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Ensaios em economia dos recursos naturais
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The problem of overexploitation of resources, either renewable or exhaustible, is a fundamental issue in Natural Resource Economics. The present dissertation is composed of four chapters in Natural Resource Economics. Chapter 1 addresses the preservation of environmental assets under uncertain future preferences, while Chapters 2, 3 and 4 focus on Fisheries Economics, in particular, on the management of highly migratory species.
Irreversibility associated with the consumption and destruction of exhaustible resources imposes a severe externality across different generations: future generations will suffer from the destruction of a unique asset and it is not clear how such a loss could be compensated in terms of other goods. Moreover, future generations may value natural resources differently from us. This has important implications for current decisions about environmental preservation. In the first chapter, the impact of resource amenity values on the optimal growth of an economy that depends upon those resources for the production of goods and services is examined. In particular, in the context of a capital -resource growth model, we examine the conditions under which it is optimal to preserve the environmental asset when there are two sources of uncertainty about future preferences: (i) uncertainty about the time of change in preferences and (ii) uncertainty about the change in preferences itself. We show that, under mild assumptions, in the presence of uncertain future preferences, the chances for optimal preservation increase. These results depend on the characteristics of the
distribution that governs the time at which preferences change.
Focusing now on renewable resources, the last few decades have been characterised by the collapse of several valuable resources, namely fish stocks in the high seas.
Several species are clearly overexploited and many fishery activities are characterized by overcapacity. The main challenge of Fisheries Economics is to avoid depletion by encouraging fishing nations to manage the resources in a sustainable way. The stock of the Northern Atlantic Bluefin tuna has decreased substantially in the last decades and has reached levels of great concern. The last three chapters of this dissertation concentrate on the analysis of this species.
In the second chapter, a brief description of the fishery studied is presented as well as the United Nations' legal framework for the management of high seas fisheries.
In the third chapter, the optimal management of the Northern Atlantic Bluefin tuna in the presence of uncertain recruitment is examined. The purpose of this chapter is to study the implications of introducing a stochastic recruitment function on the optimal management of this fishery, as historical evidence points out to occasionally huge recruitment. To this end, a multi -gear and age structured bio-economic model was developed for this species, in order to compare the deterministic and stochastic results. Specifically, the goal is to examine whether the deterministic optimal policy
remains robust to the presence of uncertainty in the recruitment, in particular, in limit cases such as situations of low recruitment. These are the most relevant situations, as they endanger stock preservation.
In the East Atlantic, the results show that uncertainty on the recruitment should be taken into account in order to satisfy the recommended precautionary approach.
If uncertainty is disregarded, the probability of having low recruitment is ignored and, thus, the Bluefin tuna stock may not be able to recover. In fact, there would be a short run effect, as the stock recovers initially due to the moratorium, but in the medium and long run the intervention would produce no impact. The case of the West Atlantic is of less concern, since the fishery was severely restricted in the past and the stock stabilised.
The optimal management of the Bluefin tuna turns out to be a problem, since this species is targeted by several nations using different gears. In these cases, international agreements between nations are required. The main question that arises concerns the stability of these agreements. Chapter 4 examines the stability of the agreement solution for the management of the Northern Atlantic Bluefin tuna defined by the United Nations Agreement on straddling and highly migratory fish stocks, within a Regional Fisheries Management
Organisation. The purpose is to compare the agreement solution with two alternative non-cooperative solutions: the myopic open access and the time consistent feedback Nash equilibrium. The agreement solution is shown to be preferred to both noncooperative solutions (open access and feedback Nash), but it may be unstable both with and without side payments, as there are free riding incentives by some of the players. In contrast to the open access case, in the feedback Nash case, the only source of instability comes from the distant water fishing nations, which, however,
can be eliminated. In fact, in its legal framework, the United Nations Agreement eliminates all nations from the Bluefin tuna harvest unless they are members of a Regional Fisheries Management Organisation and abide by its rules. If this legal constraint is enforced, we show that the feedback Nash solution, based on non-linear Markov strategies, with side payments distributed according to the Shapley value rule almost replicates the agreement solution.