The value of paddock trees for regional conservation in an agricultural landscape

Authors

  • Philip Gibbons,

  • Miles Boak


  • Philip Gibbons and Miles Boak work for the New South Wales National Parks & Wildlife Service. Philip is based at their Woodland Ecology Unit located in CSIRO Sustainable Ecosystems (GPO Box 284, Canberra, ACT 2601, Australia. Tel: +61-2 6242 1774, Fax: +61-2 6242 1705, Email: Phil.Gibbons@csiro.au) and Miles is based at the Southern Directorate office (PO Box 2115, Queanbeyan, NSW 2620, Australia. Tel: +61-2 6298 9708, Email: Miles.Boak@npws.nsw.gov.au). Discussions with the Riverina Highlands Regional Vegetation Committee who were developing a regional vegetation plan for the upper Murray and Murrumbidgee catchments, provided the catalyst for this research.

Abstract

Summary Isolated trees and small patches of trees – paddock trees – are a prominent feature of agricultural landscapes in Australia, but are declining in many areas due to natural senescence, clearing, dieback and the general absence of recruitment. We assessed the importance of paddock trees for woodland conservation in a 30 000 ha sample of the New South Wales (NSW) South-west Slopes using Satellite Pour l’Observation de la Terre (SPOT) panchromatic satellite imagery combined with models predicting the original distribution of vegetation communities. Tree-cover occurred over 12% of the study area. The patch-size distribution of vegetation in the study area varied between woodland types. For woodland communities that were confined to hills and ridges, most tree-cover occurred as few, large remnants. For woodland communities of the foothills and plains (Blakely's Red Gum, Eucalyptus blakelyi and Yellow Box, Eucalyptus melliodora, or White Box, Eucalyptus albens and Red Stringybark), 54% of remnant tree-cover occurred as patches < 1 ha. The loss of paddock trees will cause substantial reductions to some woodland communities. For example, the loss of patches < 1 ha in woodlands dominated by Blakely's Red Gum and Yellow Box would reduce this association from 7.4% to 3.4% of its predicted pre-1750 distribution. Mean distance to tree-cover across the study area increased almost fourfold if patches < 1 ha were removed from the landscape, which may have consequences for movements of some flora and fauna. Failure to protect and perpetuate paddock trees will diminish the likelihood of achieving the conservation objectives of comprehensiveness, adequacy and representativeness in agricultural landscapes.

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