Phenotypic signatures of urbanization are scale-dependent : a multi-trait study on a classic urban exploiter

Understanding at which spatial scales anthropogenic selection pressures operate most strongly is a prerequisite for efficient conservation and management of urban biodiversity. Heterogeneity in findings on the strength and direction of urbanization effects may result from a lack of consensus on which spatial scales are most adequate when studying biotic effects of urbanization. Therefore, here, using the house sparrow (Passer domesticus) as model, we test the hypothesis that more than one spatial scale will explain variation among phenotypic stress markers. By applying a unique hierarchical sampling design enabling us to differentiate between local and regional effects of urbanization, we here show that the strength and direction of relationships with the percentage of built-up area - a simple structural measure of urbanization - vary among phenotypic stress markers and across the spatial range over which urbanization is measured. While inverse relationships with scaled body mass and bill height of adult house sparrows (Passer domesticus) were strongest when the degree of urbanization was quantified at city-level, similar relationships with corticosterone concentrations in feathers were only detected at the scale of individual home ranges. In contrast, tarsus length, wing length, and two measures of feather development were not significantly related to urbanization at any spatial scale. As the suite of phenotypic stress markers applied in this study revealed signatures of urbanization over a broad spatial range, we conclude that measures aimed at mitigating impacts of urbanization on free-ranging populations should best be implemented at multiple spatial scales too

Urbanization without growth : a not-so-uncommon phenomenon

To find out why African countries'experience with urbanization and sustained growth appeared to differ from that of other countries, the authors investigated the determinants of urbanization across countries over 40 years. Rather than studying individuals'decisions to migrate, they relied on macroeconomic data and cross-country comparisons. A central hypothesis of their study: that individuals move (with varying degrees of ease) in response to economic incentives and opportunities. If location incentives are distorted, so is growth. The authors find that urbanization levels are closely correlated with levels of income. But urbanization continues even during periods of negative growth, carried by its own momentum, largely a function of the level of urbanization. From that viewpoint, Africa's urbanization without growth is not a puzzle. Factors other than income that help predict differences in levels of urbanization across countries include: a) income structure; b) education; c) rural-urban wage differentials; d) ethnic tensions; and e) civil disturbances. In addition, the relationship between economic incentives and urbanization is weaker in countries with fewer civil or political liberties. Factors other than initial urbanization level that help explain the speed of urbanization include: 1) The sector from which income growth is derived; 2) ethnic tensions; 3) civil disturbances and democracy (these two slow the pace of urbanization if all else is constant); 4) rural-urban wage differentials, whether they represent an urban bias or simply lower productivity in agriculture relative to other sectors. The weak relationship that this study shows between urbanization and traditionally accepted migration factors suggests that in Africa economists are overlooking part of the urbanization story. The fact that the informal sector appears to provide a significant source of income for urban migrants, coupled with the overlap between rural and urban activities, may shed light on the nature of urbanization in Africa.Banks&Banking Reform,National Urban Development Policies&Strategies,Urban Housing and Land Settlements,Public Health Promotion,Urban Services to the Poor,Urban Housing and Land Settlements,National Urban Development Policies&Strategies,Governance Indicators,Banks&Banking Reform,Urban Services to the Poor

Urban Settlement: Data, Measures, and Trends

This paper examines data on urbanization. We review the most commonly used data sources, and highlight the difficulties inherent in defining and measuring the size of urban versus rural populations. We show that differences in the measurement of urban populations across countries and over time are significant, and discuss the methods used to obtain these measurements, as well as those for projecting urbanization. We also analyze recent trends and patterns in urbanization. Finally, we describe the principal channels of urbanization and examine their relative contributions to the global urbanization process.Urbanization, measurement, urban population

Urbanization Sans Development?

From a theoretical standpoint, the question has to be asked whether or not the census should retain its present definition of urban areas. There is a need for a more meaningful integration of the structural, institutional and demographic criteria, if the term is to hold substantive meaning. In this light, this paper proposes that a two-tier urban definition be employed. The old definition should be retained for trend analysis purposes while a new definition that incorporates socioeconomic purposes should be instituted.urban management, population and family relation, urbanization, data and statistics

Effects of urbanization on host-pathogen interactions, using Yersinia in house sparrows as a model

Urbanization strongly affects biodiversity, altering natural communities and often leading to a reduced species richness. Yet, despite its increasingly recognized importance, how urbanization impacts on the health of individual animals, wildlife populations and on disease ecology remains poorly understood. To test whether, and how, urbanization-driven ecosystem alterations influence pathogen dynamics and avian health, we use house sparrows (Passer domesticus) and Yersinia spp. (pathogenic for passerines) as a case study. Sparrows are granivorous urban exploiters, whose western European populations have declined over the past decades, especially in highly urbanized areas. We sampled 329 house sparrows originating from 36 populations along an urbanization gradient across Flanders (Belgium), and used isolation combined with 'matrix-assisted laser desorption ionization-time of flight mass spectrometry' (MALDI-TOF MS) and PCR methods for detecting the presence of different Yersinia species. Yersinia spp. were recovered from 57.43% of the sampled house sparrows, of which 4.06%, 53.30% and 69.54% were identified as Y. pseudotuberculosis, Y. enterocolitica and other Yersinia species, respectively. Presence of Yersinia was related to the degree of urbanization, average daily temperatures and the community of granivorous birds present at sparrow capture locations. Body condition of suburban house sparrows was found to be higher compared to urban and rural house sparrows, but no relationships between sparrows' body condition and presence of Yersinia spp. were found. We conclude that two determinants of pathogen infection dynamics, body condition and pathogen occurrence, vary along an urbanization gradient, potentially mediating the impact of urbanization on avian health

The Weight of Economic Growth and Urbanization on Electricity Demand in UAE

This study aims to explore the relationship between economic growth, urbanization, financial development and electricity consumption in case of United Arab Emirates. The study covers the time period of 1975-2011. We have applied the ARDL bounds testing to examine long run relationship between the variables in the presence of structural breaks. The VECM Granger causality is applied to investigate the direction of causal relationship between the variables. Our empirical exercise found cointegration between the series in case of United Arab Emirates. Further, results reveal that inverted U-shaped relationship is found between economic growth and electricity consumption i.e. economic growth raises electricity consumption initially and declines it after a threshold level of income per capita. Financial development adds in electricity consumption. The relationship between urbanization and electricity consumption is also inverted U-shaped. This implies that urbanization increases electricity consumption initially and after a threshold level of urbanization, electricity demand falls. The causality analysis finds feedback hypothesis between economic growth and electricity consumption i.e. economic growth and electricity consumption are interdependent. The bidirectional causality is found between financial development and electricity consumption. Economic growth and urbanization Granger cause each other. The feedback hypothesis is also found between urbanization and financial development, financial development and economic growth and same is true for electricity consumption and urbanization.

World Urbanization Prospects

This paper proposes to critically examine the United Nations projections on urbanisation. Both the estimates of current trends based on national data and the method of projection are evaluated. The theory of mobility transition is used as an alternative hypothesis. Projections are proposed using a polynomial model and compared to the UN projections, which are based on a linear model. The conclusion is that UN projections may overestimate the urban population for the year 2030 by almost one billion, or 19% in relative term. The overestimation would be particularly more pronounced for developing countries and may exceed 30% in Africa, India and Oceania.developed countries, developing countries, environment, model, poverty, projections, urban transition, urbanization

CityScapeLab Berlin: A Research Platform for Untangling Urbanization Effects on Biodiversity

Urban biodiversity conservation requires an understanding of how urbanization modulates biodiversity patterns and the associated ecosystem services. While important advances have been made in the conceptual development of urban biodiversity research over the last decades, challenges remain in understanding the interactions between different groups of taxa and the spatiotemporal complexity of urbanization processes. The CityScapeLab Berlin is a novel experimental research platform that allows the testing of theories on how urbanization affects biodiversity patterns and biotic interactions in general and the responses of species of conservation interest in particular. We chose dry grassland patches as the backbone of the research platform because dry grasslands are common in many urban regions, extend over a wide urbanization gradient, and usually harbor diverse and self-assembled communities. Focusing on a standardized type of model ecosystem allowed the urbanization effects on biodiversity to be unraveled from effects that would otherwise be masked by habitat- and land-use effects. The CityScapeLab combines different types of spatiotemporal data on (i) various groups of taxa from different trophic levels, (ii) environmental parameters on different spatial scales, and (iii) on land-use history. This allows for the unraveling of the effects of current and historical urban conditions on urban biodiversity patterns and the related ecological functions.BMBF, 01LC1501, BIBS-Verbund: Bridging in Biodiversity Science (BIBS

Economic Growth, Size of the Agricultural Sector, and Urbanization

This paper exploits the significant positive response of the share of agricultural value added and GDP per capita growth to variations in the international prices for agricultural commodities and rainfall to construct instrumental variables estimates of the causal effect that changes in the size of the agricultural sector and GDP per capita growth have on the urbanization rate for a panel of 41 African countries during the period 1960-2007. The paper's two main findings are that: (i) decreases in the share of agricultural value added lead to a significant increase in the urbanization rate; (ii) conditional on changes in the share of agricultural value added GDP per capita growth does not significantly affect the urbanization rate. The empirical results confirm the predictions of theoretical models that economic shocks which differentially affect the return across sectors matter for the rural-urban migration decision, and that economic growth mostly affects the urbanization rate through a sector shift out of agriculture.economic growth, sectoral shocks, urbanization

Entrepreneurship and market size. The case of young college graduates in Italy

We analyse empirically the effects of urbanization on Italian college graduates' work possibilities as entrepreneurs three years after graduation. We find that doubling the population density of the province of work reduces the chances of being an entrepreneur by 2-3 percentage points. This result holds after controlling for regional fixed effects and is robust to instrumenting urbanization. Provincial competition, urban amenities and disamenities, cost of labour, earning differentials between employees and self-employed workers, unemployment rates and value added per capita account for more than half of the negative urbanization penalty. Our result cannot be explained by the presence of negative differentials in returns to entrepreneurship between the most and the least densely populated areas either. In fact, as long as they succeed in entering the most densely populated markets, young entrepreneurs are able to reap the benefits of urbanization externalities: doubling the population density of the province of work increases entrepreneurs' net monthly earnings by 2-3 per cent.Labour market transitions, urbanization