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One of the most important challenges in defining and understanding a landscape is choosing an appropriate conceptual model that is consistent with the stated objectives and that can identify its structure and represent different perspectives regarding its heterogeneity and complexity. According to an ecological perspective, Forman and Godron (1986) define landscape as a heterogeneous land area composed of a cluster of interacting ecosystems that is repeated in similar form. Turner, Gardner and O’Neill (2001) define landscape as an area that is spatially heterogeneous in terms of at least one factor of interest. The European Landscape Convention (Council of Europe, 2000) has radically shifted the concept of landscape towards a systemic view in which the whole is more than the sum of its parts, thus moving away from reductionist thinking that tends to overestimate the importance of the parts to the detriment of the system (Capra, 1996). Landscape is thus considered a system characterized not only by its ecological components but also by its social, economic, cultural, morphologic, and urban ones (Bartel, 2000). Over the past years many international programs have sought to inventory and assess landscapes and to monitor their variations (Swanwick, 2002; Vervloet & Spek, 2003; Pinto-Correia, Cancela d’Abreu & Oliveira, 2004; Wrbka, Erb, Schulz, Peterseil, Hahn & Haberl, 2004; Mücher, Wascher, Klijn, Koomen & Jongman, 2006; van Eetvelde & Antrop, 2009a), taking into account that many changes in the traditional concept of landscape are related to urbanisation, transport, recreation, tourism, etc. New uses define new landscapes and identify new values. In many cases, landscape values depend on heterogeneity relating to biodiversity, cultural heritage and human appreciation (Dramstad, Tveit, Fjellstad & Fry, 2006). Consistent with the European Landscape Convention, landscape character is defined as a distinct and recognizable pattern of elements that makes one landscape different from another and renders a given area unique (Swanwick, 2002; 2004). Increasing need for landscape inventorying, assessment, and monitoring also requires indicators that can help evaluate the impact of policy measures and their effect on landscape change (Parris, 2004), and that can also be applied to the sustainable conservation and protection of natural and cultural capital, spatial planning, and landscape management (Selman, 2006).
In our study on the urban landscape, particular importance is placed on the component of the so-called “third landscape” conceived as fragmentary and uncertain green areas included in the urban fabric due mostly to the decommissioning of human activities (Clement, 2004). The fragmentation of green areas is a result of the city’s exponential growth and sprawl and is also one of the most important factors contributing to the loss of biodiversity (Zeng & Ben Wu, 2005; Llausàs & Nogué, 2011). In this sense, this paper also seeks to focus on the study of fragmentation generated by human processes having important impacts on a territorial context. In relation to the case study presented in the paper’s following sections, such processes basically consist of the construction of buildings and infrastructure which interrupt ecological exchanges between urban ecosystems generating a series of problems such as: increasing isolation of patches in which the landscape system can be divided, the reduction of their original size and their increasing exposure to external disturbances like highways and railways (Geneletti, 2003). In order to study fragmentation, it is necessary to define a set of indicators deriving from the patches’ specific metrics and which, understood within a given time frame, could contribute significantly to understanding the landscape’s future tendencies (Geneletti, 2011; Scolozzi & Geneletti, 2012).