From sprawl to compactness and back: population dynamics (1848–2011) and the economic structure of a Mediterranean city

In the recent decades southern European cities experienced morphological changes and a demographic transition towards zero (or negative) growth and aging. Population dynamics shifted from the impressive growth of the post-industrial period into recent de-concentration processes determining the spillover of commercial and residential settlements across the surrounding rural areas. Based on long-term demographic data, the present study hypothesizes that urban expansion did not follow a one-way linear path from compactness to dispersion while reflecting differentiated growth patterns based on the specific socioeconomic context at the local scale. Along a sufficiently long time period non-linear expansion waves alternating settlement densification and scattering are expected to be found especially in complex urban contexts such as those developed in the Mediterranean region. This hypothesis was tested for a paradigmatic case study in southern Europe (Athens, Greece) using demographic data covering 160 years (1848–2011). Urban growth in Athens was assessed through the analysis of long-term census data made available on a district level. These data provide information on the spatial distribution of resident population and characterize distinct expansion waves according to the dominant socioeconomic context. Results of the study were discussed in the light of the debate on future development of the Mediterranean cities and the (changing) economic relations with the surrounding region.     

On the expansion of supernova shells

We have investigated a simple model for the effects of a central pulsar on the expansion of supernova shells. Some numerical results relevant to the Crab Nebula are also reported.     

Amplifying (or Reversing) the Territorial Disparities in Land Vulnerability to Soil Degradation: The Case of Italy

This article analyzes the territorial disparities in the level of land vulnerability (TDLV) to soil degradation caused by five processes (soil erosion, salinization, sealing, contamination, and compaction) as well as by climate variations in Italy in 1990 and 2000. The analysis reveals, for each soil degradation process, a typical spatial distribution across Italy. Three processes (soil salinization, compaction, and sealing) contribute significantly to the increase in land vulnerability, which is mainly concentrated in risky areas. The observed disparities highlight a growing environmental divide between northern Italy (an economically developed region, not at risk of desertification) and southern Italy and the two main islands (dry, disadvantaged regions at risk of desertification). The knowledge of such a territorial divide and of the underlying soil degradation processes is regarded as important for environmental policies at the country and regional scales aimed at sustaining the economic and socioenvironmental cohesion between areas that are either vulnerable or nonvulnerable to soil degradation. The proposed approach should be seen as part of a decision-making tool informing policies and supporting the design of management solutions, hopefully reversing disparities in land vulnerability to soil degradation.     

Population distribution and urban growth in Southern Italy, 1871–2011: emergent polycentrism or path-dependent monocentricity?

This study assesses changes in population distribution and the expansion of urban settlements in Southern Italy between 1871 and 2011. Four demographic phases are identified: (i) spatially balanced, mild population growth (1871–1921); (ii) moderate population increase concentrated in coastal and lowland areas (1921–1951); (iii) rapid and diffused population growth (1951–1981); and (iv) population stability with settlement dispersion (1981–2011). While urban growth in the years preceding the 1980s reinforced the polarization in rich and poor areas along the urban-to-rural gradient, since the early 1990s both urban and rural areas showed population dynamics that consolidated low-density settlements scattered around the largest cities. This path, however, does not reflect the evolution towards a more spatially balanced urban development, as observed in other European regions. Causes and consequences of the persistence of a fragmented urban hierarchy with dense settlements and sprawl concentrated around the main cities are finally discussed.     

An approximate analytical representation of the atmospheric gamma-ray flux at balloon altitudes

The general behaviour of the atmospheric -ray flux as a function of the residual atmosphere, zenith angle, and photon energy is approximated with simple analytical expressions. The free parameters are determined by comparison with the most recent models and the existing experimental measurements. The resulting formulae have an accuracy comparable to the mutual consistency of the available pieces of information, and at the same time are very convenient to use in numerical simulations.     

Long-term growth and metropolitan spatial structures: an analysis of factors influencing urban patch size under different economic cycles

Urban forms are increasingly reflective of socio-economic change in metropolitan regions. The present study illustrates an original approach to identify latent mechanisms of urban growth through the analysis of metropolitan spatial structures and their proximate drivers of change. Urban transformations are evaluated here using built-up patches as the elementary analysis unit and background socio-economic attributes at four stages of the “city life cycle” (urbanization, suburbanization, dis-urbanization, re-urbanization). Regression models based on 13 indicators assessing urban patch area and shape, nearest neighbour urban patch area and shape, elevation, distance from 5 urban centres, 2 road infrastructures and sea coastline, were run with the aim to investigate direction and intensity of metropolitan growth in post-war Athens (1948–2012), a southern European city shifting from a compact mono-centric form towards discontinuous urban structures. Mono-centric configurations were characterized by linear dependence of urban patch size from the distance to central cities. Shifts toward scattered urban forms were associated with changes in the multivariate relationship between urban patch size and territorial drivers, pointing out the increased complexity of dispersed metropolitan structures. Our approach integrates economic and ecological visions of urban landscapes and contributes to understanding long-term mechanisms of metropolitan growth under dynamic spatial equilibriums. Investigating the multiple relationships between form and functions at the base of socio-economic transformations are relevant issues when identifying and profiling urbanization cycles.     

Latent Exurban Development: City Expansion Along the Rural-To-Urban Gradient in Growing and Declining Regions of Southern Europe

This paper quantifies the extent of exurban development in Mediterranean Europe. The assessment was carried out by studying changes in the urban-to-rural population density gradient between the years 1950 and 2010. Three of the six urban regions in this study have experienced population growth and moderate urban concentration, while two regions appear to be shifting toward population decline and urban de-concentration after having experienced compact expansion. A phase of recent re-urbanization has been observed in one region. Altogether, these findings indicate a common path of urban expansion among representative Mediterranean regions between 1950 and 1980 while, in the following period, the cities experienced distinct development phases. From this study, we conclude that exurban development is mainly the product of a shift from compact and dense to semi-compact and intermediate-density settlements. [Key words: semi-dense urban growth, density-distance curve, Mediterranean Europe].     

Not only tourism: unravelling suburbanization,second-home expansion and “rural” sprawl in Catalonia,Spain

This study illustrates multifaceted urbanization patterns and processes in a coastal region of Catalonia (northeastern Spain) as a paradigmatic example of the socio-economic transformations typically observed in the northern Mediterranean basin since World War II. By focusing on the expanding tourism industry, second-home expansion, infrastructural development and sprawl around traditional rural centres, the paper assesses the effects of long-term economic, demographic, social and cultural transformations on rural landscapes in Alt Empordà, the so-called “Catalan Tuscany”. The stratification of distinct urbanization waves and the underlying socio-economic processes observed in Alt Empordà reflect population dynamics and settlement morphologies typical of rural districts moving rapidly towards a suburban spatial organization. Recent urban dynamics in Mediterranean rural systems deserve further investigation in order to shed light on latent suburbanization processes involving marginal European regions.