Changes between Version 3 and Version 4 of EwEugSpatialOptimizations


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Timestamp:
2010-11-23 03:36:05 (8 years ago)
Author:
shermanl
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  • EwEugSpatialOptimizations

    v3 v4  
    11== 11.4 Spatial optimizations == 
    2 [[Image(wiki:EwEugImages:mgel_logo2.gif)]] [[Image(wiki:EwEugImages:Lenfest Logo_50px.jpg)]] 
     2[[Image(wiki:EwEugImages:mgel_logo2.gif)]] [[Image(wiki:EwEugSettingImportanceLayers:Lenfest_logo.gif)]] 
    33 
    44EwE6 now allows you to use Ecospace to search for optimum placement of marine protected areas (MPAs) that would maximize a user-defined objective function. This routine is implemented using the ''Spatial optimizations'' form (''Spatial dynamic (Ecospace) > Tools > Spatial optimizations''). 
     
    88'''Introduction''' 
    99 
    10 While Ecospace has been applied quite extensively in a gaming- and scenario-development mode, we have only seen very limited effort applied to spatial optimization and zoning. A first attempt in this direction is represented, though, by the ‘Ecoseed’ approach, developed for Ecospace some years ago as part of a thesis project (Beattie 2001; Beattie et al. 2002), but never fully implemented and released as part of the software. We have developed this approach to incorporate a new objectivity function, bringing it to a level where it is part of the released EwE6. Further, we describe a new spatial optimization module, which uses the same objectivity function as the updated seed cell, but where the spatial cell selection process is influenced by spatial reference layers, typically of conservation interest. 
     10While Ecospace has been applied quite extensively in a gaming- and scenario-development mode, we have only seen very limited effort applied to spatial optimization and zoning. A first attempt in this direction is represented, though, by the 'Ecoseed' approach, developed for Ecospace some years ago as part of a thesis project (Beattie 2001; Beattie et al. 2002), but never fully implemented and released as part of the software. We have developed this approach to incorporate a new objectivity function, bringing it to a level where it is part of the released EwE6. Further, we describe a new spatial optimization module, which uses the same objectivity function as the updated seed cell, but where the spatial cell selection process is influenced by spatial reference layers, typically of conservation interest. 
    1111 
    1212Two alternative approaches to running the routine have been developed: (i) 'Seed cell' selection, based on the original approach of Beattie (2001) and Beattie et al. (2002); and (ii) 'Importance layer' sampling, an alternative approach, which allows the user to incorporate other forms of spatial information in the selection of protected areas. 
     
    1414'''Seed cell selection procedure ('Seed cell' method)''' 
    1515 
    16 This optimization method (user selects 'Seed cell' method) is based on a previous study (Beattie 2001; Beattie et al. 2002), in which we use a very simple optimization scheme to evaluate the trade-off between proportion of area protected and the value of the objective function. We have modified the previous approach by securing a better program flow, and by changing the objective function from considering only profit from fishing and existence value of biomass groups to a more detailed objective function described in Equation 2 of [[Spatial optimization procedures.htm|Spatial optimization procedures]]. 
     16This optimization method (user selects 'Seed cell' method) is based on a previous study (Beattie 2001; Beattie et al. 2002), in which we use a very simple optimization scheme to evaluate the trade-off between proportion of area protected and the value of the objective function. We have modified the previous approach by securing a better program flow, and by changing the objective function from considering only profit from fishing and existence value of biomass groups to a more detailed objective function described in Equation 2 of [EwEugSpatialOptimizationProcedures Spatial optimization procedures]. 
    1717 
    18 The procedure takes as its starting point the designation of one, more, or all spatial cells as ‘seed cells’, i.e. cells that are to be considered as potential protected cells in the next program iteration. The procedure will then run the Ecospace model repeatedly between two time steps, closing one of the seeds cells in each run, while storing the ecosystem objective function value. The seed cell that results in the highest objective function value is then closed for fishing, and its four neighbouring cells (above, below, left, right) are then turned into seed cells, unless they are so already, or already are protected, or are land cells. This procedure will continue until all cells are protected. Finally, the routine will return the set of cells to be protected that would maximize the objective function. 
     18The procedure takes as its starting point the designation of one, more, or all spatial cells as 'seed cells', i.e. cells that are to be considered as potential protected cells in the next program iteration. The procedure will then run the Ecospace model repeatedly between two time steps, closing one of the seeds cells in each run, while storing the ecosystem objective function value. The seed cell that results in the highest objective function value is then closed for fishing, and its four neighbouring cells (above, below, left, right) are then turned into seed cells, unless they are so already, or already are protected, or are land cells. This procedure will continue until all cells are protected. Finally, the routine will return the set of cells to be protected that would maximize the objective function. 
    1919 
    2020The time over which the selection procedure is run is dependent on the application. Typically, an ecosystem model is initially developed and tuned using time series data to cover a certain time period, e.g., from 1950 to 2005. Subsequently, the model is used in a scenario development mode to evaluate, for instance, protected area placement covering the period 2006-2020. 
     
    2626An advantage of the seed cell modelling approach described above is that it allows a comprehensive overview of the trade-off between proportion of area closed to fishing, and the ecological, social, and economical benefit and costs of the closures. This is done, based on the information already included in the EwE modelling approach, with no new information being needed. While this may be an advantage from one perspective, it does not allow use of other form for information, notably in form of spatial information, e.g., critical fish habitat layers from GIS. 
    2727 
    28 To address this shortcoming, we have developed a new optimization routine for the Ecospace model (user selects 'Importance layer' method), which uses spatial layers of conservation interest (‘importance layers’) to set likelihoods for spatial cells being considered for protection. The optimizations are performed using a Monte Carlo approach where the importance layers are used for the initial cell selection in each MC realization. The Ecospace model is then run, the objective function (Equation 2 in[[Spatial optimization procedures.htm| Spatial optimization procedures]]) is evaluated, and the results, including which cells were protected, are stored for each run. 
     28To address this shortcoming, we have developed a new optimization routine for the Ecospace model (user selects 'Importance layer' method), which uses spatial layers of conservation interest ('importance layers') to set likelihoods for spatial cells being considered for protection. The optimizations are performed using a Monte Carlo approach where the importance layers are used for the initial cell selection in each MC realization. The Ecospace model is then run, the objective function (Equation 2 in[EwEugSpatialOptimizationProcedures Spatial optimization procedures]) is evaluated, and the results, including which cells were protected, are stored for each run. 
    2929 
    3030NOTE: importance layers are not used to evaluate the objective function. The information in the importance layers is used only to influence initial cell selection. 
    3131 
    32 The importance layers are defined as raster layers, with dimensions similar to the base map layers in the underlying Ecospace model, i.e. they are rectangular cells in a grid with a certain number of rows and columns. Each cell in a given layer has a certain ‘importance’ for conservation, expressed, e.g., as the probability of occurrence for an endangered species. For each importance layer (''l''), we initially scale the importance layer values to sum to unity, and then calculate an overall cell weighting (''w,,c,,'') for each cell (''C'') from 
     32The importance layers are defined as raster layers, with dimensions similar to the base map layers in the underlying Ecospace model, i.e. they are rectangular cells in a grid with a certain number of rows and columns. Each cell in a given layer has a certain 'importance' for conservation, expressed, e.g., as the probability of occurrence for an endangered species. For each importance layer (''l''), we initially scale the importance layer values to sum to unity, and then calculate an overall cell weighting (''w,,c,,'') for each cell (''C'') from 
    3333 
    3434[[Image(wiki:EwEugImages:ImportanceLayerEquation.bmp)]] 
     
    6868'''Objectives''' 
    6969 
    70 The objective function used in the routine is analogous to that used in Ecosim's [wiki:EwEugImplementingPolicyOptimizationInEcospace Policy optimization] routine. It is strongly recommended you read Spatial optimization procedures for detailed description of the objective function. 
     70The objective function used in the routine is analogous to that used in Ecosim's [EwEugImplementingPolicyOptimizationInEcosim Policy optimization] routine. It is strongly recommended you read Spatial optimization procedures for detailed description of the objective function. 
    7171 
    7272Use the '''Objectives'''table (Figure 11.3) to define objective function weights for '''Net economic value''' (total landed value of catch minus total operating cost); '''Social value (employment)''', i.e., a social indicator, assumed proportional to gross landed value of catch for each fleet with a different jobs/landed value ratio for each fleet; and two ecological objectives: 1. '''Mandated rebuilding''' of one group (value of the objective function is measured by departures of biomasses over time from target biomass levels specified by entering ratios of target to Ecopath base biomasses); and 2.''' Ecosystem structure''', which favours biomasses of large, long-lived organisms. See '''Policy objectives''' in [wiki:EwEugFishingPolicySearch Fishing policy search] and Christensen and Walters (2004b) for more details about these objectives. 
     
    122122'''Importance layer''' 
    123123 
    124 When '''Importance layer''' has been selected on the''' Configuration''' tab, the '''Layers''' panel (see image below) is used to set '''Importance layers''' (users do not set seed cells). Note that importance layers are not used in calculation of the objective function, but rather are used to give greater importance to certain cells during random selection of seed cells. There are a number of ways to read in data for setting or importing importance layers. See [[Setting importance layers.htm|Setting importance layers]] for full details on importing data importance layers. See [wiki:EwEugSpatialOptimizationProcedures Spatial optimization procedures] for more on Importance layers. 
     124When '''Importance layer''' has been selected on the''' Configuration''' tab, the '''Layers''' panel (see image below) is used to set '''Importance layers''' (users do not set seed cells). Note that importance layers are not used in calculation of the objective function, but rather are used to give greater importance to certain cells during random selection of seed cells. There are a number of ways to read in data for setting or importing importance layers. See [EwEugSettingImportanceLayers Setting importance layers] for full details on importing data importance layers. See [wiki:EwEugSpatialOptimizationProcedures Spatial optimization procedures] for more on Importance layers. 
    125125 
    126126After you have imported the importance layers, they will be displayed in the '''Layers''' panel.