Greenhouse Gas Emissions

Agriculture is also the 2nd largest contributor to greenhouse gas emissions, i.e. about 16% of Australia’s greenhouse gas emissions. Agriculture is the 2nd largest contributor behind stationary energy. This figure is conservative as other agriculture emissions from energy, transport and land-use change are not included. Hence, total national emission is considerable higher if viewed within a supply-chain context.

The three main greenhouse gases emitted from agriculture activities are methane, nitrous oxide and carbon dioxide:
- Methane: sheep and cattle produce methane from digestion of feedstuff in the rumen (the first stomach). Between 10 – 15% of all ingested energy comes back as methane and this represents 12% of Australia’s greenhouse emission i.e. the 3rd highest single source.

- Nitrous Oxide: A high percentage (from 30% - 70%) of nitrogenous fertiliser added to crops is lost via leaching, run off or evaporation and not channelled into plant growth. The use of nitrogenous fertilizer accounts for about 80% of Australia’s emission of nitrous oxide.

- Carbon Dioxide: energy usage all along the production chain (from farm to processing to marketing) is a major cost for agriculture. Fossil fuel use as well as electricity consumption gives rise to carbon emissions. 

Climate Change

More droughts and less rainfall in Australia are forecast from climate change. Annual rainfall in the south west of Western Australia has declined by about 10% since the mid 1970s. The mean May – July rainfall for the 50 years prior to 1975 was 323mm, while for 1976 – 2003 it was 276mm (a 15% decrease).

Annual rainfall is predicted to generally decrease in the south and east (mainly winter/spring). Some inland and eastern coastal areas may experience wetter summers. Average annual rainfall is projected to decrease in the southwest (–20% to +5% by 2030 and –60% to +10% by 2070, rounded to the nearest 5%).

There is no doubt that the decline in rainfall and increases in temperatures and evaporation rates will have an impact on agriculture. Some of the likely impacts are reduced crop yield, increased risk of pests, parasites and pathogens, to name just a few.

Likely impacts on horticulture:
- changes in frost frequency and severity may cause lower yields and reduced fruit quality;
- damage from more extreme events such as hail, wind and heavy rain;
- increased risk of pests and disease;
- warmer conditions may impact on chilling requirements of some fruit cultivars.

Likely impacts on viticulture:
- higher ripening temperatures may reduce optimum harvesting times;
- potential changes to phenology and wine quality;
- reduced water supply for irrigated crops;
- investment impacts due to long investment cycles.

Likely impacts on grazing and livestock:
- higher temperatures reducing milk yields;
- decreases in forage quality;
- increased rainfall variability reducing livestock carrying capacity;
- heat stress in Northern Australia impacting on productivity and animal welfare;
- increased risk and rates of salinisation in some areas;
- increased risk of pests, parasites and pathogens.  

Adaptations to a new climate
How can current agricultural practices be changed so that it can adapt to climate change?

Changing land use
Some new ideas for farming (from the Department of Agriculture and Food, WA) include:
- no-till farming that leaves the soil undisturbed to reduce erosion;
- perennial pastures that use more water so reduce salinity;
- adding lime to the soil to reduce soil acidity;
- planting crops between rows of trees that use more water and also prevent soil erosion;
- farming along the contours of hills so rainfall is ‘caught’ and doesn’t erode the soil; and
- farming trees (e.g. eucalypts and pines) for their wood instead of farming wheat and sheep.

Some suggestions from the Australian Greenhouse Office, Department of Environment and Heritage: Improving nutrient and soil management through:
- Better fertiliser management based on characteristic of the farming practice i.e. timing application of fertiliser to maximise nutrient uptake or improving fertiliser application techniques;
- Better soil management e.g. continuous plant cover (rotating with perennials in some areas), conserving soil structure.

Improving management practices in regards to livestock emissions through:
- Better nutrition and feed management to livestock i.e. quality and digestibility of feed;
- Managing herds – reducing number of unproductive animals;
- Improving animal health management through vaccination.

Vegetation establishment on farms
Revegetation and managing remnant vegetation to act as wind breaks or shelter for livestock can contribute to improving biodiversity and reducing on-farm emissions. Replanting for continuous cover, selection of species suitable for landscape use and careful site preparation are some examples of good farm management practices.