Updated: Jul 29, 2020
Intact old forests contain significantly higher levels of biodiversity than recently logged areas. The biodiversity and connectivity benefits of old intact native forests have been documented many times in the scientific research and literature.
Old forests have a significantly more complex structure than logged and regrowth forests. Take the forest canopy for example. A tree takes a minimum of 100 years, and generally more than 150 years to produce hollow bearing limbs that provide habitat for a myriad of hollow dependent bird and mammal species. For larger species such as the Masked Owl and wedge tailed eagle, they predominantly nest in trees that are over 300 years old.
Old forest canopies help create microclimates by providing shade for lower plant communities and canopies, all the way to the forest floor. This helps retain moisture in the system creating the perfect conditions for rainforest species to survive. If left unlogged, these wet mixed species Eucalypt forests can eventually become rainforests. The decomposition of old trees on the forest floor is an essential process in the recycling of forest nutrients and the formation of soil. Insects such as the endemic Simsons Stag Beetle found only in the forests of north east Tasmania are heavily reliant on old unburnt forests and play a key role in the decomposition process, returning essential mineral nutrients back to the soil. Old fallen trees can provide denning sites for the Tasmanian Devil and spotted-tailed Quoll. These fallen trees often serve as nurseries for the germination of seeds and the establishment of moisture dependent seedlings.
Old wet forests are important fire breaks in the landscape and help to slow or stop wildfires. Recent studies by Melbourne University, ANU and UTAS found that after severe bushfires in Tasmania, Victoria and around the World have demonstrated that fires are more intense in recently logged forests.
Our old Eucalytus regnan forests, like those around Derby and the Blue Tier, are the most carbon dense forests in the world. This helped Tasmania become the first jurisdiction in Australia to achieve zero net emissions. We achieved this thanks to our forests which absorb 7500 killo-tonnes of carbon every year. This amount offsets Tasmania’s entire emissions in a year.
The use of high intensity burns by the forest industry after logging destroys the majority of living creatures in that zone. After forestry reseeds by helicopter, what comes back is a dense, even aged regrowth that becomes impenetrable for several decades as the seeded eucalypts and pioneer plant species compete for available light and nutrients. This type of forest has been scientifically demonstrated to be low in biodiversity and highly susceptible to fire which facilitates the spread of wildfire in the landscape more than any other forest vegetation type.
The use of buffers, or as the logging industry calls them ‘visual amenity strips’ and aggregated retention is often spruiked by forestry as a sustainable approach to logging. Unfortunately the fragmentation of the landscape increases what’s referred to by scientists as edge effect. If you look at the trees on the edge of a logging coupe they are often severely burnt by the high intensity burns from within the logged zones. They are then subject to increased sunshine, heat, drying wind and storm events that contribute to an overall decline in tree health often leading to death. These effects extend deep into the remaining forest areas and continue to negatively influence tree health for decades.