Forest Ecology - Snapshot of Key Findings

Koala density and black summer fires

Law B, Gonsalves L, Burgar J, Brassil T, Kerr I and O'Loughlin C. (2022) Fire severity and its local extent are key to assessing impacts of Australian mega-fires on koala (Phascolarctos cinereus) density, Global Ecology and Biogeography, 31(4): 714-726.

In contrast to harvesting, koala density was found to be significantly reduced by high and medium severity wildfires.
Low severity fire had no detectable effect on koala density.
Severe wildfires and increasing frequency with climate change is perhaps the most significant threat to koalas in public forests.

Law B, Slade C, Gonsalves L, Brassil T, Flanagan C and Kerr I. (2022) Tree use by koalas after timber harvesting in a mosaic landscape, Wildlife Research, 50(7): 581-592.

Male and female koalas commonly used small trees both during the day and at night. Medium-sized trees were preferred over small and large trees.
Koalas used trees across the full range of the landscape available to them, including in the net harvest area (5-10 years post-harvest) and harvest exclusion zones.
Tallowwood was the most commonly used species for browsing at night, and this species is targeted for retention during harvesting planning.
Tracking results support results from other acoustic studies showing koalas are resilient to harvesting.

Law B, Gonsalves L, Burgar J, Brassil T, Kerr I, O'Loughlin C, Eichinski P and Roe P. (2022) Regulated timber harvesting does not reduce koala density in north-east forests of New South Wales, Sci Rep, 12: 3968.

Koala density was found to be similar between national park (controls) and state forest (harvested) sites.
No change in koala density was observed from before to after timber harvesting, most likely because of the extent of environmental exclusions during harvesting.
The study provides rigorous data to demonstrate koalas are resilient to carefully regulated harvesting.

An assessment in 2016 found that 43% of the state forest landscape was excluded for harvesting for environmental reasons.
These 'informal' reserves provide a substantial level of protection for biodiversity and are a key step in ecologically sustainable harvesting.

Gonsalves L, Law B, Brassil T, Waters C, Toole I and Tap P. (2018) Ecological outcomes for multiple taxa from silvicultural thinning of regrowth forest, Forest Ecology and Management, 425: 177-188.

Thinning of dense, regrowth forests had neutral to positive effects on biodiversity and responses were species-specific.
Unthinned forest represented habitat of similar value to thinned forest for some taxa, indicating that regrowth patches of varying size should be retained across the landscape to provide a mosaic forest structure suitable for a diverse suite of flora and fauna.

Law B and Chidel M. (2008) Quantifying the canopy nectar resource and the impact of logging and climate in spotted gum Corymbia maculata forests, Austral Ecology, 33(8): 999-1014.

Eucalypts are important for producing nectar for a diverse suite of native fauna and commercial honeybees.
This study measured canopy nectar production in recently harvested, regrowth and mature spotted gum forest.
When nectar production was scaled up to the forest stand (incorporating flower and tree density) mature forest produced almost 10 times as much sugar per ha as recently logged forest, with regrowth being intermediate, however, forest practices reduce this difference between mature forest and recently logged forest to a factor of two. Further, nectar availability was only slightly depleted when flowering was extensive.