This blog is inspired by a field trip to the Warra long-term ecological research site in South-East Tasmania during a summer course at the University of Tasmania. We observed alternative forestry logging methods in wet native forests. Personal notes and readings were used to write the blog.
Clear felling forests should stop on environmental and ethical grounds. During a field trip we saw alternative logging systems and regenerating forests after clear felling, including a recently logged coupe. As the lecturer said “it looks like a bomb’s gone off”. Humans seem to be more interested in obtaining resources cheaply than caring for the world and sustaining beautiful ecosystems. It is sad that this destroys habitat for a mammal, bird or even invertebrate, but to obtain wood or paper, trees have to be felled. Is there an ecologically sustainable way of logging native forests?
Forestry Tasmania previously used the clear fell, burn and sow method (CBS) in Tasmania’s wet forests. This involves felling all the trees and taking away the desired timber. The coupe is burnt in a high intensity fire to clear the ground cover. Seed from local eucalypts is then aerially sowed. The fire aims to replicate natural conditions of forest regeneration where a huge, very rare fire (every ~300 years) kills the mature trees. The resulting open conditions allow for these high light requiring eucalyptus seedlings to grow (E. regnans and E. obliqua).
Due to concerns on the impacts of CBS on biodiversity and social unacceptance of it, alternatives were tested. The Tasmanian community forest agreement stated that by 2010 a minimum of 80% of old growth forest being logged was to be by non-clearfell methods.
The method currently used is aggregated retention (ARN). ARN retains the forest in at least 1 ha aggregates inside (as islands) or on the edge of a coupe during logging. The aim is to maintain ‘biological legacies’ (live or dead trees, logs, coarse woody debris) that occur in natural forest regeneration where naturally heterogeneous fires leave logs and unburnt or low intensity burnt patches. Another aim is to maintain ‘forest influence’ over the logged area. This is the influence of the remnant forest on biophysical conditions in the logged coupe such as seedfall, litter accumulation, light, temperature, humidity and wind speed. This then affects the recolonisation of flora and fauna into the logged area from the remnants functioning as refuges. Forestry Tasmania considers it to extend one tree height from the edge of the retained forest, however it is unknown if this is ecologically meaningful. In ARN, the remnants maintain forest influence more than 70% of the logged area. This is the main difference with CBS.
I can’t make a judgment on the long-term ecological sustainability of the practice. It seems like a huge improvement on CBS! Dr Nicki Munro has explained that no restored landscapes have equal functionality as undisturbed remnants. Regenerating ARN coupes will not be as functional as remnants and habitat will be lost. Humans will always have some impact on the environment. The challenge is to make our impacts small enough so that our kids inherit a world in the same condition as we found it. If the impact of ARN is small (what is small enough?) such that it is sustainable then it may be it is an acceptable practice.
Here’s hoping that forestry continues to be guided by conservation aims and research and that beautiful ecosystems are conserved!
Benjamin Huttner-Koros (Bachelor of Science)
- Forestry Tasmania, Achieving good ecological outcomes in aggregated retention coupes. Viewed 20 May 2013, <http://www.forestrytas.com.au/science/research-stories/achieving-good-ecological-outcomes-in-aggregated-retention-coupes>
- Forestry Tasmania (2009). A New Silviculture for Tasmania’s Public Forests: a review of the variable retention program. Available at: <http://www.forestrytas.com.au/uploads/File/pdf/pdf2009/a%20new%20silviculture%20web%20version.pdf>.
- Forestry Tasmania . A new siliviculture for Tasmania’s public forests. Viewed 20 May 2013, <http://www.forestrytas.com.au/science/research-stories/a-new-silviculture-for-tasmanias-public-forests>