Interpretation & Analysis

With our large species database and library of GIS data, we are able to carry out a wide range of analysis tasks. One such analysis task we completed for Natural England was to identify areas on the South Downs with the greatest potential for habitat recreation for the Adonis Blue (Polyommatus bellargus) butterfly.

Habitat Potential for the Adonis Blue

In order to demonstrate the versatility of the Habitat Potential Model, Natural England asked us to engage in an analysis project that would combine butterfly species data with the power of GIS. The brief was to identify areas of greatest potential for habitat recreation for the Adonis Blue butterly using the newly created South Downs Habitat Potential Model (SDHPM).

Data Cleansing

Since the butterfly data were being extrated from Levana, a butterfly database, an extensive data cleansing operation had to be undertaken in order to make them fit for analysis in GIS. This included normalising the wide variety of abundance values into a numerical form, thus enabling us to perform calculations on the data.

The SDHPM is based on a hectare (100 meter) grid and so grid references below 100 meters in resolution had to be discarded.

Plotting

The species data were then plotted within the GIS, overlaying the SDHPM. Each datum point was given a high, medium or low symbol based on the normalised abundace data. This allows us to see, at a glance, where areas of high abundance are. Once plotted, the species data could then pinpoint hectare cells within the SDHPM.

Finding Areas of Potential

We know the Adonis Blue's habitat is calcareous grassland, preferring sunny south-facing slopes on the South Downs. We also know that during its lifetime, and Adonis Blue can travel 500 metres from its place. Armed with these facts we were able to extract cells from the SDHPM meeting these critera. Initially we ran a search on all cells with a high calcareous grassland potential, south facing (east to west aspect) and within 500m of an existing Adonis Blue colony. We were also able to easily create variations on these critera: we created a variation that included only a south-west to south-east aspect.

Results

The results were a series of maps highlighting areas of greatest potential for habitat recreation for the Adonis Blue. With these maps, ecologist are able to prioritise which areas should be researched further and ground truthed. The guidance this GIS analysis provides can help employ human resources far more efficiently than random, or even informed yet anecdotal, selection alone.