COPPER PRICE STABILIZATION: WELFARE CONSEQUENCES AND BUFFER STOCK COSTS

International debate and economic literature on export earnings from trade in raw materials have focused on two main subjects: the ability to increase incomes arising from the exports and the possibility of stabilizing these incomes. One alternative that has been suggested and discussed with regard to the second issue is a buffer stock that would decrease the fluctuations in raw material prices. Two objections that have been made to this proposal are that, with stabilization, producers could lose their welfare benefits; and that financial costs are too great. In this article, market conditions required so that copper producers may be benefited by price stability are discussed, and the profitability of a copper buffer stock is measured. Depending on the characteristics of demand and supply curves in the copper market, the article concludes that producers may obtain welfare and income benefits from price stabilization and that for certain degrees of stability the management of the copper buffer stock can yield a positive internal rate of return close to that of alternative investments. Des discussions au niveau international et des ouvrages économiques en matière de recettes d'exportation provenant du commerce des matiêres premières ont mis l'accent sur deux sujets principaux: la capacité d'accroître les revenue de ces exportations et la possibilité de stabiliser ces revenue. Une option, suggérée et débattue au sujet du second point, consiste en l'établissement d'un stock régulateur qui tendrait à diminuer les fluctuations des prix des matiêres premières. Cependant, deux objections ont été soulevées, à savoir: la stabilisation pourrait avoir des repercussions néfastes sur les bénéfices des producteurs et les coûts financiers pourraient être trap élevés. L'article considère les conditions de marché requises pour permettre aux producteurs de cuivre de bénéficier de la stabilité des prix ainsi que la rentabilité d'un stock régulateur en matière de cuivre. En se basant sur les caractéristiques des courbes de l'offre et de la demande dans le marché du cuivre, l'article conclut que les producteurs peuvent bénéficier de la stabilisation des prix et que, à certains degrés de stabilité, la gestion d'un stock régulateur de cuivre peut engendrer un taux de rendement interne positif avoisinant ceux d'autres investissements. Los debates internacionales y la literature sobre los ingresos de exportatión de materias primas han enfocado dos temas principals: la habilidad de aumentar el ingreso resultante de estas exportaciones y la posibilidad de estabilizar dichos ingresos. La creación de una reserva de compensación para contrarrestar las fluctuaciones de los precios de materias primas ha sido propuesto y discutido. Las objeciones hechas a esta propuesta argumentan que los beneficios para los productores disminuiría con la estabilización y que los costos financieros serian demasiado grandes. En este artículo se discuten las condiciones de mercado que permitirían a los productores de cobre beneficiarse de la estabilidad de precios y se mide también la rentabilidad de la reserva de compensación para el cobre. Basándose en las características de las curvas de demanda y oferta en el mercado del cobre, el artículo concluye que los productores pueden salir gananciosos con la estabilización de precios y que para ciertos grados de estabilidad, la administración de la reserva de compensación del cobre puede producir una tasa interna de retorno positive, comparable a otras inversiones alternatives.     

Removal of Aldrin,Dieldrin, Heptachlor,and Heptachlor Epoxide Using Activated Carbon and/or Pseudomonas fluorescens Free Cell Cultures

Degradation of aldrin (1,2,3,4,10,10-Hexachloro-1,4,4a,5,8,8a-hexahydro-1,4:5-8-dimethanonaphthalene), heptachlor (1H-1,4,5,6,7,8,8-heptachloro-3a,4,7,7a-tetrahydro-4,7-methano indene), dieldrin (1aα,2β,2aα,3β,6β,6aα,7β,7aα)-3,4,5,6,9,9-Hexachloro-1a,2,2a,3,6,6a,7,7a-octahydro-2,7:3,6-d-methanonaphtha[2,3-b]oxirene, and heptachlor epoxide (1aα, 1bβ,2α,5α,5αβ,6β,6aα-2,3,4,5,6,7,7-Heptachloro-1a,1b,5,5a,6,6a-hexahydro-2,5-methano-2H-inden[1,2-b]-oxirene) was tested using free cultures of Pseudomonas fluorescens under controlled conditions. Pesticide concentrations were monitored by gas chromatography during 120 h. Percentages of degradation and biodegradation rates (BDR) were calculated. Data showed a trend suggesting a relation between chemical structure and degradability. Degradation kinetics for each pesticide tested showed that the highest degradation rates were found in the first 24 h. Kinetics data were adjusted to an empirical equation in order to predict their behavior, and the correlation coefficients obtained were satisfactory. Gas chromatography/mass spectrometry (GC/MS) analysis of the final extracts allowed the identification of chlordene and monodechlorodieldrin, which have been reported as final metabolite produced in the biodegradation of this kind of compounds. Regarding adsorption of pesticides on activated vegetal carbon, we concluded that removal efficiencies between 95.45 and 97.18% can be reached, depending on the pesticide and the carbon dose applied. The values for K from the Freundlich equation were quite similar for the four pesticides (between 1.0001 and 1.04), whereas the n values were quite different for each pesticide in the following order of affinity: dieldrin > aldrin > heptachlor epoxide > heptachlor. Equilibrium times, very important for scaling up the process, were between 43 min and 1 h, for the heptachlor epoxide and the heptachlor, respectively.     

Meta‐Analysis of the Effects of Forest Fragmentation on Interspecific Interactions

Forest fragmentation dramatically alters species persistence and distribution and affects many ecological interactions among species. Recent studies suggest that mutualisms, such as pollination and seed dispersal, are more sensitive to the negative effects of forest fragmentation than antagonisms, such as predation or herbivory. We applied meta‐analytical techniques to evaluate this hypothesis and quantified the relative contributions of different components of the fragmentation process (decreases in fragment size, edge effects, increased isolation, and habitat degradation) to the overall effect. The effects of fragmentation on mutualisms were primarily driven by habitat degradation, edge effects, and fragment isolation, and, as predicted, they were consistently more negative on mutualisms than on antagonisms. For the most studied interaction type, seed dispersal, only certain components of fragmentation had significant (edge effects) or marginally significant (fragment size) effects. Seed size modulated the effect of fragmentation: species with large seeds showed stronger negative impacts of fragmentation via reduced dispersal rates. Our results reveal that different components of the habitat fragmentation process have varying impacts on key mutualisms. We also conclude that antagonistic interactions have been understudied in fragmented landscapes, most of the research has concentrated on particular types of mutualistic interactions such as seed dispersal, and that available studies of interspecific interactions have a strong geographical bias (arising mostly from studies carried out in Brazil, Chile, and the United States). Meta‐Análisis de los Efectos de la Fragmentación del Bosque sobre las Interacciones Interespecíficas