The urban coastal systems

The coast can be seen as a system in order to help to understand the processes and interactions involved. In theory, the inputs, processes and outputs work together to create coastal equilibrium. However, as we will see in this unit human actions affect the state of equilibrium within the coastal system. Coastal landscapes are open systems. This means energy and matter can enter and leave the system.

We propose a system dynamics approach for Ecologically Sustainable Development (ESD) in urban coastal systems. A systematic analysis based on theoretical considerations, policy analysis and experts’ knowledge is followed in order to define the concept of ESD. The principles underlying ESD feed the development of a System Dynamics Model (SDM) that connects the pollutant loads produced by urban systems’ socioeconomic activities with the ecological condition of the coastal ecosystem that it is delineated in operational terms through key biological elements defined by the EU Water Framework Directive. The receiving waters of the Athens Metropolitan area, which bears the elements of typical high population density Mediterranean coastal city but which currently has also new dynamics induced by the ongoing financial crisis, are used as an experimental system for testing a system dynamics approach to apply the concept of ESD. Systems’ thinking is employed to represent the complex relationships among the components of the system. Interconnections and dependencies that determine the potentials for achieving ESD are revealed. The proposed system dynamics analysis can facilitate decision makers to define paths of development that comply with the principles of ESD.

Human systems are strongly interrelated with coastal ecosystems. Various human activities (e.g. wastewater discharging, over fishing) affect the water quality of coastal ecosystems, while the goods and services provided by the coastal ecosystem are essential for the economic process and human well-being (e.g. fisheries, recreation). When it comes to urban systems, the interactions between human activities and coastal systems are more intensified due to the increase in population density and associated economic activities. For example, the high urbanization rates in the Mediterranean coastal countries along with the lack of wastewater infrastructure in many coastal areas exacerbate the degradation of coastal waters (Diaz and Rosenberg, 2008; Iglesias et al., 2007; UNEP, 2008).

Systems’ thinking facilitates the recognition that fundamental laws of physics are relevant to the economic processes as there is no way “to create something from nothing” or “to create nothing from something” (Farley, 2012; Georgescu-Roegen, 1971). System dynamics approaches have been used in the relevant literature to explore the interactions between human and coastal systems with respect to the sustainability prospects and especially the sustainable management of water resources (Chang et al., 2008; Hopkins et al., 2012; Mavrommati et al., 2013; Mirchi et al., 2012; Newton, 2012).The methodology of system dynamics traces the roots of the problem, and both qualitative and quantitative analyses can reveal the causes of unsustainable water resources management (Mirchi et al., 2012; Sterman, 2012). Studying the structure and processes underlying the relationships between the human and natural systems can enable decision makers to learn systems’ responses under alternative scenarios of socio-ecological evolution and define sustainable paths of development. Systems thinking facilitates holistic considerations, without which may result in the adoption of ineffective and inefficient policies (Hopkins et al., 2012). Recently, the methodology of system dynamics has been also proposed for studying water and wastewater network management with respect to the prospects of financially self-sustaining water utility (Rehan et al., 2011).

We built a System Dynamics Model (SDM) to quantify the effects of human activities of urban coastal cities on the ecological condition of the receiving waters. The model focuses on examining the impacts of pollutant loads from point sources on the ecological status of the receiving waters. The model adopts the environmental objective of Good Ecological Status (GES) as proposed by the Water Framework Directive (WFD) (Commission of the European Communities, 2000). To operationally assess the ecological status of coastal waters the “Ecological Evaluation Index” (EEI) has been applied (Orfanidis et al., 2001a, 2003; Panayotidis et al., 2004). Based on the EEI, the current study proposes a SDM for linking anthropogenic activities taking place in the Athens Metropolitan Area with the ecological status of the Inner Saronikos Gulf. GES is clearly connected to sustainability. The preservation of GES ensures the provision of the main ecosystem services to the urban population, such as fisheries, recreation, waste assimilation capacity and other cultural amenities. In addition, the concept of GES reflects an operational policy objective that is accepted by coastal experts within the context of interdisciplinary consideration of ESD (Mavrommati and Bithas, 2013; Mavrommati and Richardson, 2012). The methodological contribution of the paper is the integration of sub-models inspired by different disciplines (hydrology, biology, economics) into a simple and operational model that serves the aspirations of sustainability science and addressing the needs of decision makers.