A realistic method for identifying occupied Koala habitat

NEFA engaged Biolink to undertake rapid assessments for Koalas in seven areas of State forests proposed for logging. The ‘Rapid-SAT’ methodology involves searching for Koala scats around the bases of patches of 5–7 Preferred Koala Food Trees (PKFTs - certain species ≥ 30 cm Diameter at Breast Height) to determine whether Koalas are using them. This is repeated for the next patch found >500m along the road.

This resulted in the identification of patches of occupied habitat in all areas, with the extent of occupancy estimated to vary from less than 10% to 67% of the otherwise available habitat. High occupancy was identified for Braemar, Myrtle and part of Bulga State Forests.

Biolink make recommendations for supplementary surveys, considering “The next step in effective management is to identify areas of habitat that are supporting resident koala population cells in those areas where koala ‘presence’ has been established”.

Biolink recommended that in the absence of more systematic survey effort that the occupied habitat patches identified “become the centre of a 2 km x 2 km (400-ha) grid cell, within which the harvesting of PKFTs > 300 mm DBH should not be permitted, accompanied by no more than a 30% reduction in the Compartment level basal stem area of PKFTs < 30 cm DBH > 20 cm DBH”.

Biolink report for NEFA

Biolink note:

For purposes of the Coastal Integrated Forestry Operations Approval (CIFOA) current koala management prescriptions typically require retention of a small number (e.g. 10) ‘koala browse trees’ > 20cm DBH / unit area. However, this approach has no scientific basis and contradicts available scientific knowledge regarding both the importance of PKFTs at local population level (they are a finite ecological resource and the subject of 100% utilisation by resident koalas), while also being ignorant of the fact that on low nutrient soils, PKFTs do not typically become palatable to koalas until their DBH exceeds 30 cm.

The Rapid SAT methodology had been developed in 2016 in response to a request by the EPA and DPIE as a cheap and quick way to assess forestry compartments to identify areas inhabited by Koalas. Regrettably in 2018 the EPA instead decided to rely upon an inaccurate model of Koala habitat and set minimal retention requirements for Koala feed trees based on the modelled habitat, irrespective of where Koalas occur.

There was strong disagreement between the EPA and Forestry Corporation about the size and numbers of browse trees to be retained under the CIFOA. The EPA (NRC 2016) proposed a retention rate of ‘25 trees per hectare in High/high quality habitat, 20 trees per hectare in High/moderate quality habitat, and 15 trees per hectare in Moderate/moderate quality habitat’, with retained trees >25cm DBH. The NRC (2016) resolved the dispute on the basis of resource impacts, by adopting the Forestry Corporation’s proposed retention rate of ‘10 healthy trees per hectare … in High/high quality habitat, 5 trees per hectare … in High/moderate or moderate/moderate cells over 25 percent or more of compartment’, with a minimum size of 20cm DBH. the Office of Environment and Heritage (2018) complained that the new tree retention rates are less than half the number and of a smaller size than proposed by the Expert Fauna Panel, concluding that the increased logging intensity proposed under the new rules is expected to impact Koalas through diminished feed and shelter tree resources.

It is also relevant that numerous studies have identified Koalas as preferring trees >30 cm DBH, with Brad Law from DPI forestry (Law et. al. 2022) even recommending “Currently, trees for browse retention need to be >20 cm dbh. Although trees at the smaller end of this range are commonly used by koalas, preference for medium-sized trees (30–60 cm dbh), suggests weight should be given to retaining trees in those size classes”.

While Rapid SAT has limitations, it is a simple and realistic method that could be adopted for pre-logging surveys if there was a genuine intent to protect Koala habitat. The recommended additional surveys should also be undertaken to identify the full extent of significant koala activity.

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