Geographical gradients in diet affect population dynamics of Canada lynx

Geographical gradients in the stability of cyclic populations of herbivores and their predators may relate to the degree of specialization of predators. However, such changes are usually associated with transition from specialist to generalist predator species, rather than from geographical variation in dietary breadth of specialist predators. Canada lynx (Lynx canadensis) and snowshoe hare (Lepus americanus) populations undergo cyclic fluctuations in northern parts of their range, but cycles are either greatly attenuated or lost altogether in the southern boreal forest where prey diversity is higher. We tested the influence of prey specialization on population cycles by measuring the stable carbon and nitrogen isotope ratios in lynx and their prey, estimating the contribution of hares to lynx diet across their range, and correlating this degree of specialization to the strength of their population cycles. Hares dominated the lynx diet across their range, but specialization on hares decreased in southern and western populations. The degree of specialization correlated with cyclic signal strength indicated by spectral analysis of lynx harvest data, but overall variability of lynx harvest (the standard deviation of natural-log-transformed harvest numbers) did not change significantly with dietary specialization. Thus, as alternative prey became more important in the lynx diet, the fluctuations became decoupled from a regular cycle but did not become less variable. Our results support the hypothesis that alternative prey decrease population cycle regularity but emphasize that such changes may be driven by dietary shifts among dominant specialist predators rather than exclusively through changes in the predator community.     

Raman spectroscopic documentation of Oligocene bladder stone

Discovery of a fossil (30–35 million-year-old) urolith from Early Oligocene deposits in northeastern Colorado provides the earliest evidence for the antiquity of bladder stones. These are spherical objects with a layered phosphatic structure and a hollow center. Each layer is composed of parallel crystals oriented perpendicular to the surface. Macroscopic and microscopic examination and X-ray diffraction analysis, along with comparison with 1,000 contemporary uroliths, were used as evidence in the confirmation of this diagnosis. Raman microspectroscopy verified the presence of organic material between layers, confirming its biologic origin.     

Mapping socio-economic scenarios of land cover change: a GIS method to enable ecosystem service modelling

We present a GIS method to interpret qualitatively expressed socio-economic scenarios in quantitative map-based terms. (i) We built scenarios using local stakeholders and experts to define how major land cover classes may change under different sets of drivers; (ii) we formalized these as spatially explicit rules, for example agriculture can only occur on certain soil types; (iii) we created a future land cover map which can then be used to model ecosystem services. We illustrate this for carbon storage in the Eastern Arc Mountains of Tanzania using two scenarios: the first based on sustainable development, the second based on 'business as usual' with continued forest-woodland degradation and poor protection of existing forest reserves. Between 2000 and 2025 4% of carbon stocks were lost under the first scenario compared to a loss of 41% of carbon stocks under the second scenario. Quantifying the impacts of differing future scenarios using the method we document here will be important if payments for ecosystem services are to be used to change policy in order to maintain critical ecosystem services.     

Prenatal sonographic features of esophageal and ileal duplications at 18 weeks of gestation

We present a case of esophageal and ileal duplications at 18 weeks of gestation. Transabdominal ultrasonography of the fetus showed multiple cystic masses of 12 to 17 mm in diameter and continuity with each other in the abdomen and a unilocular cystic mass of 15 mm in diameter in the posterior mediastinum. The cystic mass filled the abdominal cavity with signs of intestinal obstruction. The thoracic cystic mass was tubular, sausage-shaped and behind the heart, which was displaced to the antero-lateral wall of the chest. Amniocentesis revealed a normal fetal karyotype 46,XY. Peristaltic movements in the abdominal cystic structure at 30 weeks of gestation suggested dilated intestinal loops. Follow-up ultrasound examinations showed polyhydramnios with amniotic fluid index of 30 cm and gradual enlargement of the cystic structures to 50 mm in the abdomen and 30 mm in the posterior mediastinum at 38 weeks of gestation. A male infant weighing 3900 g was delivered. Postnatal ultrasonographic examination and the findings of magnetic resonance imaging also suggested enteric duplication cysts. Prenatal diagnosis allowed prompt neonatal evaluation and surgical treatment of the esophageal and the ileal duplications, which was confirmed by pathological examination. Copyright © 2004 John Wiley & Sons, Ltd.     

Transnational environmental problems — The United States,Canada, Mexico

Summary The paper examines the problems associated with transboundary environmental pollution. While briefly recording the efforts of international organizations in this area, the main content of the paper is concerned with an analysis of problems arising between the United States and Mexico, and between the United States and Canada. The paper also discusses new organizational forms that have been developed to bring transboundary issues to a higher policy-making level.Professor Wilcher entered the academic profession after a career in government service. He holds Masters Degrees from West Virginia University and the University of Pittsburgh and a Doctoral Degree from West Virginia University. He is currently Assistant Professor of Political Science at The Pennsylvania State University, New Kensington Campus. He is the author ofEnvironmental Cooperation in the North Atlantic Area published by the University Press of America.     

THE COST OF PEAK CAPACITY WATER1

ABSTRACT: Calgary, the fastest growing city in Canada, is about to expand its urban water supply facilities in order to meet peak summer demands. Most of Calgary's residential water is sold by flat rate. The effect of this pricing policy on peak and average demands is discussed. The true marginal cost of peak capacity from the new expansion is calculated. The effect of a proposed metering program on capacity expansion requirements is computed. It is concluded that metering should preceed the next capacity expansion.     

Predicting arsenic concentrations in groundwater of San Luis Valley,Colorado: implications for individual-level lifetime exposure assessment

Consumption of inorganic arsenic in drinking water at high levels has been associated with chronic diseases. Risk is less clear at lower levels of arsenic, in part due to difficulties in estimating exposure. Herein we characterize spatial and temporal variability of arsenic concentrations and develop models for predicting aquifer arsenic concentrations in the San Luis Valley, Colorado, an area of moderately elevated arsenic in groundwater. This study included historical water samples with total arsenic concentrations from 595 unique well locations. A longitudinal analysis established temporal stability in arsenic levels in individual wells. The mean arsenic levels for a random sample of 535 wells were incorporated into five kriging models to predict groundwater arsenic concentrations at any point in time. A separate validation dataset (n = 60 wells) was used to identify the model with strongest predictability. Findings indicate that arsenic concentrations are temporally stable (r = 0.88; 95 % CI 0.83–0.92 for samples collected from the same well 15–25 years apart) and the spatial model created using ordinary kriging best predicted arsenic concentrations (ρ = 0.72 between predicted and observed validation data). These findings illustrate the value of geostatistical modeling of arsenic and suggest the San Luis Valley is a good region for conducting epidemiologic studies of groundwater metals because of the ability to accurately predict variation in groundwater arsenic concentrations.     

Improving species status assessments under the U.S. Endangered Species Act and implications for multispecies conservation challenges worldwide

Despite its successes, the U.S. Endangered Species Act (ESA) has proven challenging to implement due to funding limitations, workload backlog, and other problems. As threats to species survival intensify and as more species come under threat, the need for the ESA and similar conservation laws and policies in other countries to function efficiently has grown. Attempts by the U.S. Fish and Wildlife Service (USFWS) to streamline ESA decisions include multispecies recovery plans and habitat conservation plans. We address species status assessment (SSA), a USFWS process to inform ESA decisions from listing to recovery, within the context of multispecies and ecosystem planning. Although existing SSAs have a single-species focus, ecosystem-based research can efficiently inform multiple SSAs within a region and provide a foundation for transition to multispecies SSAs in the future. We considered at-risk grassland species and ecosystems within the southeastern United States, where a disproportionate number of rare and endemic species are associated with grasslands. To initiate our ecosystem-based approach, we used a combined literature-based and structured World Café workshop format to identify science needs for SSAs. Discussions concentrated on 5 categories of threats to grassland species and ecosystems, consistent with recommendations to make shared threats a focus of planning under the ESA: (1) habitat loss, fragmentation, and disruption of functional connectivity; (2) climate change; (3) altered disturbance regimes; (4) invasive species; and (5) localized impacts. For each threat, workshop participants identified science and information needs, including database availability, research priorities, and modeling and mapping needs. Grouping species by habitat and shared threats can make the SSA process and other planning processes for conservation of at-risk species worldwide more efficient and useful. We found a combination of literature review and structured discussion effective for identifying the scientific information and analysis needed to support the development of multiple SSAs. Article impact statement: Species status assessments can be improved by an ecosystem-based approach that groups imperiled species by shared habitats and threats.     

Analyzing maps of dispersal around a single focus

The spatial pattern of organisms may be used to characterize their dispersal, quantify spread or estimate the point of introduction of an alien species. Their distribution may be represented by maps of individuals, or by counts or by presence/absence at known positions within a sampled area. The problems and relative merits of these different forms of data for spatial inference are discussed. Three datasets concerning dispersal from a single focus are analyzed: counts of aphids, Rhopalosiphum padi and Sitobion avenae, on barley plants, Hordeum vulgare, grown in experi- mental trays; mapped locations of couch grass, Elymus repens, tillers within plots of a field experiment; locations of sightings of the lupin aphid, Macrosiphum albifrons, as it invaded Great Britain between 1981 and 1984. A method for generating maps from counts is proposed to overcome problems caused by recording imprecision. Several statistics are used to quantify dispersal and spatial pattern in the experimental data and together provide a clear picture of the spatial pattern observed; they enabled several effects of the experimental treatments to be identified. The value of the statistics are compared. Estimates of the source of the lupin aphid invasion are obtained using the backtracking methods of Perry (1995b) and do not contradict previous suggestions.