Feed base variability

Pastures in the rangelands and parts of the wheat sheep zone are likely to be more severely affected by anticipated climate changes than in the high rainfall zone.

While elevated CO2 can make plants grow faster, the benefit is predicted to diminish in areas getting less than 300 to 500 millimetres of rain each year, even where water use efficiency offsets lower precipitation.

This means the quantity of feed for the extensive livestock industries could become increasingly variable in the drier parts of the State.

The effect on feed quality may be variable, but could often be negative - elevated CO2, coupled with warming, has been shown to exacerbate nutrient deficiencies in systems which are already deficient in nitrogen.

Elsewhere in the wheat sheep zone, and in the high rainfall zone, pasture production is less likely to be affected by climate change, and forage quality in grasslegume pastures may even be enhanced.

However, changes in seasonal growth patterns, such as a shortening of the growing season for temperate species, may reduce production in some areas.

Where irrigation contributes to the feed base, increasing variability of rainfall and the amplified effects on stream flow and runoff into farm dams is likely to reduce feed availability.

In terms of forage quantity and quality in higher rainfall environments, it may be possible to adapt to climate change by breeding adapted lines of key forage species or by carefully selecting existing genotypes.

In rangelands, however, the capacity of native communities to continue to support economic levels of livestock production will depend critically on the capacity of species to cope with grazing in changed conditions.

This is particularly the case given the increasing adoption of shedding sheep breeds in the Western Division with the reputed capacity to survive at very low levels of forage availability.

A 2007 research paper (Harle et al) concludes that while the Australian wool industry would be affected by climate change to 2030, as a whole it is likely to be fairly robust.

Effects on the feed base as well as impacts on water resources, land carrying capacity and sustainability, animal health, and competition with other sectors (particularly cropping) are predicted to be the major areas of concern.

Early adaptation through the development of low emission grazing systems, more sustainable management especially in the rangelands, and improved management of climate variability could significantly reduce the downsides of climate change impacts.

Impacts on the beef industry will result from changes to the feed base and may also include increased ectoparasite impact due the increased incidence of tick and buffalo fly, and heat stress.

This could result in reduced levels of growth, reproduction and age at slaughter.

However there may be changes in other factors to compensate, including infusion of appropriate genetics, such as for heat tolerance, feed efficiency, resistance to warm climate ectoparasites and walking ability.

This article is an edited extract from a background paper prepared by NSW DPI staff on Climate change impacts and priority actions in the agriculture sector.