5.3.1. Climate change

The National Greenhouse Gas Inventory (NGGI) is the principal source of data regarding Australia’s greenhouse gas emissions. According to these figures, Australia produced an estimated 546 million tonnes of greenhouse gases in the four quarters leading up to June 2011. Agriculture is responsible for emissions totalling 83 million tonnes of CO2-equivalent (83 Mt CO2-e), accounting for approximately 15% of the national total. This places agricultural ahead of fugitive energy emissions (42 Mt CO2-e), industrial emissions (33 Mt CO2-e), and emissions associated with waste management (14 Mt CO2-e) as a contributor to climate change. On the other hand, agriculture contributes significantly less than energy production (194 Mt CO2-e for electricity; 94 Mt CO2-e for non-electric sources) and slightly less than transport (86 Mt CO2-e). These figures may be slightly misleading, however, as the reported total for agricultural emissions does not include (for example) fuel combustion associated with agricultural practices. For the purposes of the NGGI, agricultural emissions are chiefly those produced by enteric fermentation, burning off of crop stubbles, the application of fertilisers, and so on. Fuel combustion for transport or energy production will be subsumed under those headings, whether or not it takes place in an agricultural setting. Taking these figures as they are, however, it is still the case that the emission by agriculture of greenhouse gases, especially carbon dioxide and methane, represents a major contribution to the ongoing problem of climate change.

The first effects of climate change may already be making themselves known. According to a 2006 report by CSIRO, the average annual temperature in the Murrumbidgee Catchment has risen by 0.8°C since 1950, in line with the state-wide average of 0.9°C. It is likely, the authors report, that this is at least partly due to human activity. Efforts have been made to predict the future impacts of climate change on the Murrumbidgee. These are confounded to some extent by natural climatic variability and by the diversity of local climates. Climate change may not affect the alpine regions of the eastern catchment and the semi-arid regions of the western catchment equally. The authors of the report acknowledge this difficulty and their predictions allow for a range of possible outcomes. In brief, the authors conclude that the Murrumbidgee is likely to become warmer and drier, although an increase in the frequency of severe weather events is possible. The report predicts an increase in average temperature of between 0.2°C and 1.8°C by 2030. By 2070, the rise is projected to be between 0.7°C and 5.6°C. The report predicts a decrease in the number of days below 0°C and an increase in the number of days above 35°C. There may also be an increase in the frequency of drought and in the number of fire days per year. Rainfall patterns are also likely to change, but the direction of that change is not clear. The report’s authors predict an overall decrease, but the figures they give allow for anything from a 40% decrease to a 20% increase in annual rainfall by 2070. These findings are summarised in Table 2 of the report.

The report also sets out possible consequences of these climatic changes, though they caution that in many cases these are based on assumptions that ultimately may not be valid. Among the more serious concerns they raise are a potential decrease in water flow in the catchment’s rivers and streams; a possible increase in soil salinity; reduced habitat area for native flora and fauna; possible heat-induced injury to crops; a lack of water for livestock; a reduction in grape quality; an increase in heat-related human illness; possible spread of infectious disease; increase in stress and damage to buildings and roads; increase in frequency of bushfire, strong winds and flash flooding; a reduction in snow cover in alpine areas; and a possible decrease in water quality as a result of increased algal and microbial activity.

It must be noted that the authors do not suggest that all of these effects are likely. They also acknowledge that, at least in the short term, there may be some benefits to increased atmospheric CO2. It may encourage faster plant growth, for example, although this may be offset by a shortage of protein. Additionally, while temperature increase might result in a decrease in grape quality, it might result in an increase in grape yield. These impacts are likely to be distributed unequally, so that some regions will profit while others will suffer.

A primary goal should be the reduction of greenhouse gas emissions. The authors also recommend a number of adaptive strategies to offset the effects of ongoing climate change:
• Improving water-use efficiency;
• Changing to heat- and drought-tolerant crops;
• Changing planting times;
• Providing more shade and cooling for stock;
• Improving snow-making capacity in the ski fields;
• Providing migration corridors for vulnerable fauna.
These, of course, will not halt climate change, but will help to reduce its impacts.

References and Resources
• Australian Government – Department of Climate Change and Energy Efficiency. Undated. National Greenhouse Gas Inventory.

• NSW Government and CSIRO. Undated. Climate change in the Murrumbidgee Catchment.