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

8. DISCUSSION AND CONCLUSIONS
8.1 Comparison of techniques
8.1.1 Australia-wide SDM and GDM comparison
There was broad spatial congruence across the final refugia models generated using
the species distribution (SDM) and generalised dissimilarity (GDM) modelling
approaches (Figure 63). In particular, both approaches found the coastal areas around
the continent, and particularly the east coast, to be the most crucial refugial areas.
Tasmania in particular rates highly, with most of Tasmania projected to contain refugia
with both analyses. Given that Tasmania is so consistently projected to contain future
refugia, and that a large proportion is already in the national reserve system and
recognised for its current biodiversity values, Tasmania should be a high priority for
future refugia considerations. South-west Western Australia and the coastal Northern
Territory also overlap as high priority refugia. Upland areas of the Wet Tropics,
Australian Alps, Flinders Lofty Block and New England Tablelands are also recognised
as high priority refugia using both techniques.
We would expect the refugial areas identified under the GDM approach to differ in
some respects from those identified under the SDM approach for two reasons. First,
the GDM approach prioritises locations that are expected to support an environment in
the future that will have become increasingly rare in the surrounding landscape, and
that biota dependent on this environment can reach by moving relatively short
distances. On the other hand, the SDM approach has focussed on minimising the loss
of local species, but also on maximising the immigration of non-local species that are
capable of moving longer distances to reach these locations. Much of the discrepancy
between GDM and SDM approaches stems from this definitional difference in what
constitutes a good quality refuge. The second reason we would expect the GDM areas
to differ from SDM areas is simply that the GDM analysis was undertaken at a much
finer spatial resolution, and gave more consideration to the effects of local topography
on radiation, temperature and moisture.
There are, therefore, some areas that were found to have high potential refugial values
for the GDM analyses, but not for the SDM. These include the inland regions such as
the Channel Country, Mount Isa Inlier, the Gibson Desert and the Pilbara. Conversely,
the SDM analyses found regions such as the Nullarbor, and much of central and inland
Queensland and NSW to have high refugial potential in comparison to findings of the
GDM analyses.
Overall, the GDM analysis identifies places expected to act as refugia within
landscapes. These are clearly important refugial areas because they are areas where
species will need to move only short distances to persist through unfavourable future
climates. The SDM analysis also points to another kind of refuge; those where species
will need to move longer distances, including between landscapes, as a means of
persistence through unfavourable future climates. Given that there are many species
for which suitable climate space will not exist in 2085 within their current range, we will
need to consider both refugial options if we are to maximise biodiversity outcomes.
Climate change refugia for terrestrial biodiversity 109