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Predicting the biodiversity benefits of the Saltshaker Project, Boorowa, NSW

Authors

  • David Freudenberger,

  • Judith Harvey,

  • Alex Drew


  • David Freudenberger, Judith Harvey and Alex Drew are with CSIRO Sustainable Ecosystems (GPO Box 284, Canberra 2601, Australia. Email: david.freudenberger@csiro.au). This article is a distillation of the findings of an assessment for Greening Australia and the Department of Environment and Heritage of the potential effectiveness of the ‘Saltshaker’ vegetation enhancement Project. This Project received the 2003 NSW Landcare Award for Bushcare Nature Conservation (Gold).

  • Box 1. Priority ‘enhancement activities

    1 Protect existing remnant vegetation by fencing out domestic livestock with a priority to protect 10 ha or larger remnants in the best condition (complex understorey).

    2 Establish native understorey plants in those protected remnants requiring enhancement of habitat complexity.

    3 Enlarge existing remnants to at least 10 ha.

    4 Create linkages between fenced remnants and other protected remnants. Linkages should be at least 25 m wide, or 10 ha stepping-stones, particularly in those areas more than 1.5 km from other patches 10 ha in size.

    5 Fencing and revegetation of at least 50 m wide along creeks and flow lines.

    6 In recharge areas, revegetate in 2-ha blocks, or greater than eight row strips to intercept deep soil water moving down-slope.

    7 Revegetate areas mapped as having a high risk of dryland salinity.

    8 Block plantings in discharge areas with links to other saline reclamation works.

  • Box 2. At what cost?

    The Saltshaker Project was funded by $845 000 from the Natural Heritage Trust Bushcare Program. In addition, there was $1 063 000 provided as in-kind support from farmers in the Boorowa Catchment, the Boorowa Shire, Boorowa Landcare and Greening Australia. Was this nearly $2 million investment spent effectively and efficiently? The Project adds to an important start. Young trees and diverse understorey is finally returning to the highly cleared valleys and lower slopes. But this has come at a high price and low efficiency of fencing, particularly for revegetation. Only 4 ha of revegetation was protected for every 1 km of new fencing. In comparison, 32 ha remnant vegetation was protected for every km of new fencing. The fencing efficiency for revegetation was much lower because the patch size for revegetation was much smaller and because much of the revegetation occurred as narrow shelterbelts or riparian strips. Narrow configurations have inherently lower area to perimeter ratios than the same area as a wide rectangle or square.

    Fencing is a large cost for both establishment and maintenance. Thus efficiency of fencing in terms of area protected by kilometre of fencing is a significant consideration. At the current fencing efficiency of 32 ha/km, it will take another 860 km of fencing to protect all existing remnant vegetation in patches at least 1 ha in size assuming remnants not fenced through Saltshaker still require fencing at the ratio of 32 ha/km. At the current rate of fencing (21 km/year) it would take over 80 years to protect all remnants assuming half the fences already exist and that each remnant is fenced as a whole block. It is not known which remnants are already fenced. Fencing of remnants is generally more efficient than fencing revegetation plots as the latter are often quite narrow.

    Improving fencing efficiency needs to be given a greater profile in all vegetation enhancement projects, particularly the amount of fencing needed for revegetation. Benchmarks for fencing efficiencies could be developed. We’ve yet to see the fencing efficiency analysis for other Natural Heritage Trust supported projects, but this may emerge through the current Monitoring and Evaluation Program of Bushcare (Environment Australia 2003).

    The assumption that additional fencing is required in the first place needs to be examined. Livestock grazing and woodland restoration may be compatible if the intensity and duration of grazing is significantly altered. Some proponents of short-duration grazing (also termed cell grazing) report significant eucalypt and native grasses regenerating in their paddocks subject to short but intense spells of grazing (R. Taylor, Grazier, Armidale, pers. comm., 2001). However, most cell grazing systems have their own high fencing costs.

  • Box 3. Mapping techniques

    Assessing the potential benefits of vegetation enhancement requires a well-constructed Geographical Information System (GIS). Greening Australia mapped all funded on-ground works in fine detail (± 2 m) into an ArcView® GIS. For each on-ground project supported by Saltshaker, GPS readings were taken at every change in direction (e.g. strainer post). Fence length was made from field calculations of distance between fence posts multiplied by the number of posts. A trundle wheel was used to measure shelterbelt widths and smaller projects. The GPS readings were downloaded into ArcView®, using OziExplorer® and Excel® for data manipulation into suitable coordinate format for import into ArcView®. The points were then added as an active theme. Dot-to-dot drawings with alterations relative to underlying imagery were then made for each patch of on-ground work. All patch (site) data was stored in the associated database file within the GIS.

    CSIRO personnel mapped the remnants from SPOT5 satellite images (taken 1999). Remnants greater than 1 ha in size were defined visually and delimited by hand as a separate layer (shape file) onto the SPOT image. The cover of native vegetation provided by isolated trees and small patches of trees less than 1 ha in size was not included in this mapping. Details of the remnant mapping are described in Freudenberger (2001).

    Area and perimeter calculations of all remnants and revegetation activities were carried out. These included the number of patches, mean size, and mean perimeter to area ratio. Size distribution histograms were produced in Excel®, and a range of statistics were generated using the software package, Patch Analyst®. Details of data analysis are provided in Freudenberger et al. (2003).

Abstract

Did the 2-year Saltshaker Project nudge the Boorowa Catchment along a new pathway towards improved biodiversity?

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