Scaling evidence of the homothetic nature of cities

E-print/Working paper (2017)

In this paper we analyse the profile of land use and population density with respect to the distance to the city centre for the European city. In addition to providing the radial population density and ... [more ▼]

In this paper we analyse the profile of land use and population density with respect to the distance to the city centre for the European city. In addition to providing the radial population density and soil-sealing profiles for a large set of cities, we demonstrate a remarkable constancy of the profiles across city size. Our analysis combines the GMES/Copernicus Urban Atlas 2006 land use database at 5m resolu- tion for 300 European cities with more than 100.000 inhabitants and the Geostat population grid at 1km resolution. Population is allocated proportionally to surface and weighted by soil sealing and density classes of the Urban Atlas. We analyse the profile of each artificial land use and population with distance to the town hall. In line with earlier literature, we confirm the strong monocentricity of the European city and the negative exponential curve for population density. Moreover, we find that land use curves, in particular the share of housing and roads, scale along the two horizontal dimensions with the square root of city population, while population curves scale in three dimensions with the cubic root of city population. In short, European cities of different sizes are homothetic in terms of land use and population density. While earlier literature documented the scaling of average densities (total surface and population) with city size, we document the scaling of the whole radial distance profile with city size, thus liaising intra-urban radial analysis and systems of cities. In addition to providing a new empirical view of the European city, our scaling offers a set of practical and coherent definitions of a city, independent of its population, from which we can re-question urban scaling laws and Zipf’s law for cities. [less ▲]

Equilibrium and first-best city with endogenous exposure to local air pollution from traffic

in Regional Science and Urban Economics (2017), 62

Exposure to urban traffic-induced air pollution is a major health concern of cities. This paper analyzes the urban structure when localized pollution exposure arises from commuting traffic and ... [more ▼]

Exposure to urban traffic-induced air pollution is a major health concern of cities. This paper analyzes the urban structure when localized pollution exposure arises from commuting traffic and investigates the feedback effect of endogenous pollution on residential choices. The presence of stronger traffic-induced air pollution exposure reduces the geographical extent and the population of cities. Land rents fall with distance from the city center while population densities may be non-monotonic. Cleaner vehicle technologies reduce pollution exposure everywhere, increase population and density everywhere and do not affect the spatial extent of the city. The paper compares the urban equilibrium with the first-best. The first-best structure is a less expanded city with higher densities at the center and lower densities at the fringe. [less ▲]

Bee Species Richness in Europe

Cartographic material (2017)

This map portfolio compares maps of bee species richness in Europe automatically aggregated per country from the IUCN Red List with national numbers obtained from various other sources.

An agent-based model to simulate the feedback effect between traffic-induced air pollution and urban structure

Scientific Conference (2016, September 22)

A spatial complexity currently of increasing concern is the relation between the internal structure of urban areas and traffic‐induced air pollution. Urban air pollution has severe impacts on the ... [more ▼]

A spatial complexity currently of increasing concern is the relation between the internal structure of urban areas and traffic‐induced air pollution. Urban air pollution has severe impacts on the environment and on human health with traffic being its major source. Air pollution from traffic varies locally within the city depending on traffic patterns that arise from the spatial arrangement of land uses and subsequent travel demand across time. In this paper, we contribute a dynamic agent‐based residential model (ABM) applied to 2D theoretical space based on micro‐economic principles with local exposure and pollution externalities arising from car commuting traffic and an endogenous road network. We analyse the effects of households’ aversion to generating and being exposed to local traffic pollution on emerging land use patterns and pollution distribution. The focus is thereby set on endogenising local health but also global environmental concerns of traffic‐induced air pollution in location choice. The ABM framework allows discussing the spatial interactions against the background of pollution‐related (e.g., pollutant diffusion, cold‐start emissions, additional emissions through traffic congestion) and preference‐related (e.g., exposure during the commute versus at the residential location, size of the impact neighbourhood) framework conditions and planning approaches (localized lump‐sum taxes, cordon tolls, flat taxes). We discuss the stability and performance criteria of the resulting cities, which are on the one hand city aggregates (e.g., total emissions, total exposure, spatial extent of the urban area), but on the other hand and more importantly location‐dependent disaggregates (local patterns of land rents, exposure, green spaces, design of the road network). Thus, our paper interlinks pollution‐related concerns and urban structures from a health and environmental perspective, which take place at different spatial scales (different radii of interaction) and thereby ties in with the compaction‐sprawl debate in the literature. [less ▲]

Land use and density in the European city: monocentric analysis and scaling

Scientific Conference (2016, August)

In this work we study the evolution of land use and population density in European cities with respect to the distance to the city centre, and how land use and density curves scale with city population ... [more ▼]

In this work we study the evolution of land use and population density in European cities with respect to the distance to the city centre, and how land use and density curves scale with city population. The principal aim of this research is to provide stylized facts and generic formulas for the calibration of monocentric urban economic models to European cities. We use the GMES Urban Atlas database, providing a precise description of land use in the 305 major European larger urban zones (LUZ), which have more than 100.000 inhabitants. For the population density we use the Geostat population grid, which covers the whole of European Union (EU) with a 1km$^2$ grid dataset. We combine the land use and population datasets by attributing the population of the Geostat grid to the geographic units of the (much more precise) land use dataset. This attribution is proportional to the surface of each unit and weighted thanks to the nomenclature of the GMES Urban Atlas, which gives classes of soil sealing and density of urban fabric. Then we analyse the evolution with distance to the city centre, which we define for convenience as the location of the city hall, of population density and of the share of land used for different purposes: housing, roads, railways, urban green, water, agriculture, forest. To this end, we define concentric rings of fixed width around the city centre, in which we average land use and population. In order to compare results between different cities and to obtain a global picture ("average" or "standard" European city), we study simple scaling relationships for the obtained monocentric land use shares and density curves. We choose to study the scaling of these curves with respect to the city population, as has been done in the literature for different parameters (like income or road space). In our case city population is taken as the population of the LUZ, computed thanks to the population grid. It turns out that land use curves, in particular housing or roads shares, tend to scale like the square root of city population. Population curves have roughly exponential shapes, as widely modelled in the literature, and tend to scale like the city population to a power close to $1/3$. These results allow us to propose a simple monocentric description of land use shares and population curves in a representative European city, whose size can be chosen based on the scaling relationships we obtain. This result is especially interesting, and of practical use, for the purpose of calibration of monocentric urban models. [less ▲]

Land use and density in the European city: monocentric analysis and scaling

Scientific Conference (2016, July)

Land use and density in the European city: monocentric analysis and scaling

Scientific Conference (2016, May)

In this work we study the profile of land use and population density in European cities with respect to the distance to the city centre. More specifically we address the scaling of land use and density ... [more ▼]

In this work we study the profile of land use and population density in European cities with respect to the distance to the city centre. More specifically we address the scaling of land use and density curves with respect to city population and rely on fine grained land use data. Our main objective is to retrieve generic laws that can support the calibration of monocentric urban economic models for European cities. We use the GMES Urban Atlas database, providing a precise description of land use at 5m resolution in the 305 major European urban areas (more than 100.000 inhabitants). We combine this dataset with population density from the Geostat population grid, which covers the whole of European Union (EU) with a 1km2 resolution. Population is allocated proportionally to surface and weighted by soil sealing and density classes of the GMES data. We analyse the evolution with distance to the city centre, which we define for convenience as the location of the city hall, of population density and of the share of land used for different purposes: housing, roads, railways, urban green, water, agriculture, forest. To this end, we define concentric rings of fixed width around the city centre, in which we average each land use and population. In order to compare different cities and to identify a global picture, i.e. a standard representative European city, we study scaling relationships for the ob- tained monocentric land use shares and density curves. We analyse the scaling of these curves with respect to city population, following similar approaches con- ducted in the literature for different parameters (such as income or road space). The total population for each city is computed from the population grid. We find that land use curves, in particular housing and roads shares, tend to scale like the square root of city population. Population curves have roughly exponential shapes, as it has been widely modelled in the literature, although usually not based on land use and soil sealing data. Population curves tend to scale like the city population to a power close to 1/3. These results allow us to propose a simple monocentric description of land use shares and population curves in a representative European city, whose size can be chosen based on the scaling relationships we obtain. This result is especially interesting, and of practical use, for the purpose of calibration and validation of monocentric urban models, that can differentiate (or not) housing from land and include interactions between non-developed and developed land. [less ▲]

Formes Urbaines et Aménités Vertes

Conference given outside the academic context (2016)

Les Parcs naturels dans la Grande Région SaarLorLux

E-print/Working paper (2016)

The nature parks are essentially rural areas, relatively extensive, whose landscapes, shaped mainly by traditional agricultural activities, have characteristics and aesthetic qualities favourable to the ... [more ▼]

The nature parks are essentially rural areas, relatively extensive, whose landscapes, shaped mainly by traditional agricultural activities, have characteristics and aesthetic qualities favourable to the reception and development of leisure activities and green tourism. Relatively far from the major urban areas, the landscapes have undergone little transformation under the influence of suburbanisation. The nature parks were set up at different times, within an institutional framework and with objectives that differed significantly depending on the legislation in force in the four countries; the emphasis was initially placed on nature protection, but from the 1990s onwards, sustainable local development became increasingly important. [less ▲]

Possessions en prêt au Haut Moyen Âge des Abbayes de Gorze et Wissembourg, de 661 à environ 860

E-print/Working paper (2016)

In the medieval world, the abbey had multiple meanings. On the one hand, it was a place of spiritual life where the abbey community lived, prayed and worked according to the strict ideals of the rule. The ... [more ▼]

In the medieval world, the abbey had multiple meanings. On the one hand, it was a place of spiritual life where the abbey community lived, prayed and worked according to the strict ideals of the rule. The schools, libraries and scriptoriums in which manuscripts were copied and partially decorated, also made it a centre of learning and the spread of knowledge. On the other hand, the abbeys were one of the largest landowners in the Middle Ages and their abbots were not only the superiors of religious communities but also the directors of large economic centres. The endowments for their foundation and donations from royalty or nobility provided the abbeys with considerable property. These assets were by no means a coherent mass in the vicinity of the abbey, but were rather scattered over long distances. The abbeys of Wissembourg and Gorze, through the cartularies that have come down to us, lend themselves to a more precise examination of the abbeys' economy. [less ▲]