Endangered Leadbeater’s possums turned up in every harvested forest plot surveyed and none of the untouched ones

Camera traps in Victoria’s mountain ash forest recorded Leadbeater’s possums in every harvested plot the survey covered and in none of the unharvested ones. Patrick Baker, a professor of silviculture and forest ecology at the University of Melbourne, and co-authors Kaitlyn Hammond, Craig Nitschke and Raphael Trouve reported the result after returning to a field experiment that had been set up in the late 1980s and then largely forgotten.

The detections matter because the possum is a Victorian faunal emblem that depends on tree hollows, and harvesting is usually blamed for removing them.

Silvicultural Systems Project Plots at Tanjil Bren

The Silvicultural Systems Project was established between 1987 and 1989 at Tanjil Bren in the Central Highlands and at Cabbage Tree Creek in East Gippsland, funded by the Victorian government at a cost equal to about A$26 million today. According to the authors’ account of the revisit, it compared traditional clearfells 250 to 350 meters wide, small patch clearfells 50 to 140 meters wide, and heavy thinning that removed 50 to 70 percent of the trees, with unharvested forest kept as the benchmark.

The treatments are broader than thinning alone, which is why the possum finding is stated for harvested plots in general. Camera traps picked up the animals in every silvicultural treatment plot that was surveyed, and in none of the unharvested areas.

The animal itself carries a long record of near-disappearance. The state’s species page recounts that it was thought extinct until it was rediscovered near Marysville in 1961, and that colonies hold up to 12 members with a single breeding pair producing up to two young a year. Sleeping and breeding happen in tree hollows, with shredded-bark nests built in several hollows across a territory, so the hollow supply in a stand governs whether a colony can settle there at all.

Camera-Trap Detections and the Acacia Link

The authors tie the detections to understorey. Acacia grew in most of the treated areas, and the possums use it to forage and move through the forest. The same species page describes the animals as feeding at dusk on wattle sap, lerps and insects found under loose bark, so a patch of acacia is a food source as well as a travel route. Their account says nothing about the number of cameras, the survey dates or the sample sizes, so the claim is one of presence in each treatment rather than an abundance count.

The same article reports that the largest trees in the thinned stands were about 20 percent wider than the largest trees in the unharvested controls. Thinned stands averaged well over a meter in diameter at chest height at about 80 years old, and some exceeded 1.5 meters. Bigger trees are more likely to form hollows, a declining habitat the possums rely on. Baker and colleagues sum up the thinned plots with the line “The trees left behind after thinning were enormous,” and call the outcome a “win-win-win.”

Hollows, Large Trees and the 2009 Fire Toll

Hollows are the scarce resource in these forests, and the numbers behind that scarcity are stark. A research brief from the Threatened Species Recovery Hub says trees generally need to be about 190 years old to carry the hollows the possum needs, and that the 2009 Black Saturday fires cut the population from roughly 5,000 animals to roughly 2,000 while destroying 42 percent of its habitat. The conservation site Edge of Existence puts the population range at 2,000 to 11,250 and the trend as decreasing, and Australia’s species profile lists the animal as Endangered under the national environment law.

The Victorian government names bushfires, the continuing loss of hollow-bearing trees through decay, and timber harvesting that produces younger, even-aged forests without hollows as the threats to the highland population. Possums are protected from harvesting under a prescription in the state’s Code of Practice for Timber Production.

Carbon Stocks and the Limits of the Comparison

Carbon is the other half of the argument. The authors report that thinned stands stored as much carbon in wood as the controls or more, recovering everything removed during harvest and matching the controls’ gain. Baker’s group frames the combination of big trees, carbon and possum detections as evidence that “forest thinning is not a trade-off.”

The peer-reviewed side of the project appeared on July 1, 2026, in Forest Science, where the paper Alternative Silvicultural Systems Maintain Multiple Values in Tall Eucalypt Forest compares 53 plots of 20 by 20 meters established in 2019 across the treatments. Its abstract reports that overstorey retention treatments had the largest trees, and it does not itself report the possum detections or say how many of those plots carried cameras.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

More from Morning Overview