Pasture predictions for the Elliot region are based on the assumption that the pasture system is comprised of perennial ryegrass and white clover.
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 Tasmania. 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 the Elliot region, the average dryland pasture production yield in terms of tonnes of dry matter per hectare (t DM/ha) is predicted to increase by approximately 10% for perennial ryegrass/white clover pastures by 2070, and 8% by 2030. Irrigated pasture production is predicted to increase by approximately 11% and 10% by 2070 and 2030, respectively but this assumes that the increased irrigation water requirement is available.
Drainage is reduced in these pasture systems with a 5% increase in irrigation requirements in the 2030 and 2070 High scenarios compared to the baseline.
The following graphs show box-plots of predicted annual pasture production for dryland and irrigated pastures for Elliot 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 figures below show rainfall, runoff and drainage at Elliot under dryland conditions and include irrigation requirements for irrigated conditions. The data are presented for baseline (1971-2000), and the predictions by 2030 and 2070 under the high emissions scenario. As shown, drainage is reduced by both 2030 and 2070 for both dryland and irrigated conditions, with a slight increase in irrigation demand by 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.)