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Population Vulnerability (population + vulnerability)
Selected AbstractsMetapopulation Extinction Risk under Spatially Autocorrelated DisturbanceCONSERVATION BIOLOGY, Issue 2 2005A. S. KALLIMANIS patrón espacial de perturbación; simulaciones espacialmente explícitas; SLOSS; umbral de extinción Abstract:,Recent extinction models generally show that spatial aggregation of habitat reduces overall extinction risk because sites emptied by local extinction are more rapidly recolonized. We extended such an investigation to include spatial structure in the disturbance regime. A spatially explicit metapopulation model was developed with a wide range of dispersal distances. The degree of aggregation of both habitat and disturbance pattern could be varied from a random distribution, through the intermediate case of a fractal distribution, all the way to complete aggregation (single block). Increasing spatial aggregation of disturbance generally increased extinction risk. The relative risk faced by populations in different landscapes varied greatly, depending on the disturbance regime. With random disturbance, the spatial aggregation of habitat reduced extinction risk, as in earlier studies. Where disturbance was spatially autocorrelated, however, this advantage was eliminated or reversed because populations in aggregated habitats are at risk of mass extinction from coarse-scale disturbance events. The effects of spatial patterns on extinction risk tended to be reduced by long-distance dispersal. Given the high levels of spatial correlation in natural and anthropogenic disturbance processes, population vulnerability may be greatly underestimated both by classical (nonspatial) models and by those that consider spatial structure in habitat alone. Resumen:,Los modelos recientes de extinción generalmente muestran que la agregación espacial de hábitat reduce el riesgo de extinción debido a una recolonización más rápida de sitios vacíos por extinción local. Extendimos la investigación para incluir la estructura espacial en el régimen de perturbación. Desarrollamos un modelo metapoblacional espacialmente explícito en el que el patrón espacial tanto del hábitat como de los regímenes de perturbación podía variar aleatoriamente de fractal a completamente agregado (bloque) y con una amplia gama de distancias de dispersión. El incremento de la agregación espacial de la perturbación generalmente incrementó el riesgo de extinción. El riesgo relativo que enfrentan poblaciones en paisajes diferentes fue muy variable, dependiendo del régimen de perturbación. Con perturbación aleatoria, la agregación espacial de hábitat redujo el riesgo de extinción, como en estudios anteriores. Sin embargo, cuando la perturbación estaba autocorrelacionada espacialmente, esta ventaja se eliminaba o invertía debido a que las poblaciones en hábitats agregados están en riesgo de extinción masiva por eventos perturbadores a escala gruesa. Los efectos de patrones espaciales sobre el riesgo de extinción tendieron a reducirse por la dispersión de larga distancia. Debido a los altos niveles de correlación espacial en los procesos naturales y humanos de perturbación, la vulnerabilidad puede estar enormemente subestimada tanto por modelos clásicos (no espaciales) como por los que sólo consideran la estructura espacial del habitat. Los modelos que consideran la estructura espacial del hábitat solo subestiman el riesgo en comparación con modelos que consideran la estructura especial de la perturbación. [source] Life history and population size variability in a relict plant.DIVERSITY AND DISTRIBUTIONS, Issue 1 2008Different routes towards long-term persistence ABSTRACT A central tenet of conservation biology is that population size affects the persistence of populations. However, many narrow endemic species combine small population ranges and sizes with long persistence, thereby challenging this tenet. I examined the performance of three different-sized populations of Petrocoptis pseudoviscosa (Caryophyllaceae), a palaeoendemic rupicolous herb distributed along a small valley in the Spanish Pyrenees. Reproductive and demographic parameters were recorded over 6 years, and deterministic and stochastic matrix models were constructed to explore population dynamics and extinction risk. Populations differed greatly in structure, fecundity, recruitment, survival rate, and life span. Strong differentiation in life-history parameters and their temporal variability resulted in differential population vulnerability under current conditions and simulated global changes such as habitat fragmentation or higher climatic fluctuations. This study provides insights into the capacity of narrow endemics to survive both at extreme environmental conditions and at small population sizes. When dealing with species conservation, the population size,extinction risk relationship may be too simplistic for ancient, ecologically restricted organisms, and some knowledge of life history may be most important to assess their future. [source] Differences in prevalence of pressure ulcers between the Netherlands and Germany , associations between risk, prevention and occurrence of pressure ulcers in hospitals and nursing homesJOURNAL OF CLINICAL NURSING, Issue 9 2008Antje Tannen MA Aim., This study compares pressure ulcer prevalence and prevention activities in nursing homes and hospitals within two European countries. Background., Over three years stable differences have been found between the Netherlands (NL) and Germany (GER) with higher pressure ulcer rates in the NL. As previous analyses have shown, the differences cannot be entirely explained by differences in the population's vulnerability to pressure ulcers because they still remain after risk adjustment. Therefore, the differences in prevalence must be caused by other factors. The purpose of this study is to analyse if any potential differences in preventive activities can account for the varying occurrence of pressure ulcers. Method., In both countries, nation-wide surveys were conducted annually using the same standardised questionnaires. Trained nurses examined all consenting patients of the voluntarily participating facilities. This examination included a skin assessment of the entire body. Data regarding risk factors, prevention and details about wounds were then collected. Results., In-patients of 29 German (n = 2531) and 71 Dutch (n = 10 098) nursing homes and 39 German (n = 8515) and 60 Dutch (n = 10 237) hospitals were investigated. The use of pressure-reducing devices was more common in the NL than in GER, but all other interventions were more frequently provided to German risk patients than to their Dutch counterparts. The pressure ulcer prevalence was significantly higher in the Dutch sample. After adjusting for gender, age, Braden Score and prevention, the probability of having a pressure ulcer was 8·1 times higher for Dutch nursing home residents than for German residents. Conclusion., Some of the variance in pressure ulcer prevalence between the two countries can be explained by varying pressure ulcer prevention. However, some remarkable differences still remain unexplained. Relevance to clinical practice., The extent of pressure ulcer prevention, especially repositioning and nutrition intervention provided to patients at risk, is not in accordance with international guidelines. [source] Explaining the national differences in pressure ulcer prevalence between the Netherlands and Germany , adjusted for personal risk factors and institutional quality indicatorsJOURNAL OF EVALUATION IN CLINICAL PRACTICE, Issue 1 2009Antje Tannen RN MA MPH Abstract Background, Pressure ulcers have a known impact on quality of life as well as on morbidity and mortality of the persons affected. Remarkable differences in pressure ulcer prevalence between the Netherlands and Germany have been found during the last 6 years. This study explores to what extent the individual risk of the population and quality indicators of the institutions can explain the variation in national prevalence. Methods, Data of a binational multi-centred cross-sectional study in 103 hospitals (n = 21 378 patients) and 129 nursing homes (n = 15 579 residents) were analysed using random effects regression models to calculate the differences in national prevalences within the nursing homes and hospitals, adjusted for personal risk for pressure ulcer and quality indicators. Results, The prevalence of pressure ulcers among the at-risk group (Bradenscore ,20) in nursing homes was 30.8% in the Netherlands and 8.3% in Germany [OR: 4.9 (CI 95%: 4.2,5.7)]. In hospitals, the prevalence among the at-risk group was 26.1% in the Netherlands and 21.2% in Germany [OR: 1.3 (CI 95%: 1.2,1.5)]. After adjusting for individual risk factors (age, gender, Bradenscore) as well as for quality structures (use of prevention and treatment protocols, experts groups, information leaflets, nurses training, central pressure ulcer statistics and regular updating of protocols), the chance of developing a pressure ulcer was 6.05 times higher (CI 95%: 4.0,9.2) in a Dutch nursing home than in a German nursing home. Within the hospitals, the OR for Dutch patients was 2.03 (CI 95%: 1.4,3.0). Conclusion, A remarkable national variation exists in pressure ulcer prevalence and nursing practice. Neither the populations vulnerability for pressure ulcers nor pressure ulcer management as measured in this study could explain this national variation. Therefore, other risk factors should be taken into consideration. Additionally, it is possible that quality indicators are implemented in differing ways with varying levels of effectiveness. Therefore, further research is needed to examine prospectively and in more detail the reality of care within facilities in both countries. [source] | |||||||||||||