EXOTIC WOODY WEEDS Use of simulation models to predict future ...

projective foliage cover of prickly acacia is also closely related to pasture production (Carter et al.
1991) and is more likely to have a consistent meaning for field observers. The impacts of climate
change on each of these variables are presented below for a range of selected sites.
3.3.3 Effects of climate change on infestation levels of prickly acacia
As indicated by the &/,0(; analyses, climate change is estimated to increase the potential infestation
levels across all selected sites. The only expected decreases in potential infestations are likely to occur
in small areas of the wettest areas of northern Australia and were ignored for this analysis. Likewise,
the boredrain/watering point habitat constitutes only a small fraction of the productive land in a
paddock, and the effects of climate change are minimal where temperature is adequate. For these
reasons, only results for the uplands are presented here.
Upland biomass density appears to be more sensitive to the simulated increases in temperature and
water use efficiency than increases or decreases in rainfall (Table 3.1). The potential for uplands
around Hughenden to support double the current amount of biomass, approximating that of Bowen
under current conditions should provide cause for concern for pastoral land managers in the Mitchell
Grass Downs.
Table 3.1 Sensitivity of upland biomass density (t/ha) to climate change
Location
Habitat Type
Climate Scenario
Current Climate Future –10% rain Future +10% rain
Boulia Hot, dry 0.192 30.69 32.06
Bowen Warm, moist 44.1 65.06 67.14
Burren Junction Cool, moist 0.309 49.6 50.05
Cordillo Downs Cool, dry 0.0217 9.631 16.18
Hughenden Warm, moderate
moisture
21.01 43.66 42.78
Canopy cover and biomass density generally follow the same pattern of climate and [CO 2 ] sensitivity
(Table 3.2 and 3.3). The values of canopy cover and biomass density at Hughenden however are
relatively less sensitive to any of the climate change factors than other sites examined.
Table 3.2 Sensitivity of upland canopy cover to climate change
Location
Habitat Type
Climate Scenario
Current Climate Future –10% rain Future +10% rain
Boulia Hot, dry 0.005 0.35 0.351
Bowen Warm, moist 0.422 0.587 0.559
Burren Junction Cold, moist 0.005 0.501 0.506
Cordillo Downs Cool, dry 0.000 0.150 0.245
Hughenden Warm, moderate
moisture
0.338 0.356 0.341
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