Conservation assessments using CLUZ: steps 5 to 8

Step 5: Set the conserved and excluded planning units

The next step is to identify the planning units that will always be included and always be excluded from the portfolios that MARXAN identifies.

Conserved planning units will appear in every portfolio identified by MARXAN. In general, all existing protected areas (PAs) should be set as conserved, unless there are plans to radically review the existing PA network and deproclaim areas that are not needed to meet the representation targets. In some cases, it might also be useful to set planning units containing eco-tourism infrastructure as being conserved, so that MARXAN preferentially selects areas that neighbour these sites.

Excluded planning units will not appear in any portfolio identified by MARXAN. Some planning units might be excluded because it would be politically impossible to conserve them, even though they contain important biodiversity. Other units might be excluded because it is known that they will be transformed in the future, for example by new roads or housing.

Another important reason for excluding a unit is to prevent MARXAN from selecting unsuitable areas to act as corridors between important habitats. MARXAN can select units based on their connectivity value alone, so it is important to exclude units that could not play this role. For example, units that mostly contain urban or agricultural habitats should normally be excluded (Smith et al., 2006).

In step 4 you created a blank planning unit theme, where each planning units was given the Available status. In this step you need to identify which planning units need their status changed to Conserved or Excluded.

You can use ArcView's Select by Theme module to identify planning units that need a different status because they overlap with or neighbour other important features. For example, you could identify all the units that are within 500m of roads and give them the Excluded status.

You can also use the Query Builder feature to identify important planning units based on information stored in the planning unit theme table. For example, you can use CLUZ's Calculate % of unit that falls within PAs module to add a field to the table that measures the extent to which each unit falls within a PA. You could then use the Query builder to select units that are more than 50% conserved.

Once you have selected the relevant units, use the CLUZ's Change Status panel to set the status of planning units to being Conserved or Excluded.

Always use the Change Status panel to update the status of the planning units. If you change the status of units manually in the planning unit theme table then this will not update the values in the Conserved field of the target table. If you do make any changes that fail to be reflected in the target table then use CLUZ's Recalculate target table data module to overcome the problem.

Step 6: Set the targets

Your representation targets should ensure the long-term persistence of each of your conservation features and I recommend reading the Set your representation targets section before proceeding. You can now add your target values to the CLUZ target table.

You should either type in the target values to the target table or use ArcView's join option to join an existing table containing the values and copy them into the Target field.

Once you have added the target data, close the Target table and then re-open it to update the information in the Pc_target field. You can also use the target table's Total field to check whether the total amount in the planning region is less than the target amount, in which case you will need to revise the targets.

Step 7: Set your target penalty factors

Target penalty factors (also called species penalty factors) and set for each conservation feature. They specify the amount that is added to the total portfolio cost if the target for that feature is not met, so that MARXAN tends to meet each target when it acts to minimise the total portfolio cost.

In theory, you should set a penalty factor that relates to the cost of actions that address the problem of not meeting the target (Ball and Possingham, 2000). This would allow MARXAN to make trade-offs between the cost of including more planning units in the portfolio and the cost of not meeting particular targets.

In practice, very few people know what these penalty cost should be and so it is better to set penalty factors that are large enough to ensure all the targets are met. Setting these very large penalty values does not affect the final portfolio, other than making it almost certain that all the targets are met (as long as the target is not more than the total amount in the planning region).

The penalty factors need to be large enough to ensure that MARXAN always meets the targets. This means they must be much larger than the cost of individual planning units, so that MARXAN never chooses to remove a planning unit from the portfolio that prevents a target from being met.

So, set the penalty factor as being at least 100 times the value of the highest individual planning unit cost for every conservation feature. Then use ArcView's Field Calculator to enter this value into every cell in the Spf field of the CLUZ target table.

---- YOU ARE NOW READY TO CREATE THE MARXAN INPUT FILES ----

You should now convert all your CLUZ data into the correct MARXAN format. Do this by selecting the following modules: Create abundance.dat, Create target.dat, Create unit.dat and Create bound.dat

Step 8: Lock planning units together with boundary cost values

It is sometimes useful to "lock" certain planning units together, so that they are always selected in the same portfolio. For example, the diagram on the right shows the feeding and spawning sites for a fish species found in two different rivers. If the target was to represent one spawning site and one feeding site then it is obviously vital that both sites are located in the same river. This means that the planning units containing the spawning and feeding sites in river A must be locked together, and the planning units containing the spawning and feeding sites in river B must be locked together.

The way to ensure that planning units are locked together is to manipulate the boundary cost file (H. Possingham, pers. comm.). If very large boundary values are set between planning units, then MARXAN will act to reduce those boundary costs by always selecting them together. It does not matter if the planning units do not actually share a boundary - MARXAN only uses data from the bound.dat file to calculate boundary costs and so can be "tricked" into always selecting non-neighbouring planning units together in this way.

To make sure that a set of planning units always appear in the same portfolio, first use the Change Status panel to select the group of planning units that you want to 'lock together'.

Next, go to the CLUZ menu and select the module named Add to bound.dat to group selected units. In the input box, select a boundary cost value that is much larger than the normal boundary and planning unit costs to ensure that MARXAN will always select the whole group of planning units together.