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1.
PLoS Biol ; 20(12): e3001921, 2022 12.
Artigo em Inglês | MEDLINE | ID: mdl-36548240

RESUMO

Antarctic terrestrial biodiversity faces multiple threats, from invasive species to climate change. Yet no large-scale assessments of threat management strategies exist. Applying a structured participatory approach, we demonstrate that existing conservation efforts are insufficient in a changing world, estimating that 65% (at best 37%, at worst 97%) of native terrestrial taxa and land-associated seabirds are likely to decline by 2100 under current trajectories. Emperor penguins are identified as the most vulnerable taxon, followed by other seabirds and dry soil nematodes. We find that implementing 10 key threat management strategies in parallel, at an estimated present-day equivalent annual cost of US$23 million, could benefit up to 84% of Antarctic taxa. Climate change is identified as the most pervasive threat to Antarctic biodiversity and influencing global policy to effectively limit climate change is the most beneficial conservation strategy. However, minimising impacts of human activities and improved planning and management of new infrastructure projects are cost-effective and will help to minimise regional threats. Simultaneous global and regional efforts are critical to secure Antarctic biodiversity for future generations.


Assuntos
Conservação dos Recursos Naturais , Spheniscidae , Animais , Humanos , Regiões Antárticas , Biodiversidade , Espécies Introduzidas , Mudança Climática , Ecossistema
2.
Mol Ecol ; 33(6): e17282, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38299701

RESUMO

Many species are shifting their ranges in response to climate-driven environmental changes, particularly in high-latitude regions. However, the patterns of dispersal and colonization during range shifting events are not always clear. Understanding how populations are connected through space and time can reveal how species navigate a changing environment. Here, we present a fine-scale population genomics study of gentoo penguins (Pygoscelis papua), a presumed site-faithful colonial nesting species that has increased in population size and expanded its range south along the Western Antarctic Peninsula. Using whole genome sequencing, we analysed 129 gentoo penguin individuals across 12 colonies located at or near the southern range edge. Through a detailed examination of fine-scale population structure, admixture, and population divergence, we inferred that gentoo penguins historically dispersed rapidly in a stepping-stone pattern from the South Shetland Islands leading to the colonization of Anvers Island, and then the adjacent mainland Western Antarctica Peninsula. Recent southward expansion along the Western Antarctic Peninsula also followed a stepping-stone dispersal pattern coupled with limited post-divergence gene flow from colonies on Anvers Island. Genetic diversity appeared to be maintained across colonies during the historical dispersal process, and range-edge populations are still growing. This suggests large numbers of migrants may provide a buffer against founder effects at the beginning of colonization events to maintain genetic diversity similar to that of the source populations before migration ceases post-divergence. These results coupled with a continued increase in effective population size since approximately 500-800 years ago distinguish gentoo penguins as a robust species that is highly adaptable and resilient to changing climate.


Assuntos
Efeito Fundador , Spheniscidae , Humanos , Animais , Densidade Demográfica , Spheniscidae/genética , Regiões Antárticas , Sequenciamento Completo do Genoma
3.
Regul Toxicol Pharmacol ; 144: 105468, 2023 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-37562533

RESUMO

Propylene dichloride (PDC) is a chlorinated substance used primarily as an intermediate in basic organic chemical manufacturing. The United States Environmental Protection Agency (EPA) is currently evaluating PDC as a high-priority substance under the Toxic Substances Control Act (TSCA). We conducted a systematic review of the non-cancer and cancer hazards of PDC using the EPA TSCA and Integrated Risk Information System (IRIS) frameworks. We identified 12 epidemiological, 16 toxicokinetic, 34 experimental animal, and 49 mechanistic studies. Point-of-contact respiratory effects are the most sensitive non-cancer effects after inhalation exposure, and PDC is neither a reproductive nor a developmental toxicant. PDC is not mutagenic in vivo, and while in vitro evidence is mixed, DNA strand breaks consistently occur. Nasal tumors in rats and lung tumors in mice occurred after lifetime high-level inhalation exposure. Cholangiocarcinoma (CCA) was observed in Japanese print workers exposed to high concentrations of PDC. However, co-exposures, as well as liver parasites, hepatitis, and other risk factors, may also have contributed. The cancer mode of action (MOA) analysis revealed that PDC may act through multiple biological pathways occurring sequentially and/or simultaneously, although chronic tissue damage and inflammation likely dominate. Critically, health benchmarks protective of non-cancer effects are expected to protect against cancer in humans.

4.
Toxicol Ind Health ; 39(3): 169-182, 2023 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-36656073

RESUMO

The focus on occupational exposures in the first published risk evaluations of existing chemicals by the Environmental Protection Agency (EPA) under the amended Toxic Substances Control Act (TSCA) puts a welcome spotlight on protecting the health of workers in the United States. Because new, fit-for-purpose occupational exposure assessment methodologies were developed by EPA, the objective of this analysis was to evaluate these methodologies in light of other existing occupational risk assessment frameworks. We focused our analysis on three chlorinated chemicals (methylene chloride, carbon tetrachloride, perchloroethylene). The EPA's methods were evaluated relative to peer-reviewed and professional organizations' guidelines for conducting site- and facility-based exposure assessment. Analyses of several key phases in the EPA approach were conducted to evaluate the effect of alternative approaches on exposure estimates. The revised exposure estimates using these alternative approaches yielded substantially different exposure estimates from those in the TSCA risk evaluations for these chemicals. The results also demonstrated the importance of utilizing a tiered approach to exposure estimation that includes collecting qualitative data, defining similar exposure groups, and integrating well-parameterized models with empirical data. These approaches aid in preventing mischaracterization of exposures and generating exposure estimates representative of current industrial practices. Collaboration among industry, EPA, and other government agencies to develop a harmonized approach to exposure assessment would improve the methodological rigor of, and increase stakeholder confidence in, the results of TSCA risk evaluations.


Assuntos
Exposição por Inalação , Exposição Ocupacional , Estados Unidos , Humanos , Exposição por Inalação/efeitos adversos , United States Environmental Protection Agency , Exposição Ocupacional/efeitos adversos , Medição de Risco/métodos , Indústrias
5.
Toxicol Ind Health ; 39(1): 49-65, 2023 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-36420912

RESUMO

The United States Environmental Protection Agency (EPA) regulates chemical manufacture, import, processing, distribution, use, and disposal under the 2016 amended Toxic Substances Control Act (TSCA) for the purposes of protecting the public and sensitive populations-including workers-from chemical exposure risk. The publication of several TSCA risk evaluations provided a unique opportunity to evaluate the evolving regulatory approach for assessing the dermal exposure pathway in occupational settings. In this analysis, the occupational dermal exposure assessment methods employed in several TSCA risk evaluations were assessed. Specifically, a methodology review was conducted for the occupational dermal scenarios of manufacturing and feedstock use in the risk evaluations of three chlorinated organic chemicals: trichloroethylene, carbon tetrachloride, and perchloroethylene. Additionally, alternative exposure estimates were generated using the exposure model IH SkinPermTM. The review and alternative exposure analyses indicate that the current TSCA modeling approach may generate total dermal absorbed doses for chlorinated chemical manufacturing and feedstock use scenarios that are 2- to 20-fold higher than those generated by IH SkinPerm. Best-practice recommendations developed in the methodology review support a tiered, integrated approach to dermal exposure assessment that emphasizes collecting qualitative data; employing validated, peer-reviewed models that align with current industrial practices; and gathering empirical sampling data where needed. Collaboration among industry, EPA, and other stakeholders to share information and develop a standard approach to exposure assessment under TSCA would improve the methodological rigor of, and increase confidence in, the risk evaluation results.


Assuntos
Exposição Ocupacional , Humanos , Estados Unidos , United States Environmental Protection Agency , Exposição Ocupacional/efeitos adversos , Comércio , Medição de Risco , Substâncias Perigosas/toxicidade
6.
Int Soc Work ; 66(6): 1816-1830, 2023 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-37969872

RESUMO

This article contributes a comparative review of social work in Canada and Scotland to international conversations about social work and the environment. The 'environmental question' of the 21st century is a radical challenge to social work developed in relation to the 'social question' of the 19th century. Work to begin to include the natural environment within high-income state social work can expect to encounter established infrastructures of thinking and doing that will be difficult to shift. We, therefore, compare guiding social work policy documents and identify points of tension that are likely to be shared across wealthy national contexts.

7.
Glob Chang Biol ; 28(20): 5865-5880, 2022 10.
Artigo em Inglês | MEDLINE | ID: mdl-35795907

RESUMO

Antarctic biodiversity faces an unknown future with a changing climate. Most terrestrial biota is restricted to limited patches of ice-free land in a sea of ice, where they are adapted to the continent's extreme cold and wind and exploit microhabitats of suitable conditions. As temperatures rise, ice-free areas are predicted to expand, more rapidly in some areas than others. There is high uncertainty as to how species' distributions, physiology, abundance, and survivorship will be affected as their habitats transform. Here we use current knowledge to propose hypotheses that ice-free area expansion (i) will increase habitat availability, though the quality of habitat will vary; (ii) will increase structural connectivity, although not necessarily increase opportunities for species establishment; (iii) combined with milder climates will increase likelihood of non-native species establishment, but may also lengthen activity windows for all species; and (iv) will benefit some species and not others, possibly resulting in increased homogeneity of biodiversity. We anticipate considerable spatial, temporal, and taxonomic variation in species responses, and a heightened need for interdisciplinary research to understand the factors associated with ecosystem resilience under future scenarios. Such research will help identify at-risk species or vulnerable localities and is crucial for informing environmental management and policymaking into the future.


Assuntos
Biodiversidade , Ecossistema , Regiões Antárticas , Biota , Mudança Climática , Vento
8.
J Anim Ecol ; 91(12): 2437-2450, 2022 12.
Artigo em Inglês | MEDLINE | ID: mdl-36266757

RESUMO

The population dynamics of many colonially breeding seabirds are characterized by large interannual fluctuations that cannot be explained by environmental conditions alone. This variation may be particularly confounded by the use of skipped breeding by seabirds as a life-history strategy, which directly impacts the number of breeding pairs and may affect the accuracy of breeding abundance as a metric of population health. Additionally, large fluctuations in time series may suggest that the underlying population dynamics are heavy tailed, allowing for a higher likelihood of extreme events than expected under Gaussian dynamics. Here, we investigated the effect of demography on time series for abundance of the Adélie penguin Pygoscelis adeliae and explored the occurrence of heavy-tailed dynamics in observed Adélie time series. We focus this study on the Adélie penguin as it is an important bellwether species long used to track the impacts of climate change and fishing on the Southern Ocean ecosystem and shares life-history traits with many colonial seabirds. We quantified the impacts of demographic rates, including skipped breeding, on time series of Adélie abundance simulated using an age-structured model. We also used observed time series of Adélie breeding abundance at all known Antarctic colonies to classify distributions for abundance as Gaussian or non-Gaussian heavy tailed. We then identified the cause of such heavy-tailed dynamics in simulated time series and linked these to spatial patterns in Adélie food resource variability. We found that breeding propensity drives observed breeding fluctuations more than any other vital rate, with high variability in skipped breeding decoupling true abundance from observed breeding abundance. We also found several Antarctic regions characterized by heavy-tailed dynamics in abundance. These regions were often also characterized by high variability in zooplankton availability. In simulated time series, heavy-tailed dynamics were strongly linked to high variability in adult survival. Our results illustrate that stochastic variability in abundance dynamics, particularly the presence of variable rates of skipped breeding, can challenge our interpretation of fluctuations in abundance through time and obscure the relationship between key environmental drivers and population abundance.


Assuntos
Ecossistema , Animais , Regiões Antárticas , Dinâmica Populacional
9.
Glob Chang Biol ; 26(7): 3788-3798, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32190944

RESUMO

Understanding the scales at which environmental variability affects populations is critical for projecting population dynamics and species distributions in rapidly changing environments. Here we used a multilevel Bayesian analysis of range-wide survey data for Adélie penguins to characterize multidecadal and annual effects of sea ice on population growth. We found that mean sea ice concentration at breeding colonies (i.e., "prevailing" environmental conditions) had robust nonlinear effects on multidecadal population trends and explained over 85% of the variance in mean population growth rates among sites. In contrast, despite considerable year-to-year fluctuations in abundance at most breeding colonies, annual sea ice fluctuations often explained less than 10% of the temporal variance in population growth rates. Our study provides an understanding of the spatially and temporally dynamic environmental factors that define the range limits of Adélie penguins, further establishing this iconic marine predator as a true sea ice obligate and providing a firm basis for projection under scenarios of future climate change. Yet, given the weak effects of annual sea ice relative to the large unexplained variance in year-to-year growth rates, the ability to generate useful short-term forecasts of Adélie penguin breeding abundance will be extremely limited. Our approach provides a powerful framework for linking short- and longer term population processes to environmental conditions that can be applied to any species, facilitating a richer understanding of ecological predictability and sensitivity to global change.


Assuntos
Spheniscidae , Animais , Regiões Antárticas , Teorema de Bayes , Mudança Climática , Camada de Gelo , Crescimento Demográfico
10.
PLoS Biol ; 15(3): e2001656, 2017 03.
Artigo em Inglês | MEDLINE | ID: mdl-28350825

RESUMO

The Strategic Plan for Biodiversity, adopted under the auspices of the Convention on Biological Diversity, provides the basis for taking effective action to curb biodiversity loss across the planet by 2020-an urgent imperative. Yet, Antarctica and the Southern Ocean, which encompass 10% of the planet's surface, are excluded from assessments of progress against the Strategic Plan. The situation is a lost opportunity for biodiversity conservation globally. We provide such an assessment. Our evidence suggests, surprisingly, that for a region so remote and apparently pristine as the Antarctic, the biodiversity outlook is similar to that for the rest of the planet. Promisingly, however, much scope for remedial action exists.


Assuntos
Biodiversidade , Conservação dos Recursos Naturais/tendências , Regiões Antárticas , Conservação dos Recursos Naturais/métodos
11.
Conserv Biol ; 34(1): 256-265, 2020 02.
Artigo em Inglês | MEDLINE | ID: mdl-31460682

RESUMO

Antarctic fur seals (Arctocephalus gazella) were commercially exploited on the subantarctic island of South Georgia for over 100 years and nearly driven to extinction. Since the cessation of harvesting, however, their populations have rebounded, and they are now often considered a nuisance species whose impact on the terrestrial landscape should be mitigated. Any evaluation of their current population requires the context provided by their historic, pre-exploitation abundance, lest ecologists fall prey to shifting baseline syndrome in which their perspective on current abundance is compared only with an altered state resulting from past anthropogenic disturbance. Estimating pre-exploitation abundance is critical to defining species recovery and setting recovery targets, both of which are needed for the International Union for the Conservation of Nature's recent efforts to develop a green list of recovering species. To address this issue, we reconstructed the South Georgia fur seal harvest from 1786 to 1908 from ship logbooks and other historical records and interpolated missing harvest data as necessary with a generalized linear model fit to the historical record. Using an approximate Bayesian computation framework, harvest data, and a stochastic age-structured population model, we estimated the pre-exploitation abundance of Antarctic fur seals on South Georgia was 2.5 million females (95% CI 1.5-3.5 million). This estimate is similar to recent abundance estimates, and suggests current populations, and the ecological consequences of so many fur seals on the island, may be similar to conditions prior to human harvest. Although the historic archive on the fur sealing era is unavoidably patchy, the use of archival records is essential for reconstructing the past and, correspondingly, to understanding the present. Article impact statement: Defining species recovery requires an understanding of baseline population state, which can be estimated through statistical methods.


Un Método para Estimar el Tamaño Poblacional Previo a la Explotación Resumen La foca antártica (Arctocephalus gazella) fue explotada comercialmente en la isla subantártica de Georgia del Sur durante más de 100 años y esto casi la llevó a la extinción. Sin embargo, desde que se detuvo la captura de esta especie, su población se ha recuperado y actualmente se le considera con frecuencia una especie molesta cuyo impacto sobre el paisaje terrestre debería ser mitigado. Cualquier evaluación de la población actual requiere del contexto proporcionado por su abundancia histórica previa a la explotación para así evitar que los ecólogos sufran del síndrome de la línea base cambiante, en el cual la perspectiva de la abundancia contemporánea se compara solamente con un estado alterado resultante de perturbaciones antropogénicas pasadas. La estimación de la abundancia previa a la explotación es sumamente importante para definir la recuperación de una especie y para establecer los objetivos de recuperación, ambos requisitos necesarios para los esfuerzos recientes de la Unión Internacional para la Conservación de la Naturaleza (UICN) por desarrollar una lista verde de especies en recuperación. Para tratar este tema reconstruimos la captura de la foca antártica en la isla de Georgia del Sur desde 1786 hasta 1908 a partir de bitácoras de navíos y otros registros históricos e interpolamos los datos faltantes de las capturas conforme fuera necesario con un modelo lineal generalizado que se ajustara al registro histórico. Con un marco de trabajo de cómputo bayesiano aproximado, los datos de las capturas y un modelo poblacional estocástico estructurado por edades estimamos que la abundancia previa a la explotación de la foca antártica en la isla de Georgia del Sur era de 2.5 millones de hembras (95% IC1.5 - 3.5 millones). Este estimado es similar a las estimaciones recientes de abundancia y sugiere que las poblaciones actuales y las consecuencias ecológicas de la presencia de tantas focas en la isla podría ser similar a las condiciones previas a la captura. Aunque el archivo histórico sobre la era de la caza de focas antárticas presenta vacíos inevitablemente, el uso de registros archivados es esencial para la reconstrucción del pasado y, correspondientemente, para entender el presente.


Assuntos
Conservação dos Recursos Naturais , Animais , Regiões Antárticas , Teorema de Bayes , Feminino , Georgia , Humanos , Densidade Demográfica
12.
Crit Rev Toxicol ; 49(7): 597-613, 2019 08.
Artigo em Inglês | MEDLINE | ID: mdl-31965908

RESUMO

Esophageal cancers comprise about 1% of all cancers diagnosed in the US but are more prevalent in other regions of the world. Several regulatory agencies have classified asbestos as a known human carcinogen, and it is linked to multiple diseases and malignancies, including lung cancer and mesothelioma. In a 2006 review of the epidemiological literature, the Institute of Medicine (IOM) did not find sufficient evidence to demonstrate a causal relationship between asbestos exposure and esophageal cancer. To reevaluate this conclusion, we performed a critical review of the animal toxicological, epidemiological, and mechanism of action literature on esophageal cancer and asbestos, incorporating studies published since 2006. Although there is some evidence in the epidemiological literature for an increased risk of esophageal cancer in asbestos-exposed occupational cohorts, these studies generally did not control for critical esophageal cancer risk factors (e.g. smoking, alcohol consumption). Furthermore, data from animal toxicological studies do not indicate that asbestos exposure increases esophageal cancer risk. Based on our evaluation of the literature, and reaffirming the IOM's findings, we conclude that there is insufficient evidence to demonstrate a causal link between asbestos exposure and esophageal cancer.


Assuntos
Amianto , Exposição Ambiental/estatística & dados numéricos , Neoplasias Esofágicas/epidemiologia , Substâncias Perigosas , Animais , Humanos
13.
J Anim Ecol ; 87(3): 682-690, 2018 05.
Artigo em Inglês | MEDLINE | ID: mdl-29277890

RESUMO

Phenological changes have been observed in a variety of systems over the past century. There is concern that, as a consequence, ecological interactions are becoming increasingly mismatched in time, with negative consequences for ecological function. Significant spatial heterogeneity (inter-site) and temporal variability (inter-annual) can make it difficult to separate intrinsic, extrinsic and stochastic drivers of phenological variability. The goal of this study was to understand the timing and variability in breeding phenology of Adélie penguins under fixed environmental conditions and to use those data to identify a "null model" appropriate for disentangling the sources of variation in wild populations. Data on clutch initiation were collected from both wild and captive populations of Adélie penguins. Clutch initiation in the captive population was modelled as a function of year, individual and age to better understand phenological patterns observed in the wild population. Captive populations displayed as much inter-annual variability in breeding phenology as wild populations, suggesting that variability in breeding phenology is the norm and thus may be an unreliable indicator of environmental forcing. The distribution of clutch initiation dates was found to be moderately asymmetric (right skewed) both in the wild and in captivity, consistent with the pattern expected under social facilitation. The role of stochasticity in phenological processes has heretofore been largely ignored. However, these results suggest that inter-annual variability in breeding phenology can arise independent of any environmental or demographic drivers and that synchronous breeding can enhance inherent stochasticity. This complicates efforts to relate phenological variation to environmental variability in the wild. Accordingly, we must be careful to consider random forcing in phenological processes, lest we fit models to data dominated by random noise. This is particularly true for colonial species where breeding synchrony may outweigh each individual's effort to time breeding with optimal environmental conditions. Our study highlights the importance of identifying appropriate null models for studying phenology.


Assuntos
Mudança Climática , Comportamento de Nidação , Spheniscidae/fisiologia , Fatores Etários , Animais , Animais Selvagens/fisiologia , Animais de Zoológico/fisiologia , Regiões Antárticas , California , Processos Estocásticos , Fatores de Tempo
14.
Environ Res ; 160: 391-397, 2018 01.
Artigo em Inglês | MEDLINE | ID: mdl-29059621

RESUMO

To determine whether evidence indicates that short-term exposure to ambient concentrations of ozone in the United States can affect asthma severity, we systematically reviewed published controlled human exposure, epidemiology, and animal toxicity studies. The strongest evidence for a potential causal relationship came from epidemiology studies reporting increased emergency department visits and hospital admissions for asthma following elevated ambient ozone concentrations. However, while controlled exposure studies reported lung function decrements and increased asthma symptoms following high ozone exposures 160-400 parts per billion [ppb]), epidemiology studies evaluating similar outcomes reported less consistent results. Animal studies showed changes in pulmonary function at high ozone concentrations (> 500ppb), although there is substantial uncertainty regarding the relevance of these animal models to human asthma. Taken together, the weight of evidence indicates that there is at least an equal likelihood that either explanation is true, i.e., the strength of the evidence for a causal relationship between short-term exposure to ambient ozone concentrations and asthma severity is "equipoise and above."


Assuntos
Poluentes Atmosféricos/toxicidade , Asma/epidemiologia , Exposição Ambiental/efeitos adversos , Hospitalização/estatística & dados numéricos , Ozônio/toxicidade , Animais , Asma/induzido quimicamente , Serviço Hospitalar de Emergência/estatística & dados numéricos , Humanos , Estados Unidos/epidemiologia
15.
Regul Toxicol Pharmacol ; 97: 189-196, 2018 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-29964120

RESUMO

In 2016, the American Conference of Governmental Industrial Hygienists (ACGIH) lowered the 8-hr Threshold Limit Value - time-weighted average (TLV-TWA) for toluene diisocyanate (TDI) from 5 ppb to 1 ppb, and the 15-min short-term exposure limit (STEL) from 20 ppb to 5 ppb. We evaluated ACGIH's basis for lowering these values. It is our opinion that the ACGIH's evaluation of the evidence for occupational asthma and respiratory effects from TDI exposure does not fully integrate the results of all the available human and animal studies. We found that some studies reported occupational asthma cases at TWAs less than 5 ppb, but these cases were likely caused by peak exposures above 20 ppb. Advances in industrial hygiene have reduced peak exposures and the incidence of upset conditions, such as spills and accidents, in modern TDI facilities. Taken together, the human evidence indicates that adherence to the previous 8-hr TLV-TWA and 15-min STEL (5 ppb and 20 ppb, respectively) prevents most, if not all, cases of occupational asthma, and eliminates or reduces the risk of lung function decrements and other respiratory effects. While limited, the animal literature supports the human evidence and indicates that TDI-induced asthma is a threshold phenomenon. We conclude that ACGIH's decision to lower the TLV-TWA and STEL values for TDI is not adequately supported.


Assuntos
Poluentes Ocupacionais do Ar/efeitos adversos , Asma Ocupacional/induzido quimicamente , Exposição Ocupacional/efeitos adversos , Tolueno 2,4-Di-Isocianato/efeitos adversos , Animais , Humanos , Saúde Ocupacional , Níveis Máximos Permitidos , Tolueno 2,4-Di-Isocianato/administração & dosagem
16.
Ecology ; 98(7): 1764-1770, 2017 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-28452047

RESUMO

Analyses of point process patterns and related techniques (e.g., MaxEnt) make use of the expected number of occurrences per unit area and second-order statistics based on the distance between occurrences. Ecologists working with point process data often assume that points exist on a two-dimensional x-y plane or within a three-dimensional volume, when in fact many observed point patterns are generated on a two-dimensional surface existing within three-dimensional space. For many surfaces, however, such as the topography of landscapes, the projection from the surface to the x-y plane preserves neither area nor distance. As such, when these point patterns are implicitly projected to and analyzed in the x-y plane, our expectations of the point pattern's statistical properties may not be met. When used in hypothesis testing, we find that the failure to account for the topography of the generating surface may bias statistical tests that incorrectly identify clustering and, furthermore, may bias coefficients in inhomogeneous point process models that incorporate slope as a covariate. We demonstrate the circumstances under which this bias is significant, and present simple methods that allow point processes to be simulated with corrections for topography. These point patterns can then be used to generate "topographically corrected" null models against which observed point processes can be compared.


Assuntos
Ecologia , Modelos Teóricos , Análise por Conglomerados
17.
Ecology ; 98(4): 940-951, 2017 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-28129431

RESUMO

Evidence of climate-change-driven shifts in plant and animal phenology have raised concerns that certain trophic interactions may be increasingly mismatched in time, resulting in declines in reproductive success. Given the constraints imposed by extreme seasonality at high latitudes and the rapid shifts in phenology seen in the Arctic, we would also expect Antarctic species to be highly vulnerable to climate-change-driven phenological mismatches with their environment. However, few studies have assessed the impacts of phenological change in Antarctica. Using the largest database of phytoplankton phenology, sea-ice phenology, and Adélie Penguin breeding phenology and breeding success assembled to date, we find that, while a temporal match between Penguin breeding phenology and optimal environmental conditions sets an upper limit on breeding success, only a weak relationship to the mean exists. Despite previous work suggesting that divergent trends in Adélie Penguin breeding phenology are apparent across the Antarctic continent, we find no such trends. Furthermore, we find no trend in the magnitude of phenological mismatch, suggesting that mismatch is driven by interannual variability in environmental conditions rather than climate-change-driven trends, as observed in other systems. We propose several criteria necessary for a species to experience a strong climate-change-driven phenological mismatch, of which several may be violated by this system.


Assuntos
Mudança Climática , Spheniscidae/fisiologia , Animais , Regiões Antárticas , Ecologia , Fenótipo , Reprodução , Estações do Ano
18.
Toxicol Appl Pharmacol ; 319: 39-46, 2017 03 15.
Artigo em Inglês | MEDLINE | ID: mdl-28162991

RESUMO

BACKGROUND: The International Agency for Research on Cancer (IARC) recently developed a framework for evaluating mechanistic evidence that includes a list of 10 key characteristics of carcinogens. This framework is useful for identifying and organizing large bodies of literature on carcinogenic mechanisms, but it lacks sufficient guidance for conducting evaluations that fully integrate mechanistic evidence into hazard assessments. OBJECTIVES: We summarize the framework, and suggest approaches to strengthen the evaluation of mechanistic evidence using this framework. DISCUSSION: While the framework is useful for organizing mechanistic evidence, its lack of guidance for implementation limits its utility for understanding human carcinogenic potential. Specifically, it does not include explicit guidance for evaluating the biological significance of mechanistic endpoints, inter- and intra-individual variability, or study quality and relevance. It also does not explicitly address how mechanistic evidence should be integrated with other realms of evidence. Because mechanistic evidence is critical to understanding human cancer hazards, we recommend that IARC develop transparent and systematic guidelines for the use of this framework so that mechanistic evidence will be evaluated and integrated in a robust manner, and concurrently with other realms of evidence, to reach a final human cancer hazard conclusion. CONCLUSIONS: IARC does not currently provide a standardized approach to evaluating mechanistic evidence. Incorporating the recommendations discussed here will make IARC analyses of mechanistic evidence more transparent, and lead to assessments of cancer hazards that reflect the weight of the scientific evidence and allow for scientifically defensible decision-making.


Assuntos
Pesquisa Biomédica/normas , Carcinógenos/toxicidade , Agências Internacionais/normas , Neoplasias/induzido quimicamente , Pesquisa Biomédica/tendências , Tomada de Decisões , Humanos , Agências Internacionais/tendências , Neoplasias/diagnóstico , Neoplasias/epidemiologia
20.
Regul Toxicol Pharmacol ; 76: 187-98, 2016 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-26743741

RESUMO

Approaches for the systematic review and evaluation of chemical toxicity are currently being reconsidered, with a specific focus on the evaluation of individual studies and their integration into the overall body of evidence. This renewed interest has arisen, in part, as a result of several prominent reviews of these approaches by special committees of the National Research Council (NRC), among others. We conducted a critical evaluation of several available frameworks for evaluating study quality. We assessed the criteria separately for human, animal, and in vitro studies as well as for systematic reviews. We then evaluated commonalities across disciplines. We also considered the potential implications of applying criteria frameworks and how they bear on fundamental risk assessment questions. We found that the available frameworks within each discipline differed in terms of their intended purpose and level of guidance for decision making. All the frameworks across disciplines shared common themes, however, including the adequate reporting of specific details of study conditions and design/protocol, selection and randomization of study groups (where applicable), outcome assessment methods and applicability (e.g., validity and reliability), avoidance of selective reporting, and the consideration of potential confounders or bias. We identified the most informative study quality considerations, which will enable researchers to implement more objective and standardized methods for evaluating studies and, ultimately, improve risk assessment methods.


Assuntos
Confiabilidade dos Dados , Projetos de Pesquisa/normas , Literatura de Revisão como Assunto , Testes de Toxicidade/normas , Animais , Viés , Interpretação Estatística de Dados , Guias como Assunto , Humanos , Projetos de Pesquisa/estatística & dados numéricos , Medição de Risco , Testes de Toxicidade/estatística & dados numéricos
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