TIMBER HARVEST ADJACENCY ECONOMIES, HUNTING, SPECIES PROTECTION, AND OLD GROWTH VALUE: SEEKING THE OPTIMUM

Spatial forest management models recognize that nontimber benefits cat1 be influenced by the status of adjacent land. For instance, contiguous old growth provides habitat, aesthetic value, and environmental services. Conversely, edge areas provide forage and cover habitat for game and non-game wildlife. However, adjacency externalities are not limited to nontimber concerns. Larger harvest areas generate average cost savings as fixed harvesting costs are spread across greater acreage, a problem excluded from most literature on optimal harvesting. Hence, it is typical that economies and diseconomies of adjacency in harvesting occur simultaneously. This complicates the determination of optimal ecosystem management behavior, which recognizes timber, aesthetic, wildlife protection, and hunting values. This paper conceptually portrays economies of adjacency in competing objectives using multiple management strategies.Resource /Energy Economics and Policy,

Benefits of Spatial Regulation in a Multispecies System

Spatial heterogeneity in multispecies systems affects both ecological interactions and the composition of harvest. A bioeconomic model is used to analyze the nonselective harvest of two stocks with generalized ecological interaction and different persistent distributions across two spatial strata. Harvester response to aggregate effort controls is shown to partially dissipate rents relative to the case where the spatial distribution of effort can be specified. Numerical solutions for time paths of spatial (first-best) and aggregate (secondbest) input constraints indicate factors affecting their relative efficiency. In the scenarios studied, benefits of spatial specificity range from 0 to 15% of total net present value (NPV), depending upon the spatial correlation of stocks, their relative growth rates and prices, and the cost gradient across space. The benefits of spatial regulation are also heightened by the presence of ecological interaction, especially predator-prey dynamics.Bycatch, multispecies system, second-best regulation, spatial, Q20, Q22, Q28, Resource /Energy Economics and Policy,

Controlling the Biological Invasion of a Commercial Fishery by a Space Competitor: A Bioeconomic Model with Reference to the Bay of St-Brieuc Scallop Fishery

This paper presents a bioeconomic model of a commercial fishery facing biological invasion by an alien species acting as a space competitor for the native species. The model is illustrated in a case study of the common scallop fishery of the Bay of St-Brieuc (France), where biological invasion by a slipper-limpet (Crepidula fornicata) is now addressed by a control program. First we present the model, which combines the dynamics of the two competing stocks. We then use the model to analyze the equilibrium of the fishery under various assumptions concerning invasive species control, and to assess the social cost of the invasion. Finally we propose a set of dynamic simulations concerning the ongoing program, emphasizing the influence of its starting date on its overall economic results.aquatic invasive species, biological invasion control, common scallop, ecosystemic fisheries management, plurispecies bioeconomic modeling, slipper-limpet, Resource /Energy Economics and Policy,

When a Fish is a Fish: The Economic Impacts of Escaped Farmed Fish

The escape of cultured fish from a marine aquaculture facility is a type of biological invasion that may lead to a variety of potential ecological and economic effects on native fish. This paper develops a general invasive species impact model to capture explicitly both the ecological and economic effects of invasive species, especially escaped farmed fish, on native stocks and harvests. First, the possible effects of escaped farmed fish on the growth and stock size of a native fish are examined. Next, a bioeconomic model to analyze changes in yield, benefit distribution, and overall profitability is constructed. Different harvesting scenarios, such as commercial, recreational, and joint commercial and recreational fishing, are explored. The model is illustrated by a case study of the interaction between native and farmed Atlantic salmon in Norway. The results suggest that both the harvest and profitability of a native fish stock may decline after an invasion, but the total profits from the harvest of both native and farmed stocks may increase or decrease, depending on the strength of the ecological and economic parameters.

Towards the Optimal Management of the Northeast Arctic Cod Fishery

The objectives pursued by governments managing fisheries may include maximizing profits, minimizing the impact on the marine ecosystem, or securing employment, which all require adjusting the composition of the fishing fleet. We develop a management plan that can be adapted to those objectives and allows the regulator to compare the long-run profits between the various management options. We apply the model to the case of Northeast Arctic cod, and estimate the cost and harvesting functions of various vessel types, the demand function, and a biological model to provide key insights regarding the optimal management of this valuable fish species.Built Coastal Environment, Natural Coastal Environment, Ecosystem Service Valuation, Geographic Information Systems, Mapping Ecosystem Values, Marine Biodiversity, Scaling up, Spatial Analysis, Spatial Economic Valuation, Value Transfer

CONTROLLING WILDLIFE AND LIVESTOCK DISEASE WITH ENDOGENOUS ON-FARM BIOSECURITY

The spread of infectious disease among and between wild and domesticated animals has become a major problem worldwide. We analyze the socially optimal management of wildlife and livestock, including choices involving environmental habitat variables and on-farm biosecurity controls, when wildlife and livestock can spread an infectious disease to each other. The model is applied to the problem of bovine tuberculosis among Michigan white-tailed deer. The optimum is a cycle in which the disease remains endemic in the wildlife, but in which the cattle herd is depleted when the prevalence rate in deer grows too large.Research Methods/ Statistical Methods,

'El Niño' Effects and Biomass Endogeneity in a Harvest Function: The Chilean Jack Mackerel Fishery

The main goal of this paper consists in estimating the input parameters of an annual harvest function for the Chilean jack mackerel stock; particularly, the effects of biomass on catch. One of the main problems faced is that the biomass variable is possibly endogenous, which would bias the estimators if the problem remains unsolved. Our empirical strategy consists in estimating a per vessel harvest function using panel data, which allows us to control for vessels' unobserved heterogeneity, and episodes of 'El Niño' phenomenon as valid instrumental variable for biomass, which allows us to control for the potential biomass endogeneity. This strategy produces consistent estimates of the biomass coefficient. The results, using a panel of industrial vessels operating in the central-southern region of Chile during the period 1985-2002, show that the endogeneity of the biomass variable biases upwardly the magnitude of its coefficient in a Cobb-Douglas harvest function. In the case of our data, the endogeneity bias even changes the sign of the catch-to-biomass elasticity. A first contribution of the paper is to address the endogeneity of biomass in a harvest function, an issue often underestimated in the empirical literature. A second contribution is related to 'El Niño' effects on the Chilean jack mackerel stock. The results show that an oceanic 'El Niño' episode not only has negative contemporaneous effects on jack mackerel biomass but also negative biomass effects lasting for at least two additional years.El Niño phenomenon; pelagic fisheries; Chilean jack mackerel; Instrumental variable estimation; marginal stock effects; endogenous biomass

Growth and competition model for organic weed control

There is a more detailed Executive Summary at the top of the attached document, which is the final report for Defra Project OF0177. The project aimed to examine the organic extension of a simple mechanistically-based growth and competition model, calibrated to data originally gained from conventional vegetable production. Essentially the model simulation follows the growth of each crop and weed plant as they compete for space and light during and after canopy closure. The growth and competition model has been modified to simulate crop and weed growth of multiple cohorts so that the onset of crop weed competition can be predicted. This onset of competition marks the point when it is essential to remove weeds (i.e. critical weeding time); otherwise, there will be a penalty to crop yield. The model can be applied to determine the onset of competition between competing species (i.e. crop and weed). In organic crops this would be the time when physical removal of the weeds (either by means of mechanical or hand weeding methods) was essential to prevent yield loss. To test the ability of the model to identify critical weeding times, model predictions were compared with historical experimental data. The inputs to the model are starting plant weights and the numbers of individuals per unit area of the crop and weed species for each cohort at each day of the simulation. Solar radiation was used to drive the model. All the growth parameters were species specific and where a number of weed species are competing with the crop in a mixed population, then a general set of parameters representing the mean of a range of parameterised weed species were used. Repeatedly running the simulation with different starting inputs from a range of historical data sets indicated that the observed critical weeding time was described well by the model. To examine the applicability of the principle of the growth model to an organic cropping situation, the predicted optimum timing of weed removal simulated by the model was incorporated as a treatment into an existing organic carrot trial. The aim was to see whether the weeding time simulated by the model achieved comparable or better results than the weeding by the unaided judgement of the grower.The results demonstrated that there was certainly no disadvantage to using the model in that year to aid in the decision making process. A small-scale trial was made in year 3, incluing cabbage plus three previously unparameterised crops; broccoli, cauliflower and leeks. The crop parameters for cabbage were used to drive the cauliflower and broccoli simulations and onion parameters for leeks. Three treatments were; weeding once as recommended by advisors at HDRA, weeding once as predicted by the model and left weedy throughout to test the competitive level of the weed flora. Inputs into the model were solar radiation, crop transplant weights and numbers, and weed weights and numbers during the early weeks of crop growth. Adjustment of the model using the final crop weights was related to the different relative growth rates of the crops in organic soils, compared with the higher N levels in conventional soils from where the parameters had been originally derived. After recalibration, the model re-confirmed the mid-August onset of competition, but tended to over predict the degree of weed competition. The notable exception was the leek crop which was more sensitive to competition than its brassica counterparts and gave a good illustration of the potential power of the model. As part of the project several presentations have been made to growers during the final year, which have allowed a dialogue and awareness to develop highlighting the practical and scientific implications of the model

Extending Feynman's Formalisms for Modelling Human Joint Action Coordination

The recently developed Life-Space-Foam approach to goal-directed human action deals with individual actor dynamics. This paper applies the model to characterize the dynamics of co-action by two or more actors. This dynamics is modelled by: (i) a two-term joint action (including cognitive/motivatonal potential and kinetic energy), and (ii) its associated adaptive path integral, representing an infinite--dimensional neural network. Its feedback adaptation loop has been derived from Bernstein's concepts of sensory corrections loop in human motor control and Brooks' subsumption architectures in robotics. Potential applications of the proposed model in human--robot interaction research are discussed. Keywords: Psycho--physics, human joint action, path integralsComment: 6 pages, Late