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We are now ready to add the statistical surface summaries of the Environmental RiskModel (ERS) and begin to identify planning units that have high RBN values (above themean) and low risk values (below the mean). These planning units could be candidatesites for high conservation value that are in relatively low-risk environments, accordingto our modeled ERS surface. If you have not already run Zonal Statistics using a modeledERS surface, follow the instructions in the first module, using theyour_output_name_RBI_SUMMARY output shapefile as the Zone dataset and join theoutput statistics table back to theyour_output_name_RBI_SUMMARYoutput shapefile.Now determine what the mean valuesare for both the ERS surface and the RBIoutput shapefile. This can be done bydouble clicking on each layer and goingto Symbology > “Classify” or“Histogram” option. In either option themean for the dataset will be reported.For the ERS surface, the mean is 12.55and for the your_output_name_RBI_SUMMARY output, the mean is 1.056.Now we will use these numbers tothreshold out high RBI pockets that havelow risk value.Go to Selection > Select by Attributes inthe main ArcGIS toolbar. When thedialog box appears, enter the followingformula:" your_output_name_RBI_SUMMARY.RBNT1" > 1.056 AND "ers_stats.MEAN" < 12.55TNC Protected Area Tools (PAT) Version 3.0The Nature Conservancy, August 200940