Changes between Version 4 and Version 5 of EwEugSpatialOptimizationProcedures


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Timestamp:
2010-01-31 16:05:02 (10 years ago)
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varunr
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  • EwEugSpatialOptimizationProcedures

    v4 v5  
    11== 4.8 Spatial optimization procedures == 
    2  
    32[[Image(wiki:EwEugImages:mgel_logo2.gif)]] [[Image(wiki:EwEugImages:Lenfest Logo_50px.jpg)]] 
    43 
    5 This section contains the methodology and scientific material for the ''Spatial optimizations'' tool in Ecospace. This routine is implemented using the ''Spatial optimizations'' form (''Spatial dynamic (Ecospace) > Tools > Spatial optimizations''). For instructions on implementing the routine, see [[Spatial optimizations.htm|Spatial optimizations]]. 
     4This section contains the methodology and scientific material for the ''Spatial optimizations'' tool in Ecospace. This routine is implemented using the ''Spatial optimizations'' form (''Spatial dynamic (Ecospace) > Tools > Spatial optimizations''). For instructions on implementing the routine, see [wiki:EwEugSpatialOptimizations Spatial optimizations]. 
    65 
    76We describe two approaches for spatial optimization of protected area placement, both based on maximizing an objective function that incorporates ecological, social, and economical criteria. Of these, a seed cell selection procedure works by evaluating potential cells for protection one by one, picking the one that maximizes the objective function, add seed cells, and continue to full protection. The other is a Monte Carlo approach, which uses a likelihood sampling procedure based on weighted importance layers of conservation interest (similar to Marxan’s) to evaluate alternative protected area sizing and placement. The two approaches are alternative options in a common spatial optimization module, which uses the time- and spatial dynamic Ecospace model for the evaluations. The optimizations are implemented as components of the Ecopath with Ecosim approach and software. In a case study, we find that there can be protected area zoning that will increase economical and social factors, without causing ecological deterioration. We also find a tradeoff between including cells of special conservation interest and the economical and social interest, and while this does not need to be a general feature, it emphasizes the need to use modeling techniques to evaluate the tradeoff. 
     
    1110We view the new importance layer sampling procedure as complimentary to the Marxan approach in that its strong side, through the underlying trophic modeling background is in evaluating ecological processes, including spatial connectivity; topics that are not well covered in Marxan analysis. In doing so, we, however, involve a rather complicated dynamic model, even if user-friendly, and this unavoidably has a cost. We therefore advocate that the two approaches, with their given advantages and limitations, be applied in conjunction – using two sources to throw light at a problem from different angles, beats one, any time. We have in order to facilitate such comparative studies developed a two-way bridge between Marxan and EwE, enabling exchange of spatial information and of optimization results between the two approaches. We describe only briefly aspects of this below, as we have applied the bridge elsewhere for a formal comparison (Ferdaña et al., MS). 
    1211 
    13 === Methodology === 
    14 ==== Objective function ==== 
     12'''__Methodology__''' 
     13 
     14'''Objective function''' 
     15 
    1516We employ an objective function for the optimizations, which corresponds to the objective function used in the policy optimization module of EwE. This module, which has been applied to a number of case studies, (e.g., Christensen and Walters, 2004; Araújo et al., 2008; Arreguin-Sanchez et al., 2008) uses a non-linear search routine to find a combination of effort by fishing fleets that will maximize the objective function. The objective function in turn includes ecological, economical and social indicators, even legal constraints if pertinent, through considering profit, number of jobs, stock rebuilding, and two ecological measures. For the spatial optimizations we add a further indicator in form of a boundary weight factor (See Table 1) 
    1617 
    17 The profit objective is calculated by summing revenue across all fleets, and subtracting the cost for operating. Cost is considered a linear function of effort with a fixed cost added. The following calculation is performed for each time (../Resources/Images/03000001.png) step to estimate the revenue (../Resources/Images/03000002.png), 
     18The profit objective is calculated by summing revenue across all fleets, and subtracting the cost for operating. Cost is considered a linear function of effort with a fixed cost added. The following calculation is performed for each time ([[Image(wiki:EwEugImages:03000001.png)]]) step to estimate the revenue ([[Image(wiki:EwEugImages:03000002.png)]]), 
    1819 
    19 ../Resources/Images/03000003.png        Equation 1 
     20[[Image(wiki:EwEugImages:03000003.png)]]       '''Equation 1''' 
    2021 
    21 with../Resources/Images/03000004.png being the fishing mortality for group (../Resources/Images/03000005.png) caused by fleet (../Resources/Images/03000006.png), ../Resources/Images/03000007.png is the biomass of (../Resources/Images/03000005.png), and ../Resources/Images/03000008.png is the ex-vessel value per unit weight of (../Resources/Images/03000005.png) caught by (../Resources/Images/03000006.png). ../Resources/Images/03000009.png is the relative effort for (../Resources/Images/03000006.png), the ../Resources/Images/0300000A.png is variable cost per unit effort for (../Resources/Images/03000006.png), and ../Resources/Images/0300000B.png is the fixed cost for fleet (../Resources/Images/03000006.png). 
     22with [[Image(wiki:EwEugImages:03000004.png)]] being the fishing mortality for group ([[Image(wiki:EwEugImages:03000005.png)]]) caused by fleet ([[Image(wiki:EwEugImages:03000006.png)]]), [[Image(wiki:EwEugImages:03000007.png)]] is the biomass of ([[Image(wiki:EwEugImages:03000005.png)]]), and [[Image(wiki:EwEugImages:03000008.png)]] is the ex-vessel value per unit weight of ([[Image(wiki:EwEugImages:03000005.png)]]) caught by ([[Image(wiki:EwEugImages:03000006.png)]]). [[Image(wiki:EwEugImages:03000009.png)]] is the relative effort for ([[Image(wiki:EwEugImages:03000006.png)]]), the [[Image(wiki:EwEugImages:0300000A.png)]] is variable cost per unit effort for ([[Image(wiki:EwEugImages:03000006.png)]]), and [[Image(wiki:EwEugImages:0300000B.png)]] is the fixed cost for fleet ([[Image(wiki:EwEugImages:03000006.png)]]). 
    2223 
    2324The calculations in Equation 1 are, as indicated, performed for each time step, with benefit summed over time. We, however, discount future values based on either a traditional discount rate, or an inter-generational discount rate (Sumaila and Walters, 2005), based on user preference. 
    2425 
    25 As a social indicator, we use the number of jobs over time (../Resources/Images/0300000C.png) created in the ecosystem, and we estimate this for each time step (../Resources/Images/03000001.png) from the landed value of the exploited group times the relative number of jobs per unit value (../Resources/Images/0300000D.png, or 
     26As a social indicator, we use the number of jobs over time ([[Image(wiki:EwEugImages:0300000C.png)]]) created in the ecosystem, and we estimate this for each time step ([[Image(wiki:EwEugImages:03000001.png)]]) from the landed value of the exploited group times the relative number of jobs per unit value ([[Image(wiki:EwEugImages:0300000D.png)]], or 
    2627 
    27 ../Resources/Images/0300000E.png 
     28[[Image(wiki:EwEugImages:0300000E.png)]] 
    2829 
    2930Similar to the profit objective, we discount the number of jobs over time. 
    3031 
    31 We estimate the mandated rebuilding objective (../Resources/Images/0300000F.png) for each time step (../Resources/Images/03000001.png) from 
     32We estimate the mandated rebuilding objective ([[Image(wiki:EwEugImages:0300000F.png)]]) for each time step ([[Image(wiki:EwEugImages:03000001.png)]]) from 
    3233 
    33 ../Resources/Images/03000010.png 
     34[[Image(wiki:EwEugImages:03000010.png)]] 
    3435 
    3536where ../Resources/Images/03000011.png  is baseline Ecopath biomass for group (../Resources/Images/03000005.png), and ../Resources/Images/03000012.png equals the group biomass ../Resources/Images/03000007.png if ../Resources/Images/03000013.pngis lower than the mandated biomass, ../Resources/Images/03000014.png for the group, and ../Resources/Images/03000014.png if it is not.