Pasture predictions for the Terang region are based on the assumption that although the pasture systems has become increasingly varied in recent years it is generally characterised by autumn sowing of perennial ryegrass pastures which are supplemented with various winter cereals crops and annual ryegrasses, with less presence of sub-clover species.
The predictions suggest that:
The following graph shows predicted pasture growth under three possible scenarios of:
Currently, emissions are tracking the high global emissions scenario and therefore, it is the most relevant for western Victoria. One can assume that something like this high scenario will occur in the absence of major global emission reductions.
The following graphs are expressed as ‘box plots’, which need some explaining in order to be easily understood. The box plot is interpreted as follows:
It is important to note that the predictions are not attempting to describe exactly what will actually happen in the specific year of 2030 or 2070, but indicate a the range pasture production conditions that might be expected at that time in the future, based on the current climate change scenarios.
For Terang, the average dryland annual pasture production yield in terms of tonnes of dry matter per hectare (t DM/ha) is predicted to increase by approximately 4% by 2030 under the high emission scenario but is reduced by about 20% under the high 2070 scenario.
The following graphs show box-plots of predicted annual pasture production for dryland pastures for Terang by 2030 and 2070. The far left plot is the baseline or current situation, while the second, third and fourth plots show predicted pasture yields under low, medium and high climate change scenarios.
The figure below shows rainfall, runoff and drainage at Terang for dryland conditions. The data are presented for baseline (1971-2000), and the predictions by 2030 and 2070 under the high emissions scenario. As shown, rainfall and drainage are reduced by both 2030 and 2070.
(Hotlink to report: Eckard R, Cullen B, 2008 WFSAT Phase II – Final Report: Whole Farms Systems Analysis and Tools for the Australian and New Zealand Grazing Industries, published by MLA, DA, AgResearch Limited, December.)