Soil and Land
Soil and Land summary
For the Glenelg Hopkins region, climate change modelling and projections indicate that increasingly hotter and drier conditions can be expected. Temperature is expected to increase in all seasons with an increasing number of hot days and fewer very cold days overall. Average annual temperatures are projected to rise by between 0.5 and 1.1 ºC by 2030. Winter rainfall is likely to decrease and summer rainfall expected to increase. Despite a decrease in winter rainfall by up to 30% by 2090, the intensity of extreme rainfall events is likely to increase. Because of the natural variability in rainfall across the region, the overall trends may be masked for decades to come, particularly in summer[i].
Despite these changes, the impact of climate change on agriculture is expected to be less damaging to south west Victoria than other parts of the state[ii]. Temperatures are expected to remain moderate while rainfall is anticipated to remain adequate in the medium term, particularly in the region’s south[iii]. It is likely that the area most suitable for grain production will move southward due to the drying of the region’s climate, increases in international prices, raised bed technology and the decline in the region’s wool industry[iv].
The Glenelg Hopkins region may become more attractive to agricultural producers in northern Victoria, who may experience more negative production impacts due to climate change and wish to relocate. An increase in cropping has already occurred within the region. From 1990 to 2010 an average of 12,000 ha per year of grazing pastures were converted to cropping[v].
Plant production in the Glenelg Hopkins region is likely to be affected by an increase in the number of hot days, resulting in poor fertilisation when occurring at flowering time[vi]. The likely response is a change to sowing crops earlier and applying more nitrogen at sowing. Although an effective productivity response, this practice could act against greenhouse gas mitigation. Pasture-based systems in the Glenelg Hopkins region such as dairy, beef cattle, sheep and lambs are likely to be affected by a decrease in pasture production and reliability[vii]. This decrease may have implications for the region’s feed management systems, with a potential increase in dependence on cool season production, grain feeding and stored fodder[viii].
Average annual runoff into the region’s waterways is expected to decrease. This will have significant impacts for agricultural industries. It is likely that the proportion of years when no water is available for agricultural diversion will increase and the potential for on-farm water supplies to be exhausted will rise[ix].
Climate has a direct impact on soil health and has its most severe impacts in extremes of dryness leading to wind erosion and, in extremes of wetness, leading to sheet, rill and gully erosion. Soil erosion is likely to be exacerbated throughout the Glenelg Hopkins region due to an overall reduction in rainfall in combination with increases in intense rainfall events occurring on dry, denuded soils. In combination, drier soils, reduced vegetation cover and more intense rainfall will present significant challenges to soil conservation even with moderate climate change[x].
Soil health is also linked to climate benefits on a global scale because soils can store carbon, leading to improved soil quality and reduced greenhouse impacts[xi]. Carbon within the terrestrial biosphere can behave either as a source or sink for atmospheric carbon dioxide depending on land management, thus potentially mitigating or accelerating the greenhouse effect[xii]. Soil carbon in the region is expected to decrease under climate change due to decreased net primary production and conversion of pastures to cropping[xiii]. Any gains in increased efficiency of plant water use due to elevated carbon dioxide levels are likely to be outweighed by increased carbon mineralisation after episodic rainfall and reduced annual and growing season rainfall.
Changes in average temperatures and rainfall patterns in the Glenelg Hopkins region will also influence soil organic matter. This in turn will affect important soil properties such as aggregate formation and stability, water holding capacity, and soil nutrient content[xiv]. Increasing the amount of carbon sequestered in soil has the potential to contribute greatly to mitigation and adaptation in response to climate change.
Increasing soil carbon is possible through the management of arable and degraded soils to increase carbon sequestration and by increasing plant diversity. Increased diversity enhances community-level carbon dioxide uptake and below ground allocation to roots and mycorrhizal fungi, which is a key mechanism governing carbon sequestration in soil[xv]. Increasing the cover and diversity of species has multiple benefits and contributes to the increased resilience and adaptive capacity of both agricultural and ecological systems.
Soil biology and microbial populations are also expected to change under conditions of elevated carbon dioxide and changed moisture and temperature regimes. As soil biology regulates nutrient dynamics and many disease risks, nutrient availability to crops and pastures could change, as could the exposure to soil-borne diseases[xvi].
While carbon fertilisation and certain climatic changes could benefit some crops in some regions of the world, its overall impacts are expected to be negative, threatening global food security[xvii]. Without effective global mitigation through a reduction in greenhouse gas emissions, there will be major declines in agricultural production across much of Australia by mid-century[xviii].
Considerable research has been and is being undertaken, to assess the potential impacts and adaptation strategies for Australian food and fibre producers under various climate change scenarios. The publication, Adapting agriculture to climate change, provides a comprehensive reference source covering climate change impacts and adaptation research into fisheries, forestry and key agricultural industries in Australia[xix].
[i] CSIRO, Interim climate projection statement, CSIRO, Canberra, 2013.
[ii] Department of Primary Industries, Climate change impacts and adaptation responses for south-west Victoria’s primary industries, a DPI VCCAP discussion paper, Department of Primary Industries, Melbourne 2010.
[iii] B Cullen, I Johnson, R Eckard, G Lodge, R Walker, R Rawnsley, and M McCaskill, Climate change effects on pasture systems in south-eastern Australia. In: Crop and pasture science, CSIRO Publishing, 2009.
[iv] E Liu & P Fitzsimons, Regional economic profile of south west Victoria, Victorian Department of Primary Industries, Melbourne, 2009.
[v] Water and Land use Change Study Steering Committee and Sinclair Knight Merz, Water and land use change study, Water and Land use Change Study Steering Committee and Sinclair Knight Merz, Hamilton, 2005
[vi] GJ O’Leary, B Christy, A Weeks, J Nuttal, P Riffkin, C Beverly, G Fitzgerald, Biophysical modelling: likely response of wheat crop yield to climate change across Victoria, VCCAP Project Biophysical Modelling Theme Final Report, Victorian Department of Primary Industries, Horsham, 2010.
[vii] V Sposito, C Pelizaro, K Benke, M Anwar, D Rees, M Elsley, G O’Leary, R Wyatt, B Cullen, Climate change impacts on agriculture and forestry systems in south west Victoria, Victorian Department of Primary Industries, Melbourne, 2008.
[viii] C Stokes, M Howden, Adapting Agriculture to climate change – preparing Australian agriculture, forestry and fisheries for the future, CSIRO publishing, Victoria, 2010.
[ix] N Tostovrsnik, M Morris, R Eckard, G O’Leary, C Pettit, P Fitzsimons, B Christy, J Sandall, L Soste, V Sposito, Climate change impacts and adaptation responses for south-west Victoria’s primary Industries, Victorian Department of Primary Industries, Victoria, 2010.
[x] J Nuttall, R Armstrong, M Crawford, Climate change – identifying the impacts on soil health in Victoria, Department of Primary Industries, Victoria, 2007.
[xi] R MacEwan, Soil health for Victoria’s agricultural context, terminology and concepts, Department of Primary Industries, 2007
[xii] J Nuttall, R Armstrong, M Crawford, Climate change – identifying the impacts on soil health in Victoria, Department of Primary Industries, Victoria, 2007.
[xiii] J Nuttall, R Armstrong, M Crawford, Climate change – identifying the impacts on soil health in Victoria, Department of Primary Industries, Victoria, 2007.
[xiv] E Brevik, The potential of climate change on soil properties and processes and corresponding influence of food security, Agriculture, 2013
[xv] RD Bardgett, C Freeman, NJ Ostle, Microbial contributions to climate change through carbon cycle feedbacks, The ISME Journal (2008) 2, 805–814, 2008.
[xvi] J Nuttall, R Armstrong, M Crawford, Climate change – identifying the impacts on soil health in Victoria, Department of Primary Industries, Victoria, 2007.
[xvii] G Nelson, Climate change: impact on agriculture and costs of adaptation, International Food Policy Research Institute, Asian Development Bank, 2009.
[xviii] R Garnaut, The Garnaut climate change review final report, Australian government, Canberra, 2008.
[xix] C Stokes, M Howden, Adapting agriculture to climate change: preparing Australian agriculture, forestry and fisheries for the future, CSIRO Publishing, 2010