On natural resource substitution

We present a simple dynamic model to get some key insights about the substitution of renewable for nonrenewable resources in production and the consequences for sustainability. We highlight the role of the elasticity of substitution (technological component) to determine the adjustment of every sector as a response to scarcity and growing ability of resources (environmental component). Sometimes, the model predicts a smooth substitution of renewable resources for nonrenewables, but this process could work in the opposite direction if renewable resources are temporarily beyond their maximum sustainable yield, so that their marginal natural growth is negative. If substitution possibilities are high enough, it may be optimal to suspend the extraction of a resource, for example, to allow for regeneration of the biomass. We show analytically that a production process is more likely to be sustainable the more heavily it depends on renewable, rather than nonrenewable resources.Renewable resources, Nonrenewable resources, Production, Optimal control.

OPTIMAL SUBSTITUTION OF RENEWABLE AND NONRENEWABLE NATURAL RESOURCES IN PRODUCTION

A theoretical model is presented in order to study the optimal combination of natural resources, used as inputs, taking into account their natural growth ability and the technical possibilities of input substitution. The model enables us to consider renewable resources, nonrenewable, or both. The relative use of resources evolves through time according to the difference between both resources' natural growth and technological flexibility, as measured by the elasticity of substitution of the production function. Output evolves according to a version of the traditional Keynes-Ramsey rule, where the marginal productivity of capital is substituted by the ''marginal productivity of natural capital'', that is a combination of both resources' marginal growth weighted by each resource return in production.Renewable Resources, Nonrenewable Resources, Production, Optimal Control.

Análisis del valor económico de la información meteorológica utilizada en la toma de decisiones sobre cultivos, en un contexto dinámico de gestión de riesgos

[EN] We evaluate the added value of a forecast service that can provide probabilistic predictions for adverse weather events for two differentiated seasons, corresponding to the same productive cycle. The paper builds on a cost-loss dynamic model, by considering the role of forecasting systems in the decision making process. We present the analytical solution for this problem which is consistent with the numerical results in the literature. However, we prove that there is a range of regions for the opti-mal policy depending on the cost of crop protection, the avoided loss and the quality of the information available. Finally, we illustrate the results with a numerical example.[ES] Evaluamos el valor añadido de los servicios meteorológicos que proporcionan predicciones probabilísticas para eventos climáticos adversos considerando dos estaciones diferentes, correspondi-entes a un mismo ciclo productivo. Este artículo se apoya en un modelo coste-pérdida dinámico para considerar el papel de los sistemas de predicción y alerta temprana en los procesos de toma de decisión. Se presenta la solución analítica para este problema, que es consistente con los resultados numéricos en la literatura. Sin embargo, probamos que la política óptima presenta numerosas regiones distintas depen-diendo del coste de proteger, la pérdida evitada y la calidad de la información disponible. Finalmente, ilustramos los resultados con un ejemplo numérico.We thank Barry Readman for the linguistic revision of the text. Emilio Cerdá thanks funding from the Spanish Ministry of Economía and Competitividad through the research project ECO2012-39553-C04-01.Cerdá, E.; Quiroga, S. (2015). Analysing the economic value of meteorological information to improve crop risk management decisions in a dynamic context. Economía Agraria y Recursos Naturales - Agricultural and Resource Economics. 15(2):5-30. https://doi.org/10.7201/earn.2015.02.01SWORD53015

A class of learning by doing model with multiplicative uncertainty: economic implications

Learning by doing denotes the cost reduction in production that firms achieve with their output. We check if the known properties of deterministic models, concerning the behaviour of the finns, hold under uncertainty. A discrete time and finite horizon model is considered: a monopolist, facing a linear demand, maximizes the expected profit flow, with multiplicative uncertainty on the cost reduction and an upper bound for this reduction. We show analytically that some properties do hold and some others do not

Balance de la cumbre de Copenhague sobre Cambio Climático

En este trabajo se pasa revista al camino recorrido en cuanto a acuerdos ambientales internacionales hasta llegar a la cumbre de Copenhague. Se examina y valora el Acuerdo de Copenhague y se avanzan algunas ideas sobre el camino tras Copenhague

Duality in Fractional Programming Involving Locally Arcwise Connected and Related Functions

A nonlinear fractional programming problem is considered, where the functions involved are diferentiable with respect to an arc.Necessary and su±cient optimality conditions are obtained in terms of the right diferentials with respect to an arc of the functions. A dual is formulated and duality results are proved using concepts of locally arcwise connected, locally Q-connected and locally P-connected functions .Our results generalize the results obtained by Lyall, Suneja and Aggarwal, Kaul and Lyall and Kaul et.al.Generalized convexity; Fractional programming; Optimality conditions, Duality

Analysis and Comparisons of some Solution Concepts for Stochastic Programming Problems

The aim of this study is to analyse the resolution of Stochastic Programming Problems in which the objective function depends on parameters which are continuous random variables with a known distribution probability. In the literature on these questions different solution concepts have been defined for problems of these characteristics. These concepts are obtained by applying a transformation criterion to the stochastic objective which contains a statistical feature of the objective, implying that for the same stochastic problem there are different optimal solutions available which, in principle, are not comparable. Our study analyses and establishes some relations between these solution concepts.Stochastic Programming, Optimal solution concepts.

Stochastic Approach versus Multiobjective Approach for Obtaining Efficient Solutions in Stochastic Multiobjective Programming Problems

In this work, we deal with obtaining efficient solutions for stochastic multiobjective programming problems. In general, these solutions are obtained in two stages: in one of them, the stochastic problem is transformed into its equivalent deterministic problem, and in the other one, some of the existing generating techniques in multiobjective programming are applied to obtain efficient solutions, which involves transforming the multiobjective problem into a problem with only one objective function. Our aim is to determine whether the order in which these two transformations are carried out influences, in any way, the efficient solution obtained. Our results show that depending on the type of stochastic criterion followed and the statistical characteristics of the initial problem, the order can have an influence on the final set of efficient solutions obtained for a given problem.Stochastic Multiobjective Programming, Efficiency, Stochastic Approach, Multiobjective Approach.

Different interpretations of the cost-effectiveness of renewable electricity support: Some analytical results

The costs of support for electricity from renewable energy sources are an issue of concern for governments all over the world. The cost-effectiveness of such support is one of the main criteria to assess the success of policy instruments. However, significant confusion exists in the literature about which costs should be minimised. Some authors define the concept of cost-effectiveness as that which minimises the generation costs of renewable energy. Others define it as that which minimises the costs of support. In this paper, the optimisation problems corresponding to each of the approaches are formally stated, the corresponding optimality conditions are obtained, the optimal solutions of both approaches are compared and some mechanism of transfer of rents from consumers to producers, with good properties, are proposed