Ground Cover North : Ground Cover 065 November-December 2006 - North
ADAPTING IS ESSENTIAL IN CHANGING CLIMATE BY STEVEN CRIMP and MARK HOWDEN CSIRO Sustainable Ecosystems, Canberra and HOLGER MEINKE Queensland Department of Primary Industries and Fisheries, Toowoomba n Graingrowers have generally been quick to adapt to variable seasons, so are well placed to respond to challenges posed by global warming. Successful adaptation will require a combination of expert grower and science knowledge to deliver practical and sustainable actions. On-farm adaptations available include: n CUTTING RISK: Develop risk improvement approaches, such as no-till, retain residue, extend fallows, optimise row spacing and planting density, stagger planting times, introduce controlled traffic and erosion control infrastructure. n BEING MORE OPPORTUNISTIC: Flexible planting decisions to exploit environmental conditions such as soil moisture, seasonal climate forecasting and market conditions. n RECORD KEEPING: Expand routine record keeping of weather, production, degradation, pest and diseases, weed invasion. n BEING WEATHER WISE: Incorporate seasonal climate forecasts and climate change into farm enterprise plans. n CONSERVING WATER: Reduce leakage and evaporation from water distribution systems, improve irrigation practices and moisture monitoring. n LEARNING: Listen to growers in more marginal areas. n BEING SELECTIVE: Choose crops that have appropriate thermal time and vernalisation needs, heat shock resistance, drought tolerance, high protein levels, resistance to new pests and diseases and able to set flower in hot/windy conditions. n USE SUPPORT TOOLS. Enhance decision support tools/training to access/ interpret climate data and analyse alternative management options, such as Yield Prophet. The last 10 years of the 20th century were the warmest ever recorded, and the 20th century, the warmest century. The consequence is record-breaking temperatures and changes in rainfall patterns, sea levels and rates of glacial retreat. However, these might only be the beginning of the changes ahead. Computer modelling predicts that global average temperatures could increase by one to 5.8ºC by 2100. A one-degree rise in average temperature would make southern Victoria’s climate similar to Wagga Wagga, NSW. A six- degree rise would put southern Victoria into a climate zone like that of southern Queensland. Warmer temperatures, increases in atmospheric carbon dioxide and shifting rainfall patterns will mean significant agricultural adjustments. However, adaptation must be tailored to meet each farm’s needs. For example, in the Pittsworth region near Toowoomba, Queensland, the annual rainfall record from 1900 to 2005 shows no long- term trend, but considerable variability within certain decades, with rainfall over the past 10 years similar to that of 1930s and 1960s. In the case of Pittsworth, reliable temperature records are available only from 1960. For this period, May to October average maximum temperatures have risen by almost a degree, but annual average minimum temperatures have changed little. The first frost is about six days later and the last frost about three days later, making the frost-prone period about three days shorter. If temperature trends continue, there are likely to be fewer frosts and a shorter frost period. In the Dalby region, rainfall figures from 1900 to 2005 showed no significant trend, but May to October maximum and minimum temperatures exhibit significant warming trends since 1960. The first frost is about 11 days later and the last frost about three days earlier, so the frost- prone period is about 14 days shorter and there are now seven fewer frosts. In the Goondiwindi region, records for 1900 to 2005 show a slight increasing trend in rainfall. The annual average maximum temperatures have changed little while the annual average minimum temperatures have increased. The first frost is about 13 days later and the last frost about 12 days earlier, so the frost-prone period is about 25 days shorter. More information: Steve Crimp, CSIRO Sustainable Ecosystems, 02 6242 1649, Steven.Crimp@csiro.au Weather: northern zone GROUND COVER NOVEMBER -- DECEMBER 2006 30 HARVEST RADIO www.grdc.com.au/radio/main.htm The long dry The Bureau of Meteorology has closely monitored the dry period since October 1996, finding temperatures have been well above normal, raising questions about its relationship to climate change BY BLAIR TREWIN, ROBERT FAWCETT and ANDREW WATKINS National Climate Centre, Australian Bureau of Meteorology n The first sign of a possible new (and drier) rainfall regime for south-east South Australia, southern Victoria and north-east Tasmania started with a dry October in 1996. This followed several months of widespread rainfall above to very much above the average across the southern half of the country. For Victoria at least, this wet period was the state’s last experience of above-average rainfall. Other regions in the south-east and Tasmania have experienced only brief, and unfulfilling, relief from drought. The Bureau of Meteorology has monitored the dry period closely via its Drought Statements (and associated Drought Reviews), slowly revealing a picture of a widespread and prolonged event, possibly matched only by that of the early 1940s. However, unlike the 1940s, temperatures have been well above normal, raising not only evaporation but also questions about its relationship to climate change. The protracted period of below-average rainfall has now lasted 10 years, with the areas affected remaining consistent throughout. Figure 1 shows the national rainfall deciles for October 1996 to September 2006, using gridded rainfall data from 1900 to the present. The strongest impacts have been in a region around Melbourne and Port Phillip Bay, extending from Geelong to Wilsons Promontory, and across another region straddling the South Australia/Victoria border. In the first half of the period, a single very wet month (June 1998) helped disguise the extent to which eastern Victoria was being affected. Around Melbourne, rainfall totals for the past 10 years have widely been about 20 per cent below the long-term average, and 10 per cent below those of any other 10-year period in recorded history. Although much of tropical and central Australia has seen wet conditions through most of the last 10 years, for many parts of the south 1996 was the last year with substantially above-average rainfall. Significantly, the last five to eight years have been so dry in other parts of the country that they too show up on this 10-year analysis. Around Perth, there was a run of eight successive drier than average years from 1997 to 2004. In New South Wales and Queensland, the downturn in rainfall has generally been a more recent phenomenon, starting in 2000 near the east coast and in 2001 further inland (see Figure 2). The area of drier-than-average conditions now covers most of southern and eastern Australia, including all major Australian cities except Darwin, and includes the vast majority of the nation’s cropping areas. In the south-west these are an extension of a downward trend which has been present since around 1970. In the south-east however, they come at the end of a period of generally rather high rainfall which has been in place since about 1950. A clear trend towards higher temperatures and air pressures has accompanied the lower rainfall. Figure 3 shows maximum temperature deciles for the past 10 years (based on gridded temperature data from 1950 to the present). The 10-year average is highest on record over an astonishing quarter of the country.
Ground Cover 064 September-October 2006 - North
Ground Cover 066 January-February 2007 - North