There has been much debate nationally, and recently particularly in NSW, as to whether net carbon (C) emissions are lower under non-harvest management than for sustainable harvesting of native forests. Some claim that cessation of harvesting can create large amounts of C credits that can be monetised and used to fund alternative forest management.
A recent detailed review of relevant scientific evidence published in the journal Australian Forestry (Raison, 2024) reached the following conclusions:
Point 1: Reliable assessment of the complete C balance associated with harvested native forests requires the application of a full Life Cycle Analysis (LCA) framework that accounts for temporal changes in C stock at the harvested site; C emissions associated with managing and harvesting the forest, transporting and processing harvested wood products (HWP); storage of C in wood products in service and landfill; any C emissions saved by using residues to generate energy otherwise produced by combustion of fossil fuels; benefits of substituting wood for more C-intensive materials such as steel, aluminium or concrete in construction; and the C footprint of wood products sourced from overseas to replace Australian production.
Point 2: Only one Australian study has adopted a complete LCA approach. That study concluded that harvesting of sustainably managed native forests and the subsequent use of forest biomass to produce HWP or energy can make a positive contribution to mitigating national net C emissions. Other studies claiming that native forest harvesting increases net C emissions have either been incomplete, used inappropriate parameters to estimate components of the total C balance, or overestimated the rate of C gain in older forests and the ability of unharvested forests to store C for the long-term under threat from wildfires, and consequently have underestimated the C benefits due to wood harvest and use. This has led to the erroneous conclusion that cessation of harvesting would provide better C outcomes than sustainable management for wood production.
Point 3: Changes to C storage in Australian native forests are driven much more by extensive wildfire than by harvesting. Harvesting affects only a small proportion of the forested landscape, and logs harvested annually from all Australian native forests contain only about 2.5 Mt CO2-equivalent or about 0.6 % of Australia’s total net anthropogenic greenhouse gas (GHG) emissions. Additional emissions of C from the decomposition or combustion of slash produced during harvest are about a third of this figure. These C removals from the forest are offset by sequestration of C in new regrowth and are supplemented by benefits derived from harvested wood. In contrast, in very bad fire seasons such as the summer of 2019-20, C emissions were about twice Australia’s total annual anthropogenic (i.e. excluding wildfire emissions) GHG emissions and about 200 times greater than C removals in wood plus emissions from logging slash.
Point 4: When examined at the landscape scale, there is no credible evidence that harvesting leads to increased area burnt, fire severity or C emissions caused by wildfires. However, wildfires in the large and contiguous areas of thick regrowth created after the ‘black summer’ fire season will pose a major threat to C stocks in all forests during the coming decades.
Point 5: Timber harvesting in native forests, providing it is well conducted in carefully selected parts of the landscape, can provide ongoing C benefits.
These findings mean that a proposal to establish a new INFM (Improved Native Forest Management) methodology to estimate C emissions savings from the cessation of harvesting in State forests lacks any scientific logic. The method development is backed by the NSW government’s Department of Climate Change, Energy, the Environment and Water, and it has been prioritised by the Federal Government via the Emissions Reduction Assurance Committee for further development. The Australian Climate and Biodiversity Foundation claim that ceasing native forest harvesting could generate abatement of more than a million tonnes of carbon dioxide equivalent (CO2-e) annually, with a value of approximately $100 million. Such claims are fanciful and ignore scientific knowledge and the following facts about native forestry in NSW.
Just 9.1% of the forest estate in NSW is State Forest, and only a small part of this is harvested annually using mainly selective harvesting practices. Privately owned native forests occupy a much larger area (33.8%), some of which is actively managed for wood production. National parks represent 25.1% of the forest estate. Publicly available data (ABARES, 2024) shows that in 2022-23, only about 650,000 cubic metres of logs were removed from the State’s native forests (public + private) – annual log production from native forests has declined markedly during the last 20 years.
Detailed research shows that each cubic metre of harvested wood contains approximately 1 tonne of carbon dioxide equivalent (CO2-e). We also know from extensive field measurements across many forest harvesting operations that approximately 70% of felled biomass is removed off-site in harvested logs (considerably more than the 40% claimed by anti-logging advocates), whilst currently, the remaining 30% is waste that is left in the forest to be either burnt or to decay over time.
Using the above information, the total C in all the felled trees in native forests that produced 650,000 m3 of logs annually is approximately 0.93 Mt CO2-e or about 0.8 % of the annual anthropogenic GHG emissions in NSW. This figure sets an upper limit for C emissions caused by harvesting if we assume that all that C was immediately emitted into the atmosphere. However, part of the carbon in harvested wood enters long-term storage either whilst in service or in landfill.
Wood is also used in construction to substitute for high-emission alternative materials (steel, concrete, and aluminium) and to create wood products that might otherwise be sourced from overseas, where production emissions are much higher than in Australia. When properly assessed in lifecycle analysis, sustainable harvesting does not cause net C emissions but instead leads to greater mitigation of C emissions than an alternative no-harvesting forest management option.
