Key Takeaways
- A 30-year-old Victorian forestry experiment demonstrated that heavily thinned forests produced trees 20 percent larger than those in untouched areas.
- Thinned forest sections recovered all harvested carbon and stored as much carbon as the unharvested control zones.
- The managed areas encouraged specific understory growth that attracted rare wildlife, including the Leadbeater’s possum.
Rediscovering a landmark forestry project
In the late 1980s, the Victorian government invested the equivalent of A$ 26 million to establish the Silvicultural Systems Project. The initiative was designed to explore alternatives to clearfell logging in the mountain ash forests of Tanjil Bren and Cabbage Tree Creek. Researchers tested various approaches, including traditional clearfelling, small patch clearfells, and heavy thinning where up to 70 percent of trees were removed. Unharvested areas were also preserved as benchmark comparisons.
Although the experiment was largely forgotten as access roads overgrew and project signs collapsed, university researchers returned to the Tanjil Bren site in 2014 to observe the long-term outcomes. The discoveries made at the site three decades later offered highly encouraging news for sustainable forest management.
Accelerated growth and carbon storage
The researchers observed that the heavily thinned sections of the forest had produced massive trees. Benefiting from increased space and resources, the largest 80-year-old mountain ash trees averaged over a meter in diameter, with some exceeding 1.5 meters. These trees were 20 percent larger than those in the unharvested control areas.
Furthermore, the heavily thinned forest stands successfully recovered all the carbon that was removed during the initial harvesting. Within just 30 years, these areas gained enough additional carbon to equal the storage levels of the completely untouched forest zones, demonstrating that active management can effectively support climate goals.
Creating vital habitat for rare wildlife
The benefits of tree thinning extended beyond carbon storage and timber production. The larger trees are more resilient to fires and are more likely to develop hollows, which serve as crucial habitats for rare wildlife. The thinned areas also encouraged the growth of acacia trees in the understory.
This specific understory growth proved highly beneficial for local fauna. Camera traps confirmed the presence of the rare Leadbeater’s possum in every surveyed silvicultural treatment plot, whereas none were found in the unharvested areas. The findings highlight that strategic forest thinning can simultaneously supply wood for local industries, absorb carbon, and significantly improve habitats for vulnerable wildlife.
