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Evaluation of the impact of climate change on northern Australian grazing industries

Objective:

To evaluate the impact of climate change and CO2 increase on the management of northern Australian grazing industries.

McKeon, G.M., Dr.; Ph.: (07) 3896 9548; Fax: (07) 3896 9606; greg.mckeon@dnr.qld.gov.au

Research organisations: Queensland Centre for Climate Applications (QCCA), 80 Meiers Road, Indooroopilly Qld 4068; CSIRO Tropical Agriculture, Davies Laboratory, PMB, Aitkenvale Qld 4814; Bureau of Resource Sciences, PO Box E11, Kingston ACT 2604; CSIRO Atmospheric Research, PMB No 1, Aspendale Vic 3195; CSIRO Wildlife and Ecology, PO Box 2111, Alice Springs NT 0871

Sponsor: RIRDC, Rural Industries Research and Development Corporation

Background:

Climate change, increase in atmospheric carbon dioxide, and policies on greenhouse gas emissions are important issues for the northern Australian grazing industries. The majority of sheep and beef cattle in northern Australia graze the large extent of native pastures in this region. The number of animals stocked, individual animal production, and the risks of land and pasture degradation are strongly affected by climatic variability.

As well as emissions from grazing animals, land use management options such as tree clearing and pasture burning are important components of the national greenhouse gas inventory. Thus, the grazing industries are in a difficult position with their production and sustainability being sensitive to climate change and the industries also being seen to be a major contributor to national greenhouse gas emissions. This project sought to kick start climate change impact studies and to commence analysis on the impact of grazing and climate on soil organic carbon.

Methodology:

To address these issues, the project examined current trends in the climate of Queensland grazing lands; developed models of animal production from native pastures in cooperation with other RIRDC and LWRRDC projects, and as part of two PhD theses; evaluated different approaches to simulate climate change scenarios; modified a native tropical pasture model GRASP to include the effects of increasing atmospheric carbon dioxide concentration; and developed comprehensive maps of soil organic carbon, soil phosphorus, soil nitrogen and other resource attributes.

Outcome:

Most of the project's limited objectives were met in combination with other RIRDC and LWRRDC projects. However, several aspects proved too difficult to complete given a rapidly changing work environment. Resources have now been allocated in the new Queensland Centre for Climate Applications (QCCA) to improve the models developed in this project and to simulate the possible economic impact of climate change scenarios.

The simulation models will require further development to more correctly represent the effects of different climate variables (such as temperature, vapour pressure deficit) and the interaction of C02 concentration and biological responses (for example, water stress on growth, nutrient concentration). The major outcome of the project will be an evaluation of the impact of climate change and possible adaptive strategies for each grazing industry. The evaluation will be the first analysis of its type and is designed to convert industry from a reactive to a pro-active approach to climate change.

Implications:

Although climate change has been firmly established as a core business research activity, the lack of clear view of likely climate change for northern Australia limits current extension or policy formulation. The major policy issues for the grazing industries (tree clearing, woodland thickening, possible negative impacts of global warming) can not be separated from other major issues such as property viability.

Progress: Trends in the major driving forces affecting the climate of Queensland's grazing lands, and the trends in climate variables for monthly, seasonal and annual periods were examined. The most significant trends were: warming trends in May minimum temperature; warming trends in winter; and annual minimum temperatures; increasing May vapour pressure and increasing May cloud cover. The trend in May minimum temperature alone accounted for 25 per cent of the annual trend. The major phenomenon affecting year-to-year variation in rainfall in Queensland's grazing lands is the El Niņo-Southern Oscillation (ENSO). Over the last 20 years, more frequent El Niņo conditions (negative SOI) have occurred. Continued monitoring of these trends will be an important component in adapting to climate change.

To assess the impact of climate change and CO2 increase on Queensland's grazing industries, animal production models of wool and cattle growth were developed using both grazing trial data and producer surveys. A model of cattle liveweight production in Queensland using 12 regions was developed by relating spatial variation in key variables such as annual steer liveweight gain and carrying capacity to soil attributes (phosphorus) and simulated pasture variables respectively. The Statewide model agreed well with previously reported analyses on whole State production. Sensitivity tests highlighted the potential impact of climate change with a 10 per cent decline in the duration of the growing season resulting in a 30 per cent decline in total liveweight production. The wool and cattle models are yet to be integrated.

Alternative representations of climate change in daily climate files were investigated by comparing weather generated climate data with a simpler climate change representation (e.g. adding 5oC to each day). A superceded scenario, 1992, was used because of the ready availability of General Circulation Model (GCM) output. A simplified model of a native pasture grazing system was developed, i.e. an average C4 native pasture without trees, to provide a bioassay of different methods of representing climate change. The differences between the alternative representations of climate change were important enough to warrant further investigation of the use of weather generators despite their cost of implementation. These differences also indicate that alternative representations of climate change scenario should be assessed when conducting climate change impact studies.

The representation of CO2 effects on C4 native pasture growth was investigated by reviewing current glasshouse and growth cabinet experiments on relevant grass species and modifying key parameters in the above native pasture model, i.e. 100 per cent increase in transpiration efficiency, 100 per cent reduced daily water use per unit of green biomass, 50 per cent increased rate of nitrogen uptake per mm of transpiration, small changes to regrowth and radiation use efficiency, and no change in maximum possible annual nitrogen uptake. A major finding of the simulation study was the beneficial effects of doubling CO2 on pasture growth (+10 to +30 per cent) which could offset the negative effects of the example, but superceded, warmer climate change scenario used. The approach adopted here showed that growth cabinet/chamber research on the effects of increasing CO2 on relevant species could be used in simple models of native pasture growth.

A major uncertainty in simulating the effects of doubling CO2 was the possible effect on changes in temperature, soil water and carbon cycling on nitrogen availability. To address this issue as well as the regional impact of climate change, a detailed analysis of soil organic carbon and other soil attributes (phosphorus) was undertaken using available field measurements and a previously established spatial modelling capability namely the National Drought Alert Strategic Information System. Relationships between climate and soil carbon for the major soil groups, i.e. principal profile forms were derived from these data. These relationships were used to examine the consequences of warmer climate change scenario on soil organic carbon highlighting the sensitivity of this attribute to small changes in temperature, e.g. +2.7oC would reduce soil carbon by 50 per cent once a new equilibrium was achieved.

Period: starting date 1992-07; completion date 1995-12

Status: completed.

Publications:

Campbell, B.D., Stafford Smith, D.M. and McKeon, G.M. (1997). Elevated CO2 and water supply interactions in grasslands: a pastures and rangelands management perspective. Global Change Biology 3, 177-189.

Campbell, B.D., McKeon, G.M., Gifford, R.M., Clark, H., Stafford Smith, D.M., Newton, P.C.D. and Lutze, J.L. (1995). Impacts of atmospheric composition and climate change on temperate and tropical pastoral agriculture. In Greenhouse 94: Climate Change, CSIRO, Melbourne, pp. 171-189.

Hall, W.B., McKeon, G.M., Carter, J.O., Day, K.A., Howden, S.M., Scanlan, J.C., Johnston, P.W. and Burrows, W.H. (in press). Climate Change in Queensland's Grazing Lands: II. An assessment of the impact on animal production from native pastures, The Rangeland Journal.

Howden, S.M. and Turnpenny, J. (1997). Modelling heat stress and water loss of beef cattle in subtropical Queensland under current climates and climate change. Proceedings of the Modsim '97 International Congress on Modelling and Simulation, 8-11 December, University of Tasmania, Hobart, edited by D.A. McDonald and M. McAleer, Modelling and Simulation Society of Australia, Canberra. pp.1103-1108.

Howden, S.M., McKeon, G.M., Walker, L., Carter, J.O., Conroy, J.P., Day, K.A., Hall, W.B., Ash, A.J. and Ghannoum, O. (1997). Integrating global change impacts on native pastures in the Burnett Region of Queensland. Proceedings of the Modsim '97 International Congress on Modelling and Simulation, 8-11 December, University of Tasmania, Hobart, edited by D.A. McDonald and M. McAleer, M., Modelling and Simulation Society of Australia, Canberra, pp. 123-130.

McKeon, G.M. and Howden, S.M. (1992). Adapting Grazing Management to climate change and seasonal forecasting. Australian Rangeland Society 7th Biennial Conference, Cobar, New South Wales, pp. 12-18.

McKeon, G.M., Howden, S.M., Abel, N.O.J. and King, J.M. (1993). Climate change: adapting tropical and subtropical grasslands. Proceedings of the XVIIth International Grassland Congress, 13-16 February 1993, Palmerston North, New Zealand, pp.1181-1190.

McKeon, G.M., Howden, S.M., Abel, N.O.J. and King, J.M. (1993). Climate change: adapting tropical and subtropical grasslands. In Grasslands for our World, edited by M.J. Baker, SIR Publishing, Wellington pp. 426-435.

McKeon, G.M., Hall, W.B., Crimp, S.J., Howden, S.M., Stone, R.C. and Jones, D.A. (in press). Climate Change in Queensland's Grazing Lands: I. Approaches and climatic trends, The Rangeland Journal.

Moore, J. L., Howden, S. M., McKeon, G.M., Carter, J.O. and Scanlan, J.C. (1997). A method to evaluate greenhouse gas emissions from sheep grazed rangelands in south-west Queensland. Proceedings of the Modsim '97 International Congress on Modelling and Simulation, 8-11 December, University of Tasmania, Hobart, edited by D.A. McDonald and M. McAleer, Modelling and Simulation Society of Australia, Canberra. pp137-142.

Reyenga, P.J., Howden, S.M., Meinke, H. and McKeon, G.M. (1997) Global change impacts on wheat cropping in the Burnett Region of Queensland: a simulation approach. Proceedings of the Modsim '97 International Congress on Modelling and Simulation, 8-11 December, University of Tasmania, Hobart, edited by D.A. McDonald and M. McAleer, Modelling and Simulation Society of Australia, Canberra, pp149-154.

 

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