1 Introduction

Multi-criteria and suitability analyses are useful methods to map the relative habitat suitability of species or vegetation. Although suitability maps can provide useful insights, to support actual decisions or answer specific questions, follow-up steps are often required.

In the nature and biodiversity conservation domain, a common follow-up task is to identify potential areas or regions for nature conservation. GRASS GIS provides several tools that can be used to accomplish this. For example, the r.clump function can be used to group cells with contiguous cell category values into unique categories. This could be raster cells with a certain minimum suitability score. The r.reclass.area function can do the same, but also to reclassify regions that are larger or smaller than a user-specified area size.

The r.suitability.regions add-on1 combines these different functions to identify regions with a minimum area size consisting of contiguous raster cells with a suitability score above a certain user-defined threshold. It can do this using the original suitability scores, or by first calculating for each cell an aggregated suitability score (median, maximum, 1st or 2nd quartile) of the bordering raster cells within a user-defined radius.

The add-on can be used for any analysis aimed at delineating contiguous regions of high suitability based on a suitability raster layer. It makes the consequences of some basic selection criteria more explicit and helps to visualize the results of specific threshold values for area size and suitability scores.