El impacto del policentrismo sobre el consumo de suelo y la movilidad laboral. Un estudio comparado para las 7 principales áreas metropolitanas españolas

Abstract

The spatial distribution of population and employment is an important issue in contemporary metropolises, especially when facing the expansion and the unstructured urban growth, which involve a high risk of damage to the environment. Within this frame, new policies, especially the European ones, have promoted a polycentric development as an alternative model to the dispersion, as it theoretically leads to cohesion, competitiveness and sustainability. The research problem arises as a response to this new metropolitan dimension of sustainability, and in particular, to this new polycentric structure, which makes imperative to evaluate its characteristics, evolution and influence on the general urbanization process. Two main hypotheses have been considered in the research: 1) Polycentric systems are potentially sustainable, from an environmental perspective, by generating more compact territories reducing the consumption of the land. 2) In addition, a polycentric urban structure is expected to offer more job opportunities throughout the territory, which would impact labor mobility (displacements between home and work, named, as commuting), in such a manner that, the more significant the decentralized urban-concentration (polycentrism), the shorter the distance from residence to work. The main objective of this doctoral thesis is to evaluate, through both theoretical and empirical analysis, in which extent the polycentric systems make urbanization efficient, in terms of reducing and shortening commuting, as well as minimizing the consumption of the land (inverse of the urban density), one of the scarcest resources within our cities. The methodology used in the empirical analysis is divided into: 1) characterization of the urban structure, by determining the limits of the metropolitan systems and detection and identification of the structuring elements: subcenters and center; 2) characterization of the concept of polycentrism, under the approaches, morphological of the polinucleation and, functional of the polycentricity; 3) characterization of the land use (inverse of the urban density) from the territorial, economic and urban point of view; 4) characterization of labor mobility, through the analysis of certain indicators such as the excess of mobility or the distances covered by workers from home to work; and 5) finally, linear regression analysis was used to first of all study the relationship between polynuclear urban structure and land consumption, and secondly, the relationship between polycentrism and the reduction of labor mobility. First, the impact of polycentrism on the increase of urban density in subcenters shows that beyond subcenters itself, the impact is no longer significant, and suggests that there are other territorial factors that have a greater explanatory power, such as is the case of the fragmentation of urbanized fabrics. Therefore, the question is whether polycentric developments promoted by territorial planning policies have such environmental advantages. To close, the results concerning the impact of the subcenters on the reduction of labor mobility reflect that not only the proximity to the subcentres makes the mobility more efficient, but other factors also contribute to the reduction of commuting distance, as is the diversity of the housing supply. On the contrary, there are other variables that increase the patterns of metropolitan mobility, such as transport infrastructure (private and public) or employment/housing ratio, especially the relationship within industrial estates.