Stochastic perturbations and fisheries management

International audienceAs most natural resources, fisheries are affected by random disturbances. The evolution of such resources may be modelled by a succession of deterministic process and random perturbations on biomass and/or growth rate at random times. We analyze the impact of the characteristics of the perturbations on the management of natural resources. We highlight the importance of using a dynamic programming approach in order to completely characterize the optimal solution, we also present the properties of the controlled model and give the behavior of the optimal harvest for specific jump kernels

Inverting Regional Sensitivity Analysis to reveal sensitive model behaviors

We address the question of sensitivity analysis for model outputs of any dimension using Regional Sensitivity Analysis (RSA). Classical RSA computes sensitivity indices related to the impact of model inputs variations on the occurrence of a target region of the model output space. In this work, we invert this perspective by proposing to find, for a given target model input, the region whose occurrence is best explained by the variations of this input. When it exists, this region can be seen as a model behavior which is particularly sensitive to the variations of the model input under study. We name this method iRSA (for inverse RSA). iRSA is formalized as an optimization problem using region-based sensitivity indices and solved using dedicated numerical algorithms. Using analytical and numerical examples, including an environmental model producing time series, we show that iRSA can provide a new graphical and interpretable characterization of sensitivity for model outputs of various dimensions

Faustmann Rotation and Aquaculture in the presence of an epidemic risk

Keywords: Fisheries Economics, Aquaculture and Risk, Aquacultur

EvaSylv: A user-friendly software to evaluate forestry scenarii including natural risk

Forest management relies on the evaluation of silviculture practices. The increase in natural risk due to climate change makes it necessary to consider evaluation criteria that take natural risk into account. Risk integration in existing software requires advanced programming skills.We propose a user-friendly software to simulate even-aged and monospecific forest at the stand level, in order to evaluate and optimize forest management. The software gives the possibility to run management scenarii with or without considering the impact of natural risk. The control variables are the dates and rates of thinning and the cutting age.The risk model is based on a Poisson processus. The Faustmann approach, including tree damage risk, is used to evaluate future benefits, economic or ecosystem services. It relies on the calculation of expected values, for which a dedicated mathematical development has been done. The optimized criteria used to evaluate the various scenarii are the Faustmann value and the Averaged yield value.We illustrate the approach and the software on two case studies: economic optimization of a beech stand and carbon sequestration optimization of a pine stand.Software interface makes it easy for users to write their own (growth-tree damage-economic) models without advanced programming skills. The possibility to run management scenarii with/without considering the impact of natural risk may contribute improving silviculture guidelines and adapting them to climate change. We propose future lines of research and improvement

The Faustmann model under storm risk and price uncertainty: A case study of European beech in Northwestern France

International, economic and environmental contexts in this century are strongly affected by risks and uncertainties. Due to the long-term nature of forest investment, forest managers must integrate risks and uncertainties into their decisions. Our objective is to build a decision support tool to optimize forest management under multiple risks: extreme events and price variations. Our method integrates, into an economic model, different types of models on forest growth, price functions, predicted storm intensity and intervals, and damage functions. A numerical simulation applied to European beech (Fagus sylvatica) in Northwestern France shows that price variation as between 1974 and 2016 produces higher economic loss than does storm damage. We conclude on the need to concentrate forest policy on the development of new technologies and wood industry practices to increase the value of this natural resource. However, future climate change may well influence storm frequency and intensity, and this places limits on our conclusions

The Faustmann model under storm risk and price uncertainty: A case study of European beech in Northwestern France

International, economic and environmental contexts in this century are strongly affected by risks and uncertainties. Due to the long-term nature of forest investment, forest managers must integrate risks and uncertainties into their decisions. Our objective is to build a decision support tool to optimize forest management under multiple risks: extreme events and price variations. Our method integrates, into an economic model, different types of models on forest growth, price functions, predicted storm intensity and intervals, and damage functions. A numerical simulation applied to European beech (Fagus sylvatica) in Northwestern France shows that price variation as between 1974 and 2016 produces higher economic loss than does storm damage. We conclude on the need to concentrate forest policy on the development of new technologies and wood industry practices to increase the value of this natural resource. However, future climate change may well influence storm frequency and intensity, and this places limits on our conclusions

Private environmental incentive contract and a weather signal

The authors of the paper are interested in an environmental incentive payment mode for risk-averse contracting farmers. The incitement joins the environmental output produced by the farmer to his effort through an environmental contract reported to be motivating. However, we suppose an environmental output depending on a weather signal and we consider the effect of a weather variable on the incentive contract. The first and usual incentive contract studied takes into account the average effect of a weather indicator on the farmer's environmental output. The paper studies a second incentive contract taking into account the instantaneous effect of a weather indicator on the fanner's environmental output. Then in complement of the reservation farmer's utility, authors consider a minimum incentive payment given to the farmer through a constraint of a minimum payment for every point of farmer's output. It is possible to increase this minimum payment in the second type contract (compared to the first one) without reducing the expected utility of the principal and the expected utility of the fanner, by increasing the level of the farmer's environmental action. The use of such minimum farmer's payment and the increase of this minimum payment could be very conclusive to bind a farmer by an environmental contrac

The Declining Price Anomaly in Sequential Auctions with Asymmetric Bidders: The Case of Nephrops norvegicus in Lorient

The declining price anomaly for sequential sales of identical commodities challenges auction theory which predicts constant prices within a day. Among hypotheses explaining the phenomenon stands the dual value of goods including a risk premium in early transactions. We consider that asymmetric bidder groups and shortage periods may also affect the daily price pattern. This hypothesis is tested through various econometric models (OLS, MG, FE, LSDVC) on a fish market (Nephrops norvegicus sold alive in Lorient, France). The overall risk attitude is doubled in our case study with the presence of asymmetric buyer groups in the bidding process and their distinct marketing strategies. Our results show that one of the groups (supermarkets) bid more aggressively for a longer period of daily sales when they decide to target this species for discount selling campaigns. This strategy pushes them to outbid other competitors until they can obtain the required tonnage for their own retail shops, and such a strategy delays the time of price decline compared to other buyer groups. The declining price anomaly in sequential auctions with asymmetric bidders. Evidence from the Nephrops norvegicus market in France.Proceedings of the Eighteenth Biennial Conference of the International Institute of Fisheries Economics and Trade, held July 11-15, 2016 at Aberdeen Exhibition and Conference Center (AECC), Aberdeen, Scotland, UK