Fire and carbon

by Dr Steve Read, Chief Scientist, Division of Forest Research and Development

FIRE and carbon are at the heart of forest management in Tasmania but are often misunderstood due to the complex nature of eucalypt forests.

Eucalypts have evolved with fire over millions of years, developing flammable oils and hanging strips of bark, as well as adaptations to survive fire. This adaptation makes for efficient and effective sustainable timber harvesting, as many species can regenerate without replanting, and a complex and biologically diverse and resilient forest ecosystem can develop without further intervention.

Inadequate levels of fire can cause significant ecological changes, and in managed native forests has been linked to forest health issues such as dieback and chronic decline of eucalypts.

 Prescribed burns can have a patchy impact, with areas within burn boundaries often left unburnt. This can have beneficial ecological consequences as in general diverse landscapes are healthy and ecologically resilient. Variability across the landscape can also be achieved through a mix of coupes and unburnt reserves.

Managing solely for old-growth forest does not necessarily give the maximum reduction of atmospheric carbon. Old-growth forests have the lowest sequestration rate of any forest stage. They also have the largest emissions when they burn, and do not offer the chance to accumulate wood products.

The absence of smaller controlled fires can increase the risk of future large-scale wildfires which release large amounts of carbon into the atmosphere. It is estimated that 150 million tonnes of carbon were added to the atmosphere in the 2003 and 2006/7 wildfires in Victoria, with similarly large amounts being released from wildfire annually in the United States.

On the other hand management involving short-term carbon loss, such as thinning or fuel-reduction burning, can decrease the intensity of subsequent large fires and lead to smaller carbon emissions over the long-term.

To read Dr Read’s report Fire and Carbon in Managed and Unmanaged Forests click here or to read to a summary of the report click here.