Short Virtual Presentation & Digital Poster 10th Australian Stream Management Conference 2021

Delta Green –a new metric for predicting trends in riparian vegetation recovery (#7)

Timothy Pietsch 1 , James Daley 1 , Justin Stout 1 , Andrew Brooks 1
  1. Griffith University, Gold Coast Campus, QUEENSLAND, Australia

Managing riparian vegetation is the principle tool available to natural resource managers to effect catchment-scale improvements in the river environment. But how much active revegetation needs to be undertaken, and how much can be left to ‘natural’ regeneration?

We used high resolution lidar to map riparian woody vegetation across the Manning, Great Lakes and Karuah Catchments. We cross-referenced this with contemporaneous Landsat data to develop a model relating Persistent Green to tree cover. We then used the entire Persistent Green record (beginning 1988-89) to derive the historical trend in vegetation cover. We then projected forward from the observed trend in vegetation cover to arrive at a likely year 2040 vegetation status for riparian zones.

We predict that over the next 20 years ~3000ha of additional woody vegetation will become established in the riparian and littoral zones of the catchments, without any direct intervention – assuming the socio-economic drivers responsible for reducing land-use intensity continue. Particularly important will be a continued reduction in riparian cattle grazing. This ‘natural’ increase will result in all but 10 streams or lakes achieving a woody vegetation cover greater than 70% . The ten remaining streams and lakes require amongst them a total of just 117ha of additional woody vegetation to be established, by direct intervention, for all streams and lakes to have 70% or more cover by 2040. Thus equates to just under 6ha/year.

This work indicates that in excess of 95% of the revegetation task could be achieved by continuing to support natural regeneration.

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