What is the best way to manage a forest? For decades, Australians have argued fiercely over this fundamental question, often trapping the discussion in a rigid, binary frame: do we protect our native forests entirely, or do we harvest trees to support local economies and regional communities?
The reality on the ground, however, is far more nuanced and interesting than this polarized debate suggests. A newly published scientific study examining a long-forgotten, decades-old experiment in Victoria’s iconic mountain ash forests reveals that forest management is not necessarily a zero-sum game between conservation and industry.
Since the 1970s, scientists, environmentalists, and the general public have heavily scrutinized and questioned the practice of clearfell logging—a method where virtually all trees within a designated block of forest are cut down simultaneously. Conservationists have long argued that clearfelling devastates vital habitats for rare and endangered species while severely reducing the overall ecological value of the landscape. On the other side of the debate, foresters and industry advocates have historically countered that mountain ash ecosystems are naturally adapted to catastrophic, high-severity bushfires, and that clearfelling essentially serves as the forestry equivalent of these natural disturbance cycles.
The argument was exceptionally heated, and the resulting polarization proved largely unhelpful for finding common ground. Yet, despite the intense public friction, the fundamental, underlying questions regarding the true ecological impacts of clearfelling—and how those impacts directly compared to less intensive forestry practices—remained largely unresolved.
A Landmark Experiment
In the mid-1980s, the Victorian government initiated a major structural reform of the timber industry and made a substantial financial investment, equivalent to approximately A$26 million today, to rigorously explore alternatives to traditional clearfelling. This initiative relied on silviculture, the specialized branch of forestry that deals with establishing, growing, and tending forest stands.
The initiative, known as the Silvicultural Systems Project (SSP), was established between 1987 and 1989 across two distinct field sites: Tanjil Bren, located in Victoria’s rugged Central Highlands, and Cabbage Tree Creek, situated further east in East Gippsland.
It was a landmark, comprehensive experiment designed to compare forest regeneration and ecological recovery across the full spectrum of silvicultural approaches. The trial included traditional clearfells with blocks ranging between 250 and 350 meters wide, small patch clearfells with blocks measuring 50 to 140 meters wide, and heavy thinnings, where 50% to 70% of the standing trees were systematically removed. Additionally, extensive areas of unharvested forest were set aside as untouched benchmarks to serve as scientific controls for comparison.
At the Tanjil Bren site, the forest consisted of dense mountain ash regrowth that had regenerated following the devastating 1939 bushfires. Researchers established hundreds of permanent survey plots and meticulously monitored thousands of individual seedlings over the subsequent years. By the early 2000s, the initial results appeared definitive: mountain ash regenerated most successfully on the traditional clearfell sites. Conversely, where tall canopy trees were retained or where the cleared patches were kept relatively small, common understory species such as acacia quickly dominated the landscape.
The findings were formally published, the research access roads slowly grew over with vegetation, the project signs weathered and collapsed, and the experiment was largely forgotten by the public. The broader societal debates over native forestry, however, continued unabated.
Yet, while the human arguments raged on and the project faded from memory, the trees kept growing.
Astounding Results
In 2014, researchers visited the Tanjil Bren site as part of a University of Melbourne academic subject focusing on native forest silviculture. A colleague, Simon Murphy, who had been directly involved in establishing the experiment decades earlier, suggested that students visit the area to observe the long-term, real-world outcomes of different silvicultural systems standing side-by-side. What the academic team found upon arrival was nothing short of astounding.
The original findings from the early 2000s still held true: 30 years after the initial intervention, the mountain ash in the large cleared patches and traditional clearfelled areas remained vigorous, healthy, and abundant. However, it was the heavily thinned sections of the forest that truly captured the researchers’ attention.
The surviving trees left standing after the thinning operation had grown enormous. Although they were only approximately 80 years old, the largest specimens averaged well over a meter in diameter at chest height, with several individuals exceeding 1.5 meters in diameter. The thinning process had provided these remaining trees with significantly more growing space, sunlight, soil moisture, and nutrients, and the trees had responded to this release with dramatic growth spurts. In fact, the largest trees located within the thinned stands measured a remarkable 20% bigger in diameter than the largest trees found within the unharvested control areas.
Even more remarkable was the discovery regarding carbon storage. The heavily thinned stands of trees had managed to store just as much, or in some cases even more, carbon within their wood compared to the untouched, unharvested control areas. In the span of just three decades, the heavily thinned forest had not only successfully recovered all the carbon that had been physically removed during the initial harvesting process, but it had also accumulated enough additional carbon to match the structural carbon gains observed in the unharvested controls.
These scientific findings carry profound implications for modern forest management and conservation strategy. Larger trees possess thicker bark and greater structural resilience, making them significantly more resistant to severe fires; consequently, when the next wildfire sweeps through the landscape, these massive trees stand a much higher chance of survival. Furthermore, bigger trees are far more likely to develop natural tree hollows—a critical, declining habitat resource required by rare and threatened arboreal marsupials such as the greater glider and Leadbeater’s possum.
At the same time, the acacia trees that naturally proliferated across most of the experimental silvicultural treatments proved to be equally vital for local wildlife. Leadbeater’s possums rely heavily on acacia for foraging and as a structural pathway to move safely through the forest canopy. Automated camera traps deployed across the study sites confirmed this ecological dependency: Leadbeater’s possums were detected within every single silvicultural treatment plot surveyed, whereas none were found within the unharvested control areas.
Lessons for the Future
The insights yielded by the long-forgotten Tanjil Bren Silvicultural Systems Project offer three critical lessons for the future of land management in Australia and beyond.
First, the research highlights that long-term silvicultural and ecological experiments are fundamentally irreplaceable. Australia’s public and private forests contain many historical, forgotten experiments that possess the potential to fundamentally transform our contemporary understanding of how complex forest ecosystems respond to human intervention and management over decades. Yet, all too often, these valuable scientific assets end up neglected, underfunded, and entirely forgotten. Finding, securing, and rehabilitating these long-term study sites before it is too late should be a high priority for the scientific community.
Second, the findings demonstrate that forest thinning does not have to be a zero-sum trade-off between economic extraction and environmental protection. While these results specifically illuminate the dynamics of mountain ash ecosystems, parallel studies conducted in North American conifer forests have reported similar outcomes. Thoughtful thinning can successfully deliver sustainable timber supplies for local processing industries, absorb and store significant volumes of carbon, and simultaneously improve structural habitat diversity for native wildlife. It represents a rare win-win-win outcome that directly challenges the rigid dichotomy of conservation versus production which has dominated public discourse for generations.
While forest thinning cannot—and certainly should not—be applied everywhere, it serves as a valuable management tool to cultivate greater structural variety in tree ages and stem sizes, particularly in native forests that have been previously impacted by intensive clearfelling or high-severity wildfire events.
Third, and perhaps most importantly, the research underscores that there is no single silvicultural silver bullet for managing complex forest landscapes. The lessons learned from the long-forgotten experiment at Tanjil Bren demonstrate that there are viable, science-based options available for managing native forests well beyond traditional clearfelling. These alternative approaches can successfully contribute to societal demands for sustainable wood products, maintain vital carbon stocks, and actively conserve regional biodiversity, pointing the way toward more sophisticated and adaptable forest management strategies in the future.
