Ecosystem services appreciation of urban lakes in Romania. Synergies and trade-offs between multiple users
Introduction
Ecosystem services (ES) are the benefits people obtain from ecosystems (Millennium Ecosystem Assessment (MEA), 2005) indispensable for human well-being. Current classifications such as Millennium Ecosystem Assessment (MEA), the Common International Classification of Ecosystem Services (CICES), the Economics of Ecosystems and Biodiversity (TEEB) or the US National Ecosystem Services Classifications Systems (NESCS) divide ES into three main categories: provisioning (which include the material and energetic outputs from ecosystems), supporting (all the ways in which ecosystems mediate the environment on which people depend for their livelihood) and cultural services (all non-material characteristics of ecosystems important for people’s mental well-being) (Haines-Young and Potschin, 2016). Studies on ES provided by terrestrial ecosystems, such as forests, agricultural lands, wetlands have rapidly grown during the last decade (García-Llorente et al., 2012, García-Nieto et al., 2013, Ghermandi et al., 2010, Vihervaara et al., 2012), but a less focus has been given to aquatic ecosystems, especially to lakes (Reynaud and Lanzanova, 2017).
With the persisting growth of cities, the pressures on all types of urban ecosystems and in particular on freshwater ecosystems will increase (Gavrilidis et al., 2019). Although lakes provide essential resources and will have critical importance as water reservoirs for human societies in a changing world, they are lost at an increasing rate in the urban areas (Henny and Meutia, 2014) or are under high pressure from the effects of nutrient enrichment (Verburg et al., 2013), eutrophication (Smith, 2003), modification of hydrology (Schallenberg et al., 2013), climate change (Schmid et al., 2014) and urban expansion (Inostroza, 2014).
Urban lakes have been often described as artificial ecosystems, usually small in size and shallow in depth, with flood-control roles and recreational purposes (Birch and Mccaskie, 1999). Through their ecological and functional characteristics, urban lakes can provide several ES, such as fishing, reeding, phosphorus and nitrogenous retention, biodiversity, local climate change regulation, maintaining species population and habitats, regulation of the urban climate, flood protection, as well as educational and recreational services (Reynaud and Lanzanova, 2017, Schallenberg et al., 2013, Vilbaste et al., 2016).
Interactions among ES are increasingly studied by researchers (Bennett et al., 2009, Braat and de Groot, 2012, Cord et al., 2017, Reynaud and Lanzanova, 2017). They are relational, emerging from the complex interaction between natural, social, individual and built capital (Costanza et al., 2017) rather than linear as highlighted by the ‘ecosystem services cascade model’ (Haines-Young and Potschin, 2010). Such interactions could be non-existent, positive or negative unidirectional or bidirectional (Bennett et al., 2009). They have been often categorized as synergies and trade-offs, where a synergy refers to positive interactions, emerging when more services are enhanced simultaneously (i.e., the efforts to protect the coral can increase algal grazing and enhance recreation opportunities (Hughes et al., 2007)). Trade-offs arise when the use of one service decreases the benefits provided by another service (i.e., recreational hunting has a negative effect on beekeeping (García-Nieto et al., 2013)). Current ES research has focused on assessing such interactions, particularly looking at bundles of ES (Inostroza and de la Barrera, 2019) as well as the relevant synergies and trade-offs to put the ES into practice (Inostroza et al., 2017). However, there is still a gap in including the societal feedback in the study of ES interactions which is of particular importance as it represents a potential cause of trade-offs and synergies (Martín-López et al., 2012, Turkelboom et al., 2018).
Perceptions on the importance of different ES can serve as a robust basis for the development of sustainable urban lakes management. People’s perception highlights which services are important for people, a relevant fact to identify ES synergies and trade-offs (Martín-López et al., 2012). In ecosystem decision making, experts often use the scientific results produced by researchers, who base their findings on civic society experiences (Steiner, 2008). Bringing together the perception and knowledge from such diverse groups is a challenging task due to differences in terms of interests, culture or level of knowledge (García-Nieto et al., 2015, Renn and Rohrmann, 2000) but is essential to allow the best decisions in ecosystem management (Tudor et al., 2015).
Our study aims (i) to explore user preferences toward different ES and (ii) to assess the synergies and trade-offs among the ES provided by urban lakes. The assessment was based on the perceptions of three user groups: residents, visitors and experts. Although a few studies deal with the assessment of the ES provided by lakes (Reynaud and Lanzanova, 2017, Schallenberg et al., 2013, Vilbaste et al., 2016), the focus on urban lakes is still lacking, as a results of the challenging task to assess ES in urban regions (Haase et al., 2012). We explored the assessments of diverse user groups to comprehensively capture the diversity of knowledge and perception they could bring to decision making (García-Nieto et al., 2015). Furthermore, the analysis of interactions represents a new approach to study ES (Costanza et al., 2017) which has not received sufficient consideration in urban regions (Haase et al., 2012). This knowledge gap might be essential to understand how bundles of ES interact in terms of synergies and trade-offs, a fundamental information to pursue a better ES management.
The study area covers three artificial urban lakes located in three Romanian cities: Bucharest (1.7 million inhabitants), Targu-Jiu (80,548 inhabitants) and Orșova (9692 inhabitants) (Fig. 1). All three lakes are artificial, used primarily for flood control and energy production. They have a poor connection to urban green areas.
Morii Lake is located in the west part of Bucharest, and it is the largest lake in the city, covering a total area of 2.46 km2. It has a mean depth of 4 meters. The lake is located in an area with mixed land-uses (i.e., residential, derelict industrial sites, abandoned land, green areas). The left shore of the lake provides some facilities for tourists (i.e., alleys, benches, lights) and is connected to a small urban park (Crangasi park) (Iojă et al., 2018). The lake is used for yachting and a few aquatic sports events.
Lake Targu-Jiu is located in the west part of Targu-Jiu city and covers 0.56 km2. It has a mean depth of 2 meters. The right shore of the lake is designated for residential and industrial uses while the left shore for green areas, specifically the main park in the city. The primary functions of the lake are flood control and recreation.
Cerna Bay is part of the Danube’s Iron Gates I Lake which is the largest lake in Romania (253 km2). Orsova city surrounds the Bay which covers 5.1 km2 and has a mean depth of 7 meters. On the shores, patches of green areas can be found with poor connectivity due to the development of built-up areas. Teams training for boats contests use the lake.
Section snippets
Data collection
The data on the ES provided by urban lakes was collected through two different types of surveys: face-to-face written surveys and web-based surveys, from residents, visitors and experts. Face-to-face surveys were chosen to evaluate residents and visitors’ assessments of the ES provided by urban lakes to achieve a high response rate among such user groups. To obtain a representative sample of residents and visitors, we applied a stratified random sampling approach. The participants were randomly
Informant characteristics
Almost half of the residents (49.54%) and over half of visitors (61.96) are females which fit each city’s demography data (National Institute of Statistics, 2016). Over half of the experts are males (52%). This can be the effect of gender bias in the composition of experts. Respondents of 18–35 years of age expressed greater interest in participating in the study (48.62% for residents group and 66.85% for visitors group), while for experts the predominant age group was 36–50 years, respectively
Residents, visitors and experts’ preferences
Previous studies have found variability in people’s preferences toward different ES. Some studies showed the strong importance assigned to provisioning services (Hartel et al., 2014, Torralba et al., 2018), others to regulating services (Martín-López et al., 2012) or even to cultural services (Darvill and Lindo, 2015). Our results showed that cultural services provided by urban lakes are mostly valued by visitors and experts, while the regulating and maintenance services are mostly valued by
Conclusion
According to the three user groups, urban lakes are offering more cultural as well as regulating and maintenance ES than provisioning ES. The assessment of different user groups’ preferences toward the ES provided by urban lakes could guide an ES-based management of the urban lakes where diverse interests overlap.
The identified synergies and trade-offs are providing useful information for sustainably managing urban lakes. In each ES trade-off, the cultural ES emerged. This highlights not only
Acknowledgements
We are sincerely grateful to the anonymous reviewer for the insightful comments and suggestions. This work was supported by a grant from the Romanian National Authority for Scientific Research, UEFISCDI, project number PN-III-P4-ID-PCE-2016-0635.
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