Regional Warming

Regional warming in the Southwest Pacific will pose significant challenges to agriculture and forestry. Although warming in the lower range will be beneficial, challenges will be posed if water is limiting. Warming in the upper range will pose significant challenges and it is these that are highlighted here.

Warming and associated rainfall changes in Australia give varied impacts on wheat production regionally. Studies show that Western Australian regions are likely to have significant yield reductions by 2070 (Reyenga et al., 2001). In southern Australia cropping is likely to become unviable at the dry margins where rainfall is reduced substantially. Warming is likely to make a major pest, the Queensland fruit fly, a significant threat in southern Australia (Sutherst et al. 2000). Warming suggests a large expansion in its normal range across many non-arid areas of Australia. Pastoral and rangeland farming is very significant in Australia. A 20% reduction in rainfall is likely to reduce pasture productivity by 15% (Crimp et al. 2004). Climate change is also likely to increase major land degradation problems of erosion and salinization with the potential spread of weeds (Kriticos et al. 2003). Heat stress on livestock is also likely to increase (Howden et al. 1999b) with pests such as cattle tick likely to increase and spread southwards (White and Sutherst 2003). Reductions in production from this source are likely to be very high in Queensland.

For forestry in Australia warming increases fire risk and pest damage in southern Australia, ttose areas where water resources, such as run-off, decline combined with an increased fire risk will face reduced production, and increases in rainfall intensity are likely to exacerbate soil erosion during forestry operations (Howden et al. 1999a).

For New Zealand crops, the principal effect will be the drying in eastern regions: this will be dependent on the availability of irrigation, tte increased frequency of drought has already decreased pasture growth for dryland farms, and warming has meant that lower feed quality subtropical pastures continue to spread south. Warming is likely to increase the range and incidence of many pests and diseases. Plantation forestry in east coast areas is likely to experience growth reductions with rainfall decreases.

In the South Pacific islands there is little forestry, and traditionally agriculture has been based on subsistence and cash crops for survival and economic development. Subsistence agriculture has existed for several hundreds of years, tte projected impacts of climate change include both extended periods of droughts, and the loss of soil fertility as a result of increased precipitation, both which will impact on agriculture, tte consequences of the loss in agricultural productivity for both subsistence and cash cropping, including other impacts has been estimated at 2-3 percent of Fiji's 2002 GDP, and 17-18 percent ofKiribati's 2002 GDP (World Bank 2002). Fisheries are important for many island states in the South Pacific. Tuna fishing is particularly important, and warming is likely to produce a decline in total stock and a migration westwards, both of which will lead to changes in catches in different countries.

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