While globally there is a growing interest in the importance of green infrastructure for the quality of life in cities (Hubacek and Kronenberg 2013), in some regions, such as Central and Eastern Europe, urban green areas are shrinking, despite the physical growth of cities (Kabisch and Haase 2013). Street trees are often presented as an easy to understand and well-known source of benefits (McPherson 2007, 2010), but they are also particularly exposed to the risks of urbanization (e.g., pollution and modernizing or developing infrastructure). People tend to protest when street trees are removed, including in Central and Eastern Europe, but they do so on a case by case basis, and usually without reference to the broader scale of this problem. In this light, it is interesting to study more systematically if street trees are important to people in cities where urban green areas are shrinking. In other words, it is useful to know if the trend of shrinking urban green areas is in line with people’s preferences, or if it is something that people would prefer to counteract.
Street trees are specific in that while most of them are public, some of their services and disservices accrue only to those who live nearby (Donovan and Butry 2010). Moreover, the perceptions of street trees in a city center might vary considerably between people living in the center and outside of it. Economic valuation methods can be used to study such various aspects of the management of urban trees, and some of them are particularly suited for this purpose.
The objectives of this article are to investigate the usefulness of one of these methods, choice experiment, to estimate the economic value of street trees in a city center, and to test this approach in the context of an understudied region of Central and Eastern Europe. Using a case study of Lodz in Poland, we investigate the specific implications of this valuation exercise for governance of urban ecosystem services. To the best of our knowledge, there have been few studies that looked at the value of trees in a city center and no study used a choice experiment to value street trees. Furthermore, we were only able to identify two studies on the value of urban ecosystem services in Central and Eastern Europe: Melichar and Kaprová (2013) performed a spatial hedonic analysis of urban green spaces in Prague, while Pavlyuk and Jankowska (2012) used a choice experiment to assess the value of different types of management of urban and suburban forests in Riga.
Before we move to a description of our study, its results and implications for governance in the following sections, we first compare the different methods used to value urban street trees.
Methods Used to Value Street Trees
In North American cities, tree valuations have been mostly based on replacement cost or avoided cost methods, thus offering an opportunity to investigate the monetary value of individual trees. The authors of these studies differentiate between what they call benefit-based and cost-based approaches (McPherson 2007). “Cost-based approach” uses the trunk formula method developed by the Council of Landscape and Tree Appraisers for calculating the replacement cost of a tree. “Benefit-based approach” focuses on the net present value of a stream of benefits that a tree is expected to deliver (avoided costs of emissions of CO2 and other pollutants, of energy use, and of stormwater management; increased property value), less the costs of the tree’s maintenance. Thus framed benefits are easy to grasp by decision makers and in some instances they served to underpin important political commitments to increasing the numbers of trees, for example, in New York City (McPherson 2010). However, both approaches are entirely expert led and do not investigate the preferences of city inhabitants.
One of the most common methods to estimate the value of urban greenery based on revealed preferences of city inhabitants is hedonic pricing, the use of which in the context of urban trees dates back to the 1970s (Payne and Strom 1975; Morales et al. 1976). Very rarely, however, this method has been applied specifically to street trees (Donovan and Butry 2010; Pandit et al. 2013), and these studies focused on residential areas, not necessarily in city centers. For example, in twelve Japanese cities, increasing street greenery was found to have higher impacts on land prices, than increasing the amount of urban park area (Ishikawa and Fukushige 2012). Nevertheless, there may always be some additional factors which account for the price differences among the analyzed properties and which have not been included in a model (Ishikawa and Fukushige 2012). Furthermore, Orland et al. (1992) called for caution in linking property prices with the adjacent trees in hedonic pricing models, based on their empirical study on the perceived impacts of street trees on property values.
Qualitative methods were also used to perform non-monetary valuation of street trees, involving various survey procedures for assessing people’s response to street trees (Getz et al. 1982; Sommer et al. 1990; Todorova et al. 2004; Lohr et al. 2004; Schroeder et al. 2006). Some of these authors investigated general perceptions of street trees, others focused on specific issues. Most of qualitative studies confirm positive attitudes of urbanites toward trees in different geographical contexts. Qualitative, non-monetary studies depict aspects which are difficult to grasp with the use of monetary valuation methods. For example, people who volunteered in urban tree planting programs were found to be motivated more by values, such as spiritual benefits and bringing nature closer, than by practical benefits, such as reducing noise and increasing property value (Westphal 1993; Austin 2002). It was also found that the perception of street trees may depend on whether one has contact with these trees (Gorman 2004).
In a country such as Poland, where it is often suggested in public discussions that people cannot afford the “luxury” of environmental protection (or just do not want to “waste” their money on it), it is particularly interesting to investigate the actual preferences in monetary terms. Furthermore, not all urbanites buy houses or apartments and thus their preferences would not be depicted using hedonic pricing. Among the stated preferences valuation methods, choice experiments are considered to be able to elicit these preferences in the most complex and comprehensive manner, permitting to study preferences for different attributes of a good (Hanley et al. 1998).
Choice experiments were very rarely used in the case of urban green spaces and, to the best of our knowledge, so far they have not been applied specifically to street trees. Bullock (2008) investigated the Dubliners’ value ranking of different aspects of urban parks, such as size, type, opportunities for diverse activities, etc., and identified their willingness to pay for visiting parks of different characteristics as compared to a baseline park with only some of those attributes. Other applications of choice experiments in urban settings included studies on the public rights of way in the UK (Morris et al. 2009), multiuse trails in urban and suburban environments (Reichhart and Arnberger 2010), preferences for environmental amenity improvements related to regeneration initiatives (Lanz and Provins 2011), and urban stream restoration (Bae 2011). Scenarios put forward during choice experiments are often built based on previous work with experts or focus groups (Davies and Laing 2002).
Taking into consideration the above features of different methods used to estimate the value of urban trees, we decided to use a choice experiment. It seems to be an innovative approach to value street trees in a city center, and it provides meaningful information that can constitute an input to local decision making and support local governance of ecosystem services. We wanted to get to know how city inhabitants value street trees and to check whether the current approach of city authorities to street trees corresponds with those preferences.