a very small amount in comparison to Amsterdam.

Other mitigation strategies in the built environment There are many more mitigation strategies that can be applied in the building environment. Strategies such as cool roofs, or painting roofs white are discussed in the interviews, but there are no examples of other strategies in the built environment that are being applied.

8.3 Concluding remarks In both cities, vegetation is the primary mitigation strategy in the outdoor space. Vegetation has many benefits against the urban heat island effect, such as creating shadows and cooling down the city. In comparison to Rotterdam, Amsterdam is a much greener city. However, both cities have various programs that lead to more vegetation in the city, which could mitigate the urban heat island effect to a large extend.

The main mitigation strategies applied on the built environment are the greening of houses. Both cities have green roofs programs, and Amsterdam has a green façade program. Isolation of houses is happening a lot in order to make the houses more energy efficient. However, this could lead to an increase of the indoor temperature, which is unfavorable. In order to prevent the indoor temperature rise, some sort of ventilation is needed. The indoor temperature rise is often adapted by using air conditioning. Within municipal health services, air conditioning is seen as a positive adaptation strategy, because it could prevent health risks in vulnerable groups. However, despite the advantages of air conditioning, air conditioning can lead to an average increase of the outdoor temperature. Both housing corporations are doing a good job regarding the use of air conditioning, which is barely used.

Regarding social adaptation strategies, Amsterdam and Rotterdam have to act according to the national heat plan when a heat wave occurs. Amsterdam has created an infographic that informs people how to act during warm periods. Rotterdam has launched an app that calculates if you are at risk based on your location, personal data and temperature, and shows the cool spots near you.

9 Results: Implementation of adaptation and mitigation strategies

9.1 Heat stress adaptation and mitigation as primary or secondary objective? Both municipalities have yet to implement physical adaptation or mitigation strategies that are directly aimed at reducing heat stress and its effects. The only strategies that are directly aimed at heat stress are social adaptation strategies, such as the heat app in Rotterdam or the infographic and mailing in Amsterdam. When looked at all the physical adaptation strategies in both municipalities, you can conclude that all the strategies are primarily intended for other purposes than the urban heat island effect. The two most common primary purposes are to reduce water stress and to improve the livability of the city. As described earlier in this report, this is called co-benefits, where heat stress is mainly adapted through strategies aimed at reducing heat or improving livability.

In Amsterdam, there are many co-benefits strategies that reduce heat stress. From a health perspective, green does not only mitigate the urban heat island effect, but also improves the air quality and is better for one’s mind, Ben Rozema argues. Removing impervious surfaces and greening schoolyards also has many co-benefits. Trees in schoolyards create shadows, absorb water, improve the playing environment for children, and also reduces heat stress, according to AM1. However, Amsterdam primarily focuses on other effects than heat.

“Actually, for the past four years, heat stress has been free riding on a variety of measures. So, we do not aim specifically on heat, but on water stress, which we are trying to address with Amsterdam Rainproof since 2013/ 2014. Back then, heat was not such a focal point to address with climate adaptation. But now, in many public space designs, heat stress adaptation is applied. (…) But we do not have a specific heat policy” (AM1).

In Rotterdam, this is practically the same phenomenon. According to RM1, almost all the measures that are taken that have an effect on reducing heat stress are in the context of water issues. The green roof program in Rotterdam also originates from water storage but has as co- benefit strategy that also reduces heat stress, RM2 argues. Roland van der Heijden mentions that he has the idea that the urban heat island is free riding on several other policy themes, such as water, energy and elderly care through which the urban heat island effect is reduced as well.

Adapting or mitigating to heat via co-benefits is seen as beneficial. Some experts see this as beneficial because of the lack of interest otherwise:

“You should combine the urban heat island measures with other measures, otherwise there is not enough interest. (…) And maybe the urban heat island becomes a lot more apparent. As you can see now, it is not much of an issue” (Alexander Wandl).

“It could be that we can agree on this. We have recently started a research. On one hand, we have to look at the heat goals and issues. What measures suit this? How effective are these measures? It could be that it will be all about greening. Green has many benefits for the city, including cooling the city” (Jeroen Kluck).

In addition to this, although adapting to heat stress is often viewed as a secondary benefit when applying adaptation or mitigation strategies, some adaptation strategies can be described as primary strategies. For instance, green roofs, if irrigated, serve as a primary mitigation strategy against the urban heat island effect.

“If it’s an accessible rooftop that improves the quality of space, any kind of improvement is good. In order of it to function as a mitigation measure against the UHI, it needs to be irrigated, so that the evapotranspiration is functioning” (Alexander Wandl).

9.2 Policy: top-down or bottom-up? The vast majority of adaptation and mitigation strategies against heat that implemented in both cities, are implemented from a top-down perspective, with often some consultation with the inhabitants.

“The majority of strategies in the city are implemented top-down. With every project we do, the neighborhood is involved, but often, it is initiated from the municipality” (AM1).

The same goes for Rotterdam, where most projects are indeed implemented top-down. This does not mean that there are no bottom-up projects in both cities. There are many projects set up by residents in Amsterdam in Rotterdam. In Rotterdam, for instance, the Zomerhof neighborhood has goals to become a climate neutral neighborhood in Rotterdam. This district has also applied strategies to mitigate heat stress, for instance with removing impervious surfaces and making roofs greener. “The inhabitants of Zomerhof have contacted us that they want to improve their neighborhood” (RM1). “Resilience is not something we do for the city, but together with the city. So here, we have a more facilitating and framework-setting role. This is to look how we can ensure that the people want to participate in our program” (RM2). The same trend in Amsterdam is happening, where bottom-up initiatives are increasing, or where Amsterdam only plays a facilitating role. “Many initiatives are bottom-up. When an initiative set up by residents is presented, it often needs collaboration with the municipality. So, there are all kinds of initiatives where we collaborate with residents as the municipality. Besides that, due to our subsidy scheme, initiatives can request subsidies at the municipality” (AM1). Bottom-up strategies are not always the best solution. According to AM1, top-down strategies are sometimes needed because some neighborhoods are not taking action by themselves. However, it is important that citizens who live in the neighborhood where strategies are applied will be involved in the decision making, Livien van de Ven argues.

9.3 Area-oriented or generic adaptation and mitigation? As shown in the literature review, the urban heat island effect does not occur equally over both cities. Some neighborhoods, such as the Amsterdam city center and Delfshaven in Rotterdam experience the urban heat island effect in a heavier form, whereas neighborhoods such as Amsterdam Zuid and Kralingen in Rotterdam experience less heat stress.

Currently, both cities apply strategies that are not area-oriented. The municipality of Amsterdam currently applies generic adaptation because it would not be fair if some neighborhoods are prioritized over others. In other words, every citizen has to be treated equally. AM1 states that this could change in the upcoming period due to to new plans revolving around green in Amsterdam. The municipality of Rotterdam also applies generic strategies. The municipality is aware that mainly the pre-war districts are more vulnerable to heat stress than the post-war districts, but currently, the municipality applies generic policies. According to RM1, the municipality of Rotterdam is currently revisiting the ideas of changing to more area-specific adaptation and mitigation strategies.

The fact that only generic policy is applied, could be because the current policies against heat stress are primarily focused on issues such as water stress. On the other hand, area-oriented policy could be seen as disadvantageous because it could lead to undesirable situations in other areas.

“This is debatable in my opinion. If you have one neighborhood with many vulnerable residents, and an adjacent neighborhood with a few vulnerable residents, you would think the neighborhood with many vulnerable residents should be prioritized. But, the neighborhood with less vulnerable residents should get attention as well. It could be that the less vulnerable neighborhood will get more vulnerable residents in the future and vice versa” (Jeroen Kluck).

9.4 Concluding remarks The urban heat island is mainly adapted and mitigated through co-benefit strategies, where heat mitigation is often seen as side effect. An example is the construction of green roofs. Green roofs serve as a water buffer in order to prevent water stress, but if irrigated, green roofs also serve as mitigation strategy against the urban heat island effect. This could be seen as beneficial, because multiple issues are addressed simultaneously. However, it might be necessary to mitigate the urban heat island effect through co-benefit strategies because there could be not enough interest otherwise.

Although the majority of the adaptation and mitigation strategies are applied through top-down policy, there are also some examples of strategies that are applied bottom-up. For instance, there are some initiatives set up by residents where the municipality has a more facilitating role.

Overall, both cities apply adaptation and mitigation strategies through generic policy that is not area-oriented. It is debatable if this is the right way to implement strategies. On one hand, some neighborhoods deserve more attention than others, but on the other hand, it might be unfair if some neighborhoods are getting less attention than others.

10 Discussion 10.1 Co-benefits, the only way to adapt? In general, co-benefits might sound as the ideal solution because multiple issues are mitigated at the same time. As Roland van der Heijden argues it is important that all climate goals will be reached.

“Eventually, we should succeed work on all the climate goals that are set. If we are using strategies that reduce water stress or lead to energy neutrality, it is beneficial is we could mitigate the urban heat island simultaneously” (Roland van der Heijden).

As cited in the previous chapter, Alexander Wandl argues that co-benefit strategies are not advantageous, but necessary. This is because there would be not enough interest if adaptation and mitigation strategies would solely aim to reduce the urban heat island effect. Throughout their interviews, both Alexander Wandl and Jeroen Kluck stressed that there is not enough heat awareness on the side of the developers as well as citizens in the Netherlands. This is a primary reason for applying co-benefit strategies against heat stress. Moreover, it is expected that heat will primarily be adapted through co-benefit strategies as long as awareness is not rising.

10.2 Rising heat awareness Although heat awareness is starting to rise, it could be that heat awareness will not reach the point it should be. As shown earlier, water-related issues are often seen as the biggest threat for the Netherlands, whereas heat stress, especially among citizens, it not taken as seriously as it should be. This could mean that the urban heat island effect is not mitigated enough, which could eventually lead to unwanted consequences.

Alexander Wandl is also quite skeptical about the current urban heat island awareness. He argues that heat awareness could rise to the point it should be if a catastrophic summer takes place in the Netherlands. This is relatable to the catastrophic summer in France in 2003, which encouraged the French government to introduce adaptation and mitigation strategies against heat stress (Poumadère et al., 2005).

While Jeroen Kluck argues that heat awareness is slowly rising, he agrees with Alexander Wandl that a catastrophic summer will lead to more awareness.

“A heat wave will help, preferably a very long heat wave, so that the city will get really unpleasant. This way, we can really think about the urban design of cities” (Jeroen Kluck).

To summarize, it is likely that a “catastrophic summer” or long heat wave is needed in order for heat awareness to rise. However, this is a quite worrying prospect, because this means that the thousands of people, mainly those who are in vulnerable population groups will experience negative effects from heat stress which could eventually lead to fatalities.

10.3 Differences in adaptation and mitigation between Amsterdam and Rotterdam In this research, I looked into the different adaptation and mitigation strategies applied by Amsterdam and Rotterdam to combat heat stress. From analyzing the interviews, it turns out that there are actually a lot of similarities in adaptation and mitigation strategies between Rotterdam. Applying vegetation is the primary mitigation strategy in the outdoor space, both cities have green roof programs, and both cities have to work according to the national heat plan when a heat wave occurs. There are also many similarities between the cities regarding the way adaptation and mitigation strategies are applied. Co-benefit strategies are used a lot in both cities, and most strategies are implemented top-down. There are some differences in adaptation and mitigation between Amsterdam and Rotterdam. Amsterdam has more green façades than Rotterdam, but Rotterdam has introduced an app specifically aimed at adapting to heat stress.

It seems that Rotterdam is applying more adaptation and mitigation strategies that are aimed at mitigating the urban heat island. An example is the heat app, but Rotterdam also has more policy reports that describe future strategies that are aimed at reducing the impacts of the urban heat island effect. Amsterdam currently only applies heat strategies through co-benefits, mainly by applying vegetation in the outdoor space and on the built environment. This might be because Rotterdam needs to apply more adaptation and mitigation strategies than Amsterdam. Amsterdam has a lot more trees and significantly more green façades than Rotterdam. Besides that, Rotterdam has much more flat roof surface than Amsterdam, which often leads to more heat stress indoors. According to Roland van der Heijden, this is why Rotterdam has set strategies such as having 800.000 square meters of green rooftop surface in 2030, because the need for improvement is bigger in Amsterdam.

“I can imagine that the average housing stock in Amsterdam is better prepared against the urban heat island than in Rotterdam. But I think Rotterdam is currently doing more than Amsterdam, because there is more need for improvement” (Roland van der Heijden).

Hence, it is difficult to conclude which municipality is doing better on urban heat island effect adaptation and mitigation. What is certain, is that the urban heat island despite the rising awareness does not receive the attention it deserves in both cities. In other words, there is a lot of work to do in both cities to reduce heat stress. However, even if more strategies are going to be applied in both cities, it is still possible that the urban heat island effect will not be reduced.

“I think there will be change. More green, more imperviousness. I am not sure if this will lead to a decrease in the urban heat island. You can mitigate the urban heat island, but if the temperature rises, the city will still get hot” (Alexander Wandl).

10.4 A polycentric approach to the urban heat island effect? In the theoretical framework, I introduced the polycentric approach for coping with collective action and global environmental change by Ostrom (2010) as a prime example how environmental change should be approached. Both Amsterdam and Rotterdam have implemented plans that can be considered polycentric. The “postzegelparkjes” in Amsterdam and the Zomerhof district in Rotterdam both include collaboration on multiple levels and sharing joint goals and wishes for the neighborhood. This is a good start, but (in my opinion) not enough in order to become resilient cities, let alone mitigating to the urban heat island effect.

In order to become a resilient city, more effort has to be put in the polycentric system by Ostrom. Hence, more effort has to be put in bottom-up initiatives and collaborating with locals, as well as implementing area-oriented adaptation and mitigation.

11 Conclusion The aim of this research was to compare the way Amsterdam and Rotterdam apply adaptation and mitigation strategies against the urban heat island effect. Before comparing both cities, I analyzed heat awareness, the adaptation and mitigation strategies as well as the way both strategies are implemented in each city.

When comparing the two municipalities in heat awareness, it seems that Rotterdam is more aware of the urban heat island and its implications than Amsterdam. In 2012, Rotterdam was one of the few municipalities than acknowledged heat stress as an issue where Amsterdam, had yet to view heat stress as an issue. Rotterdam also has implemented heat adaptation and mitigation strategies in its policy reports. In the policy reports from the municipal reports of Amsterdam, heat stress remains absent. However, it seems that institutional heat awareness in both municipalities is slowly rising, and that it might be the next subject on the climate change agenda. The municipalities, municipal health services and housing corporations are putting more effort in combatting heat stress by adaptation and mitigation strategies. This could eventually lead to the implementation of more adaptation and mitigation strategies against the urban heat island effect. However, the pace in which the heat adaptation strategies are taken might be too slow.

The public, on the other hand, seems not to be very aware of the urban heat island effect and its implications on one’s health. The interviewees agree that that most citizens are unaware of the dangerous effects of heat stress, mainly because they care more about other issues than heat stress. The experts agree that a hot, catastrophic summer could lead to an increase of adaptation and mitigation strategies.

A common adaptation strategy in both cities is the use of air conditioning in houses, because it makes the inside temperature more pleasant during hot periods. This is not an optimal adaptation strategy, because the energy use of air conditioning leads to an increase in the outside temperature. Other adaptation strategies include informing citizens through the media due to the national heat plan. Both municipalities have also worked on other adaptation strategies, such as a heat app and an infographic.

Mitigation strategies that are applied often include vegetation, which is seen in both open spaces and the built environment. In the built environment, this is mainly seen in green roofs, which are practiced in both Amsterdam and Rotterdam, and green façades, which are mostly seen in Amsterdam.

Mitigation strategies against urban heat are often applied through co-benefit strategies where heat mitigation is often seen as a side effect. Strategies such as green roofs and vegetation often have as main purpose mitigating water stress or improving the living environment. Although there are some examples of heat that is mitigated bottom-up, most mitigation strategies are applied through top-down policies. Concerning scale, most mitigation strategies are applied through generic policy, and not area-oriented policy.

As shown in the results, there are many similarities between urban heat island adaptation and mitigation in Amsterdam and Rotterdam. However, there are some significant differences between both cities. The key difference in adaptation and mitigation strategies is that Amsterdam is overall a greener city, which is visible in the outdoor space as well as the built environment. Rotterdam, on the other hand is applying more adaptation and mitigation strategies that are aimed at the urban heat island effect. Examples are the extrema heat app and the fact that heat stress is considered a threat within municipal reports from Rotterdam, whereas it is not mentioned in the municipal reports of Amsterdam. The reason for this might be that in Rotterdam, there is more need for heat-specific adaptation strategies, because it can become warmer in summers due to Amsterdam being a much greener city.

In order for both cities to become a resilient city, or at least resilient to the urban heat island effect, I suggest making use of the polycentric approach by Ostrom. Interviews have shown that the municipalities are happy with the initiatives such as the “postzegelparkjes” in Amsterdam and the Zomerhof district in Rotterdam. Hence, I suggest that more effort has to be put in bottom-up initiatives, collaborating with locals and implementing area-oriented adaptation and mitigation.

For this research, I have tried to interview as many actors as possible that are related to heat stress adaptation and mitigation in Amsterdam and Rotterdam. There are some actors that have to be covered in order to create a more accurate image of the current state of urban heat island adaptation and mitigation in both cities.

Firstly, I have not included urban planners, urban architects and urban engineers. These actors do have the knowledge about urban heat island adaptation and mitigation, especially in the built environment. Although I have collected enough data about heat adaptation and mitigation strategies through interviews with the municipalities, I suggest having interviews with urban planners, urban architects and urban engineers for more in-depth results regarding urban heat island adaptation and mitigation applied on the built environment. Moreover, I suggest that future research using the same methods should consider the heat-stress framework by Hatvani- Kovacs et al. (2018) by interviewing people that are more active in one of the four following sectors: public health services, the building and construction industry, urban planning and infrastructure services and utilities.

Secondly, I have covered public awareness in this research. However, I have only investigated this through the knowledge of experts. For a more accurate analysis of the public awareness in relation to heat stress and the urban heat island effect, I suggest having a quantitative research where inhabitants of both cities are surveyed on heat stress.

Finally, this research is done from a social- scientific perspective. I have not measured the effects of the adaptation and mitigation strategies on the urban heat island effect in both cities. In order to do a more accurate analysis on the impact of the adaptation and mitigation strategies, I suggest doing a more natural scientific approach.

12 References Adams, W.M. (2009). Green Development: Environment and Sustainability in a Developing World, London: Routledge.

Akbari, H., Pomerantz, M., Taha, H. (2001) Cool surfaces and shade trees to reduce energy use and improve air quality in urban areas. Solar Energy 70(3): 295-310.

Amelung, B., Moreno, A. (2012) Costing the impact of climate change on tourism in Europe: results of the PESETA project. Climatic Change. 112(1): 83-100.

Arnette, A.N. (2013) Integrating rooftop solar into a multi-source energy planning optimization model. Applied Energy 111: 456-467.

Ashtiani, A., Mirzaei, P.A., Haghighat, F. (2014) Indoor thermal condition in urban heat island: Comparison of the artificial neural network and regression methods prediction. Energy & Buildings 76: 597-604.

Barbera, E., Currò, C., Valenti, G. (2010) A hyperbolic model for the effects of urbanization on air pollution. Applied mathematical modelling 34(8): 2192-2202.

Brasseur, G.P., Granier, C. (2013) Mitigation, adaptation or climate engineering? Theoretical Inquiries in Law 14(1): 1-20.

Bryman, A. (2012) Social research methods (Fourth edition). New York: Oxford University Press.

Congres Hittestress (Heat Stress Congress) (2018) Eerste congres hittestress op 25 juni (First heat stress congress on June, 25). https://ruimtelijkeadaptatie.nl/actueel/actueel/nieuws/2018/congres-hittestress/ (retrieved on May 23, 2018).

Corburn, J. (2009) Cities, Climate Change and Urban Heat Island Mitigation: Localising Global Environmental Science. Urban Studies 46(2): 413-427.

Davis, D.E., Keating, A.M. (2015) Development and urbanization. International Encyclopedia of the Social & Behavioral Sciences.

De Groene Stad (2018) De Groene Stad. http://degroenestad.nl/ (retrieved on June 24, 2018).

Debbage, N., Shedherd, J.M. (2015) The urban heat island effect and city contiguity. Computers, Environment and Urban Systems 54: 181-194.

Dietz, T., Den Hertog, F., Van der Wusten, H. (2008) Van Natuurlandschap tot Risicomaatschappij: De Geografie van de Relatie tussen Mens en Milieu (Translation: From nature landscape to risk society: the geography of relation between humans and the environment). Amsterdam: Amsterdam University Press.

Doulos, L., Santamouris, M., Livada, I. (2004) Passive cooling of outdoor urban spaces. The role of materials. Solar Energy 77(2): 231-249.

Emmanuel, R., Krüger, E. (2012) Urban heat island and its impact on climate change resilience in a shrinking city: The case of Glasgow, UK. Building and Environment 53: 137-149.

Leal Filho, W., Echevarria Icaza, L., Neht, A., Klavins, M., Morgan, E.A. (2018) Coping with the impacts of urban heat islands. A literature based study on understanding urban heat vulnerability and the need for resilience in cities in a global climate change context. Journal of Cleaner Production 171: 1140-1149.

Franck, U., Schwarz, N., Grossmann, K., Röder, S., Schlink, U. (2013) Heat stress in urban areas: Indoor and outdoor temperatures in different urban structure types and subjectively reported well-being during a heat wave in the city of Leipzig. Meteorologische Zeitschrift 22(2): 167-177.

Gemeentelijke Geneeskundige Dienst Amsterdam (Municipal Medical Service Amsterdam) [GGD Amsterdam] (2018) Hitte (Heat). Amsterdam: Municipal Medical Service Amsterdam

Golden, J.S., Kaloush, K.E. (2006) Mesoscale and microscale evaluation of surface pavement impacts on the urban heat island effects. International Journal of Pavement Engineering 7(1): 37-52.

Grimmond, S. (2007) Urbanization and environmental change: local effects of urban warming. The Geographical Journal. 173(1): 83-88.

Hansen, A., Bi, P. (2017) Climate change adaptation: no one size fits all. The Lancet Planetary Health 1(9): 353- 354.

Harlan, S.L., Ruddell, D.M. (2011) Climate change and health in cities: impacts of heat and air pollution and potential co-benefits from mitigation and adaptation. Current Opinion in Environmental Sustainability 3(3): 126-134.

Hasson, R., Åsa, L., Visser, M. (2010) Climate change in a public goods game: Investment decision in mitigation versus adaptation. Ecological Economics. 70(2): 331-338.

Hatvani-Kovacs, G., Bush, J., Sharifi, E., Boland, J. (2018) Policy recommendations to increase urban heat stress resilience. Urban Climate 25: 51-63.

Hendel, M., Gutierrez, P., Colombert, G., Diab, Y., Royon, L. (2016) Measuring the effects of urban heat island mitigation techniques in the field: Application to the case of pavementwatering in Paris. Urban Climate 16: 43-58.

Hendel, M., Azos-Diaz, K., Tremeac, B. (2017) Behavioral adaptation to heat-related health risks in cities. Energy & Buildings 152: 823-829.

Heusinkveld, B.G., Steeneveld, G.J., Van Hove, L.W.A., Jacobs, C.M.J., Holtslag, A.A.M. (2014) Spatial variability of the Rotterdam urban heat island as influenced by urban land use. Journal of Geophysical Research: Atmospheres 119: 677–692.

Intergovernmental Panel on Climate Change [IPCC] (2014a) Climate Change 2014: Impacts, Adaptation, and Vulnerability. Part A: Global and Sectoral Aspects. Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Field, C.B., V.R. Barros, D.J. Dokken, K.J. Mach, M.D. Mastrandrea, T.E. Bilir, M. Chatterjee, K.L. Ebi, Y.O. Estrada, R.C. Genova, B. Girma, E.S. Kissel, A.N. Levy, S. MacCracken, P.R. Mastrandrea, and L.L. White (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 1132 pp. Intergovernmental Panel on Climate Change [IPCC] (2014b) Summary for policymakers. In: Climate Change 2014: Impacts, Adaptation, and Vulnerability. Part A: Global and Sectoral Aspects. Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Field, C.B., V.R. Barros, D.J. Dokken, K.J. Mach, M.D. Mastrandrea, T.E. Bilir, M. Chatterjee, K.L. Ebi, Y.O. Estrada, R.C. Genova, B. Girma, E.S. Kissel, A.N. Levy, S. MacCracken, P.R. Mastrandrea, and L.L. White (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 1-32. Keessen, A.M., Hamer, J.M., Van Rijswijck, H.F.M.V., Wiering, M. (2013) The Concept of Resilience from a Normative Perspective: Examples from Dutch Adaptation Strategies. Ecology and Society 18(2): 45. Keller, C. (2013) Place Matters: Mortality, Space, and Urban Form in the 2003 Paris Heat Wave Disaster. French Historical Studies 36(2): 299-330.

Kennis voor klimaat (knowledge of climate) [KVK] (2011) Hittestress in Rotterdam (Heat stress in Rotterdam). Bussum: Kennis voor Klimaat. Rotterdam: Municipality of Rotterdam. Ketterer, C., Matzarakis, A. (2014) Human-biometeorological assessment of the urban heat island in a city with complex topography – The case of Stuttgart, Germany. Urban Climate 10: 573-584. Keuning, W. (2009) Koele kleuren voor daken in hete steden (translation: cool colors for roofs in hot cities) De Volkskrant. December 19, 2009. https://www.volkskrant.nl/wetenschap/koele-kleuren-voor-daken-in-hete- steden~a374417/ Kim, M., Kim, H., You, M. (2014) The role of public awareness in health‐protective behaviours to reduce heat wave risk. Meteorological Applications 21(4): 867-872. Kleerekoper, L., Van Esch, M., Salcedo, T.B. (2012) How to make a city climate-proof, addressing the urban heat island effect. Resources, Conservation & Recycling 64: 30-38. Klein R.J.T., Huq S. et al. (2007b) Inter-relationships between adaptation and mitigation. In: Parry M.L., Canziani O.F., Palutikof J.P., van der Linden P.J., Hanson C.E. (eds) Climate change 2007: impacts, adaptation and vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, pp 745–777 Klok, L., Kluck, J. (2018) Reasons to adapt to urban heat (in the Netherlands). Urban Climate 23: 342-351. Kluck, J. Klok, L., Kleerekoper, L., Loeve, R., Bakker, W., Boogaard, F. (2017) De Klimaatbestendige Wijk (the climate-prof neighborhood). Amsterdam: Hogeschool van Amsterdam (Amsterdam University of Applied Sciences). Kohler, M., Tannier, C., Blond, N., Aguejdad, R., Clappier, A. (2017) Impacts of several urban-sprawl countermeasures on building (space heating) energy demands and urban heat island intensities. A case study. Urban Climate. 19: 92-121. Koninklijk Nederlands Meteorologisch Instituut (Dutch Royal Meteorological Institute) [KNMI] (2015) Klimaatscenario’s voor Nederland (Translation: Climate Scenarios for the Netherlands). De Bilt: KNMI. Koomen, E., Hettema, J., Oxenaar, S., Diogo, V. (2013) Analysing Urban Heat Island Patterns and simulating potential future changes. Conference Proceedings of Impacts World 2013: 705-711. Koomen, E., Diogo, V. (2017) Assessing potential future urban heat island patterns following climate scenarios, socio-economic developments and spatial planning strategies. Mitigation and Adaptation Strategies for Global Change 22(2): 287-306. Koopmans, S., Theeuwes, N.E., Steenveld, G.J., Holtslag, A.A.M. (2015) Modelling the influence of urbanization on the 20th century temperature record of weather station De Bilt (the Netherlands). International Journal of Climatology 35(8): 1732-1748. Kuypers. V., De Vries, B., Peeters, R.G.J.M. (2008) Groen voor Klimaat (Green for Climate). Wageningen: Wageningen University. The Hague: Ministry of Agriculture/ Nature and Food Quality. Lane, K., Wheeler, K., Charles-Guzman, K., Ahmed, M., Blum, M., Gregory, K., Graber, N., Clark, N., Matte, T. Extreme Heat Awareness and Protective Behaviors in New York City. Journal of Urban Health 91(3): 403-414. Leichenko, R. (2011) Climate change and urban resilience. Current Opinion in Environmental Sustainability 3(3): 164-168. Li, B. (2013) Governing urban climate change adaptation in China. Environment & Urbanization 25(2): 413-427.

Li, W., Cao, Q., Lang, K., Wu, J. (2017) Linking potential heat source and sink to urban heat island: Heterogeneous effects of landscape pattern on land surface temperature. Science of the Total Environment 586: 457-465.

Ma, K., Zhou, L., Niu, S., Nakagoshi, N. (2005) Beijing urbanization in the past 18 years. Journal of international development and cooperation 11(2): 87-96.

Masson, V., Ebonhomme, M., Esalagnac, J., Briottet, X., Elemonsu, A. (2014) Solar panels reduce both global warming and urban heat island. Frontiers in environmental science 2: article 14.

Moghbel, M., Erfanian Salim, R., (2017) Environmental benefits of green roofs on microclimate of Tehran with specific focus on air temperature, humidity and CO2 content. Urban Climate 20: 46-58.

Mohajerani, A., Bakaric, J. & Jeffrey-Bailley, T. (2017) The urban heat island effects, its causes, and mitigation, with reference to the thermal properities of asphalt concrete. Journal of Environmental Management 197: 522-538.

Moser, S. (2012) Adaptation, mitigation, and their disharmonious discontents: an essay. Climatic Change 111(2): 165-175.

Municipality of Amsterdam (2017a) Amsterdam in Cijfers 2017 (Amsterdam in Figures 2017). Amsterdam: Municipality of Amsterdam.

Municipality of Amsterdam (2017b) Ontwikkelingsstrategie Haven-Stad (development strategy Haven-Stad). Amsterdam: Municipality of Amsterdam.

Municipality of Amsterdam (2018) Amsterdam zet haar bomen op de kaart (Amsterdam maps its trees). https://www.amsterdam.nl/bestuur-organisatie/college/individuele-paginas/abdeluheb- choho/persberichten/amsterdam-zet-bomen/ (retrieved on May 24, 2018).

Municipality of Rotterdam (2013) Rotterdamse Adaptatiestrategie (Adaptation strategy Rotterdam). Rotterdam: Municipality of Rotterdam.

Municipality of Rotterdam (2018) Bomen (Trees). https://www.rotterdam.nl/wonen-leven/bomen/ (retrieved on May 24, 2018).

Nationale Adaptatiestrategie (National Adaptation Strategy [NAS] (2018) Uitvoeren met ambitie (perform with ambition). The Hague: Ministerie van Rijkswaterstaat.

Nelson, D.R., Adger, W.N., Brown, K. (2007) Adaptation to Environmental Change: Contributions of a Resilience Framework. Annual Review of Environment and Resources 32: 395-419.

Niederer, S. Priester, R. (2016) Smart Citizens: Exploring the Tools of the Urban Bottom-Up Movement. Computer Supported Cooperative Work (CSCW)25(2): 137-152.

Nu.nl (2018) Liveblog: Westerstorm zorgt voor schade en vertragingen (Liveblog: Weterstorm leads to damage and delays). https://www.nu.nl/binnenland/5071979/liveblog-westerstorm-zorgt-schade-en-vertragingen- gesloten.html?redirect=1 (retrieved on May 20, 2018).

Oke, T.R. (1987) Boundary Layer Climates (Second edition). Methuen Press, London

Oleson, K.W., Monaghan, A., Wilhelmi, O., Barlage, M., Brunsell, N., Feddema, J., Hu, L., Steinhoff, D.F. (2015) Interactions between urbanization, heat stress, and climate change. Climatic ChangeI 129(3): 525-541.

Onderzoek, Informatie en Statistiek (research, information and statistics Amsterdam) [OIS] (2017) Amsterdam in Cijfers 2017 (Amsterdam in figures 2017). Amsterdam: Municipality of Amsterdam.

Ostrom, E. (2010) Polycentric systems for coping with collective action and global environmental change. Global Environmental Change 20(4): 550-557.

Parag, L. (2008) Transparent heat trap insulation system. Espacenet (European Patent Office).

Peng, S., Piao, S., Ciais, P., Friedlingstein, P., Ottle, C., Breon, F.M., Nan, H., Zhou, L., Myneni, R.B., (2012) Surface urban heat island across 419 global big cities. Environmental Science and Technology 46: 696–703.

Port of Amsterdam (2013) Verzelfstandigd havenbedrijf van Amsterdam kan van start (translation: the independent port of Amsterdam can start). Amsterdam: Port of Amsterdam. https://web.archive.org/web/20150420084226/http://www.portofamsterdam.nl/Ned/(18491)-Content- Nieuws/(18491)-Content-Nieuws-Pers--en-nieuwsberichten/Persberichten-Archief-2013/Persberichten-Archief- 2013-Maart/Verzelfstandigd-Havenbedrijf-Amsterdam-kan-van-start.html (retrieved on March 15, 2018).

Port of Rotterdam (2017) Jaarverslag 2017 (translation: annual report 2017). Rotterdam: Port of Rotterdam.

Poumadère, M., Mays, C., Le Mer, S., Blong, R. (2005) The 2003 Heat Wave in France: Dangerous Climate Change Here and Now. Risk Analysis 25(6): 1484-1493.

Rafiee, A., Dias, E., Koomen, E. (2016) Local impact of tree volume on nocturnal urban heat island: a case study in Amsterdam. Urban forestry & urban greening 16: 50-61.

Rawding, C. (2000) Tourism in Amsterdam: marketing and reality. Geography 85(2): 167-172.

Rijksinstituut voor Volksgezondheid en Milieu (National Institute for Public Health and the Environment) [RIVM] (2012). Gezondheidsrisico’s van zomerse omstandigheden (health risks during summer conditions). Bilthoven (the Netherlands): RIVM.

Rijksinstituut voor Volksgezondheid en Milieu (National Institute for Public Health and the Environment) [RIVM] (2014). Nationaal Hitteplan 2015 (National Heat Plan 2015). Bilthoven (The Netherlands): RIVM.

Rijkswaterstaat (2018) About us. https://www.rijkswaterstaat.nl/english/about-us/index.aspx (retrieved on May 23, 2018).

Rockefeller Foundation (2018) 100 Resilient cities. https://www.rockefellerfoundation.org/our-work/initiatives/100- resilient-cities/ (retrieved on May 20, 2018).

Rombouts, R., Van Zoelen, B. (2015) Dit zijn de warmste plekken van Amsterdam (these are the warmest locations in Amsterdam), Het Parool, June 30, 2015.

Rotterdam Climate Initiative (2018) Rotterdam Climate Initiative. http://www.rotterdamclimateinitiative.nl/

Runhaar, H., Mees, H., Wardekker, A., van der Sluijs, J., Driessen, P., (2012). Adaptation to climate change-related risks in Dutch urban areas: stimuli and barriers. Regional Environmental Change 12, 777–790.

Rushayati, S.B., Prasetyo, L.B., Puspaningsih, N., Rachmawati, E. (2016) Adaptation strategy toward urban heat island at tropical urban area. Procedia Environmental Sciences 33: 221-229.

Santamouris, M., Synnefa, A., Karlessi, T. (2011) Using advanced cool materials in the urban built environment to mitigate heat islands and improve thermal comfort conditions. Solar Energy 85(12): 3085-3102.

Santamouris, M., Cartalis, C., Synnefa, A., Kolokotsa, D. (2015) On the impact of urban heat island and global warming on the power demand and electricity consumption of buildings—A review. Energy and Buildings. 98:119- 124.

Schiphol (2018) Amsterdam Airport Schiphol Airport Facts. https://www.schiphol.nl/nl/route- development/pagina/amsterdam-airport-schiphol-airport-facts/ (retrieved on March 15, 2018).

Shafique, M., Kim, R. (2017) Application of green blue roof to mitigate heat island phenomena and resilient to climate change in urban areas: A case study from Seoul, Korea. Journal of Water and Land Development 33(1): 165-170.

Sherwood, S.C., Huber, M. (2010) An adaptability limit to climate change due to heat stress.Proceedings of the National Academy of Sciences 107(21): 9552- 9555.

Skarp, K., Varis, K., Kettunen, J. (2017) Evaluation of Top-down and Bottom-up Leadership Development Programs in a Finnish Company. World Academy of Science, Engineering and Technology International Journal of Economics and Management Engineering 11(4): 781-786.

Staatsen, B., Franssen, E., Lebret, E. (1994) Health impact assessment Schiphol airport. Bilthoven: National institute of public health and environmental protection.

Statistics Netherlands (2006) Door hitte in juli duizend extra doden (a thousand extra fatalities in June due to heat). https://www.cbs.nl/nl-nl/nieuws/2006/35/door-hitte-in-juli-duizend-extra-doden (retrieved on May 1, 2018).

Statistics Netherlands (2014) Renewable energy, domestic products, import and export. http://statline.cbs.nl/StatWeb/publication/?DM=SLNL&PA=70789NED&D1=1,3,7&D2=0-2,5,9-12,16&D3=0- 8,10-11,16,21,26,31,36,41,46,51&HDR=G2&STB=T,G1&VW=T (retrieved on April 17, 2018).

Stone, B., Hess, J.J., Frumkin, H. (2010) Urban Form and Extreme Heat Events: Are Sprawling Cities More Vulnerable to Climate Change Than Compact Cities? Environmental Health Perspectives 118(10): 1425-1428.

Stone, B. (2012) The city and the coming climate: Climate change in the places we live. Cambridge University Press, New York

Susca, T., Pomponi, F. (2018) Making cities cooler is a no-brainer, so why are we doing so little about it? The Conversation.

Synnefa, A., Karlessi, T., Gaitani, N., Santamouris, M., Assimakopoulos, D., N. & Papakatsikas, C. (2011) Experimental testing of cool colored thin layer asphalt and estimation of its potential to improve the urban microclimate. Building and Environment 46: 38-44.

Synnefa, A., Saliari, M., Santamouris, M. (2012) Experimental and numerical assessment of the impact of increased roof reflectance on a school building in Athens. Energy and Buildings 55: 7-15.

Taleghani, M. (2018) Outdoor thermal comfort by different heat mitigation strategies- A review. Renewable and Sustainable Energy Reviews 81: 2011-2018.

Tan, J, Y Zheng, X Tang and C Guo (2010), The urban heat island and its impact on heat waves and human health in Shanghai. International Journal of Biometeorology 54: 75−84.

Tremeac, B., Bousquet, P., De Munck, C., Pigeon, G., Masson, V., Marchadier, C., Merchat, M., Poeuf, P., Meunier, F. (2012) Influence of air conditioning management on heat island in Paris air street temperatures Applied Energy 95: 102-110.

United Nations (2012) Sustainable Land Use for the 21st Century. New York: United Nations.

United Nations (2014) World Urbanization Prospects. New York: United Nations. Van der Hoeven, F., Wandl, A. (2013) Amsterwarm: gebiedsypologie warmte-eiland Amsterdam (Amsterwarm: aerial typology heat island Amsterdam) (full report). Delft: TU Delft (the Netherlands).

Van der Hoeven, F., Wandl, A. (2015) Hotterdam: Hoe ruimte Rotterdam warmer maakt, hoe dat van invloed is op de gezondheid van inwoners, en wat er aan te doen is (Hotterdam: how space is heating up Rotterdam, its influence on the inhabitants’ health, and what can be done about it). Delft: TU Delft (the Netherlands). Van Hove, L.W.A., Jacobs, C.M.J., Heusinkveld, B.G., Elbers, J.A., Steeneveld, G.J., Koopmans, S., Moors, E.J., Holtslag, A.A.M. (2011) Exploring the Urban Heat Island Intensity of Dutch Cities. National Academic Research and Collaborations Information System 2011. Van Zoelen, B. (2017) Scheepvaart Amsterdamse haven moet schoner (translation: Shipping in the port of Amsterdam must be cleaner) Het Parool, November 1, 2017. https://www.parool.nl/amsterdam/scheepvaart- amsterdamse-haven-moet-schoner~a4527548/ Volkskrant (2007) Storm veroorzaakt hoog water, schade en vertragingen (Storm causes high water, damage and delays). De Volkskrant, November 9, 2007. https://www.volkskrant.nl/nieuws-achtergrond/storm-veroorzaakt-hoog- water-schade-en-vertragingen~b4f552f7/ Wang, M., Zhang, X. & Yan, X. (2013) Modeling the climatic effects of urbanization in the Beijing-Tianjin- Hebei metropolitan area. Theoretical and Applied Climatology 113: 377-385. Wang, Z., Naterer, G.F. (2014) Integrated fossil fuel and solar thermal systems for hydrogen production and CO2 mitigation. International Journal of Hydrogen Energy 39(26): 14227-14233. Yamamoto, Y., (2006). Measures to mitigate urban heat islands. Science and technology trends 18(1): 65-83. Yang, P., Xiao, Z., Ye, M. (2016) Cooling effect of urban parks and their relationship with urban heat islands. Atmospheric and Oceanic Science Letters 9(4): 298-305. Yao, R., Wang, L., Huang, X., Niu, Z., Liu, F., Wang, Q. (2017) Temporal trends of surface urban heat islands and associated determinants in major Chinese cities. Science of the Total Environment 609: 742-754.

Yow, D.M. (2007) Urban Heat Islands: Observations, Impacts, and Adaptation. Geography Compass 1(6): 1227- 1251.

Zhou, D., Zhao, S., Zhang, L., Sun, G., Liu, Y., 2015. The footprint of urban heat island effect in China. Scientific Reports 5, 11160.

13 Appendix 13.1 The heat stress framework by Hatvani-Kovacs et al. (2018)

13.2 Screenshots of the Extrema Rotterdam weather app The extrema app shows your location. On the basis of satellite data, the app calculates the outside temperature and the humidity. In combination with your personal data, the app calculates your personal risk, and shows the cool spots in Rotterdam (for instance cinema’s, public libraries, fountains) where you can cool down.

13.3 Infographic municipality of Amsterdam This infographic shows the groups that are the most vulnerable during heat waves, the dangers of overheating and the measures to take in order to prevent negative effects during hot periods.

13.4 Positions of the interviewees Amsterdam Municipality of Amsterdam: - AM1: advisor climate adaptation, green in the city, Amsterdam rainproof at the municipality of Amsterdam. Municipal health service: - Ben Rozema: doctor health and society, working at the municipal health service Amsterdam (GGD) at the department of the living environment. Housing corporation: - Wim de Waard: head communication at housing corporation Eigen Haard in Amsterdam.

Rotterdam Municipality of Rotterdam: - Roland van der Heijden: urban planner, product manager digital city at the municipality of Rotterdam, has worked on sustainability topics. - RM1: advisor at the sustainability program at the municipality of Rotterdam, specialized in the adaptation strategy of Rotterdam and energy transition. - RM2: advisor city development for multifunctional rooftops and specialized in heat within the adaptation strategy for the municipality of Rotterdam.

Municipal health service: - RHS1: environmental medical advisor at the municipal health service in Rotterdam (GGD), specialized in heat.

Housing corporation: - Hanneke van der Heijden: sustainability specialist at housing corporation Woonstad Rotterdam.

Extern parties: Researcher 1: - Alexander Wandl: researcher at TU Delft at the department of environmental technology and design, co- author of scientific reports Amsterwarm, Hotterdam and other reports on the urban heat island effect. Researcher 2: - Jeroen Kluck: lector water in the city at Amsterdam University of Applied Sciences, co-author of research reports about climate-proof cities and neighborhoods.

Greening company: - Livien van de Ven: Junior communication advisor at De Groene Stad (The Green City), a company that aims to inform and stimulate the interest with authorities, organizations and companies which are professionally involved in planning and developing the urban area, ensuring green will be applied appropriately.