Angels Xabadia

Maximum principle for a size-structured model of forest and carbon sequestration management

Abstract The paper analyzes nonlinear optimal control of integral–differential equations that describe the optimal management of a forest taking into account intra-species competition and carbon sequestration. The objective function includes the revenues from timber production, operational expenses, and the net benefits from carbon sequestration. A dual system is derived and a necessary extremum condition is established.

The Gains from Differentiated Policies to Control Stock Pollution when Producers Are Heterogeneous

We derive optimal input taxes to control stock pollution problems generated by heterogeneous agents. The taxes vary over time and in response to differences of asset quality and technology choice. We also derive second-best policies and compare them to the efficient policy and also among themselves. Different policies will affect the timing for when, and the extent to which, conservation technologies are adopted. A numerical example, based on the California drainage problem, shows significant efficiency gains from the optimal policy compared to no intervention, but much of the gains are lost with second-best interventions. The gains from optimal policies do not always increase with the degree of heterogeneity. Copyright 2008, Oxford University Press.

Using the Escalator Boxcar Train to Determine the Optimal Management of a Size-Distributed Forest When Carbon Sequestration Is Taken into Account

We present a theoretical model to determine the optimal management of a size-distributed forest.The decision model is given in form of a distributed optimal control problem that cannot be solved analytically. Thus, the paper presents a numerical technique that allows transforming the original distributed control problem into an ordinary control problem. The method has the advantage that it does not require programming numerical algorithms but rather can be implemented with standard commercial optimization packages such as GAMS. The empirical application of our model for the case of forest management allows determining the selective cutting regime when carbon sequestration is taken into account.

Optimal harvesting in forestry: steady-state analysis and climate change impact

We perform the steady-state analysis of a nonlinear partial differential equation model that describes the dynamics of a managed size-structured forest. The harvesting policy is to maximize the net benefits from timber production over an infinite planning horizon. The existence and uniqueness of the steady-state trajectories are analysed. Closed-form steady states are obtained in meaningful special cases and are used to estimate how climate change affects the optimal harvesting regime, diameter of cut trees, number of logged trees, and net benefits in the long run.

Optimal Forest Management in the Presence of Intraspecific Competition

The Escalator Boxcar Train method is used to solve the distributed optimal control problems of forest management numerically. It takes into account intraspecific competition for scarce resources such as light, space, and nutrients during reproduction, growth, and mortality. It provides an alternative to gradient projection methods and Markov processes. It is implemented with standard software. The application is on the optimal forest management regime in the presence of intraspecific competition.

Efficiency and acceptance of new water allocation rules - The case of an agricultural water users association

Water scarcity is one of the major environmental problems in Southern Europe. High levels of water stress and increasing frequency of droughts, along with a greater environmental protection, make it necessary to design water management strategies that are allocative efficient and balance supply and demand. When functioning markets cannot be developed, the allocation rules proposed in the literature of social choice have been recognized as a suitable alternative. However, the application of new water allocation rules can be impaired by a lack of acceptance and implementation problems. This paper examines these obstacles for the case of an agricultural water users association (WUA), situated in the basin of the River Ebro, in relation to the governance structure and collective decision rule of the WUA. It analyzes the extent to which the gains and losses of the farmers affect their acceptance, and examines conditions for building agreements with side payments that provide incentives for the majority of the farmers to form part of a possible agreement. The results show that the uniform and sequential rules improve the allocative efficiency under normal conditions compared to the status quo and the sequential rule even in the case of droughts. In the presence of side payments this rule is likely to be accepted and has only an insignificant impact on distributional inequality.

Solving the Two-Period Consumer Choice Model with Excel-Solver

In this paper we present a classroom exercise where students can solve the basic two-period consumer choice model using the Excel-Solver, and explore the main features of the model. We also include a static comparative analysis and a borrowing constraint in the optimization problem.

MANAGING FORESTS FOR CARBON AND BIODIVERSITY UNDER CLIMATE CHANGE

Over recent decades forest management has recognized the fact that forests provide a wide variety of services besides timber, such as carbon sequestration and the preservation of biodiversity. During this time, science has found significant evidence that climate change is actually taking place. Since the change in climatic conditions will affect the vital cycle of trees, the optimal management of forests needs to be adapted to these new conditions to make the best use of forests from the social point of view. From the policy side, forest management is confronted with the task of balancing the objectives of competitiveness, compliance with international agreements with respect to climate change mitigation and the preservation of biodiversity. This study aims to analyze the optimal management regime of forests under changing climatic conditions, taking timber, carbon and biodiversity into account. It finds that the objectives of carbon sequestration and biodiversity should target different stands. The cost of the latter can be reduced substantially if only mature stands are pursued and not young stands.

Sustainable dynamics of size-structured forest under climate change

Abstract This work investigates the impact of global climate change on the sustainable growth of forest, namely, on its aggregated characteristics such as the number of trees, the basal area, and the amount of carbon sequestrated in the stand. The forest dynamics is described by a nonlinear size-structured population model. The existence of a steady state regime is proven and explicit formulas for the aggregated characteristics are obtained. A numeric simulation on realistic data illustrates and extends the analytic results obtained.

Forest Management and Biodiversity in Size-Structured Forests Under Climate Change

Climate change is threatening biodiversity conservation at a global scale, urging the need for action in order to prevent current and future losses. In forestry, the consideration of some stand features such as requiring a certain volume of deadwood and/or large trees as a part of the management regime may help to preserve and enhance biodiversity. However, it is likely to lead to a decrease in the benefits obtained from timber sales. This chapter presents a bioeconomic model that allows the optimal selective logging regime of a size-distributed forest to be determined, while taking climate change and biodiversity into account. It analyzes to what extent structural targets related to biodiversity affect the optimal forest management regime and the profitability of forests. For this purpose, an empirical analysis under various climate change scenarios is conducted for two diameter-distributed stands of Pinus sylvestris in Catalonia. The results show that the costs of biodiversity conservation in terms of reduced profitability can be significant, and augment with climate change.