The impacts of climate change on field crops, pastures and rangelands

The effects of climate change on field crops, pastures and rangelands will include:

• increased variability and changes to seasonality of rainfall
• reduced soil moisture
• changes to the dynamics of pests, diseases and weeds
• increased heat shock/stress
• reduced grain quality or nutrient content
• increased yields in higher rainfall areas due to decreased incidence of soil water logging
• higher temperatures (and their effects on plants, e.g. earlier or extended ripening) will cause the distribution of existing insect pests to widen, and may allow the establishment of new pests in cropping areas, resulting in reduced production and increased pest control costs.

Source: Department of Climate Change, 2009

Field crops

• It is likely to be that field crops will be most impacted by the effects of climate change, principally through problems of water availability and the predicted hotter and drier conditions.
• Excess carbon dioxide in the atmosphere has the potential to increase crop growth, yet the quality of the product may suffer. For example, elevated levels of carbon dioxide reduce the protein content of wheat grain. This can have follow-on consequences for the livestock industry when wheat grain is used as stock feed.

The increasing occurrence or intensity of extreme storms is likely to impact field crops, pastures and rangelands. 

Irrigated field crops

A cotton plant

• 1.5% of agricultural land in NSW is irrigated each year, but this area contributes 30% of the total value of NSW agricultural production.¹
• In the past, rice and cotton have together contributed more than $1 billion annually to the NSW economy. Yet in recent years, a problem with water availability has meant that crop values have been reduced from around $930 million to $500 million for irrigated cotton, and from $350 million down to $178 million for rice.²
• Cotton grows best in warm climates and is affected by temperatures below 12°C and above 36°C. Increasing temperatures would reduce the incidence of cold shock, but the very hot days would threaten crops.  
• Water shortages have already forced farmers to accept lower production yields, and the availability of water in future is predicted to have the greatest impact on irrigated crops.

Read about some of the adaptations farmers have come up with already to cope with the challenges posed by our climate.

Pastures

Sheep grazing on pasture at Wagga Wagga

In the past, farmers used introduced pasture species not native to Australia, believing them to be better, with extended growing seasons and providing more nutritious feed. Nevertheless, native species are still very common and are valued for their hardiness.

• Increased levels of CO₂ in the air could result in increased pasture growth, yet growth will always depend on the availability of other critical requirements such as water and soil nutrients. So if average rainfall were to decrease by around 10%, this would likely result in reduced pasture growth, which is not only important for animal production, but could also lead to potential environmental damage to some grazing lands.
• The combinations of plants that make up current pastures may change in time, and the nutritional value of pastures may decline under future predicted climate change scenarios.
• There may be some changes in distribution of pasture plants in NSW: in some areas tropical or summer-active species may become more important, and hardier introduced pasture plants and some native species may be better at adapting to changes in temperatures, particularly extreme temperatures, and decreased rainfall.
• It is possible that there will be a natural shift toward more native grass varieties or weedy species, if temperatures and limited water availability prevent the healthy survival of traditional introduced pasture species.
• As pasture production for grazing animals will likely be affected by water availability, so too will the price and availability of grain. There could be flow on effects to the community as consumers, for example the price of produce may increase.

Rangelands

Sheep on the rangelands

Rangelands are important for wool and meat production in Australia. Environmental problems have already been caused by poor animal production practices and the introduction of exotic animal species such as rabbits. Climatic factors have compounded the problems. Some of the issues currently affecting NSW rangelands are:

• land degradation from accelerated soil erosion;
• woody weed invasion and subsequent decreases in the productivity of the land.

Photos showing the problems on the rangelands of (from left) erosion, salinity and woody weeds.

¹NSW Irrigators 2002, NSW Irrigators Council, http://www.nswirrigators.org.au

²Fairweather and Cowie, 2007