Predicting the economic impact of an invasive species on an ecosystem service.

Quantifying the impact of alien invasive species on ecosystem services is an essential step in developing effective practices and policy for invasive species management. Here we develop a stochastic bioeconomic model that enables the economic impact of an invasive pest to be estimated before its arrival, based on relatively poorly specified ecological and economic parameters. We developed the model by using a hypothetical invasion of the varroa bee mite (Varroa destructor) into Australia and the negative flow-on effects that it would have on pollination by reducing honey bee populations, giving rise to a loss of pollination services, reduced crop yields, and additional production costs. If the mite were to continue to be prevented from entering the country over the next 30 years, we estimate that the economic costs avoided would be U.S. $16.4-38.8 million (Aus $21.3-50.5 million) per year. We suggest that current invasion response funding arrangements in Australia, which do not acknowledge these avoided damages, require amendment.     

Application of an evolutionary algorithm to the inverse parameter estimation of an individual-based model

Inverse parameter estimation of individual-based models (IBMs) is a research area which is still in its infancy, in a context where conventional statistical methods are not well suited to confront this type of models with data. In this paper, we propose an original evolutionary algorithm which is designed for the calibration of complex IBMs, i.e. characterized by high stochasticity, parameter uncertainty and numerous non-linear interactions between parameters and model output. Our algorithm corresponds to a variant of the population-based incremental learning (PBIL) genetic algorithm, with a specific “optimal individual” operator. The method is presented in detail and applied to the individual-based model OSMOSE. The performance of the algorithm is evaluated and estimated parameters are compared with an independent manual calibration. The results show that automated and convergent methods for inverse parameter estimation are a significant improvement to existing ad hoc methods for the calibration of IBMs.     

Harvesting in an eight-species ecosystem

The theory for a general equilibrium ecosystem model that can include large number of interacting species is presented. Features include: (1) individual plants and animals are assumed to behave as if they are maximizing their net energy intake, (2) short- and long-run equilibriums are obtained, (3) species’ population adjustments depend on individual net energies. The theory is applied using simulations of an eight-species Alaskan marine ecosystem for which a “natural” equilibrium is calculated. Humans are introduced by adding a regulated open access fishery that harvests one of the species. Fishing impacts the fish population as well as the populations of other species, including Stellar sea lions, an endangered species. The sensitivity of fish and nonfish species populations to harvesting are calculated.     

Debt-for-nature swaps: an overview

SUMMARY

The debt crisis of developing countries in the early 1980s has been linked with environmental degradation. In order to combat the debt and environmental crisis, debt-for-nature swap transactions were proposed by Lovejoy in 1984. They involve a mechanism of exchange in which a certain amount of the debtor's foreign debt is cancelled or forgiven, in return for local currency from the debtor government to be invested in a domestic environmental protection project. The swaps may involve two governments, and in most cases, are aided by an International Non-Governmental Organization (INGO), who must have a local contact with a domestic NGO. The first swap (1987), between Bolivia and Conservation International (US-INGO) involved cancellation of $650 000 Bolivian foreign debt for exchange of $100 000 worth of local currency to be used towards the Beni Biosphere Reserve. Since 1987, swaps have resulted in an excess of US$1.5 billion in transactions. Debt-for-nature swaps may not provide debt relief of significant magnitude nor solve the world's environmental or conservation problems, they have enabled provision of additional funding to ailing environmental organizations (more than $100 million), raised a sense of awareness about environmental protection, and some environments especially in Costa Rica are benefiting from the process.     

Berechnungen zur Lufthygiene an Autobahnen

Protecting people from excessive noise near freeways is usually achieved by use of walls or wall-mound combinations. Calculations have shown that such walls reduce not only noise but, in addition, NO₂ concentrations can be lowered to 50 [μg/m³]. This papier shows that concentrations lower than the limiting values are possible even under difficult meteorological and topographic conditions. The position and hight of such noise protective walls can be optimized by sensitivity analyses.     

Population as an oscillating system

In this paper we present a new approach describing population dynamics based on the view of a population as an oscillating system. To develop a mathematical model of an oscillating population, we applied a third-order differential equation. Our model describes population dynamics within a parametric-temporal continuum, formed by the relative values of population growth and decrease over time. In this paper we also illustrate how our oscillative model effectively compliments the existing suite of models in population dynamics.     

气升式反应器中微生物对H2S的脱除研究

筛选驯化得到具有高效脱硫性能的菌群,在气升式反应器中进行了H2S脱除实验研究. 在温度为28 ℃、初始pH 8.0的条件下考察了不同通气量对反应体系中H2S脱除能力、脱除效率的影响以及H2S进气负荷和通气量对SO2-4生成率的影响. 结果表明,最佳通气量为0.2 L/min.在此通气量下,当H2S进气负荷为5.76 kg m-3 d-1时,脱除负荷可达5.62 kg m-3 d-1,而脱除率可以保持在97.8%以上;当H2S负荷为4.37～4.93 kg m-3 d-1时, H2S去除率可达到99%以上,且主要副产物为单质硫.通过增大进气负荷、降低通气量可以获得较高的单质硫回收率.图3表2参15     

Avian herbivory: an experiment, a field test, and an allometric comparison with mammals

Mechanistic studies on herbivore functional responses have largely taken place in mammals; very little has been done in herbivorous birds so far. Here we aim to fill that gap by experimentally quantifying the (short-term) functional response of a large avian herbivore, the Bewick's Swan (Cygnus columbianus bewickii). We explicitly distinguish between encounter-limited and handling-limited foraging by analyzing the results in the framework of the models of D. E. Spalinger and N. T. Hobbs, originally developed for mammalian herbivory. Bite size in captive swans was experimentally manipulated by varying sward height. The time interval between two bites increased with bite size, which supports the handling-limited model (process 3) and rejects the encounter-limited models (processes 1 and 2). Subsequently, we took the obtained functional response parameters into the field in order to predict, from measurements of sward height, (1) bite sizes, (2) handling times, and (3) short-term intake rates in free-ranging swans. Indeed, for all three variables, the observed values closely matched the experimentally based predictions. Finally, we review functional response parameters available in the literature on avian herbivores and scale them allometrically in relation to mammals. This analysis revealed that maximum bite sizes, and therefore maximum intake rates, in herbivorous birds are smaller than in herbivorous mammals. We hypothesize and provide evidence that birds compensate by longer daily foraging times.     

Gastric cancer: an epidemiological review

An attempt is made to synthesize the epidemiological literature and identify salient factors from the multitude of potential antecedents of gastric cancer, factors which to a greater or lesser degree create nonrandom variations in the distribution of the disease. Implicit in this approach is the notion that observation of spatial variations in the incidence of gastric cancer may lead to hypotheses relating to the biological, personal and physical environmental factors. An extensive bibliography accompanies the text.Formerly of the Department of Town Planning, University of Wales, College of Cardiff, PO Box 906, Cardiff CF1 3YN, Wales.     

Designing an efficient adaptive cluster sample

The choice of neighborhood definition and critical value in adaptive cluster sampling is critical for designing an efficient survey. In designing an efficient adaptive cluster sample one should aim for a small difference between the initial and final sample size, and a small difference between the within-network and population variances. However, the two aims can be at odds with each other because small differences between initial and final sample size usually means small within-network variance. One way to help in designing an efficient survey is to think in terms of small network sizes since the network size is a function of both critical value and neighborhood definition. One should aim for networks that are small enough to ensure the final sample size is not excessively large compared with the initial sample size but large enough to ensure the within-network variance is a reasonable fraction of the population variance. In this study surveys that had networks that were two to four units in size were the most efficient.     

Monopoly exploitation of an exhaustible resource

The popular notion that a monopolist will exhaust a nonrenewable natural resource at a slower than socially optimal rate is examined. Contrary to the prevailing belief, instances do exist for which the monopolist uses the resource faster than the social maximizer. This is demonstrated first by finding conditions for which the expected result—a monopoly rate which is slower than optimal-will always hold, and second, by showing that for situations where these conditions are violated the result may be reversed.     

Animal social networks: an introduction

Network analysis has a long history in the mathematical and social sciences and the aim of this introduction is to provide a brief overview of the potential that it holds for the study of animal behaviour. One of the most attractive features of the network paradigm is that it provides a single conceptual framework with which we can study the social organisation of animals at all levels (individual, dyad, group, population) and for all types of interaction (aggressive, cooperative, sexual etc.). Graphical tools allow a visual inspection of networks which often helps inspire ideas for testable hypotheses. Network analysis itself provides a multitude of novel statistical tools that can be used to characterise social patterns in animal populations. Among the important insights that networks have facilitated is that indirect social connections matter. Interactions between individuals generate a social environment at the population level which in turn selects for behavioural strategies at the individual level. A social network is often a perfect means by which to represent heterogeneous relationships in a population. Probing the biological drivers for these heterogeneities, often as a function of time, forms the basis of many of the current uses of network analysis in the behavioural sciences. This special issue on social networks brings together a diverse group of practitioners whose study systems range from social insects over reptiles to birds, cetaceans, ungulates and primates in order to illustrate the wide-ranging applications of network analysis. This contribution is part of the special issue “Social Networks: new perspectives” (Guest Editors: J. Krause, D. Lusseau and R. James).     

Sperm allocation in an uncertain world

Models of optimal sperm allocation are constructed using stochastic dynamic programming techniques, yielding predictions about sperm allocation when males mate sequentially, breeding time is finite, sperm stores are limited and females vary in quality. The models suggest that uncertainty of future reproductive opportunities should favour withholding of sperm, so that males tend to allocate less (for a given level of stored sperm) earlier in the breeding season. This effect is more pronounced the greater the variance in female quality. We also show that while allocation will be influenced by mate value, it is not necessarily optimal to allocate preferentially to high-quality females, since the benefits of a higher-quality mate may be offset by increased risk of rejection of sperm or higher sperm competition. The relationship between mate quality and level of allocation will depend strongly on the amount of remaining stored sperm, with males whose supplies are depleted being more likely to favour lower-quality partners. Received: 12 September 1997 / Accepted after revision: 28 June 1998     

Expression of multiple forms of an adhesive plaque protein in an individual mussel, Mytilus edulis

Individual blue mussels, Mytilus edulis L., can express at least 20 variants of a small protein known as M. edulis foot protein 3 or Mefp3. Mefp3 has been shown to be a component of the adhesive plaque of the byssus, the structure securing mussels to solid substrata. The cDNAs and deduced fp3 protein sequences display more variation at the carboxy-terminus than at the N-terminus, although there is some variation present throughout the protein. This indicates that there most likely are multiple copies of the gene encoding this protein. Each protein sequence contains a signal peptide, 24 to 25 residues in length, and a mature protein sequence of 44 to 54 residues. Gly is the most common amino acid in the mature protein at 20 to 25 mol%. Tyr and Arg follow closely at 20 to 23 and 16 to 21 mol%, respectively. Both of these amino acids were previously shown to be post-translationally modified to 3,4-dihydroxyphenylalanine (Dopa) and 4-hydroxyarginine, respectively, in this protein. MALDI-TOF (matrix-assisted laser desorption ionization with time-of-flight) mass spectrometric analysis of the underside of adhesive plaques reveals the presence of Mefp3-like proteins. Curiously, only four or five out of 20 possible fp3 variants are detectable in plaques deposited on glass or plastic. This would suggest that selection of protein variants for deposition onto surfaces is determined at the level of translation. Received: 11 August 1998 / Accepted: 15 April 1999