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Williams-Climate-change-refugia-for-terrestrial-biodiversity_0

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expected to be considerably less extensive in the surrounding landscape than it is a<br />

present, indicating good potential <strong>for</strong> this location to serve as a refugium <strong>for</strong> biota<br />

associated with this particular environment. Applying the same logic to the other<br />

labelled locations, location A (a relatively high outcrop, or sheltered topographic<br />

position in the middle of a flat plain) and location D (at mid-elevation in highly dissected<br />

terrain) exhibit moderate levels of <strong>refugia</strong>l potential (but less than location E), whereas<br />

location C has relatively low <strong>refugia</strong>l potential (but more than location B).<br />

Figure 37: Diagrammatic representation of the shifting relationship between<br />

geographical space and biotically scaled environmental space under climate<br />

<strong>change</strong>. For ease of explanation, both geographical space and environmental<br />

space have been simplified to a single dimension each. The geographical<br />

dimension can be thought of as a straight-line transect across a landscape, and<br />

the environmental dimension can be thought of as a biotically scaled<br />

temperature gradient. The labelled locations (A to E) are discussed in the text.<br />

The concentric ellipses centred on each of these locations depict decreasing<br />

levels of compositional similarity with increasing distance from a location in<br />

biotically scaled environmental space, and decreasing likelihood of dispersal<br />

with increasing distance in geographical space.<br />

The calculation of <strong>refugia</strong>l potential was carried out using the MPI/ OpenMP hybrid<br />

implementation of the Muru GDM model, developed by Tom Harwood and Maciej<br />

Golebiewski at CSIRO. Utilising 120 to 160 parallel processes, the required CPU time<br />

of 344 hours (<strong>for</strong> each combination of biological group, climate scenario, and dispersal<br />

distance, across the entire continent at 250 m resolution) was reduced to a more<br />

manageable 3.6 hours, subject to availability of the required number of nodes on the<br />

CSIRO High Per<strong>for</strong>mance Computing cluster.<br />

4.4 Results and outputs<br />

4.4.1 Fitted compositional-turnover models<br />

Models of compositional turnover were developed <strong>for</strong> 15 different taxonomic<br />

(biological) groups across continental Australia using 9-second gridded predictor data.<br />

62 <strong>Climate</strong> <strong>change</strong> <strong>refugia</strong> <strong>for</strong> <strong>terrestrial</strong> <strong>biodiversity</strong>

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