Climate change effects on pasture systems in south-eastern Australia

Abstract

Abstract. Climate change projections for Australia predict increasing temperatures, changes to rainfall patterns, and elevated atmospheric carbon dioxide (CO 2 ) concentrations. The aims of this study were to predict plant production responses to elevated CO 2 concentrations using the SGS Pasture Model and DairyMod, and then to quantify the effects of climate change scenarios for 2030 and 2070 on predicted pasture growth, species composition, and soil moisture conditions of 5 existing pasture systems in climates ranging from cool temperate to subtropical, relative to a historical baseline. Three future climate scenarios were created for each site by adjusting historical climate data according to temperature and rainfall change projections for 2030, 2070 mid-and 2070 high-emission scenarios, using output from the CSIRO Mark 3 global climate model. In the absence of other climate changes, mean annual pasture production at an elevated CO 2 concentration of 550 ppm was predicted to be 24-29% higher than at 380 ppm CO 2 in temperate (C 3 ) species-dominant pastures in southern Australia, with lower mean responses in a mixed C 3 /C 4 pasture at Barraba in northern New South Wales (17%) and in a C 4 pasture at Mutdapilly in south-eastern Queensland (9%). In the future climate scenarios at the Barraba and Mutdapilly sites in subtropical and subhumid climates, respectively, where climate projections indicated warming of up to 4.48C, with little change in annual rainfall, modelling predicted increased pasture production and a shift towards C 4 species dominance. In Mediterranean, temperate, and cool temperate climates, climate change projections indicated warming of up to 3.38C, with annual rainfall reduced by up to 28%. Under future climate scenarios at Wagga Wagga, NSW, and Ellinbank, Victoria, our study predicted increased winter and early spring pasture growth rates, but this was counteracted by a predicted shorter spring growing season, with annual pasture production higher than the baseline under the 2030 climate scenario, but reduced by up to 19% under the 2070 high scenario. In a cool temperate environment at Elliott, Tasmania, annual production was higher than the baseline in all 3 future climate scenarios, but highest in the 2070 mid scenario. At the Wagga Wagga, Ellinbank, and Elliott sites the effect of rainfall declines on pasture production was moderated by a predicted reduction in drainage below the root zone and, at Ellinbank, the use of deeper rooted plant systems was shown to be an effective adaptation to mitigate some of the effect of lower rainfall.

Beneficial impacts of climate change on pastoral and broadacre agriculture in cool-temperate Tasmania

“…Atmospheric CO 2 concentrations were increased annually, taken from the Integrated Science Assessment Model (ISAM) model conversion of the A2 emissions scenario, beginning at 338 ppm in 1981 and reaching 819 ppm by 2100 (Nakicenovic and Swart 2000). The function and response to elevated atmospheric CO 2 concentrations in the model are described by Cullen et al (2009). Growth-limiting factors of temperature (GLF temperature ) and water (GLF water ) are used in SGS to identify the extent of limitation to simulated pasture growth.…”

“…The impact of climate change on crop and pasture production is uncertain and will vary regionally depending on the extent and timing of changes in key climate variables such as rainfall and temperature (Cullen et al 2009). Specific effects may range from changes in growth patterns, yields and quality, to changes in the type and timing of farm operations such as planting and harvesting.…”

“…Before the study by Holz et al (2010), studies of climate change impacts on Tasmanian pastures (Cullen et al 2009;Cullen et al 2012;Bell et al 2013) and cereal cropping systems used perturbed historical climate data with anomalies calculated from GCMs such as OzClim . Holz et al (2010) tested the suitability of the biasadjusted climate data for use in biophysical models by comparing the simulated pasture yield between the biasadjusted CFT projections and the Australian Water Availability Project (AWAP) gridded climate data (Jones et al 2009).…”

Identifying the future water and salinity risks to irrigated viticulture in the Murray-Darling Basin, South Australia

“…Even if rainfall levels are unaffected, the risk of intense droughts will increase due to the augmentation of the atmospheric evaporative demand as a result of warming (Alcamo et al, 2007). Increased temperatures coupled with reduced rainfall may increase the salt accumulation in upper soil layers and hence affect plant growth (Cullen et al, 2009). It is essential to understand the impact of future climate drivers on irrigation requirements and soil salinity so that appropriate adaptation and mitigation strategies can be adopted for sustainable viticulture production.…”

Use of functional traits to identify Australian forage grasses, legumes and shrubs for domestication and use in pastoral areas under a changing climate

“…Rainfall distribution and evaporation will have an impact on pasture production and perennial plant persistence. Cullen et al (2009) predicted a 22-37% increase in dry-matter production of temperate-grass-dominated pastures in southern Australia, stimulated by raising the atmospheric CO 2 from 380 to 550 ppm. In addition to this, the rising temperatures could result in a longer growing season and a reduction in frost damage .…”