Mountain Ash Forests as a Carbon Store


My recent article (see below) on jobs and timber towns has been criticised in some quarters. I suspect these arose mainly because of my adoption of a powerful meme to illustrate the article and that the critics saw the meme and did not bother to read the article. The article explained my long association with timber towns and how I came relatively late to the cause of complete protection of our native forests – a long process completely separate from the wider environment movement.

Several myths are mentioned by the critics the most prominent of which has been to downplay the importance of old growth forest as a carbon store. It has been clearly documented that old growth mountain ash forest is one the best carbon stores on earth. An ABC article by Anne Salleh in 2009 entitled “Australian forests lock up most carbon” summarised the work of Professor Mackey and colleagues of the ANU published in the Proceedings of the National Academy of Science. Their work involved calculating “the total biomass locked up in living and dead plant material and the soil” in each of the forests they studied around the world. They discovered that the “highest amount of carbon was contained in a forest located in Victoria’s Central Highlands, which held 1900 tonnes of carbon per hectare” and that “this most “carbon-dense” forest was a stand of unlogged mountain ash over 100 years old. Mountain ash live for at least 350 years…”

Thus when logged each hectare loses most of their 1900 tonnes of stored carbon. Assuming that at least 1000 tons is lost this translates into roughly 3000 tons of CO2 – the most long lived greenhouse gas – being added to the atmosphere and contributing to the already alarming rate of global warming. On top of this is all the CO2 added in the process of logging, milling and transporting. Examples of this include woodchips for some decades were carried in semi-trailers to Eden where they were shipped to Japan, milled timbers were often transported long distances such as from beyond Mt Murphy to Heyfield (about 300ks each way) and the timber for the Swifts Creek mill is still imported from far west Gippsland, cut into pallet timber and trucked back to Dandenong – all dependent on fossil fuel energy and full of waste and inefficiencies. The logging and processing mountain ash from 1 hectare is equivalent to the CO2 output of about 2000 adult Aussies for a year. Mackey noted: “another common misunderstanding is that younger growing forests sequester more carbon than mature forests…while growing forests have a greater rate of carbon uptake, it’s more important to look at the total amount of carbon stored in a forest…If you take one of these mature [mountain ash] forests with 1900 tonnes of carbon in it and trash it … it’s going to take hundreds of years to grow back that amount of carbon.”

Mackey also noted that rather than reducing fire “logging actually increases the risk of fire by opening up the forest, increasing the amount of fuel on its floor, and drying the forest out.” I will deal with this in a future blog but note that these forests are important and valuable in the fight against climate change and should be preserved and protected.