Global warming a hot issue

By GREG ANSLEY Canberra bureau chief

New estimates of the impact of global warming add weight to emerging evidence that the greenhouse effect is likely to cause major changes to food and fibre production in Australia.

A report focusing on New South Wales, and predicting drying soils, falling beef and dairy productivity and declining wheat yields, comes as the United Nations Environment Programme warns of heavy blows to farming elsewhere, particularly in Russia and China.

Unless urgent action is taken, Unep says in a new study, agriculture, water supplies and fishing stocks will be hammered by increasingly frequent tropical cyclones, rising sea levels and loss of productive land.

As well as direct global costs of up to $US300 billion ($686 billion) a year - with annual growth in the most vulnerable economies reduced by several per cent - the findings hold serious implications for patterns of world trade in agricultural products.

The NSW findings, based largely on research by Australia's federal science agency CSIRO, also suggest global warming will affect investment planning as production patterns change in specific industries and areas.

Climate change presents a significant threat to the survival of NSW's agricultural-based businesses and communities, researcher Anne Harrison says in a study jointly released by the state's Nature Conservation Council, Greenpeace and the Climate Action Network.

It says CSIRO predicts NSW will warm by 0.5 to 2.7 degrees by 2050, reducing available water supplies, shrinking the area of arable land and cutting the quality and volume of crop and livestock production.

Under this scenario, the number of hot summer days will increase by 20 per cent, the incidence of drought in all but the southeast corner of the state will double, bushfires will be more frequent, and warmer temperatures will push the incidence of cattle tick and buffalo fly further south.

CSIRO studies also predict that a doubling in the incidence of drought and floods will ravage arable land through erosion and landslide, and that soil moisture will fall because of greater evaporation.

Soil alkanisation and salination - already a large and growing problem - are likely to spread wider and more rapidly.

With these combined factors, research in the west of the state suggests the land available for cropping will be slashed by up to 300,000ha.

Water will become more scarce, increasing competition for an already heavily-contested resource, raising costs of production and placing river and groundwater reserves under compounding stress.



The frequency of heat stress in beef cattle - which rose by 40 per cent over the past 40 years - is expected to accelerate by a further 138 per cent over the next half-century because of global warming.

Combined with increased water consumption, possible changes in grass distribution and greater soil waterlogging and salinity, this will offset initial gains from better pasture growth and liveweight gains on the rangelands.

For the dairy industry, the study says that by 2030 milk cows without shade cover will suffer average milk losses of 280 litres a cow a year - equivalent to 4 per cent of present production - rising to up to 400 litres by 2070.

Wheat yields are expected to fall significantly, with predicted increases in carbon dioxide levels likely to reduce grain protein by 10 per cent to 12 per cent.

One message is clear, the study says: climate change will fundamentally change agricultural production in NSW.

Herald Online feature: Climate change

Intergovernmental Panel on Climate Change

* Draft summary: Climate Change 2001

  (requires Adobe Acrobat Reader)

United Nations Environment Program

World Meteorological Organisation

Framework Convention on Climate Change