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Population Decrease (population + decrease)
Selected AbstractsConsequences of climatic change for water temperature and brown trout populations in Alpine rivers and streamsGLOBAL CHANGE BIOLOGY, Issue 1 2006RENATA E. HARI Abstract Twenty-five years of extensive water temperature data show regionally coherent warming to have occurred in Alpine rivers and streams at all altitudes, reflecting changes in regional air temperature. Much of this warming occurred abruptly in 1987/1988. For brown trout populations, the warming resulted in an upward shift in thermal habitat that was accelerated by an increase in the incidence of temperature-dependent Proliferative Kidney Disease at the habitat's lower boundary. Because physical barriers restrict longitudinal migration in mountain regions, an upward habitat shift in effect implies habitat reduction, suggesting the likelihood of an overall population decrease. Extensive brown trout catch data documenting an altitudinally dependent decline indicate that such a climate-related population decrease has in fact occurred. Our analysis employs a quantitatively defined reference optimum temperature range for brown trout, based on the sinusoidal regression of seasonally varying field data. [source] The Socio-spatial Conditions of the Open City: A Theoretical SketchINTERNATIONAL JOURNAL OF URBAN AND REGIONAL RESEARCH, Issue 3 2005DETLEV IPSEN Without additional immigration of several million people over the next few decades, the demographic development of most European countries will lead to a considerable population decrease. Because such a reduction is neither desirable nor realistically possible, cities in particular will be the target of increasing immigration, and hence will undergo qualitative change. Today, there are large ethnic and cultural minorities in many German cities and suburbs; in the future, whole cities will become international, and suburbs will become ethnic-cultural communities. This article presents a theory for the discussion on how such a change can be managed productively. The concept of the ,open city' is understood as both a risk and an opportunity. This article pleads for a socio-culturally segregated division of urban space for the prevention of discrimination to be possible. The multitude of separate cultures must be supplemented by a ,hyper-culture' in order to integrate the urban culture as a whole. Sans l'apport de l'immigration de plusieurs millions de personnes au cours des prochaines décennies, l'évolution démographique de la plupart des pays d'Europe aboutira à une nette chute de population. Comme une telle diminution n'est ni souhaitable ni une réalité envisageable, les villes notamment vont être la cible d'une immigration croissante, donc subir des changements qualitatifs. Aujourd'hui, il existe d'importantes minorités ethniques et culturelles dans de nombreuses villes et banlieues allemandes: à l'avenir, la totalité des villes deviendront internationales et les banlieues se feront communautés ethno-culturelles. Cet article présente une théorie comme base de discussion sur la manière de gérer ce changement de façon productive. Le concept de ,ville ouverte' est perçu à la fois comme un risque et une opportunité. L'article plaide pour une division socio-culturelle de l'espace urbain comme moyen de prévention de la discrimination. La multitude de cultures distinctes doit être complétée d'une ,hyper-culture' afin d'intégrer en bloc la culture urbaine. [source] Non-independence of demographic parameters: positive density-dependent fecundity in eaglesJOURNAL OF APPLIED ECOLOGY, Issue 5 2008Miguel Ferrer Summary 1Using information on the Doñana population of Spanish imperial eagles Aquila adalberti from 1959 to 2004, we present strong empirical support to theoretical models on the regulation of population trajectories by the relationships between breeder mortality and floater availability. 2During the study period, the eagle population showed three distinct phases: (i) a population increase with negative density-dependent fecundity; (ii) a period of stability without any relationship between density and fecundity; and (iii) a population decrease with a positive relationship between density and fecundity. 3A dramatic increase in annual adult mortality due to an increase in poisoning in hunting areas surrounding the Doñana National Park was recorded. The use of poison against generalist predators accounted for more than 54% of the total number of breeding eagles found dead since 1990, increasing annual adult mortality from 6·07 to 12·01%. 4This high mortality reduced the population annually by 6% during the 1992,2004 period. Also, the population changed from a negative to a positive relationship between density and fecundity (Allee effect). These trends made the population approach extinction due to the double effect of increasing breeder mortality and low availability of floaters. 5A supplementary feeding programme established in 1990 did not increase fecundity because it was a consequence of high adult mortality rather than low food availability. The high mortality of adults increased the risk of breeding failure and also decreased the availability of floaters, decreasing the likelihood of mate substitution. 6Synthesis and applications. The main target in species conservation management plans is often a single demographic parameter (typically, fecundity in raptor populations). Our research demonstrates, however, that demographic parameters must not be considered as independent variables when formulating management programmes. The essential relationship between adult mortality and the availability of floaters must be better understood to avoid the risk of implementing inefficient management strategies. Although fecundity was low in this eagle population, it was a result of high adult mortality rates. Consequently, management must aim to correct the unusual mortality and recover the floater population. [source] Influence of plot characteristics and surrounding vegetation on the intra-plot spatial distribution of Empoasca vitisAGRICULTURAL AND FOREST ENTOMOLOGY, Issue 4 2009Damien Decante Abstract 1Spatial distributions of adults and nymphs of Empoasca vitis were assessed during 3 years inside two adjacent vine plots having considerable intra-plot variability, diversified natural ground cover and surrounding vegetation, and no insecticide application. 2Geostatistical analysis confirmed that, in spite of repeated adult migrations, spatial distributions of summer populations were highly aggregated, similar every year and similar between adults and nymphs. Comparison of insect distribution with intra-plot characteristics, such as vine plant vigour (leaf density and leaf chlorophyll concentration) and phenology, plot topography and surrounding vegetation, revealed that E. vitis clearly aggregates in areas with the most vigorous vine plants. 3Even though the presence of natural enemies in the surrounding vegetation was confirmed by specific observations, we did not observe significant population decrease at the contiguous plot edges. Natural ground cover, together with the absence of insecticide, might allow the spreading and perennial conservation of E. vitis natural enemies inside the plots. 4Clear adult aggregations observed along downwind woodlands suggest that this vegetation acts as a barrier and intercepts the adults flying passively across the plot. However, this surrounding vegetation could also serve as an alternative refuge when vine water deficit and vine foliage temperature increase. [source] Conservation genetics of a critically endangered Iberian minnow: evidence of population decline and extirpationsANIMAL CONSERVATION, Issue 2 2010V. Sousa Abstract The endangered minnow Iberochondrostoma almacai is an endemic Iberian cyprinid with a restricted and fragmented distribution. Here, we describe the genetic structure of the species and infer its demographic history from six nuclear-encoded microsatellite loci and mitochondrial cytochrome b sequences. Genetic diversity was low (microsatellite He<0.45; mtDNA ,<0.0015), and both markers resolved two groups: one from the northern Mira drainage and one from the Arade and Bensafrim drainages. The relatively low differentiation between these groups (0.09 Contrasting population changes in sympatric penguin species in association with climate warmingGLOBAL CHANGE BIOLOGY, Issue 3 2006JAUME FORCADA Abstract Climate warming and associated sea ice reductions in Antarctica have modified habitat conditions for some species. These include the congeneric Adélie, chinstrap and gentoo penguins, which now demonstrate remarkable population responses to regional warming. However, inconsistencies in the direction of population changes between species at different study sites complicate the understanding of causal processes. Here, we show that at the South Orkney Islands where the three species breed sympatrically, the less ice-adapted gentoo penguins increased significantly in numbers over the last 26 years, whereas chinstrap and Adélie penguins both declined. These trends occurred in parallel with regional long-term warming and significant reduction in sea ice extent. Periodical warm events, with teleconnections to the tropical Pacific, caused cycles in sea ice leading to reduced prey biomass, and simultaneous interannual population decreases in the three penguin species. With the loss of sea ice, Adélie penguins were less buffered against the environment, their numbers fluctuated greatly and their population response was strong and linear. Chinstrap penguins, considered to be better adapted to ice-free conditions, were affected by discrete events of locally increased ice cover, but showed less variable, nonlinear responses to sea ice loss. Gentoo penguins were temporarily affected by negative anomalies in regional sea ice, but persistent sea ice reductions were likely to increase their available niche, which is likely to be substantially segregated from that of their more abundant congeners. Thus, the regional consequences of global climate perturbations on the sea ice phenology affect the marine ecosystem, with repercussions for penguin food supply and competition for resources. Ultimately, variability in penguin populations with warming reflects the local balance between penguin adaptation to ice conditions and trophic-mediated changes cascading from global climate forcing. [source] A policy tool for establishing a balance between wildlife habitat preservation and the use of natural resources by rural people in South AfricaAFRICAN JOURNAL OF ECOLOGY, Issue 1 2006Oumar Bouare Abstract In this paper, a model is set up to determine the size of the wildlife population compatible with the extraction of the maximum output by rural people from natural resources. It is found that when the size of human population increases, to obtain the maximum output of food, the size of wildlife population decreases if the human population is growing faster than or at the same rate as that of the wildlife population; whereas the size of the wildlife population increases if the human population is growing slower than that of the wildlife. Furthermore, in the event that the increase in the size of the wildlife population is unable to reach the level compatible with the extraction of the maximum output of food, the improvement of the wildlife habitat and supplementing rural people's income with the proceeds of tourism are proposed as policies to maintain a balance between the preservation of the wildlife habitat and the use of natural resources by rural people. Résumé Dans cette étude un modèle est établi afin de déterminer la taille de la population faunique compatible avec l'extraction de la quantité maximale des ressources naturelles par les peuples ruraux. Les résultats montrent que quand la taille de la population humaines accroît, afin d'obtenir la quantité maximale de nourriture, la taille de la population faunique décroît si la population humaine augmente plus vite que, ou à la même vitesse que, la population faunique. Tomdis que, la population faunique saccroît si la croissance de la population humaine est plus lente. De plus, si la croissance de la taille de la population faunique n'atteint pas le niveau compatible avec l'extraction de la quantité maximale de nourriture, l'amélioration de l'habitat faunique et le rajout de recettes du tourisme aux revenus des peuples ruraux sont conseillés comme politiques afin de maintenir un équilibre entre la préservation de l'habitat faunique et l'utilisation des ressources naturelles par les peuples ruraux. [source] Hydrogen and carbon interaction in a FeNi alloy with a vacancyPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 6 2009Estela Gonzalez Abstract The bonding of hydrogen and carbon to Fe and Ni in a 50:50 alloy is analysed using density functional calculations. The changes in the electronic structure of a L10 alloy upon C and H introduction at a vacancy region are addressed and a comparison with H or C in pure metals is drawn. H in bulk FeNi alloy with a vacancy locates at a tetrahedral site shifted towards the vacancy. Instead, C prefers an octahedral site (Fe based). The vacancy acts as strong traps of both C and H. Fe,Ni atoms are initially more strongly bonded to each other due to the vacancy formation. Consequently, the Fe,Fe, Fe,Ni and Ni,Ni bond strengths are diminished as new metal,C or metal,H bonds are formed. The most affected bond is the Fe,Ni, whose overlap population decreases by 72%. An analysis of the orbital interaction reveals that the Fe,H bonding involves mainly the Fe 4s, H 1s and Ni 4s orbitals. In the case of the sequential absorption, the C,H interaction is almost zero at a distance of 2.72 Å. The main interactions of these interstitials are developed with either Fe or Ni. We also consider the absorption sequence (H first or C first) and its influence on the electronic structure. Our results could be relevant to understand some steps of the carburization process during thermal cracking operations where hydrogen atoms are present. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]
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