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

to 9 second (250 m) resolution for the whole continent and to 30 m resolution for the
Tingle Mosaic study area. The future climate predictors were used along with the
existing regolith and terrain predictors to develop projections of each fitted GDM model.
Where this occurred, the last 10% of the trendline from each end of the fitted functions
for each climatic predictor was extrapolated into novel climates. These environmental
predictors, scaled by the coefficients of the fitted compositional turnover models, are
the inputs to the analysis of refugial potential.
4.3.7.1 NSW (3-sec resolution) scenarios
Eight climate change scenarios were generated at 3-second resolution for the year
2070 using two emission scenarios (A1FI equivalent to an RCP of 8.5; A1B equivalent
to an RCP of 4), with two levels of climate sensitivity to emission concentrations (high
or medium as defined in OZCLIM, Ricketts and Page 2007), and two GCMs with
contrasting estimates of future rainfall: the MIROC-M model (wetter future, Hasumi and
Emori 2004) and the CSIRO Mk 3.5 model (drier future, Gordon et al. 2010). These
GCMs are among the top-performing models assessed for Australian conditions (Crimp
et al. 2012) and represent the best- and worst-case outcomes with respect to plausible
temperature and rainfall futures for a given emissions scenario (Clarke et al. 2011).
The monthly climate scenario data were obtained from OZCLIM (CSIRO 2007, Ricketts
and Page 2007) downscaled using ANUCLIM 6.1 software (Xu and Hutchinson 2011),
as described in (Harwood et al. 2010), with the current climate representing a 30-year
average centred on 1990.
4.3.7.2 Continental (9-sec resolution) and Tingle Mosaic (1-sec resolution) scenarios
The full downscaling approach outlined in section 4.3.2 was applied for both the
continental 9s analyses and the 30 m Tingle Mosaic region. Prior to this, change grids
at 0.5° were supplied by J. VanDerWal to maintain compatibility between the change
grids that were subsequently downscaled to different grid resolutions for the specieslevel
and community-level analyses. Due to the computational, data storage and i/o
requirements of the 9s grid (134 GB per resultant scenario) two representative GCMs
were selected, based on the same criteria as for the NSW study region. Given that the
Tyndall Centre outputs used for the species distribution modelling study (section 3.3.1)
had only the poorly performing CSIRO 3.0 GCM, the GFDL-CM2 model (Delworth et al.
2006, Gnanadesikan et al. 2006, Wittenberg et al. 2006) was selected for the drier
future, whilst using the high resolution MIROC model for compatibility with the NSW
region. These change grids were converted to the input format required for ANUCLIM
6.1, and downscaled over the v3.1 9s DEM for the continental analysis and the 30m
DEM for the Tingle Mosaic region. Downscaled maximum and miniumum temperatures
and precipitation were used as inputs to the TerraFormer software, as shown in Figure
32, and resultant summary variables derived.
4.3.8 Analysis of refugial potential
The potential of a given location (grid cell) to serve as a refugium, for a given biological
group under a given climate scenario, was estimated using predictions from the fitted
GDM model for that group. This model predicts the level of compositional dissimilarity
dij , and conversely similarity sij = 1– dij , expected between two locations i and j
knowing only the values of relevant environmental variables at these locations.
Predicted similarities can range between zero (where two locations are predicted to
have no species in common) and one (where the locations are predicted to be identical
in terms of species composition).
When predicting compositional similarity between location i and j under present
environmental conditions, we can denote this as: