Achieving a Jobs-Housing balance in the Paris region - the potential of reducing car trafic

Many experts believe that the uninterrupted lengthening of trip distances, and especially trip-to-work distances, is carried mostly by urban sprawl combined to growing functional (economic functions/residential functions) and social (high-class residential areas/low-class residential areas) specialization of urban space. According to them, these three dynamics (urban sprawl - functional specialization - social specialization) drag along quantitative and qualitative spatial imbalances between economic and residential functions and these spatial imbalances contribute to widen the distance separating workers' homes and job places, and hence, to lenghten the trips-to-work. On the basis of this diagnosis, the re-establishement of a greater balance, on both quantitative and qualitative grounds, between jobs and housing in different areas of the city is currently emerging as a major issue regarding the car-traffic reducing goal. Making the assumption that the multiplication of long-distance trips occurs as a consequence of greater difficulties encountered by households searching decent housing nearby workplaces, many experts argue that efficient urban policies promoting a diversified housing supply nearby job centres would allow more reasonable commuting distances and that such a return should go forth with a reduction in car traffic. In this paper, through a simulation model based on re-assignment of households closer to their workplaces, we examine the potential of car traffic reduction in the case of the Paris region. More precisely the impact of jobs-housing balance policy is based on a simulation model which states assignment of households located far from their work place within zones located nearer to the work place. The households that are reassigned are those where all workers travel more than a given time-threshold to reach their work place. These households are relocated within a perimeter around either the work place of the head of the household if it is a one worker household or the work place of the female worker if it is a two worker household - this perimeter is defined with reference to a time-threshold (set to 20, 30 or 45 minutes by private car or by public transport). For each type of household (defined according to social status, number of workers and family profile), the type of housing demanded by reassigned households is derived from the structure of housing detained by households that are already located within the perimeter of re-assignment. Three analyses are conducted on the basis of this simulation. According to the different time-thresholds : first, we estimate the total distances saved on home-work trips by private car when households are reassigned. Second, we identify the characteristics of reassigned households (especially social status, number of workers, family profile, residential location, job location, etc.). Third, we estimate the housing offer/demand imbalance after re-assignment (with specific interest for the case of housing for low-income groups).

Trophic consequences of an invasive, small-bodied non-native fish, sunbleak Leucaspius delineatus, for native pond fishes

Assessments of the trophic consequences of invasive fishes are important for quantifying their ecological impacts on native species more generally. A small-bodied cyprinid fish native to continental Europe and introduced in the 1970s to the U.K, the sunbleak Leuciscus delineatus, has been shown previously to establish closer social associations with native species of similar size than do native species amongst themselves. To assess the potential detrimental trophic consequences of native species associations with L. delineatus, a field-based experiment was undertaken in summer 2015 in six outdoor, artificial ponds containing three native cyprinid species (rudd Scardinius erthrophthalamus, gudgeon Gobio gobio, tench Tinca tinca). Three ponds were controls (no L. delineatus) and three were treatments (L. delineatus present). The results of stable isotope analysis (SIA) of fish tissue samples provided strong evidence that the isotopic niches of both native benthic fishes were reduced in the presence of L. delineatus, although there were no significant effects on the trophic position, body size or condition of two of the three native fish species. Introduced L. delineatus maintained a core isotopic niche that was distinct from the two native benthic fishes, with no overlap detected between native and non-native fishes when including 40 % and 95% of the data. These results indicate that the response of the native fishes to the introduction of L. delineatus was niche constriction via trophic specialisation, with this response sufficient to maintain their growth rates and condition. This result is similar to studies on a range of small-bodied invasive fishes, suggesting the trophic impacts of these invaders are relatively consistent across species and systems

Tolerance to commuting in urban household location choice: evidence from the Paris metropolitan area

International audienceMany social scientists consider improvements in urban travel facilities during the last decades of the 20th century to have significantly weakened proximity constraints, and therefore think that home-workplace proximity is no longer a major factor in household location choice. They believe that better transport conditions give households more freedom in selecting their homes and workplaces, regardless of the distance separating these two locations. We argue that this point of view underestimates the costs of daily commuting (which remains an increasing function of trip length) and consequently overestimates households' tolerance to commuting. The aim of our research is to measure how much weight households give to home-workplace proximity in actual location choices. Using survey data from the Paris-Ile-de-France metropolitan area, we carry out analyses to estimate two values: (i) the share of home and workplace changes (observed between 1991-2002) which either bring home and workplace closer to each other or keep these two places close to each other, and (ii) the "life expectancy" of job-residence combinations imposing long-distance commutes

La ville du quart d'heure : plus proche, plus lente, plus forte ? Estimation de la valeur d'une devise urbaine

Si par ville des proximités, il faut entendre une organisation urbaine où tout citadin trouve tout ce dont il a besoin pour vivre bien à l'intérieur d'un périmètre de proximité autour de son domicile, dans un rayon praticable à pied ou à vélo, le chantier semble immense à un point tel que les croyants peuvent passer pour des utopistes sans grand sens pratique. On propose ici d'examiner succinctement ces points de tension

Construire de la mixité sociale en construisant des logements sociaux ? Un bilan dans les métropoles de Paris, Lyon et Marseille

International audienceEn mobilisant les données du Recensement de la Population 2008 de l’INSEE, nous avons évalué la contribution des logements sociaux récents (construits entre 1999 et 2008) à la mixité sociale dans les trois grands métropoles français. Les résultats montrent que ces nouveaux logements sociaux dans les aires urbaines de Paris, Lyon et Marseille ont globalement produit un impact favorable à la mixité sociale mais cet effet est très modeste. Dans l’ensemble, ces logements ont augmenté la cohabitation entre tous les groupes sociaux mais de manière marginale – de l’ordre de 1%-1,5%. Pratiquement une décennie de construction de logements sociaux a donc induit un très petit supplément de mixité sociale.Cet impact limité est d’abord une conséquence de la faible quantité de logements sociaux produits sur la période. Mais il semble, au regard de nos résultats, qu’il y avait de la marge pour obtenir un effet plus important. L’évaluation au niveau micro montre que, selon les cas, une part oscillant entre 40% et 50% des logements sociaux récents ont affaibli le degré de cohabitation entre groupes sociaux. En optimisant la combinaison localisation-occupation des logements sociaux récents, il était donc possible d’augmenter l’impact de ces derniers sur la mixité sociale

Champs des possibles résidentiels: Histoires drôles et sérieuses de déménagement

Il s'agit d'un livre rédigé par l'auteur à partir d'une recherche originale et mis en ligne en accès libre.Peu d’expériences de la vie quotidienne sont aussi communes que la prospection d’un logement : toute personne ou presque se trouve, un jour ou l’autre, en situation de chercher un nouveau chez-soi et de déménager dans la foulée. Quel est le champ des possibles résidentiels qui s’ouvre devant les prospectants lorsqu’ils se lancent dans la prospection, et quel est le degré d’ouverture de ce champ, c’est-à-dire la variété des options qu’il contient en termes de géographie, de régime d’occupation (achat/location) ou encore de genre de logement (maison/appartement, par exemple) ? Cet ouvrage restitue une enquête de terrain, elle-même exercice de prospection, à la recherche d’une réponse à cette question. Trente personnes habitantes de la grande métropole parisienne ont procédé, dans le cadre d’entretiens avec l’auteur, à une rétrospective de leurs expériences de prospection, autant d’"histoires drôles et sérieuses de déménagement", revenant au passage sur les options qu’ils ont envisagées comme des "possibles" dans le déroulement de la prospection. Ce matériau, outre le fait d’alimenter en éléments empiriques la réflexion sur le degré d’ouverture des champs des possibles résidentiels, a donné matière à ce qu’on pourrait appeler une sociologie de la prospection de logement

Les nouvelles frontières des inégalités

International audienceno abstrac

Building social mix by building social housing ? An evaluation in Paris, Lyon and Marseille metropolitan areas

International audienc

Pauvreté et territoires : La diversité des situations régionales en France

The poor in places of poverty in France The poverty issue in France is back at the forefront of the public scene after a century of social policies. Unskilled young people, homeless individuals and non-European Union immigrants are increasingly becoming the new poverty-stricken characters. Degraded cities, abandoned industrial zones and depopulated country towns are just the visible manifestations of widespread precarity that is challenging the selective mechanisms of urban production.L'ajout de critères culturels aux éléments matériels de définition de la pauvreté accroît la difficulté de sa quantification. Le niveau de pauvreté s'avère moins sensible aux variations du marché de l'emploi qu'à celles du développement économique régional du fait des transferts sociaux dont bénéficient des retraités à la recherche de localisations attrayantes. Plus l'échelle d'observation s'affine aux localités, plus s'affirme le lien entre pauvreté et pression sur le marché du logement.Korsu Emre. Pauvreté et territoires : La diversité des situations régionales en France. In: Les Annales de la recherche urbaine, N°93, 2003. Les infortunes de l’espace. pp. 33-47