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PubMed2002

The potential for bias in Cohen's ecological analysis of lung cancer and residential radon.

Cohen's ecological analysis of US lung cancer mortality rates and mean county radon concentration shows decreasing mortality rates with increasing radon concentration (Cohen 1995 Health Phys. 68 157-74). The results prompted his rejection of the linear-no-threshold (LNT) model for radon and lung cancer. Although several authors have demonstrated that risk patterns in ecological analyses provide no inferential value for assessment of risk to individuals, Cohen advances two arguments in a recent response to Darby and Doll (2000 J. Radiol. Prot. 20 221-2) who suggest Cohen's results are and will always be burdened by the ecological fallacy. Cohen asserts that the ecological fallacy does not apply when testing the LNT model, for which average exposure determines average risk, and that the influence of confounding factors is obviated by the use of large numbers of stratification variables. These assertions are erroneous. Average dose determines average risk only for models which are linear in all covariates, in which case ecological analyses are valid. However, lung cancer risk and radon exposure, while linear in the relative risk, are not linearly related to the scale of absolute risk, and thus Cohen's rejection of the LNT model is based on a false premise of linearity. In addition, it is demonstrated that the deleterious association for radon and lung cancer observed in residential and miner studies is consistent with negative trends from ecological studies, of the type described by Cohen.

Air Pollutants, Radioactive↗
PubMed2005

Plant ecology of Australia's tropical floodplain wetlands: a review.

AIMS: Despite the biodiversity values of the freshwater floodplains of northern Australia being widely recognized, there has not been a concomitant investment in developing the extent of knowledge of the basic functions and ecological processes that underpin the ecological character of these habitats. This review addresses the extent of our knowledge on the plant ecology of these wetlands and covers: the relationships between the climate and the hydrological regime on the floodplain; the vegetation patterns, succession and adaptation; and primary production. SCOPE: Information is available on the seasonal, but less regularly on the inter-annual, dynamics of the macrophytic vegetation and its evident inter-relationship with the extent, depth and duration of inundation by seasonal flooding. The available scientifically collected information on plant distribution and relationship with the water regime could be complemented by more attention to traditional knowledge. The productivity of the vegetation is high-the dominant wetland grass species have an annual dry weight production of 0.5-2.1 kg m-2 and the surrounding riparian (Melaleuca) trees contribute litterfall of 0.7-1.5 kg (dry weight) m-2 year-1, approximately 70% due to leaf-fall. The availability of dissolved oxygen in the water is known to vary diurnally and seasonally, at least in some habitats. The importance of seasonal differences in the availability of dissolved oxygen for the growth of micro- and macrophytic vegetation has not been investigated. The seasonal distribution and growth of plant species on a few floodplains have been investigated, and maps at scales of 1:10,000 to 1:100,000 are available for these. However, only on a few occasions have longer term analyses been conducted and long-term changes in the vegetation measured and assessed. Species lists and categorization of growth strategies and forms are available and provide a basis for further ecological investigation. CONCLUSIONS: Despite the large investment in managing the many pressures that have degraded the ecological character of these highly valued wetlands, the fundamental ecological processes that underpin the biodiversity values have not received the same level of attention. Further information on plant growth and the environmental factors that drive seasonal and annual changes in vegetation distribution and productivity is required to assist managers in attending to changes due to increasing invasive species and changes in fire regimes.

Australia↗
PubMed1998

On the discrepancy between epidemiologic studies in individuals of lung cancer and residential radon and Cohen's ecologic regression.

There is still substantial confusion in the radiation effects community about the inherent limitations of ecologic analysis. As a result, inordinate attention has been given to the discrepant results of Cohen, in which a negative estimate is observed for the regression of county mortality rates for lung cancer on estimated county radon levels. This paper demonstrates that Cohen's ecologic analysis cannot produce valid inference on the exposure-response relationship for individuals unless lung cancer risk factors (smoking, age, occupation, etc.) for individuals are statistically uncorrelated with indoor radon level within counties or unless risk effects for radon and other factors are additive. Both of these assumptions are contradicted in the literature. Thus, contrary to common assumption, when a linear no-threshold model is the true model for radon risk for individuals, higher average radon concentration for a county does not necessarily imply a higher lung cancer rate for the county. In addition, valid inference from county-level ecologic analysis and the elimination of the ecologic bias cannot be achieved with the addition of county-wide summary variables (including "stratification" variables) to the regression equation. Using hypothetical data for smoking and radon and assuming a true positive association for radon and lung cancer for individuals, the analysis demonstrates that a negative county-level ecologic regression can be induced when correlation coefficients for smoking and radon within county are in the range -0.05 to 0.05. Since adverse effects for radon at low exposures are supported by analysis of miner data (all data and data restricted only to low cumulative exposures), a meta-analysis of indoor radon studies, and molecular and cellular studies, and since ecologic regressions are burdened by severe limitations, the negative results from Cohen's analysis are most likely due to bias and should be rejected.

Air Pollutants, Radioactive↗
PubMed2002

The irreducible uncertainty of the demography-environment interaction in ecology.

The interpretation of ecological data has been greatly improved by bridging the gap between ecological and statistical models. The major challenge is to separate competing hypotheses concerning demography, or other ecological relationships, and environmental variability (noise). In this paper we demonstrate that this may be an arduous, if not impossible, task. It is the lack of adequate ecological theory, rather than statistical sophistication, which leads to this problem. A reconstruction of underlying ecological processes can only be done if we are certain of either the demographic or the noise model, which is something that can only be achieved by an improved theory of stochastic ecological processes. Ignoring the fact that this is a real problem may mislead ecologists and result in erroneous conclusions about the relative importance of endogenous and exogenous factors in natural ecosystems. The lack of correct model identification may also have far-reaching consequences for population management and conservation.

Animals↗
PubMed2004

Protist taxonomy: an ecological perspective.

This is an exploration of contemporary protist taxonomy within an ecological perspective. As it currently stands, the 'morphospecies' does not accommodate the information that might support a truly ecological species concept for the protists. But the 'morphospecies' is merely a first step in erecting a taxonomy of the protists, and it is expected to become more meaningful in the light of genetic, physiological and ecological research in the near future. One possible way forward lies in the recognition that sexual and asexual protists may all be subject to forces of cohesion that result in (DNA) sequence-similarity clusters. A starting point would then be the detection of 'ecotypes'--where genotypic and phenotypic clusters correspond; but for that we need better information regarding the extent of clonality in protists, and better characterization of ecological niches and their boundaries. There is some progress with respect to the latter. Using the example of a community of ciliated protozoa living in the stratified water column of a freshwater pond, it is shown to be possible to gauge the potential of protists to partition their local environment into ecological niches. Around 40 morphospecies can coexist in the superimposed water layers, which presumably represent different ecological niches, but we have yet to discover if these are discrete or continuously variable. It is a myth that taxonomic problems are more severe for protists than for animals and plants. Most of the fundamental problems associated with species concepts (e.g. asexuals, sibling species, phenotypic variation) are distributed across biota in general. The recent history of the status of Pfiesteria provides a model example of an integrated approach to solving what are essentially taxonomic problems.

Animals↗
PubMed2003

Linking field-based ecological data with remotely sensed data using a geographic information system in two malaria endemic urban areas of Kenya.

BACKGROUND: Remote sensing technology provides detailed spectral and thermal images of the earth's surface from which surrogate ecological indicators of complex processes can be measured. METHODS: Remote sensing data were overlaid onto georeferenced entomological and human ecological data randomly sampled during April and May 2001 in the cities of Kisumu (population asymptotically equal to 320,000) and Malindi (population asymptotically equal to 81,000), Kenya. Grid cells of 270 meters x 270 meters were used to generate spatial sampling units for each city for the collection of entomological and human ecological field-based data. Multispectral Thermal Imager (MTI) satellite data in the visible spectrum at five meter resolution were acquired for Kisumu and Malindi during February and March 2001, respectively. The MTI data were fit and aggregated to the 270 meter x 270 meter grid cells used in field-based sampling using a geographic information system. The normalized difference vegetation index (NDVI) was calculated and scaled from MTI data for selected grid cells. Regression analysis was used to assess associations between NDVI values and entomological and human ecological variables at the grid cell level. RESULTS: Multivariate linear regression showed that as household density increased, mean grid cell NDVI decreased (global F-test = 9.81, df 3,72, P-value = <0.01; adjusted R2 = 0.26). Given household density, the number of potential anopheline larval habitats per grid cell also increased with increasing values of mean grid cell NDVI (global F-test = 14.29, df 3,36, P-value = <0.01; adjusted R2 = 0.51). CONCLUSIONS: NDVI values obtained from MTI data were successfully overlaid onto georeferenced entomological and human ecological data spatially sampled at a scale of 270 meters x 270 meters. Results demonstrate that NDVI at such a scale was sufficient to describe variations in entomological and human ecological parameters across both cities.

Journal Article↗
PubMed2002

Ecological interface design for Pasteurizer II: a process description of semantic mapping.

Ecological interface design (EID) is proving to be a promising approach to the design of interfaces for complex dynamic systems. Although the principles of EID and examples of its effective use are widely available, few readily available examples exist of how the individual displays that constitute an ecological interface are developed. This paper presents the semantic mapping process within EID in the context of prior theoretical work in this area. The semantic mapping process that was used in developing an ecological interface for the Pasteurizer II microworld is outlined, and the results of an evaluation of the ecological interface against a more conventional interface are briefly presented. Subjective reports indicate features of the ecological interface that made it particularly valuable for participants. Finally, we outline the steps of an analytic process for using EID. The findings presented here can be applied in the design of ecological interfaces or of configural displays for dynamic processes.

Animals↗
PubMed1984

Model of ecological (cultural) evolutionary neuropsychiatry.

A new model posits that there are specific patterns of groupings of several delayed human cognitive functions or dysfunctions in certain ecological circumstances which characterize a significant portion of a cultural group. It is further posited that such patterns ("ecological syndromes") are primarily based on as yet unknown neurophysiological givens . This deduction is based on the occurrence of several specific groupings of delayed cognitive functions or dysfunctions that have been identified in diverse time periods and cultural groups where no brain pathology can reasonably be expected. The "ecological syndromes" were, however, noted to be analogous to those found in neuropathology. The main factor contributing to such an "ecological syndrome" appears to be a specifically limited under-use of certain functions not needed for the survival of certain populations without implying any general cultural deprivation. Some examples of "ecological syndromes" are mentioned: low arithmetic skills linked with quantitatively inaccurate pictorial (and implied mental) representation of fingers, low literacy skills linked with specifically inaccurate pictorial (and implied mental) representation of the subtle spatial relations of the configuration of the human face, and an "ecological apractognosia " observed among wigmen of New Guinea.

Biological Evolution↗
PubMed2005

[General principles of urban ecological land classification and planning].

Urban ecological land planning is a difficult and urgent task in city layout. This paper presented the definition of urban ecological land, and according the definition, divided the urban ecological land into two groups, i. e., ecological land for service, and ecological land for functioning. Based on the principles of city layout, some measures to plan these two urban ecological land groups were proposed.

China↗
PubMed1986

Clinical ecology--a critical appraisal.

In 1981 the California Medical Association (CMA) adopted the position that clinical ecology does not constitute a valid medical discipline and that scientific and clinical evidence to support the diagnosis of "environmental illness" and "cerebral allergy" or the concept of massive environmental allergy is lacking. As a result of requests from clinical ecologists for an opportunity to present to CMA evidence justifying their diagnostic and treatment methods, the chair of the CMA Scientific Board, Allen W. Mathies, Jr, MD, appointed a task force in 1984 to review clinical ecology. The task force conducted an extensive literature review and held a hearing. CLINICAL ECOLOGY IS BASED ON TWO MAIN HYPOTHESES: first, that the total load of low-dose environmental stressors is important in the induction of illness; and, second, that changes in the frequency of and intervals between exposures to specific substances can mask the clinical manifestations of or alter the degree of sensitivity to those substances. Treatment methods used by clinical ecologists include avoidance, symptom-neutralizing doses of diluted extract of the offending agents, rotation diets and an ecologically sound workplace and home.The task force recognizes that certain environmental chemicals and allergens produce well-defined syndromes in humans and that some patients suffer from illnesses that are not readily diagnosed and for which only supportive therapy exists. The conclusions of the task force are* There is no convincing evidence that supports the hypotheses on which clinical ecology is based.* Clinical ecologists have not identified specific, recognizable diseases caused by exposure to low level-environmental stressors.* Methods to diagnose and treat such undefined conditions have not been shown to be effective.* The practice of clinical ecology can be considered experimental only when its practitioners adhere to scientifically sound research protocols and inform their patients about the experimental nature of their practice.

Environment↗
PubMed2026

Characterizing the ecological niche of insertion sequences within prokaryotic genomes.

Insertion sequences (ISs) are widespread prokaryotic transposable elements, often regarded as genomic parasites that primarily cause deleterious mutations. However, they can also promote adaptive changes. These antagonistic properties make their overall impact on prokaryotic evolution difficult to grasp. Here, we address this challenge by leveraging the framework of transposon ecology to analyze IS occurrences across and within 30 499 prokaryotic genomes. Combining phylogenomics with multi-scale genomic analysis, quantitative ecology, and mathematical modeling, we provide evidence that although genomes generally provide sufficient resources for IS coexistence, universal mechanisms shape their occurrence and chromosomal distribution across genomes. These include (i) the preferential localization of ISs within highly variable and GC-heterogeneous chromosomal regions of genomic plasticity, which act as the primary reservoir of IS niches; (ii) a linear scaling between IS abundance and niche size, with an average of $5.4$ additional accessible insertion sites per IS; (iii) a dependence of IS occurrence on the presence of other ISs, suggesting a form of group behavior; (iv) the accumulation of AT-rich sequences in both coding and noncoding regions up to 100 kb around ISs, indicative of ecological isolation; and (v) the spatial partitioning of mobile genetic elements around ISs, reminiscent of ecological niche differentiation. Besides these general principles, we also uncover niche specificities associated with particular IS families, hinting at regulatory mechanisms that modulate IS activity. Altogether, this comprehensive transposon ecology approach offers new insights and avenues for understanding IS-host interactions and genome evolution, moving beyond traditional host-centric perspectives.

DNA Transposable Elements↗
PubMed1964

SOME ECOLOGICAL ASPECTS OF THE PROBLEM OF ARTHROPOD-BORNE ANIMAL VIRUSES IN THE WESTERN PACIFIC AND SOUTH-EAST ASIA REGIONS.

In recent years there has been an increasing awareness of the importance of arthropod-borne viruses in the Western Pacific region and in South-East Asia. This realization of the importance of these viruses as causes of human morbidity and mortality and of economic loss due to infection of domestic animals has led to studies attempting to elucidate the basic ecology of some of these viruses. The author reviews the extent of knowledge of the ecology of Japanese and Murray Valley encephalitis viruses and indicates possible mechanisms for the overwintering of the viruses based on experiments in which other viruses were mainly used. He discusses the limited available knowledge on the ecology of dengue and emphasizes the necessity of research on the possibility that this disease is a zoonosis. A brief discussion is also given of the haemorrhagic diseases which are found in these regions and a brief description of the state of knowledge on the ecology of Kyasanur Forest disease and epidemic nephroso-nephritis. A brief discussion is also included on the ecology of the tick-borne Russian spring-summer encephalitis.

Animals↗
PubMed1997

Ecological constraints on the ability of precision agriculture to improve the environmental performance of agricultural production systems.

In this paper, I address three topics relevant to the ability of precision agriculture to improve the environmental performance of agricultural production systems. First, I describe the fundamental ecological factors that influence the environmental performance of these systems and address how precision agriculture practices can or cannot interact with these factors. Second, I review the magnitude of the ecological processes that we hope to manage with precision agriculture relative to agricultural inputs to determine whether managing these processes can significantly affect system environmental performance. Finally, I address scale incongruencies between ecological processes and precision agriculture techniques that could limit the ability of these techniques to manage variability in these processes. The analysis suggests that there are significant ecological constraints on the ability of precision agriculture techniques to improve the environmental performance of agricultural production systems. The primary constraint is that these techniques do not address many of the key factors that cause poor environmental performance in these systems. Further, the magnitude of the ecological processes that we hope to manage with precision agriculture are quite small relative to agricultural inputs and, finally, these processes vary on scales that are incongruent with precision management techniques.

Agriculture↗
PubMed2001

Reproductive ecology and life history of the human male.

Until recently, the reproductive ecology of human males has not been extensively investigated, primarily as a result of the need for a theoretical framework based on the reproductive constraints and energetics of mammalian males. More specifically, male reproductive ecology has necessitated an integrative interpretation of clinical and anthropological data based on the premise that the evolution of human male life histories has involved selection for physiological mechanisms aimed at optimizing trade-offs between survivorship and reproductive effort. This paper attempts to address this gap in our understanding by presenting the current state of male reproductive ecology, including physiologic data from clinical and anthropological investigations as well as recent theoretical developments. Recent investigations outlining population variation in reproductive endocrine function are discussed within the context of potential sources of variation, including energetic expediture, caloric intake, and developmental canalization during adolescence. Additional summaries of male senescence and behavior are presented to provide a complete overview of male life history. Implications of recent anthropological data on contemporary health issues such as prostate cancer and the development of a male contraceptive are also discussed. Finally, several theories are presented that may contribute to our understanding of the evolution of male life histories and reproductive ecology, including theoretical suggestions involving the role of competition, mate choosiness, and potential constraints on male insemination ability, as well as a theory suggesting that male reproductive ecology may be best understood by analyzing energetic allocation decisions between differing somatic tissues that may be indicative of the competing needs for optimizing survivorship and reproductive effort. Directions for future research are finally considered.

Aging↗
PubMed2003

Life history theory and the immune system: steps toward a human ecological immunology.

Within anthropology and human biology, there is growing interest in immune function and its importance to the ecology of human health and development. Biomedical research currently dominates our understanding of immunology, and this paper seeks to highlight the potential contribution of a population-based, ecological approach to the study of human immune function. Concepts from life-history theory are applied to highlight the major challenges and demands that are likely to shape immune function in a range of ecological contexts. Immune function is a major component of maintenance effort, and since resources are limited, trade-offs are expected between investment in maintenance and other critical life-history functions involving growth and reproduction. An adaptationist, life-history perspective helps make sense of the unusual developmental trajectory of immune tissues, and emphasizes that this complex system is designed to incorporate information from the surrounding ecology to guide its development. As a result, there is substantial population variation in immune development and function that is not considered by current biomedical approaches. In an attempt to construct a framework for understanding this variation, immune development is considered in relation to the competing life-history demands that define gestation, infancy, childhood, adolescence, and adulthood. Each life stage poses a unique set of adaptive challenges, and a series of hypotheses is proposed regarding their implications for immune development and function. Research in human ecological immunology is in its earliest stages, but this is a promising area of exploration, and one in which anthropology is well-positioned to make important contributions.

Adaptation, Physiological↗
PubMed2006

Ecological risk assessment of contaminated soil.

This review has described three cases of ecological risk assessment. The cases include two heavy metals (Cu and Zn) and an anthropogenic organic chemical (DDT). It concludes that there are at least two major constraints hampering the use of laboratory tests to predict effects under natural field conditions. One key issue is bioavailability, and another is suboptimal conditions or multiple stresses in the field such as climatic stress (drought, frost), predators, competition, or food shortage. On the basis of the presented case studies, it was possible to answer three essential questions often raised in connection to ecological risk assessment of contaminated sites. 1. To what extend does soil screening level (SSL) estimate the risk? The SSL are generally derived at levels corresponding to the lowest observed effect levels in laboratory studies, which often is close to the background levels found in many soils. In the cases of zinc and especially DDT, the SSL seemed quite conservative, whereas for copper they resemble the level at which changes in the community structure of soil microarthropods and the plant community have been observed at contaminated sites. The SSL correspond as a whole relatively well with concentrations where no effects or only minor effects were observed in controlled field studies. However, large variation in field surveys can often make it difficult to conclude to what extent the SSL corresponded to no-effect levels in the field. 2. Do bioassays represent a more realistic risk estimate? Here, there is no firm conclusion. The zinc study in UK showed a better relationship between the outcome of ex situ bioassays and field observations than the SSL. The latter overestimated the risk compared to field observations. However, this would be species dependent, as the sensitivity to metals may vary considerably between recognized test species, even within the same group of organisms, such as Folsomia candida and Folsomia fimetaria or Eisenia fetida and Lumbricus sp. Furthermore, it was demonstrated that bioassays were not useful for predicting general species diversity in the field as they are strongly influenced by natural variation and other factors not related to contamination. In the case of copper, bioassays with springtails and black bindweed seemed to underestimate the risk compared to the Cu concentrations at which significant changes in the community structure of soil microarthropods and plants have been observed at the contaminated site, and this was also the case for the DDT-contaminated soils. Here, bioassays with DDT-contaminated soils showed generally very low toxicity, with EC10 values considerably higher than the levels where clear effects on single species as well as community structure have been detected in the present field study. 3. Is it possible to make sound field surveys or do we lack suitable reference situations? Large natural variation caused by other factors than contaminants were observed in most cases, and this may have particularly hampered the conclusions made in the field surveys. These factors included pH, private and military traffic, age of vegetation, shading effects, and variations in light insensitivity as well as quantity and quality of organic matter. It was therefore concluded that field studies should always be interpreted in concert with similar data from a reference situation. Conclusions should therefore be made with caution in situations where important soil conditions vary between control plots and the contaminated sites. The cases also showed that indices focusing on species richness were unreliable. Estimates of evenness or dominance were recommended instead, and most authors concluded that multivariate analysis of community structure was a sensitive and useful method superior to single-species field data. This review concludes that there is a need for a tiered approach in ecological risk assessment of contaminated soils. Generic soil screening levels are needed as a first tier. Higher tiers of ecological risk assessment should, however, contain some kind of site-specific assessment. It is furthermore important to organize the various studies in a framework or decision support system that is transparent and useful for all stakeholders. A weight of evidence approach may be an obvious choice to deal with these uncertainties. The TRIAD approach, which incorporates and categorizes information in a triangle - chemistry, toxicology, and ecology - is an appropriate tool for handling conceptual uncertainties.

Animals↗
PubMed1999

The importance of human ecology at the threshold of the next millennium: how can population growth be stopped?

Ecology is defined as the set of complex interactions between the biotic and abiotic environments. Human ecology concerns principally the population ecology "only" of Homo sapiens, but it also includes all aspects of global ecology because humans are the most important species. Human demography is characterized by a recent decline in mortality and fertility rates. These demographic transitions have largely been completed in industrialized countries, but not in the 140 developing countries. Approximately 100 countries are following the same demographic pattern as industrialized countries, however with a time delay of several generations. China has effectively reduced its population increase by means that would be unacceptable in Western democracies. Some 44 developing countries still show increasing population growth and no detectable demographic transition in birth rate. Thus one part of the world shows limited (and, in the long run, shrinking) population growth, and another continues with a strong increase. All populations are limited in their development by their sustainability by their environment, for example, food and energy resources, and the extent of pollution which the use of these resources produces. It is argued that in the case of human population the limits of sustainability have already been reached with the 6 billion humans alive today, since at least 20% of these suffer from hunger, natural resources are overexploited, and biodiversity is threatened. In the coming 200 years it is more likely that the total population will substantially oscillate rather than approach the predicted 12 billion. The most important goal of human ecology should therefore be to slow population growth as far as possible.

Demography↗
PubMed2005

Farm riparian land use and management: driving factors and tensions between technical and ecological functions.

Because of their specific role in the fate of natural resources of landscapes, riparian lands are considered as landscape management units. Yet, they are part of many farms: In what way does this influence their land use and sustainability? In this article, farm riparian land was defined as the set of riparian fields of a given farm. Our aim was to evaluate farm riparian lands as farm management units and the balance between technical and ecological functions associated with farm riparian land-use types. Technical functions designated the role of land use in elaborating farm production and maintaining farm territory. Ecological functions corresponded to farm riparian land-use intensity and ratio of permanent vegetation. The analysis was carried on 102 farms from 5 study sites representative of dairy agriculture and landscapes in a region straddling Brittany and Normandy (France). Farm riparian land-use types were identified using statistical clustering. Technical and ecological functions associated with land-use types were expressed in the light of agronomy and landscape ecology expertise. Descriptors of farm holdings and farm riparian land were tested as explanatory factors of farm riparian land-use types. The use of farm riparian lands was diverse but well defined; they proved to be farm management units. Compatibilities or antagonisms between technical and ecological functions were underscored according to farm riparian land-use type. We argued that decision support could gain in combining perspectives on riparian lands as landscape management units and farm management units.

Agriculture↗