Greenhouse, climate change and agriculture

Climate change presents a major challenge to agriculture. Increased temperatures are expected to herald not only warmer conditions but changes in rainfall - more in some places, less in others - and increased winds, storms, floods and ironically, droughts. Two reports prepared by the CSIRO describe the likely impacts of global warming in South Australia:

• Climate change in South Australia, March 2003
• Climate change under enhanced greenhouse conditions in South Australia, June 2006

Conditions are expected to be complicated by secondary effects where, for example, traditional crops become impractical and new species are needed, or in trade, where competitor farmers become more productive as they discover conditions more conducive to their crops.

Opportunities may arise however: for example, global warming and the decline in global oil resources may provide opportunities for expansion into farm forestry for carbon sequestration and other crops for biofuel resources, and marginal agricultural land may be used to establish wind farms to generate electricity.

The approach of the South Australian Government to climate change is three-fold: Reduce, Adapt and Innovate, that is:

• reduce greenhouse gas emissions (including primarily, carbon dioxide, methane and nitrous oxide)
• adapt to the changing conditions (by establishing management defences to threatening new conditions eg strong winds, and developing more appropriate management processes)
• innovate (by seizing new opportunities to operate profitably in the new and changing environment).

Tackling Climate Change: South Australia's Greenhouse Strategy 2007 - 2020 (external site) is available online. The Natural Resources section includes industries that depend on natural resources e.g. the agriculture sector.

Adaptation to climate change in agriculture

Primary producers can play a role in slowing global warming and climate change by reducing greenhouse gas emissions from agricultural activities. Agriculture produces carbon dioxide (CO₂) through use of energy sourced from coal and gas-fired power stations, by burning gas directly for heating and processing purposes and in fuel for travel and transport. During digestion, cattle and sheep produce methane (CH₄) that is emitted as "burps" while they graze in pastures. Nitrous oxide (N₂O) escapes from disturbed soil and from fertiliser that is not rapidly incorporated into the soil or taken up by plants.

Methane and nitrous oxide exist in the atmosphere in only small amounts but their "global warming potential" is high, that is, CH₄ has about 21 times the effect of CO₂ , while N₂O has 310 times the warming potential of CO₂. As a result agriculture is responsible for about 13.5% of global greenhouse gas emissions, much more than that in countries like New Zealand which are more dependent on livestock. Importantly, these emissions represent "lost" or wasted resources. The aim of agriculture is to provide food and fibre for the community (not consume fuel, energy, fodder and fertiliser). Accordingly, if we can produce the same amount of food and fibre (or more) using less fuel, fodder, fertiliser etc then not only are we minimising our impact on the climate but, through efficiency, operating more profitably!

PIRSA has prepared A Guide to Climate Change and Adaptation in Agriculture in South Australia, 2007 (PDF) and (HTML). For a hard copy or information on Climate Risk Management contact the Climate Applications Unit of the South Australian Research and Development Institute (SARDI external site).

For further information go to the South Australian Government web-site: Tackling climate change in South Australia (external site) and the Australian Greenhouse Office (external site), now the Australian Department of Climate Change.

A Grains Industry perspective on climate change

The following is adapted from Climate Change and the Grains Industry, appendix to The Future Environment for Grain Production by Rural Solutions South Australia.

The South Australian grains industry is highly sensitive to climatic conditions. The fortunes of both individual grain-growing enterprises in South Australia and the industries that support them suffer greatly during droughts and rely on profit from good seasons. The projected changes towards a hotter and drier climate are concerning, especially for low rainfall regions. Some of the negative impacts of climate change are likely to be compensated by the beneficial effect of increased carbon dioxide concentrations in the atmosphere.

The degree to which climate change will damage the grains industry depends on the amount of warming and the extent of the rainfall decline. Most adaptations to a warmer and drier environment such as conserving more water, improving water use efficiency, timely sowing and careful management of weeds, disease and nutrition are sensible practices for the grains industry in the absence of climate change. In other words they are no-regret adaptations.

Unlike fixed horticulture (eg a vineyard with a 30 year planning horizon) or irrigation systems, grain farming is an annual crop and in the past many growers have adapted to changes in the market and seasonal conditions.

Climate change a global phenomenon

The 4th Assessment Report (IPCC, 2007) of the Intergovernmental Panel on Climate Change  (external site) concluded that: 

1. Global atmospheric concentrations of carbon dioxide, methane and nitrous oxide have increased markedly as a result of human activities since 1750 and now far exceed pre-industrial values.

2. Warming of the climate system is unequivocal, as is now evident from observations of increases in global air and ocean temperatures, widespread melting of snow and ice, and rising sea level.

3. Numerous long-term changes in climate have been observed, including changes in arctic temperatures and ice, widespread changes in rainfall, ocean salinity, wind patterns and aspects of extreme weather including droughts, heavy precipitation, heat waves and intensity of tropical cyclones.

4. Some aspects of climate have not been observed to change, for example: (1) Antarctic sea ice extent continues to vary but no statistically significant trends have emerged. (2) There is insufficient evidence to determine whether trends exist in the circulation of global oceans or in small-scale phenomena such as tornadoes, hail, lightning and dust-storms.

5. The warmth of the last half century is unusual in at least the previous 1300 years. The last time the polar regions were significantly warmer than present for an extended period (about 125 000 years ago), melting of polar ice led to 4 to 6 metres of sea level rise.

6. Increase in average temperatures since the mid-20th century is very likely due to the increase in anthropogenic (man made) greenhouse gas concentrations. Discernible human influences now extend to other aspects of climate, including ocean warming, continental-average temperatures, temperature extremes and wind patterns.

7. For the next two decades (to around 2027), a warming of about 0.2°C per decade is projected. Furthermore, even if the concentrations of all greenhouse gases and aerosols had been kept constant at year 2000 levels, a further warming of about 0.1°C per decade would be expected.

8. Continued greenhouse gas emissions at or above current rates would cause further warming and induce many changes in the global climate system during the 21st century that would very likely be larger than those observed during the 20th century.

9. Even if greenhouse gas concentrations were to be stabilised, global warming and sea level rise is expected to continue for centuries due to the time scales associated with climate processes and feedbacks.

Although there are sceptics, the science behind climate change in Australia is officially recognised by Commonwealth, State and Territory Governments, National Farmers Federation and the South Australian Farmers Federation. As sceptics are quick to point out, science is not a numbers game and majority opinions have been wrong before.

Outlook

The outlook is similar for most of the SA grains belt and can be summarised as follows:

Temperatures. In the grains region temperatures are projected to increase by 0.2 to 1.4°C by 2030 and 0.6 to 4.4°C by 2070. The projected changes are more or less uniform in each season with a slightly warmer outlook for spring. Model results indicate that future increases in daily maximum and minimum temperatures will be similar to the changes in average temperature. The frequency of extreme maximum temperatures will increase while the frequency of extreme minimum temperatures will decrease. The frequency of hot spells above 35°C and 40°C are projected to increase across most of the state

Rainfall: The drying trend and the uncertainty is much greater for 2070 than 2030. In general terms the strongest drying indications are for spring. Projections of annual potential evaporation indicate increases across the state with the largest increases seen in the ‘far-east’ and north-west of the state and the smallest increases in coastal regions around Adelaide and the Eyre Peninsula.

Average annual ‘water balance’ show deficits throughout the state with the largest values in the south-east of the state and the smallest in the west of the state. Despite decreases in average rainfall over most of South Australia in most seasons by 0% to 30%, extreme rainfall is found to increase by between 0% and 10%. All climate models show an increase in the frequency of droughts towards the end of the century.

The projected decline in rainfall, especially spring rainfall has obvious and negative implications for grain farming in the region. Recent events in the region such as the very hot and dry October 2004 and the run of poor starts to the winter cropping season, culminating in the exceptionally hot and dry Autumn of 2005, have focussed attention on the vulnerability of even the best managed grain farms to hot spells and low rainfall.

Higher CO₂ concentrations in the atmosphere are likely to lead to an increase in the water use efficiency in wheat production through an increase in photosynthesis (a process that builds plant carbohydrates and decrease in photorespiration (a process that uses plant carbohydrates). Overall indications are towards a modest increase in yields and decrease in protein levels of grain.

Costs: Pressure on the use of fossil fuels along with shortage of cheap oil could increase the cost of farm operations and energy intensive industries such as nitrogen fertilizer.

The grains industry in Australia is a small contributor to emissions making up only 2% of Agriculture compared to 67% from livestock, 10% from dairy and 21% from horticulture; hence significant changes in practice to reduce emissions are unlikely.

Even if greenhouse gas emissions were reduced to pre-industrial levels, some global warming is predicted and hence it is essential that some attention is paid to adaptation.

Adaptation

The UK Climate Impacts Programme (2003) points out that given the uncertainty of future climate change, the correct level of adaptation will always be difficult to determine. It is possible to under adapt (spend too little time and resources on adapting to worrying but uncertain climate change), to over adapt (spend too much of scarce resources) or to mal adapt (use resources in a way that severely limit future adaptation options and/or adapt to a small set of future outcomes that are unlikely).

Howden (CSIRO, 2003) listed the following adaptations to climate change in the grains industry:

• zero tillage
• retaining soil residues
• extending fallows
• changing row spacing
• changing planting density
• staggering planting times
• erosion control infrastructure.

Tactical management opportunities included soil moisture monitoring, climate forecasting and constant reviewing of market conditions. All of these are practices that are likely to have benefit in the absence of climate change and relate to the overall push towards higher water use efficiency in the SA grains industry. These adaptations are no-regret adaptations and climate change only serves to highlight the urgency of improving water use efficiency.

There are however longer term decisions at a family farm level – to sell up, to buy more land, where to invest. These are especially pertinent for farmers in low rainfall regions and it is more difficult to find no-regret decisions. These decisions, along with industry infrastructure (silos etc) and industry support (drought policy) are hard decisions and need to be made in a transparent risk management framework.

In doing this, climate science needs to be clear about the uncertainty while also providing the risk assessment of a general trend towards hotter and probably drier conditions.

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