NSW Industry and Investment has been running the NSW component of a national project to look at how producers might adapt their production systems to the anticipated change in climate from 2016 to 2045.This project is funded by the federal Department of Agriculture, Fisheries and Forestry and managed by Meat and Livestock Australia.
The aim of the project is to model future climate at a local level, using the appropriate internationally recognised Global Circulation Models (GCM). Local grazing systems are then modelled using GrassGro (CSIRO) software to see the effect on their profitability as the climate changes.
NSW livestock officers planned the locations they wished to model. Historic weather data, soil and pasture data were obtained. A common grazing system was determined.
Using GrassGro the profitability of this system was modelled for the period 1970 to 2000. This output was presented to local producers who helped finetune the grazing system.
The modelling programme WeatherMaker (CSIRO) was used to apply four GCMs to the locations' historic rainfall and temperature to produce modelled climate for the period 2016 to 2045. This new climate was overlaid into GrassGro to model the profitability of the current system in this future period.
Using input from local producers, various adaptation strategies were included in the grazing system to lessen the impact of the new climate.
To ensure the sustainability of the modelled grazing system, a minimum amount of ground cover was determined and included in the model. Stocking rate was altered as the climate and subsequent pasture growth changed based on this ground cover 'rule'. This allowed a fair comparison between historic and future production and profitability.
By June 2010 the following locations had been modelled: Yass, Moss Vale, Woodstock, Grenfell, Cootamundra, Holbrook, Culcairn and Tumbarumba. Since then work has begun at Braidwood, Deniliquin, Cooma, Bourke, Hillston and Cobar. Work is planned for the Northern Tablelands in June 2011.
The following results for one location Tumbarumba, give an indication of the available modelled data on a local basis.
All four climate change models indicated that pasture growth rates in Tumbarumba from 2016 to 2045 may be different than in the past.
Compared to the period 1970 to 2000 the four models suggest that most months will have less rain, and that on average all seasons will be warmer.
Most models trend towards a slightly shorter growing season, with autumn pasture growth starting later, more winter growth and less spring growth that finishes earlier.
A late August calving beef herd supplying 17 month old feeder steers was modelled. Based on a phalaris/ryegrass/sub clover pasture and a stocking rate of 15.4 dry sheep equivalents per hectare, the gross margin per hectare was calculated at $275 / ha.
All four models predicted lower stocking rates. The lower gross margin averages and their variation are shown here.
Stocking rates will need to be lower to maintain ground cover and the profits from breeding beef cattle may be less unless businesses make some changes to adapt.
Beef producers will need to be flexible in the number of cattle they run. Breeding cow numbers may be less but herds may consider agistment, trading cattle or fodder conservation during better seasons.
One adaptation strategy that has been modelled is to start calving earlier. Historically many producers start calving in late August. This matches production to pasture growth and lessens the incidence of grass tetany. Calving a month earlier in late July may better match animal requirements with the changed climate and growing season. Most models showed a significant increase in gross margins for July calving herds with future climate.