شاخص تناسب اراضی برای ارزیابی زیست محیطی استراتژیک در مناطق شهری

This paper presents the Land Suitability Index (LSI), a transparent, modular hierarchical system of cartographic indices aimed at delivering Strategic Environmental Assessment (SEA) of developmental land uses for regional planning (European Directive 2001/42/EC). The LSI evaluates land suitability by combining three main sub-indices concerning (i) the vulnerability of the biosphere, lithosphere, and hydrosphere to impacts arising from implementing development proposals; (ii) the natural heritage value of the target area; and (iii) its contribution to terrestrial ecological connectivity. We have used the LSI to evaluate the impact of municipal urban plans in the Barcelona Metropolitan Region (BMR). For this case study, we provide redundancy and sensitivity analyses, and a partial validation using independent studies. Results showed noticeable inconsistencies between the municipal plans and the values of the LSI and its main sub-indices. There was moderate redundancy between sub-indices but considerable sensitivity to changes in input variables. Validation showed a high degree of coincidence with previous, independent, studies as regards connectivity. The quantitative and cartographic approach adopted by the methodology facilitates conveying the results to planners and policy makers. In addition, successive iterations to check the impact related to different alternative planning scenarios can be quickly performed. We therefore propose its application to other metropolitan areas.

Land suitability assessment is the process which determines the fitness of a given tract of land for a defined use (Steiner et al., 2000), usually among multiple, competing uses. Initially, this tool was developed as a means for planners to provide a more holistic view of the target environment from a set of spatially independent factors. Land suitability assessment is a context-dependent, multi-criteria evaluation of land capacity for development, based on the opinion of experts who define the most desirable factors and their optimal values and weights for this purpose (Jiang and Eastman, 2000 and Stoms et al., 2002). Since McHarg (1969), land suitability assessment has become a standard practice in land use planning. The wide acceptance of GIS applications has permitted the development of spatially explicit approaches based on mapping parameters characterizing the land surface (Fabos et al., 1978). However, such approaches have not provided significant advances in perhaps the most important constraint of these methods: the lack of standard methodologies. In particular, the difficulties concern the choice and conceptual definition of indicators and of the mathematical model of which they form part (Andrearsen et al., 2001). The application of the European Directive 2001/42/EC on Strategic Environmental Assessment (SEA) to land use and regional planning is facing serious challenges. One of the main difficulties of applying SEA is that many regional plans frequently fail to take proper account of environmental factors. Thus it is difficult to assess the land suitability, and to compare the impacts associated to different alternatives (Sadler and Verheem, 1996, Partidário and Clark, 2000 and Bonde and Cherp, 2000). Quantitative socio-environmental indices, already in use for aquatic systems (Paul, 2003), may be a good option to assess the impact on land of diverse alternative plans, with the aim of more sucessfully integrating sustainability factors in the new generation of land use plans. There have been various attempts to establish regional parameters to provide planning tools (Ramos et al., 2000 and Lugeri et al., 2000). Most of these methods are based on mapping parameters characterizing the land surface. But the development of these cartographic indices is not trivial: land is a complex system resulting from the interaction of physical, biological, and anthropological phenomena operating over different scales of time and space (O’Neill, 1989). Landscape ecological theory has provided a working scale and a set of quantitative tools (namely landscape indices or metrics) to characterize landscapes (Turner and Ruscher, 1988 and Li, 2000) and to measure a region's landscape change through time (Reed et al., 1996). It is widely accepted that a general association exists between landscape pattern and ecological processes (Forman, 1995 and Tischendorf, 2001). However, concepts and methods of landscape ecology also are useful for land planning and design (Nassauer, 1999 and Corry and Nassauer, 2005). Indices might be a way to evaluate the consequences offered by a given plan in relation to a current scenario (Opdam et al., 2001), or they could be used to evaluate alternative plans for a particular landscape (Gustafson, 1998). In either case, they are evaluative tools for regional planning (Botequilha and Ahen, 2002). This paper proposes a Land Suitability Index (LSI) for SEA incorporating some of these concepts inherited from landscape ecology and from general ecological theory as well. This is a complex, multimetric index which tries to describe nature as the heterogeneous, dynamic, multi-scale, hierarchically organized reality suggested by Margalef (1997), and to summarise its main structural, functional, and hierarchical features. In keeping with this hypothesis, we present the index as a tool for conducting SEA in metropolitan areas, focusing on the region of Barcelona. We justify the incorporation of a new index to the battery of parametric methodologies known at international level as there is a need for objective criteria (i) when deciding the geographic situation of a specific territorial intervention, and (ii) when determining the quantitative effect associated to different alternatives in the course of evaluation.

The LSI constitutes a holistic index for SEA that makes an assessment of the suitability for land development for a given area. It is formally integrated in mathematical language, developed through GIS, and based on a hierarchical, modular structure incorporating the impacts of plans on biological, geological and hydric resilience (TVI), natural heritage (NHI), and ecological connectivity (ECI). The applications of the method to date have shown it to be highly effective and – more importantly – demonstrated the ease with which its underlying concepts and application can be grasped by planners, who are its main end-users (Marull, 2005). The quantitative and cartographic language, developed through GIS, employed by the LSI, facilitates conveying results to planners and policy makers. A further advantage is that it is straightforward to carry out the successive iterations needed to assess the environmental impacts of different alternatives of planning and corrective measures. Planners and designers should be cautious in making ecological inferences from land index values applied to alternative plans. In this context, our methodology is open for debate. The precautionary principle indicates that a lack of precise scientific data on some key features of the biosphere, lithosphere and hydrosphere cannot prevent the adoption of planning measures to counteract unsustainable development. One can envisage more environmentally appropriate planning in the future as new, more comprehensive and reliable data become available to the public and policymakers to increase general awareness and, thus, a more informed and conscious public participation.