Adopting public values and climate change adaptation strategies in urban forest management: A review and analysis of the relevant literature

Journal of Environmental Management 164 (2015) 215e221

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Research article

Adopting public values and climate change adaptation strategies in urban forest management: A review and analysis of the relevant literature
n ~ ez Barona Camilo Ordo School for Resource and Environmental Studies, Dalhousie University, 6100 University Avenue, Suite 5010, Halifax, NS, B3H 4R2, Canada

a r t i c l e i n f o

a b s t r a c t

Article history: Received 14 February 2015 Received in revised form 14 August 2015 Accepted 1 September 2015 Available online xxx

Urban trees are a dominant natural element in cities; they provide important ecosystem services to urban citizens and help urban areas adapt to climate change. Many rationales have been proposed to provide a purpose for urban forest management, some of which have been ineffective in addressing important ecological and social management themes. Among these rationales we find a values-based perspective, which sees management as a process where the desires of urban dwellers are met. Another perspective is climate change adaptation, which sees management as a process where urban forest vulnerability to climate change is reduced and resilience enhanced. Both these rationales have the advantage of complementing, enhancing, and broadening urban forest management objectives. A critical analysis of the literature on public values related to urban forests and climate change adaptation in the context of urban forests is undertaken to discuss what it means to adopt these two issues in urban forest management. The analysis suggests that by seeing urban forest management as a process by which public values are satisfied and urban-forest vulnerabilities to climate change are reduced, we can place issues such as naturalization, adaptive management, and engaging people in management at the centre of urban forest management. Focusing urban forest management on these issues may help ensure the success of programs focused on planting more trees and increasing citizen participation in urban forest management. © 2015 Elsevier Ltd. All rights reserved.

Keywords: Urban forest management Urban forest values Climate adaptation Climate vulnerability

1. Introduction Urban forests provide many services that contribute to urban quality of life and are valued greatly by people. Because of this, research on urban forests is growing (Wolf and Kruger, 2012) and municipalities around the world are launching urban forest programs (Nowak et al., 2005), updating policies (Conway and Urbani,
n ~ ez and 2007), and releasing first-ever management plans (Ordo Duinker, 2013). As urban forest management evolves it becomes important to analyse how contemporary issues are being addressed. A key question in urban forest management today is whether we can address long-term ecological challenges in urban forests, such as climate change, and satisfy what people want from them, without conflict. Discussing how public values, defined here as what people consider important in relation to a natural resource (Brown, 1984), relate to climate change is timely given two key agendas. The first is

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the aggressive tree planting programs that many cities have established to mitigate climate-change impacts (e.g City of Toronto (2008)) and engage citizens in urban tree-planting (Pincetl et al., 2013). The second is the increasing participatory aspect of urban forest management demonstrated by citizen participation in municipal steering committees (Molin & Konijnendijk van den Bosch, 2014) and stewardship groups (Jack-Scott et al., 2013). These agendas have resulted in new social and ecological challenges. For instance, many cities that are planting more trees are not considering the fact that urban forests are also vulnerable to climate change. Furthermore, many cities that are encouraging citizens to participate in management do not have a clear understanding of the public's values related to urban forests. Since climate-driven changes will affect value provision in urban forests, and people's values will determine the management direction by which we address climate change, understanding these issues together may ensure the success of current urban forest management agendas. This paper provides a critical analysis of the current literature on urban forest values and climate change adaptation in urban forests

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and what it means to adopt these two issues in urban forest management. Its goal is to provide insights on how these issues complement, enhance, and broaden the objectives in urban forest management, and how they conflict with each other. The paper is structured in the following way: In the first Section I provide some background about urban forest management to clarify why climate change adaptation and public values are critical issues. In the second Section I present a review of these two bodies of literature. The paper then discusses parallel or conflicting ideas from these bodies of literature and offers a critical view on what the implications for urban forest management are from a values and climate change-adaptation standpoint. This paper works on a broad definition of urban forests as all the natural or planted trees in urban areas (Nowak, 1994).


n ~ ez and Duinker, people assign importance to urban forests (Ordo 2013). Considering that climate change will affect value provision, and that people's values will determine the management direction through which we address climate change, including both these issues in one analysis is useful. A socio-ecological systems perspective can be used for this analysis since it allows us to view ecological and human processes as coupled processes (Berkes et al., 2003), an important consideration for urban ecosystems (Marzluff et al., 2008). This means that ecological functions and structures, such as urban tree diversity, connectivity, and survival rates, are connected to the social dynamics, including landscape use and preference, the social distribution of urban trees, and the management priorities of its actors.

2. Climate change and public values in urban forest management

2.2. Climate change in the context of urban forests

2.1. The purpose of urban forest management At a practical level, one can assume that the main purpose of urban forest management is to plant more urban trees and to keep alive those that are already there. Yet, there are many different ways to accomplish this, and in many ways, this idea is far too simplistic to provide a management direction. Many rationales have been proposed to provide a purpose for urban forest management, including problem-based, servicesbased, or values-based rationales. A problem-based rationale may be adopted when short-term environmental threats are imminent. For example, the devastating effects of insects or diseases on urban trees (Poland and McCullough, 2006) cause urban forest management to focus on the removal of a particular tree species and the planting of another one. However, a problem-based rationale is reactive and usually not enough to address long-term and complex environmental challenges, such as climate change. A services-based rationale has gained some traction in recent years. It sees urban forests as providers of services, which can defined as processes that satisfy human and non-human needs (Fisher et al., 2009), and sees urban forest management as an endeavour that provides these services. Following this rationale, service optimization is the main goal of urban forest management (Young, 2013). However, some have argued that a services-based rationale applied to ecosystem management may not necessarily address many psycho-social and ecological values held by people (Chan et al., 2012; Ruckelshaus et al., 2013). A services-based rationale has not been effective in addressing some psycho-social and ecological issues in urban forest management plans, such as planting native tree species and engaging citizens in management
n ~ ez and Duinker, 2013). (Ordo In contrast, a values-based rationale sees urban forest management as a process where the desires of urban dwellers are met. This rationale is based on the notion that values are more useful for determining people's psycho-social, cultural, and ecological priorities in ecosystem management than any other concept (Ives and Kendal, 2014). In general, a values-based rationale is being used more and more in urban forest management, particularly in North America (e.g. City of Victoria, 2009). However, satisfying what people want from urban forests may challenge our ability to address long-term ecological challenges. For instance, people may value a particular tree species that may not thrive in the future climate. An analysis of the implications of adopting public values and addressing climate change in urban forest management is needed to understand how these two issues complement or conflict with each other. Climate change is missing from most urban forest management agendas and a values-based perspective is being used in management plans without much empirical evidence of how

It is unequivocal that temperature has increased more rapidly since preindustrial times than previously in history (IPCC, 2014a). Forests are expected to change considerably in response to future changes in temperature (Parmesan and Yohe, 2003). Since cities may be affected more by temperature increases given the urban heat island effect, and possibly also droughts, floods, storms, and heat waves (Wilby, 2007; Hunt and Watkiss, 2011), climate change can be considered an added stressor for urban forests. Stressors such as changed hydrology, low soil quantity and quality (Sieghardt et al., 2005), fires and wind events (Staudhammer et al., 2011), and insects and diseases (Poland and McCullough, 2006), may all be aggravated by more frequent and intense weather events and the mal-adaptation of some urban tree species to future climate (Yang, 2009; Roloff et al., 2009). Unhealthy urban trees may be affected more strongly by insects and diseases (Tubby and Webber, 2010). Two urban forest management strategies have been suggested to address climate change, namely mitigative (i.e. reducing greenhouse gas emissions) and adaptive (i.e. adjusting the system to cope with changing environmental conditions) responses. Mitigative strategies include planting more trees, optimizing species selection for carbon capture, and optimizing the arrangement of trees in relation to buildings (Nowak et al., 2002). There are two facets of an adaptive response: using urban forests to ameliorate the effects of climate change on urban areas, termed here a city-centred response; or adjusting urban forests to cope with the effects of climate change, or an urban forest-centred response. The first type of response is the focus of much of the literature on climate change adaptation and urban trees (Shashua-Bar and Hoffman, 2000; Lindley et al., 2006; Gill et al., 2007; Hamin and Gurran, 2009; Bowler et al., 2010; Fryd et al., 2011; Tyler and Moench, 2012; Hall et al., 2012; Demuzere et al., 2014). Both the mitigative and city-centred adaptive responses provide little insight on what makes urban forests vulnerable to climate change and what it means to adopt strategies to adapt to climate change beyond planting more trees. Based on interpretations of climate adaptation (IPCC, 2014b), an urban forest-centred response can mean reducing urban forest vulnerability and increasing its adaptive capacity with a predicted climate scenario in mind and adjusting for uncertainty. By urban forest vulnerability I mean the characteristics of urban forests that make them prone or unresilient to change. This means that although planting more trees is an important climate adaptation measure, reducing urban forest vulnerability may be a more important consideration, as the positive effects of planting more
n ~ ez and trees may be reduced by a mal-adapted system (Ordo Duinker, 2014). Planting more trees, in a climate-adaptation sense, is a way to mitigate climate impacts rather than a systematic way to adapt urban forests to these changes. This paper aims to elicit information about urban forest


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vulnerability to climate change and not information on climate change mitigation. 2.3. Public values related to urban forests Considering the public in urban forest management goes beyond informing people about trees and taxing them for tree care (Clark et al., 1997). Urban citizens are the occupants of the urban forest and receivers of its services; so, at a fundamental level, the public and private institutions in charge of urban forest management serve urban citizens (Mincey et al., 2013). A values-based rationale is becoming more common in urban forest management and sees urban forest management as a process that satisfies what urban citizens consider important (Dwyer et al., 1991). For this process to be successful we need to have a thorough understanding of what people consider important in urban forests, or the public values related to urban forests. Any exploration of what people consider important in urban forests is made difficult because the terms values, attitudes, preferences, benefits, and services have been used interchangeably to mean the same thing. The literature on urban forest attitudes, preferences, and concerns focuses on associating care for the urban forest with demographic characteristics including age, income, and gender, among others (e.g. Jones et al., 2013). However, the goal of these studies is to understand whether people have a positive attitude towards urban forests or what people prefer in urban forests in terms of tree form and location. As such, it gives little insight on what people deem important in urban forests. In addition, this research usually explores these issues in spaces that do not represent the urban forest as a whole (e.g. only street trees; see Schroeder et al., 2006), or spaces that include other natural elements, such as green spaces (Balram and Dragievi, 2005) and open spaces (Chiesura, 2004). Moreover, most of the literature on urban forest services and benefits is focused on assigning a monetary value to urban forest functions. This research has been effective in advancing environmental priorities in urban forest management, such as planting more trees to increase air pollution control and carbon capture (Escobedo et al., 2008). However, most of this research is not elicited directly from urban citizens, except for a few contingent €inen and V€ €na €nen, 1998). Some auvaluation studies (e.g. Tyrva aa thors have argued that this literature does not address some ecological, psychological, or socio-cultural themes that are important to people in urban forests (Peckham et al., 2013). The concept of value may be better for capturing the priorities of the public in relation to urban forests. A value is what people consider important in relation to something, a fundamental and positive construct that informs a person's opinions and conduct (Rokeach, 1973; Schwartz and Bilsky, 1990). Ecosystem values research is not just concerned with whether people have a positive attitude towards nature or an ecosystem, but rather how people assign importance to them (Dietz et al., 2005; Reser and Bentrupperb€ aumer, 2005). This interpretation of values has been useful to identify the priorities of the public in forest management (e.g. Owen et al., 2009; Ford et al., 2012). This analysis focuses on the literature on public values, benefits, attitudes, preferences, and services that specifies how people assign importance to urban forests and which is elicited directly from urban citizens. 3. A review of public values and climate change in urban forest management 3.1. Methods A comprehensive review of the urban forest literature on public

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values and climate change vulnerability and resilience was carried out. Scopus was used for this review, an academic, peer-reviewed literature search tool with flexible functionality, covering the period from 1966 to December 2014 (http://scopees.elsevier.com). Search terms included “urban forests”, “urban trees”, “climate change”, “vulnerability”, “adaptation”, “resilience”, “values”, “services”, “benefits”, “attitudes, and “preferences”. Three key journals were reviewed thoroughly, which were Arboriculture & urban forestry, urban forestry & Urban Greening, and Landscape & Urban Planning, although relevant papers were found in other journals. Only peer-reviewed literature was included. Conference papers, magazine articles, book chapters, and research reports were avoided. The review focused on North American research, chiefly Canada and the United States. Ideas were condensed and classified according to common themes. 4. Results Only a few studies have assessed urban forest vulnerability or resilience to climate change (Table 1). For many authors, reducing urban forest vulnerability to climate change is a more complex issue than planting more of the right type of tree. They refer to a combination of ecological and social factors that contribute to this vulnerability, including species and age diversity, habitat suitability, planting techniques, maintenance strategies, coordination and cooperation, and institutional knowledge and capacity (Table 1). These ideas imply a variety of management strategies, including: increasing urban tree diversity and representativeness in terms of species, age-classes, and native, rare, endemic, and/or southern species; changing planting techniques to ensure young tree survival; reducing water stress and selecting tree species resilient to dry conditions; increasing urban forest connectivity and habitat quality; increasing cooperation and coordination among municipal entities; increasing institutional knowledge of tree mortality and urban tree inventory; increasing responsiveness to storms and fires; and increasing control over tree stock from nursery (Table 1). Furthermore, most studies on public values have focused on whether people have a positive attitude towards urban trees and their preferences (Table 2). In contrast, only a few studies give a clearer notion of how urban citizens assign importance to urban forests. These studies indicate that people assign importance to urban forests according to a rich array of descriptors, mostly referring to ecological, environmental, and psycho-social themes (Table 2). These ideas suggest that to satisfy these values management must enhance the natural, sensory, ecological, and social experience of urban forest residents. This implies the following management strategies: increasing the availability of natural urban forest spaces that provide peacefulness, calmness, tranquillity, high biodiversity, naturalness, wildlife habitat, and recreational opportunities; and increasing the social access to these spaces (Table 2). 5. Discussion 5.1. Changing management objectives Including climate change adaptation in ecosystem management is a way to complement, enhance, and broaden management objectives (Hagerman et al., 2012). Climate change adaptation is being embraced more and more in urban forest management based on the notion of planting more of the right kind of tree (e.g. Town of Ajax, 2011), but this does not necessarily address climate vulnerability at a deeper level. This review suggests that adapting to climate change may require the introduction of ecologically-sound techniques in the

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Table 1 Ideas for understanding urban forest vulnerability to climate change, including source. Main idea

Source (example)

Increased probability of tree loss due to insects and diseases and low urban forest species diversity Increased mortality of tree species that are not well represented, including some native, rare, endemic, and/or at-risk species Increased mortality of young and mature trees, considering seedlings and older trees may be less adaptable than mid-age trees, and considering calliper trees may be more vulnerable Tree species climate ranges shift north Urban tree species are vulnerable to future climate-change effects on water availability due to pavement cover and microclimatic conditions Highly urbanized habitat conditions affect tree health and tree recruitment; urban forest stressors, such as microclimatic conditions, soil compaction, wind damage, among others, may be exacerbated by climate change in these environments Lack of cooperation and coordination among municipal, management entities make climate change adaptation strategies more difficult to adopt Lack of knowledge of tree mortality and urban tree inventory, inadequate response strategies to storms and fires, and lack of control over tree stock from nursery make urban forests more vulnerable to climate change

(Poland and McCullough, 2006; Tubby and Webber, 2010)
n ~ ez and Duinker, 2014, 2015) (Tubby and Webber, 2010; Ordo
n ~ ez and Duinker, 2015) (Yang, 2009; Ordo (Yang, 2009; Woodall et al., 2010; Busotti et al., 2014) (Roloff et al., 2009; Gillner et al., 2013; Busotti et al., 2014; Bertuzzi et al., 2015) (Solecki et al., 2005; Yang, 2009; Tubby and Webber, 2010; O'Brien et al., 2012; Busotti et al., 2014)
n ~ ez and Duinker, 2014, 2015) (Ordo
n ~ ez and Duinker, 2014, 2015) (Ordo

Table 2 Ideas for understanding public values related to urban forests, including source. Main idea

Source

Most people's attitudes towards urban trees are positive; people like mostly big trees and fruit trees; women, high-income residents, those affiliated with environmental organizations, and those who have a tree in front of their home, may have a more positive attitude towards urban trees People's positive attitude towards urban trees are mostly related to aesthetics, shade, property values, and recreation People's most highly preferred urban tree benefits are shade and calming effects People value urban forests because they provide peacefulness, calmness and tranquillity, air quality, beauty, naturalness, connection to nature, biodiversity, wildlife habitat, recreation, a sense of history and place, and a place for community

(Kalmbach and Kielbaso, 1979; Sommer et al., 1990; Schroeder and Ruffolo, 1996; Barro et al., 1997; Sommer, 1997; Fraser and Kenney, 2000; Gorman, 2004; Schroeder et al., 2006; Matsouka and Kaplan, 2008; Zhang and Zheng, 2011; Dilley and Wolf, 2013; Jones et al., 2013) €inen and V€ € n€ €inen, 2001; Hunter, (Smardon, 1988; Tyrva aa anen, 1998; Tyrva 2001; Schroeder et al., 2006; Elmendorf, 2008) (Lohr et al., 2004) €inen et al., 2003; Jay and Schraml, 2009; Peckham et al., 2013; Sinclair (Tyrva et al., 2014)

management of urban trees. For instance, the idea of planting trees in bigger, connected patches, to improve growing conditions chal
n ~ ez and lenges the norm of planting calliper trees far apart (Ordo Duinker, 2015). This echoes the message emanating from climate vulnerability assessments in rural forests. Here vulnerability has been associated with low adaptability of seedlings to weather variability and extremes, and with forest fragmentation, which affect tree genetic diversity and seed dispersal (Aubry et al., 2011). Considering that natural regeneration is enhanced in places with better habitat quality (Nowak, 2012; O'Brien et al., 2012), changing planting techniques and enhancing connectivity can ensure urban tree survival. In addition, the idea of favouring native tree species challenges the long-standing notion of favouring exotics in urban forests. Many of these techniques are implied in adopting a public values perspective, considering that some studies have shown that people feel calmer and have a stronger connection to nature in more natural urban-forest spaces (Table 2). These ideas can generally be referred to as a naturalization or naturalness strategy. The use of the term naturalization is troublesome considering many interpretations of it exist. In ecology, it has been interpreted as a process where biotic and biotic barriers to survival are surmounted, for example, when exotic species are “naturalized” in an ecosystem (Richardson et al., 2000). In contrast, in management, naturalization has been broadly defined as a form of ecological restoration that increases the naturalness of an ecosystem (Toni and Duinker, 2015). Under this interpretation, naturalization has been suggested as management strategy in urban forests (e.g. Millward et al., 2011). Obviously, there are other priorities in urban forest management besides naturalization, including enhancing aesthetics and selecting adequate tree species in consideration of future climate (Tables 1 and 2). Nevertheless,

and considering a much-needed conceptual clarification regarding the meaning of naturalization in ecosystem management, finding ways to make naturalization operational is a promising avenue of research to address values and climate change adaptation in urban forest management. This simple association demonstrates the strong connection between public values and climate change adaptation in urban forest management. Satisfying public values and addressing climate change mean advocating for complementary strategies that go beyond planting more trees, which is a common but oversimplified strategy in urban forest management. For example, values-based and climate-adaptation strategies include increasing tree species representativeness and not just urban tree diversity, engaging people directly in management and not just in tree planting, and increasing the social access to urban forests. These ecological and social themes are mostly absent from urban forest
n ~ ez and Duinker, 2013), so we must look management today (Ordo to them as new areas of research. Advocating for values-based and climate-adaptation priorities does not necessarily invalidate other priorities in urban forest management. If anything, a values-based rationale provides a better sense of purpose for harmonizing social and ecological considerations. Moreover, without addressing climate change vulnerability today, current ecological and environmental challenges may become more difficult to address in the future. Climate change provides an opportunity to address issues that are either scheduled to be addressed later on or that are only partially addressed today. Undeniably, there is a need for more research in this field, particularly the development of species-based or ecological-response models. These will help us understand the meaning of climate change adaptation in urban forests in local contexts.


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5.2. Other implications There are other implications when adopting both public-values and climate-adaptation priorities in urban forest management, including: 1) being proactive and adaptive, not reactive, and responding to public values and climate change with planned measures; 2) probing people constantly about their satisfaction with the urban forest to see how the changes in urban forests are affecting values provision; 3) adopting a strong, system-scale monitoring and experimentation program in urban forest management to enhance learning and embrace uncertainty, thus finding systematic ways to reduce it; and 4) enhancing citizen engagement and stewardship. A values-based perspective has been used in management plans without much empirical evidence of how people assign importance to urban forests. There is great potential for growth in the research of public values. As more case studies and different value-elicitation methods emerge, the list of public values presented here can be validated, complemented, or challenged altogether. More values research is needed in non-North-American and non-European urban forest communities where almost no work has been done. Assessing the mortality and survival of newly planted trees must become an important aspect of urban forest management if we are to face climate change effectively (Table 1). Finding creative ways to overcome the challenges of monitoring programs in urban forests (see Roman et al., 2013) would make for a successful strategy to increase urban forest resilience to climate change. Finally, citizen engagement and stewardship are important issues considering that only by becoming better ecosystem stewards can we hope to adapt to climate change (IPCC, 2014b). urban forests may provide an opportunity for urban citizens to engage directly with climate change via direct and purposeful stewardship of the urban tree resource. Authors have demonstrated how the participation of residents in the tending of newly planted streets helps their survival (Mincey and Vogt, 2014). In general, communitybased steering committees or neighbourhood-based volunteer groups not only increase the participatory aspect of urban forest management but also ensure urban tree survival (Jack-Scott et al., 2013). Considering that a common concern about managing climate change in urban forests are its costs (Ligeti, 2007), engaging citizens may provide opportunities to reduce maintenance costs and increase citizen-based governance. This deserves more attention in urban forest management research. 5.3. Limitations Most of the literature on urban forest vulnerability and resilience to climate change is new. Some studies focus solely on understanding climate change impacts in urban forests while others extrapolate ideas about this topic from studies on rural forests. Therefore, there is a clear need for empirical studies that assess urban forest vulnerability to climate change. There is high utility in exploring climate change issues in non-North-American and nonEuropean urban forest communities where almost no work has been done (Table 1). Such case studies are important because this is where most of the urban growth is today and perhaps where climate change effects may be more significant. Earlier I suggested that the priorities of the public and climatechange related priorities may appear in conflict. For example, people may value a particular tree species that may not thrive in the future climate. The intention of values research in urban forests is not to assess specific attitudes or preferences, however important this may be for local urban forest management. Rather, it strives to understand how people assign importance to urban forests at a deeper level. The studies in this review show that people value the

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urban forests according to a rich array of psycho-social, cultural, and ecological themes (Table 2). However, they are based on a few case studies and a small sample of participants, and reveal different priorities depending on the method used. Clearly, there is great utility for exploring public values in different places and with different methods. 6. Conclusions The shared benefits of adopting public-values and climateadaptation priorities will not happen automatically or serendipitously by planting more of the right kind of trees. Rather, urban forest communities must systematically address these issues beyond every planting cycle. For instance, the scant research on climate change and urban forests may be because climate change effects are confounded, not well understood, or profoundly uncertain, or because urban forest managers are not tuned-in to these considerations. Undeniably, the effects of climate change on ecosystems will remain uncertain in the immediate future. Rather than an obstacle, uncertainty, or the expression of the degree to which something is unknown because of disagreements of what is known or even knowable, gives the opportunity to any management regime to enhance its objectives in its attempt to reduce it. Research must be advanced to specify what these objectives mean at the practical and local levels, such as how to naturalize urban forests, how to make them more socially accessible, and how to monitor them. References Aubry, C., Devine, W., Shoal, R., Bower, A., Miller, J., Maggiulli, N., 2011. Climate Change and Forest Biodiversity: a Vulnerability Assessment and Action Plan for National Forests in Western Washington. US Department of Agriculture (USDA), Forest Service, Pacific Northwest Region. Retrieved from. http://ecoshare.info/ wp-content/uploads/2011/05/CCFB.pdf. December, 2014. Balram, S., Dragievi, S., 2005. Attitudes toward urban green spaces: integrating questionnaire survey and collaborative GIS techniques to improve attitude measurements. Landsc. Urban Plan. 71 (2e4), 147e162. http://dx.doi.org/ 10.1016/j.landurbplan.2004.02.007. Barro, S.C., Gobster, P.H., Schroeder, H.W., Bartram, S.M., 1997. What makes a big tree special? Insights from the Chicagoland Tremendous Trees program. J. Arboric. 23 (6), 239e249. Berkes, F., Colding, J., Folke, C., 2003. Navigating Social-ecological Systems: Building Resilience for Complexity and Change. Cambridge University Press, Cambridge, MA, USA. Bertuzzi, S.T., Brance, S., Tretiach, M., Nardini, A., 2015. Drought-induced xylem cavitation and hydraulic deterioration: risk factors for urban trees under climate change? New Phytol. 205 (3), 1106e1116. http://dx.doi.org/10.1111/ nph.13112. Bowler, D.E., Buyung-Ali, L., Knight, T.M., Pullin, A.S., 2010. Urban greening to cool towns and cities: a systematic review of the empirical evidence. Landsc. Urban Plan. 97 (3), 147e155. http://dx.doi.org/10.1016/j.landurbplan.2010.05.006. Brown, T., 1984. The concept of value in resource allocation. Land Econ. 60 (3), 231e246. Busotti, F., Pollastrini, M., Killi, D., Ferrini, F., Fini, A., 2014. Ecophysiology of urban trees in a perspective of climate change. Agrochimica 58 (3), 247e268. http:// dx.doi.org/10.12871/0021857201431. Chan, K., Satterfield, T., Goldstein, J., 2012. Rethinking ecosystem services to better address and navigate cultural values. Ecol. Econ. 74, 8e18. http://dx.doi.org/ 10.1016/j.ecolecon.2011.11.011. Chiesura, A., 2004. The role of urban parks for the sustainable city. Landsc. Urban Plan. 68 (1), 129e138. http://dx.doi.org/10.1016/j.landurbplan.2003.08.003. City of Toronto, 2008. Ahead of the Storm... Preparing Toronto for Climate Change. Toronto Environment Office, City of Toronto, Toronto, ON, Canada. Retrieved from. www.toronto.ca/teo/pdf/ahead_of_the_storm.pdf. December 2014. City of Victoria, 2009. City of Victoria urban forest Master Plan City of Victoria. Victoria, BC, Canada. Retrieved from. www.victoria.ca/cityhall/departments_ compar_rbnfrs.shtml. December 2014. Clark, J.R., Matheny, N.P., Cross, G., Wake, V., 1997. A model of urban forest sustainability. J. Arboric. 23 (1), 17e30. Conway, T.M., Urbani, L., 2007. Variations in municipal urban forestry policies: a case study of Toronto, Canada. Urban Urban Green 6 (3), 181e192. http:// dx.doi.org/10.1016/j.ufug.2007.07.003. Demuzere, M., Orru, K., Heidrich, O., Olazabal, E., Geneletti, D., Orru, H., Bhave, A.G., Mittal, N., Feliu, E., Faehnle, M., 2014. Mitigating and adapting to climate

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