Connectivity in urbanizing landscapes: The importance of habitat configuration,urban area size,and dispersal

Human activities affect both the amount and configuration of habitat. These changes have important ecological implications that can be measured as changes in landscape connectivity. I investigated how urbanization interacts with the initial amount and aggregation of habitat to change dispersal potential, restoration potential, and the risk of spatially extensive disturbances. I used a factorial set of simulated landscapes and subjected each landscape to habitat loss by overlaying 66 different US urban areas. I used a common connectivity metric, CONNECT, to assess the magnitude and direction of changes for a range of dispersal distances. My results show that the relationship between habitat loss and connectivity loss is non-linear and subject to interactions between the spatial patterns of habitat distribution, urban morphology, and dispersal capabilities. The implications of a given urban form vary widely as a function of habitat distribution and dispersal capabilities. This implies that impact assessments, restoration activities, and conservation planning should consider historical habitat distribution when evaluating observed changes in connectivity. While my results clearly show that more aggregated or continuous habitats are more vulnerable to connectivity loss, this approach can also be used to identify landscapes where restoring connectivity will be particularly effective, for example through placement of stepping stone habitats.     

Differences in Delaying Motherhood Across European Countries: Empirical Evidence from the ECHP

Motherhood postponement and fertility decline have been observed in almost all developed countries. In this article, we aim to assess some of the potential determinants of first childbirth timing in Europe, in a comparative perspective, using data from the European Community Household Panel Survey (ECHP). We estimate, separately by country, hazard rates for the timing at first childbirth conditioning to education and work characteristics. Moreover, in order to explain differences between European countries, we decompose the differences between rates in the part due to the national population composition by specific characteristics and the part due to different propensities for women with given characteristics.     

The Extended Metropolitan Area in a New EU Member State: Implications for a Rural Development Approach

I examine the role of rural development strategies in a new member state (Romania) of the European Union and, in particular, analyse the case of the metropolitan area of the Bucharest-Ilfov region. The analysis concerns the selected strategies for rural development in the programming period 2007–2013. It must be noted that Romania is divided into nonadministrative development regions and that the process of land privatisation is not yet concluded. These factors could have a negative influence on the implementation of the interventions. The analysed region is situated in the Southern part of the country and in the central part of the Romanian Plan. The total surface is about 1.8 square kilometres, of which 12.5% are occupied by the town of Bucharest and 87.5% by Ilfov County; however, approximately 88% of the population is concentrated in the urban center and only 12% in Ilfov County. The case study is characterised on the one hand by a high growth rate of the gross domestic product, a relatively low unemployment rate, and increasing consumer good sales (mainly food and beverages); on the other, by some marked disparities in macroeconomic indicators among regions and between rural and urban areas and an enormous lack of infrastructures. The case study thus calls for a local approach in order to identify the strategies required to improve the quality of life of the regional inhabitants (both in rural and urban areas) and to prevent pressure from the urban centre from compromising the rich rural heritage      

Case study for evaluating campus sustainability: nitrogen balance for the University of Minnesota

American ecologists recently began to address the ecology of cities. Concurrently, higher education institutions have developed sustainability education programs and instituted sustainability policies and projects. This paper draws together these two disparate areas by examining the nitrogen (N) budget of the Twin Cities campus of the University of Minnesota. We addressed the question: what were the annual inputs, outputs and internal cycles of N on the University of Minnesota Twin Cities campus? We found that 508 Mg N yr-1 were brought into the campus and 494 Mg N yr-1 were emitted from the University of Minnesota campus. The largest N inputs were abiotic fixation (conversion of N₂ to NO_x by combustion) and food for humans and animals. The largest N output was NO_x, followed by wastewater. Our results expand the understanding of the ecology of institutions within an urban area and provide an opportunity for improving urban ecology education and environmental policy at educational institutions.     

Separator-based data reduction for signed graph balancing

Polynomial-time data reduction is a classical approach to hard graph problems. Typically, particular small subgraphs are replaced by smaller gadgets. We generalize this approach to handle any small subgraph that has a small separator connecting it to the rest of the graph. The problem we study is the NP-hard Balanced Subgraph problem, which asks for a 2-coloring of a graph that minimizes the inconsistencies with given edge labels. It has applications in social networks, systems biology, and integrated circuit design. The data reduction scheme unifies and generalizes a number of previously known data reductions, and can be applied to a large number of graph problems where a coloring or a subset of the vertices is sought. To solve the instances that remain after reduction, we use a fixed-parameter algorithm based on iterative compression with a very effective heuristic speedup. Our implementation can solve biological real-world instances exactly for which previously only approximations were known. In addition, we present experimental results for financial networks and random networks.     

Contexte local et migration: l’exemple des dynamiques migratoires internationales de quartiers dans la ville sénégalaise de Kaolack

Despite the diversity of the variables considered, explanatory models of migration do not fully incorporate the locality of origin as a scale of observation for migratory behaviour. Migration is often perceived to generate notions of territory; conversely, are local territories drivers of mobility? If so, in what forms, and by what means? This article analyses international migration from the city of Kaolack in Senegal, with particular focus on the role of the neighbourhood in migration dynamics. Here, the neighbourhood is seen as relatively homogeneous and singular historical and social entity. The ties that are established and maintained from one generation to the next take the form of shared lifestyles and modes of organization which may influence inhabitants’ propensity to emigrate.     

Pooling designs associated with unitary space and ratio efficiency comparison

Let \mathbbF^(2n+d)_q²\mathbb{F}^{(2\nu+\delta)}_{q^{2}} be a (2ν+δ)-dimensional unitary space of \mathbbF_q²\mathbb{F}_{q^{2}} , where δ=0 or 1. In this paper we construct a family of inclusion matrices associated with subspaces of \mathbbF^(2n+d)_q²\mathbb{F}^{(2\nu+\delta)}_{q^{2}} , and exhibit its disjunct property. Moreover, we compare the ratio efficiency of this construction with others, and find it smaller under some conditions.