Urban population density functions : the case of the Barcelona region

L'anàlisi de la densitat urbana és utilitzada per examinar la distribució espacial de la població dins de les àrees urbanes, i és força útil per planificar els serveis públics. En aquest article, s'estudien setze formes funcionals clàssiques de la relació existent entre la densitat i la distancia en la regió metropolitana de Barcelona i els seus onze subcentres.

Cubic spline population density functions and subcentre delimitation. The case of Barcelona

The presence of subcentres cannot be captured by an exponential function. Cubic spline functions seem more appropriate to depict the polycentricity pattern of modern urban systems. Using data from Barcelona Metropolitan Region, two possible population subcentre delimitation procedures are discussed. One, taking an estimated derivative equal to zero, the other, a density gradient equal to zero. It is argued that, in using a cubic spline function, a delimitation strategy based on derivatives is more appropriate than one based on gradients because the estimated density can be negative in sections with very low densities and few observations, leading to sudden changes in estimated gradients. It is also argued that using as a criteria for subcentre delimitation a second derivative with value zero allow us to capture a more restricted subcentre area than using as a criteria a first derivative zero. This methodology can also be used for intermediate ring delimitation.

Chaos and order in the contemporary city. The impact of urban spatial structure on population density and commuting distance in Barcelona, 1986-2001.

One of the criticisms leveled at the model of dispersed city found all over the world is its unarticulated, random, and undifferentiated nature. To check this idea in the Barcelona Metropolitan Region, we estimated the impact of the urban spatial structure (CBD, subcenters and transportation infrastructures) over the population density and commuting distance. The results are unfavorable to the hypothesis of the increasing destructuring of cities given that the explanatory capacity of both functions improves over time, both when other control variables are not included and when they are included.

Un nuevo problema en espacios verdes urbanos: el pulgón Myzocallis (Lineomyzocallis) walshii (Hemiptera: Aphididae) y el roble americano (Quercus rubra)

Myzocallis (Lineomyzocallis) walshii (Monell) es un pulgón nativo del este de Nor- teamérica que se detectó por primera vez en España en 1995 y cuyo principal huésped es el roble americano (Quercus rubra L.). Los robles americanos se emplean como árbol ornamental en ambientes urbanos en diversas ciudades españolas, donde las proliferaciones del pulgón generan gran cantidad de melaza provocando daños estéticos y de confort. Durante 2008 y 2009 se efectuó el seguimiento de la fenología y de la densidad de población de M. walshii y de otros pulgones en robles americanos plantados en alineación en la ciudad de Girona y se estimaron los daños producidos. Asimismo se valoró la relación entre la abundancia de pulgones y los daños ocasionados. Finalmente se identificaron los principales grupos de enemigos naturales, a la vez que se cuantificó su abundancia. M. walshii fue la única especie de pulgón que afectó a los robles americanos. Este pulgón pasa el invierno en forma de huevo, las primeras ninfas surgen a la salida de hojas y las distintas generaciones de individuos partenogenéticos se mantienen a niveles variables hasta mediados de otoño, cuando aparecen las formas sexuales. Existe una correlación positiva entre la abundancia del pulgón y los daños de confort, incluso cuando la densidad es baja. Parasitoides y coccinélidos fueron los enemigos naturales más frecuentemente registrados, aunque su abundancia fue relativamente escasa. Se discute el papel de las condiciones climáticas y de los enemigos naturales en la determinación de la abundancia de M. walshii.

A note on Spatial Autocorrelation at a Local Level

In this paper we analyze the existence of spatial autocorrelation at a local level in Catalonia using variables such as urbanisation economies, population density, human capital and firm entries. From a static approach, our results show that spatial autocorrelation is weak and diminishes as the distance between municipalities increases. From a dynamic approach, however, spatial autocorrelation increased over the period we analysed. These results are important from a policy point of view, since it is essential to know how economic activities are spatially concentrated or disseminated. Key words: spatial autocorrelation, municipalities. JEL classification: R110, R120

The Instrumental voter goes to the news-agent: demand for information, election closeness, and the media

This paper studies the impact of instrumental voting on information demand and mass media behaviour during electoral campaigns. If voters act instrumentally then information demand should increase with the closeness of an election. Mass media are modeled as profit-maximizing firms that take into account information demand, the value of customers to advertisers and the marginal cost of customers. Information supply should be larger in electoral constituencies where the contest is expected to be closer, there is a higher population density, and customers are on average more profitable for advertisers. The impact of electorate size is theoretically undetermined. These conclusions are then tested with comfortable results on data from the 1997 general election in Britain.

Descentralisation, integration and polycentrism in Barcelona

In this study the employment subcentres of the Metropolitan Region of Barcelona are identified using different criteria. Once catalogued according to their nature,i.e. subcentres arising from integration and decentralisation, they are analysed to see whether their impact on population density depends on their origin. The results obtained confirm a greater impact of integrated subcentres in comparison with decentralised ones, amplified in turn by the fact that the former are further from the CBD and present a greater degree of self-containment in the labor market.

Productive efficiency and regulatory reform: The case of vehicle inspection services

Measuring productive efficiency provides information on the likely effects of regulatory reform. We present a Data Envelopment Analysis (DEA) of a sample of 38 vehicle inspection units under a concession regime, between the years 2000 and 2004. The differences in efficiency scores show the potential technical efficiency benefit of introducing some form of incentive regulation or of progressing towards liberalization. We also compute scale efficiency scores, showing that only units in territories with very low population density operate at a sub-optimal scale. Among those that operate at an optimal scale, there are significant differences in size; the largest ones operate in territories with the highest population density. This suggests that the introduction of new units in the most densely populated territories (a likely effect of some form of liberalization) would not be detrimental in terms of scale efficiency. We also find that inspection units belonging to a large, diversified firm show higher technical efficiency, reflecting economies of scale or scope at the firm level. Finally, we show that between 2002 and 2004, a period of high regulatory uncertainty in the sample’s region, technical change was almost zero. Regulatory reform should take due account of scale and diversification effects, while at the same time avoiding regulatory uncertainty.

Anàlisi i diagnosi ambiental de la dinàmica del porc senglar (Sus scrofa) al Parc del Garraf

El Parc del Garraf (PG) és una zona on la dinàmica del porc senglar amb el medi té una alta importància, tot i que la densitat de població al PG d’aquest ungulat és de les menors de Catalunya. Els aspectes més rellevants de la relació porc senglar-medi són: la correlació que hi ha entre l’abandonament d’àrees de conreu i activitats forestals amb l’augment de la població de porc senglar, i l’afectació que per tant, provoca a les àrees de conreu que hi ha actualment, que es pot veure minvada aplicant bones mesures correctores. També la relació que té amb el margalló (Chamaerops humilis), que és positiva ajudant a la recuperació, conservació i a la dinàmica ecològica de l’espècie, així com amb el medi del PG en general, i, per últim, els impactes viaris a la xarxa viària del PG, tot i que no existeix cap TCCU (Tram de Concentració de Col·lisions amb Ungulats) dins els límits del PG. Referent a la caça, actualment és la única mesura viable de control de la població de porc senglar, tot i que no hi ha relleu generacional per a aquesta activitat.

Estudi d'impacte acústic de les obres d'un intercanviador de metro

En el territori del Barcelonès les obres han estat a l’ordre del dia. Abans de l’inici de la crisi es van encetar i programar nombroses obres tan d’immobles com de grans infraestructures com la que aquí es presenta: un intercanviador de metro. L’alta densitat demogràfica d’aquesta regió ha fet que aquests treballs realitzats a les obres siguin poc compatibles amb el benestar i la salut de la població. Un dels principals factors causants del malestar als veïns és el soroll. Mitjançant estudis de modelització acústica, com el realitzat en aquest projecte, es pretén preveure i evitar que l’afecció acústica derivada de les obres sigui perjudicial per la persona per tal de compatibilitzar al màxim possible les feines de l’obra amb el benestar general. Mitjançant el programa de monitorització acústica Cadna‐A i nombroses mesures acústiques in situ s’ha pogut preveure la futura afecció sonora de 6 fases d’obra considerades com les més sorolloses i s’han proposat un seguit de mesures preventives i/o correctores per tal d’assolir uns nivells acústics assequibles amb la legislació vigent.

Fauna silvestre del Parc del Garraf. Afectacions al sector primari

El Parc del Garraf (PG) ha estat tradicionalment una important zona agrícola, encara que actualment és molt reduïda (representa el 3% del total de la superfície del parc) i està repartida entre unes poques masies. Aquesta activitat humana conviu amb la fauna silvestre de la zona, que en alimentar-se parcialment dels cultius (cereal, vinya, oliveres, arbres fruiters i hortalisses), hi causa diversos impactes. És el cas de diverses aus, com ara la garsa (Pica Pica) i el pardal (Passer domesticus), i també d’alguns mamífers com el porc senglar (Sus scrofa). Hem observat que l’impacte produït per les aus i el porc senglar (Sus scrofa) és molt petit, el que pot ser degut a dos motius principals: possiblement per una elevada producció de fruits salvatges, esdevenint aquest aliment suficient per a les aus; i la baixa densitat poblacional de porc senglar (Sus scrofa) al parc. Els impactes observats presenten una alta variabilitat i depenen de l’època de l’any en que ens trobem. Per tant, cal fer-ne un seguiment més acurat on s’impliquin administració i pagesos per a millorar el coneixement de l’impacte de la fauna salvatge.

Bottled natural mineral water in catalonia: origin and geographical evolution of its consumption and production

During the second half of the nineteenth century a major mineral water bottling industry appeared in Catalonia which vigorously lasted until the first third of the 20th century. The fact that the industry appeared in Catalonia and in other parts of Europe and the United States almost at the same time and had not existed before can be explained by a series of factors which coincided in time. This situation encouraged producers to pack, transport and sell bottled water from their respective sources. Among these factors there is the rise of hygienism, very influential in Catalonia, the declining water quality due to industrialization, the increase in population density, the improvement in transport, the emergence of thermal tourism or the invention of better containers used to store water. This project aims to explain thoroughly all the mentioned factors, and to give some light to why, when and how the Catalan bottled water industry appeared.

Anisotropic dispersion, space competition, and the slowdown of the Neolithic transition

The front speed of the Neolithic (farmer) spread in Europe decreased as it reached Northern latitudes, where the Mesolithic (huntergatherer) population density was higher. Here, we describe a reaction diffusion model with (i) an anisotropic dispersion kernel depending on the Mesolithicpopulation density gradient and (ii) a modified population growth equation. Both effects are related to the space available for the Neolithic population. The model is able to explain the slowdown of the Neolithic front as observed from archaeological data

Preliminary results of the Social Impact Research Group of MEDEX: the request database (2000-2002) of two Meteorological Services

One of the aims of the MEDEX project is to improve the knowledge of high-impact weather events in the Mediterranean. According to the guidelines of this project, a pilot study was carried out in two regions of Spain (the Balearic Islands and Catalonia) by the Social Impact Research group of MEDEX. The main goal is to suggest some general and suitable criteria about how to analyse requests received in Meteorological Services arising out of the damage caused by weather events. Thus, all the requests received between 2000 and 2002 at the Servei Meteorològic de Catalunya as well as at the Division of AEMET in the Balearic Islands were analysed. Firstly, the proposed criteria in order to build the database are defined and discussed. Secondly, the temporal distribution of the requests for damage claims is analysed. On average, almost half of them were received during the first month after the event happened. During the first six months, the percentage increases by 90%. Thirdly, various factors are taken into account to determine the impact of specific events on society. It is remarkable that the greatest number of requests is for those episodes with simultaneous heavy rain and strong wind, and finally, those that are linked to high population density.

Experimental evidence that intra-specific competition in seagrass meadows reduces reproductive potential in the sea urchin Paracentrotus lividus (Lamarck)

To better understand the biological controls that regulate sea urchin dynamics, we studied the effects of potential inter- and intra-specific competition for food on several biological variables of the main sea urchin in the Mediterranean (Paracentrotus lividus). We carried out a caging experiment in which we manipulated sea urchin density (natural vs. high density) and herbivorous fish (Sarpa salpa) accessibility (free access vs. exclusion) in a Posidonia oceanica meadow. No evidence of competition between fish and urchins was detected. Neither density-dependent mortality nor changes in the somatic variables were found; however, we detected that intra-specific competition affected the reproductive potential of P. lividus. The gonad index of urchins at high population densities was ca. 30% lower than that of urchins at natural densities. As a spawning event had just occurred when urchins were collected, these differences probably reflect differences in reserve content, which may compromise the following reproductive period and decrease survival in the long term, as the gonads are also used as storage organs. For the time period studied, mortality rates appeared to be independent of local densities. The results indicate that a long-term negative feedback mechanism appears to take place in P. lividus in response to increased population density.