Ground Cover Supplement : GC Supplement - Adapting to climate change
3 CLIMATE GROUND COVER The big picture CLIMATE CHANGE IS MORE THAN RISING TEMPERATURES. MARK HOWDEN, STEVE CRIMP AND PETER HAYMAN EXPLORE THE CHANGES AND POTENTIAL IMPACT THEY MAY HAVE ON AUSTRALIAN CROP PRODUCTION THE IMPACT OF increased greenhouse gases is often referred to as global warming but it is not only temperature that is changing. The concentration of atmospheric carbon dioxide is increasing, sea levels will rise and global rainfall will increase. Alone and in combination these factors are predicted to result in substantial climate change over the next century. The climate record already indicates trends consistent with future projections but has also revealed some surprises; for example, increased incidence of frosts in southern parts of Australia. If Australian agriculture is to adapt, decision makers must be more aware of the new understanding of climate processes and the updating of climate change scenarios. Carbon dioxide Carbon dioxide (CO2) is considered the most problematic greenhouse gas because of the amount released from the burning of fossil fuels. Two other key greenhouse gases are methane (CH4) and nitrous oxide (N2O). Agriculture is a key contributor of both. Although these are more potent greenhouse gases, their overall contribution is less. Over the past 400,000 years, before the industrial revolution, the concentration of carbon dioxide in the atmosphere fluctuated between 150 and 280 parts per million (ppm) (Figure 1). Since the industrial revolution this concentration has steadily risen from 280ppm and now exceeds 380ppm. All indications suggest that carbon dioxide concentration will continue to increase, with current projections suggesting more than double the present concentrations by 2100. The rate and extent of the increase is largely dependent on policy decisions made by the current generation. The additional outputs of greenhouse gases are stopping heat escaping from the atmosphere, in the same way that putting on an extra jumper traps more body heat. Higher concentrations of carbon dioxide make plants more efficient at using light and water, which should result in greater forage biomass or grain production, even if rainfall decreases slightly. However, the impact in the field will be modified by EMMA LEONARD CLIMATE CHANGE u Continued page 4 FIGURE 1 THE RISE IN CARBON DIOXIDE 150 200 250 300 350 400 450 500 550 600 650 700 CO2 concentration in parts per million by volume (ppmv) Vostok record Observed record IPCC IS92a scenario Age of entrapped air (thousands of years before present) Current (2004) 378 ppmv Projected (2100) 665 ppmv 400 300 200 100 0 Figure 1: Without intervention, carbon dioxide concentrations are forecast to explode, with significant impact on global climate. In the chart, historical atmospheric concentrations of carbon dioxide have been derived from ice cores drilled at the Russian Vostok station in Antarctica. The figures were determined through an analysis of air bubbles trapped in the ice core, which contains ice slightly more than 400,000 years old. Future predictions are from the Intergovernmental Panel on Climate Change (IPCC). the same factors that influence water-use efficiency – nutrition, pests and soil constraints. Overall, expectations are for initial modest increases in yield and decreases in grain protein arising from the effects of CO2, provided rainfall does not decline too much. Temperature 2005 was the warmest year on record in Australia: 1.09ºC higher than the 1960 to 1990 average. The past 10-year period was the warmest decade recorded. Across the agricultural regions of Australia, temperatures are predicted to rise by 0.2 to 1.4ºC by 2030, rising to 0.6 to 4.4ºC by 2070. To put these figures in perspective, a 1ºC rise in average temperature would make Melbourne’s climate like that currently experienced in Wagga Wagga; a 4ºC rise like that of Moree.
GC Supplement - Integrated Weed Management
GC Supplement - Root and crown diseases