Abstract
Tree cover has declined markedly since European settlement in the agricultural areas of Australia due to land clearing and natural and stress-induced senescence of remnant trees combined with widespread regeneration failure. These decreases in tree cover have seldom been quantified on a landscape scale, but are important in understanding losses in carbon storage and biodiversity across large areas of the continent. We used historical aerial photography and satellite imagery to study changes in tree canopy cover in the southern Tasmanian Midlands, one of the oldest agricultural regions in Australia. Tree cover at 1,000 random sites was assessed from imagery captured on four occasions between 1947 and 2010. Tree cover was stable between 1947 and the 1970s, but decreased from 33 % in the 1970s to 21 % in 2010. The decrease appeared driven by transition from some cover to no cover, rather than from more cover to less cover, because sites with tree cover in 2010 showed little net change during the study period. Statistical modelling showed soils derived from igneous rocks lost more cover than did the less fertile sedimentary soils, and contrary to the expectations, if drought was the cause of cover loss, sun-exposed north-facing sites did not lose more cover than south-facing ones. We argue that these temporal and spatial patterns of tree cover change are consistent with tree clearing rather than loss of remnant isolated trees due to drought-induced dieback.
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Acknowledgments
We thank the landholder who allowed us access to his property for the field work. We also thank Grant Williamson, who compiled the geophysical data and adapted the map of rural tree dieback. We acknowledge the use of remote sensing imagery from the following sources: Spot satellite imagery—CNES 2012, Distribution Astrium Services/Spot Image S.A., France; and aerial photography—TASMAP, State of Tasmania. Vector data was supplied as base data from: theLIST, State of Tasmania. This work was funded by Greening Australia and Australian Research Council Grant LP 0991026. RH received National Climate Change Adaptation Research Facility—Terrestrial Biodiversity Network Scholarship funding.
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Prior, L.D., Sanders, G.J., Bridle, K.L. et al. Land clearance not dieback continues to drive tree loss in a Tasmanian rural landscape. Reg Environ Change 13, 955–967 (2013). https://doi.org/10.1007/s10113-012-0396-0
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DOI: https://doi.org/10.1007/s10113-012-0396-0