Threats to Avifauna on Oceanic Islands

Abstract:  Results of the study by Blackburn et al. (2004 a ) of avifauna on oceanic islands suggest that distance from the mainland and time since European colonization have major influences on species extinctions and that island area is a significant but secondary contributing factor. After augmenting the data of the study on geographical properties for some of the islands they examined, we used a causal analysis approach with structural equation modeling to reexamine their conclusions. In our model geographical properties of islands, such as island area and isolation, were considered constraints on biological factors, such as the number of introduced mammalian predators and existing number of avifauna, that can directly or indirectly influence extinction. Of the variables we tested, island area had the greatest total influence on the threat of extinction due to its direct and indirect effects on the size of island avifauna. Larger islands had both a greater number of threatened bird species and more avifauna, increasing the number of species that could become threatened with extinction. Island isolation also had a significant, positive, and direct effect on threats to island avifauna because islands farther from the mainland had fewer current extant avifauna. Time since European colonization had a significant negative, but relatively weaker, influence on threats compared with the traditional biogeographic factors of island area and distance to the mainland. We also tested the hypothesis that the amount of threat is proportionally lower on islands that have had more extinctions (i.e., there is a "filter effect"). Because the proportion of bird extinctions potentially explained only 2.3% of the variation in the proportion of threatened species on islands, our results did not support this hypothesis. Causal modeling provided a powerful tool for examining threat of extinction patterns of known and hypothesized pathways of influence.     

CHARACTERIZING DISSOLVED OXYGEN CONDITIONS IN ESTUARINE ENVIRONMENTS

Dissolved oxygen concentration, which is often measured inestuaries to quantify the results of and stresses associatedwith eutrophication, can be highly variable with time of dayand tidal stage. To assess how well dissolved oxygenconditions are characterized by typical monitoring programs,we conducted Monte Carlo sampling from 16 semi-continuous,31-day dissolved oxygen records collected from estuaries alongthe Atlantic and Gulf coasts to mimic three samplingstrategies: (1) systematic point-in-time sampling, (2) randompoint-in-time sampling, and (3) short-term continuous records.These strategies were evaluated for their accuracy inestimating mean oxygen concentration, minimum oxygenconcentration, and percent of time below a threshold value of2 ppm. Mean dissolved oxygen concentration was most accuratelyestimated in both estuarine regions by random point-in-timesampling, but this strategy required more than ten samplingsper month for the estimate to be within 0.5 ppm on 50% of thesimulations. Short-term continuous sampling (24–48 h)correctly identified estuaries in the Gulf of Mexico regionwhere dissolved oxygen concentrations of less than 2 ppm wereexperienced greater than 20% of the time. However, largetidal variations in Atlantic coast estuaries showed thismeasure to be inaccurate in these estuarine environments. Noneof the sampling strategies correctly identified month-longoxygen minima within 0.5 ppm for more than 50% of thesimulations. This inability to characterize correctlydissolved oxygen conditions could add significant uncertaintyto risk assessments, waste load allocation models, and otherwater quality evaluations that are the basis for developingwastewater treatment strategies and requirements. Perhaps moreimportantly, the inaccuracy with which conventional samplingprocedures characterize minimum dissolved oxygen valuessuggests that the extent of hypoxia in estuarine waters inbeing substantially underestimated.     

A Systematic Review of Systematic Reviews and Meta-Analyses of Animal Experiments with Guidelines for Reporting

To maximize the findings of animal experiments to inform likely health effects in humans, a thorough review and evaluation of the animal evidence is required. Systematic reviews and, where appropriate, meta-analyses have great potential in facilitating such an evaluation, making efficient use of the animal evidence while minimizing possible sources of bias. The extent to which systematic review and meta-analysis methods have been applied to evaluate animal experiments to inform human health is unknown. Using systematic review methods, we examine the extent and quality of systematic reviews and meta-analyses of in vivo animal experiments carried out to inform human health. We identified 103 articles meeting the inclusion criteria: 57 reported a systematic review, 29 a systematic review and a meta-analysis, and 17 reported a meta-analysis only. The use of these methods to evaluate animal evidence has increased over time. Although the reporting of systematic reviews is of adequate quality, the reporting of meta-analyses is poor. The inadequate reporting of meta-analyses observed here leads to questions on whether the most appropriate methods were used to maximize the use of the animal evidence to inform policy or decision-making. We recommend that guidelines proposed here be used to help improve the reporting of systematic reviews and meta-analyses of animal experiments. Further consideration of the use and methodological quality and reporting of such studies is needed.     

The Why,What, and How of Global Biodiversity Indicators Beyond the 2010 Target

Abstract: The 2010 biodiversity target agreed by signatories to the Convention on Biological Diversity directed the attention of conservation professionals toward the development of indicators with which to measure changes in biological diversity at the global scale. We considered why global biodiversity indicators are needed, what characteristics successful global indicators have, and how existing indicators perform. Because monitoring could absorb a large proportion of funds available for conservation, we believe indicators should be linked explicitly to monitoring objectives and decisions about which monitoring schemes deserve funding should be informed by predictions of the value of such schemes to decision making. We suggest that raising awareness among the public and policy makers, auditing management actions, and informing policy choices are the most important global monitoring objectives. Using four well‐developed indicators of biological diversity (extent of forests, coverage of protected areas, Living Planet Index, Red List Index) as examples, we analyzed the characteristics needed for indicators to meet these objectives. We recommend that conservation professionals improve on existing indicators by eliminating spatial biases in data availability, fill gaps in information about ecosystems other than forests, and improve understanding of the way indicators respond to policy changes. Monitoring is not an end in itself, and we believe it is vital that the ultimate objectives of global monitoring of biological diversity inform development of new indicators.     

Assessing the Potential to Restore Historic Grazing Ecosystems with Tortoise Ecological Replacements

The extinction of large herbivores, often keystone species, can dramatically modify plant communities and impose key biotic thresholds that may prevent an ecosystem returning to its previous state and threaten native biodiversity. A potentially innovative, yet controversial, landscape‐based long‐term restoration approach is to replace missing plant‐herbivore interactions with non‐native herbivores. Aldabran giant (Aldabrachelys gigantea) and Madagascan radiated (Astrochelys radiata) tortoises, taxonomically and functionally similar to the extinct Mauritian giant tortoises (Cylindraspis spp.), were introduced to Round Island, Mauritius, in 2007 to control the non‐native plants that were threatening persistence of native species. We monitored the response of the plant community to tortoise grazing for 11 months in enclosures before the tortoises were released and, compared the cost of using tortoises as weeders with the cost of using manual labor. At the end of this period, plant biomass; vegetation height and cover; and adult, seedling, flower, and seed abundance were 3–136 times greater in adjacent control plots than in the tortoise enclosures. After their release, the free‐roaming tortoises grazed on most non‐native plants and significantly reduced vegetation cover, height, and seed production, reflecting findings from the enclosure study. The tortoises generally did not eat native species, although they consumed those native species that increased in abundance following the eradication of mammalian herbivores. Our results suggest that introduced non‐native tortoises are a more cost‐effective approach to control non‐native vegetation than manual weeding. Numerous long‐term outcomes (e.g., change in species composition and soil seed bank) are possible following tortoise releases. Monitoring and adaptive management are needed to ensure that the replacement herbivores promote the recovery of native plants. Estudiando el Potencial para Restaurar Ecosistemas Históricos de Forrajeo con Reemplazos Ecológicos de Tortugas Terrestres     

RECENT COAL AND URANIUM INVESTMENT AGREEMENTS IN THE THIRD WORLD

The improvements made by developing countries in the 1970s in petroleum and mineral agreements with transnational corporations have been well documented, and substantial evidence exists to show that some real gains, in terms of host country control over operations, distribution of economic benefits, better employment and training requirements, etc., have in fact been made. In the case of the energy-related minerals, uranium and coal, however, relatively few contracts between Third World governments and transnational corporations have become public, and it is thus difficult to document whether the same gains made in the case of petroleum or non-fuel minerals have been achieved in relation to these energy resources. This article reviews a number of such recent coal and uranium agreements in developing countries. In overall terms, these agreements do not go as far in providing for the interests of host countries as do those negotiated for petroleum or hard minerals. The reasons for this apparent weakness in developing countries' bargaining power in the case of uranium and coal include the specific nature of the markets for these minerals, the structure of transnational corporations in the industry, and the very secrecy which has kept most of these contracts from public view. In the light of the relatively weak markets expected for export sales of coal and uranium through the remainder of the 1980s, it appears unlikey that developing countries can make significant advances in their negotiations to the extent of achieving terms which are more favourable than those contained in the best of the agreements reviewed in this article. It should, however, be possible for host governments to use the more favourable of the agreements reviewed here as standards for future negotiations. Une solide documentation existe sur les améliorations apportées par les pays en développement dans les années '70 dans le domaine des accords pétroliers et miniers avec les sociétés multinationales et il est maintenant bien etabli que des gains réels ont été acquis en ce qui concerne le contrôle des opérations par le pays hôte, la répartition des bénéfices, une meilleure utilisation de la main-d'oeuvre et les obligations de formation professionnelle. Cependant, dans le cas des minerais énergétiques uranium et charbon, relativement très peu de contrats intervenus entre les gouvernements du Tiers Monde et les sociétés multinationales sont tombés dans le domaine public de sorte qu'il est difficile d'établir si des gains semblables à ceux réalisés dans le cadre du pétrole et des minerais métalliques ont été obtenus. Cet article passe en revue certains des accords intervenus récemment dans les domaines du charbon et de l'uranium dans les pays en développement. En termes généraux, ces accords ne vont pas aussi loin dans la protection des intérêts des pays hôtes que ceux qui ont été négociés pour le pétrole et les minerais. La marge de manoeuvre des pays en développement dans le cadre des négociations d'accords portant sur le charbon et l'uranium est limitée en apparence du fait de la nature particulière des marchés de ces minerais, de la place qu'occupent les sociétés multinationales dans l'industrie minière et du caractère confidentiel qui entoure les transactions et les isole de la vue du grand public. Etant donné les tendances baissières des marchés du charbon et de l'uranium à l'exportation pour le reste de cette décennie, il semble peu probable que les pays en développement puissent réaliser des progrès sensibles dans leurs négociations pour atteindre des conditions plus favorables que celles qui figurent dans les meilleurs accords examinés dans cet article. Cependant, les pays hôtes devraient se prévaloir des accords qui leur sont les plus favorables parmi ceux qui sont passés en revue pour les utiliser comme base de leurs futures négociations et tout au moins pour éviter de signer des accords léonins. Los progresos alcanzados en la década del setenta por los países en desar-rollo en los acuerdos con las compañias transnacionales sobre el desarrollo del petróleo y de los minerales ha sido bien documentado y existe evidencia sustantiva de que ha habido ganancias reales en aspectos tales como control del país sobre las operaciones, distribución de beneficios económicos, mejores condiciones para el empleo y el entrenamiento, etc. Sin embargo, en el caso de minerales energéticos, tales como el uranio y el carbón, pocos contratos han sido hechos públicos y es difícil documentar si se tuvieron similares ganancias como en el caso de minerales no energéticos y petróleo. Este artículo pasa revista a un número de dichos contratos recientes sobre carbón y uranio. En términos generales estos contratos no son tan favorables a los países en desarrollo en comparación con los contratos para petróleo y minerales no energéticos. Las razones para esta aparente debilidad del poder de negociación en el caso del carbón y del uranio se debe, entre otras, a la naturaleza específica del mercado para estos minerales, la estruc-tura de las compañías transnacionales dentro de la indústria y el carácter secreto que ha tenido la mayoría de estos contratos con respecto al público en general. A la luz de la relativa debilidad del mercado para las exportaciones de carbón y uranio que se cree que imperará durante el resto de la década del ochenta, parece poco probable que los países en desarrollo puedan hacer avances significativos en sus negociaciones con el objeto de alcanzar términos que sean más favorables que los que se alcanzaron en el mejor de los contratos revisados en el presente artículo. Debería ser posible, sin embargo, que los gobiernos puedan usar como patrón para futuras negociaciones el contrato mas favorable revisado en este artículo y evitar la firma de acuerdos totalmente desfavorables al pais.     

The Relative Importance of Sources of Greenhouse-Gas Emissions: Comparison of Global Through Subnational Perspectives

Increasing atmospheric concentrations of greenhouse gases are widely expected to cause global warming and other climatic changes. It is important to establish priorities for reducing greenhouse-gas emissions, so that resources can be allocated efficiently and effectively. This is a global problem, and it is possible, on a global scale, to identify those activities whose emissions have the greatest potential for enhancing the greenhouse effect. However, perspectives from smaller scales must be appreciated, because it is on scales down to the local level that response measures will be implemented. This paper analyzes the relative importance of emissions from the many individual sources, on scales ranging from global to national to subnational. Individual country perspectives and proposed policy measures and those of subnational political entities exhibit some commonalities but differ among themselves and from a global-scale perspective in detail.