Changes between Version 7 and Version 8 of EwEugSpatialOptimizationProcedures


Ignore:
Timestamp:
2010-01-31 16:18:14 (9 years ago)
Author:
varunr
Comment:

Added images and tables.

Legend:

Unmodified
Added
Removed
Modified
  • EwEugSpatialOptimizationProcedures

    v7 v8  
    7878The major result from the seed cell selection procedure is an evaluation of the tradeoff between size of protected area, and each of the objectives in Equation 2. This can, for instance, be used to consider what proportion of the total area to close in subsequent, more detailed analysis based on importance layer sampling. 
    7979 
    80 === Importance layer sampling procedure === 
     80'''''Importance layer sampling procedure''''' 
     81 
    8182An advantage of the seed cell modeling approach described above is that it allows a comprehensive overview of the tradeoff 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 modeling 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 geospatial data, such as, for instance, critical fish habitat layers from GIS. 
    8283 
    8384To address this shortcoming, we have developed an alternative optimization routine for the Ecospace model, 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 (MC) 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) is evaluated, and the results, including which cells were protected, are stored for each run (see Figure 1). 
    8485 
    85 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 (../Resources/Images/0300002C.png), we initially scale the importance layer values to sum to unity, and then calculate an overall cell weighting (../Resources/Images/0300002D.png) for each cell (../Resources/Images/03000026.png) from 
     86The 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 ([[Image(wiki:EwEugImages:0300002C.png)]]), we initially scale the importance layer values to sum to unity, and then calculate an overall cell weighting ([[Image(wiki:EwEugImages:0300002D.png)]]) for each cell ([[Image(wiki:EwEugImages:03000026.png)]]) from 
    8687 
    87 ../Resources/Images/0300002E.png  Equation 3 
     88[[Image(wiki:EwEugImages:0300002E.png)]]  '''Equation 3''' 
    8889 
    89 where ../Resources/Images/0300002F.png are the importance layer weightings, and ../Resources/Images/03000030.pngthe cell-specific, scaled importance layer values. 
     90where [[Image(wiki:EwEugImages:0300002F.png)]] are the importance layer weightings, and [[Image(wiki:EwEugImages:03000030.png)]] the cell-specific, scaled importance layer values. 
    9091 
    9192In order to evaluate how well the importance layers are represented in each optimization run, we estimate 
    9293 
    93 ../Resources/Images/03000031.png  Equation 4 
     94[[Image(wiki:EwEugImages:03000031.png)]]  '''Equation 4''' 
    9495 
    95 Where ../Resources/Images/03000032.png indicates cells selected in a given run, and ../Resources/Images/03000033.pngthe cell with the highest weightings for the given layer. The layer-specific indicator (../Resources/Images/03000034.png) can obtain values in the range between 0 and 1. 
     96Where [[Image(wiki:EwEugImages:03000032.png)]] indicates cells selected in a given run, and [[Image(wiki:EwEugImages:03000033.png)]] the cell with the highest weightings for the given layer. The layer-specific indicator ([[Image(wiki:EwEugImages:03000034.png)]]) can obtain values in the range between 0 and 1. 
    9697 
    9798For each optimization search, one has to select the proportion of water cells to protect in the runs, as well as how many times to repeat the Monte Carlo runs. It is possible to set the search routine up to iterate over a range of protection levels, e.g., from 10% to 100% protected in steps of 10%. 
     
    99100Similar to the seed cell selection procedure, we typically develop and tune the model to an initial time period, and then use the sampling procedure to evaluate scenarios for protected areas for a subsequent time period. 
    100101 
    101 We have developed a capability for Ecospace to read raster files with spatial information such as importance layers or other Ecospace base map layers. The reading is possible from comma separated text files (.csv), ESRI ASCII files (.asc), and ESRI shape files (.shp). The files need to have layers or columns with row and column numbers matching the Ecospace model. This capability is designed to allow straightforward exchange between the Ecospace modeling and Marxan analysis, with the constraint that it needs to be possible to represent the layers in raster form. The reading of the spatial files is described in more detail in [[Spatial optimizations.htm|Spatial optimization]] and [[Setting importance layers.htm|Setting importance layers]]. 
     102We have developed a capability for Ecospace to read raster files with spatial information such as importance layers or other Ecospace base map layers. The reading is possible from comma separated text files (.csv), ESRI ASCII files (.asc), and ESRI shape files (.shp). The files need to have layers or columns with row and column numbers matching the Ecospace model. This capability is designed to allow straightforward exchange between the Ecospace modeling and Marxan analysis, with the constraint that it needs to be possible to represent the layers in raster form. The reading of the spatial files is described in more detail in [wiki:EwEugSpatialOptimizations Spatial optimization] and [wiki:EwEugSettingImportanceLayers Setting importance layers]. 
    102103 
    103 === The spatial-dynamic modelling approach === 
     104'''__The spatial-dynamic modelling approach__''' 
     105 
    104106The methodologies for spatial optimization described here rely on the Ecospace model, implemented within the Ecopath with Ecosim approach and software. The Ecospace model is described in a number of publications, notably by Walters et al. (1999; submitted). The Ecospace models builds on an underlying Ecopath trophic models, which can have any number of functional groups or age- and species-specific groups as appropriate for the questions to be addressed. The Ecospace runs picks up levels of fishing effort over time from an associated Ecosim runs, including mediation factors and most other factors that do not have a potentially important spatial dimension, which Ecosim cannot address. 
    105107 
     
    110112'''Table 1.''' objective function employed for spatial optimization. Each objective is given a weighting factor, and the optimization seeks to optimize the summed, weighted objectives. 
    111113 
    112 || <class="td_1"> '''Objective''' || <class="td_1"> '''Description''' || 
    113 || <class="td_2"> Profit || <class="td_2"> Estimated by ‘fleet’, and summed over all such || 
    114 || <class="td_3"> Jobs || <class="td_3"> Estimated from value of fisheries, and relative number of jobs/value || 
    115 || <class="td_2"> Mandated rebuilding || <class="td_2"> A minimum acceptable level, by group || 
    116 || <class="td_3"> Ecosystem structure || <class="td_3"> Default values based on biomass/productivity ratios expressing average longevity, weighted by group || 
    117 || <class="td_2"> Biomass diversity || <class="td_2"> Biomass evenness among groups || 
    118 || <class="td_3"> Boundary weight || <class="td_3"> Estimated as total boundary length over the protected area size. Captures spatial connectivity || 
     114|| '''Objective''' || '''Description''' || 
     115|| Profit || Estimated by ‘fleet’, and summed over all such || 
     116|| Jobs ||  Estimated from value of fisheries, and relative number of jobs/value || 
     117|| Mandated rebuilding || A minimum acceptable level, by group || 
     118|| Ecosystem structure || Default values based on biomass/productivity ratios expressing average longevity, weighted by group || 
     119||  Biomass diversity || Biomass evenness among groups || 
     120||  Boundary weight || Estimated as total boundary length over the protected area size. Captures spatial connectivity || 
    119121 
    120 ../Resources/Images/06000039.png 
     122 
     123[[Image(wiki:EwEugImages:06000039.png)]] 
    121124 
    122125'''Figure 1'''. Logic of the importance layer sampling procedure. For each run a given percentage of all cells are protected based on weighted likelihood in importance layers. The evaluation of each run is done independently based on a defined objective function..