Agricultural change and paddock tree loss: implications for an endangered subspecies of red-tailed black-cockatoo

Agricultural change and paddock tree loss: implications for an endangered subspecies of red-tailed black-cockatoo

Natural senescence and the intensification of agricultural practices are contributing to the continuing loss of paddock trees from agricultural regions in Australia. This is of particular concern in the southern Wimmera of western Victoria, where much of the endangered Buloke (Allocasuarina luehmannii) Woodland vegetation community is represented only by relict Buloke trees in paddocks, which also constitute critical feeding habitat for the endangered south-eastern subspecies of the Red-tailed Black-Cockatoo (Calyptorhynchus banksii graptogyne). I investigated the rate and correlates of loss of scattered Buloke trees in paddocks by examining aerial photographs taken over a period of 15 years in a region undergoing agricultural intensification. Tree loss over the period was measured using aerial photographs of five localities, covering a total of 7850 ha of agricultural land in the southern Wimmera. The average rate of loss (± 1 SE) was 25.8% ± 6.4% over the 15 years, or 1.7% per annum. The rate of tree loss was higher in areas under cultivation (32.5%) than areas under pasture (20.6%). A disproportionate number of trees was lost from locations where centre pivot irrigation systems were installed. Because of the slow growth rate of Buloke trees, revegetation efforts and offset planting are unlikely to compensate for losses of Red-tailed Black-Cockatoo habitat for approximately 100 years.

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