Using the GDM transformed environmental predictors, a measure of environmental dissimilarity between 2000 and each climate future can be made at each location within the NARCliM domain. Calculating dissimilarity of a single location across epochs uses a similar approach to deriving ecological distance between any pair of sites in the same epoch; that is, by calculating the sum of absolute distances across all dimensions of the GDM space. Rather than calculating distances in transformed predictors between two spatially distinct sites, distances are calculated at a single site between transformed predictors for the baseline and climate future epochs.

The ecological distance between current and future transformed predictors provides an indication of how much a site is likely to change in terms of suitability for present species. While such comparisons do not consider a site’s capacity, or the spatial processes required to support new or existing ecosystems, it provides an indication of the direct impacts of climate change on the compositional aspect of biodiversity, such as whether sites will continue to be suitable for existing ecosystems or to what extent species composition is likely to change in response to changing environmental conditions.

Dissimilarity Grids in GeoTiff format have been calculated between the 1990-2009 Baseline and each 2020-2039 and 2060-2079 future NARCliM projection. Averages across climate scenarios have also been calculated for 2020-2039 and 2060-2079.

Values have been scaled from their initial range of 0-1 to 0-1000 then converted to integers. Potential grid values are from Zero (no dissimilarity) indicating no compositional change, through to 1000 (complete dissimilarity) where no species are expected to be shared between the baseline and future projection.

[Report section 2.3.4] [Report Appendix C]