Climate change, carbon sequestration and Tasmania

The authors present a compelling case that forests can prevent greenhouse gas emissions as well as reduce them. Prevention occurs when:

• wood is substituted for more carbon-intensive products such as steel, concrete, brick or vinyl;
• biomass is substituted for fossil fuels;
• forest management reduces the frequency and severity of wildfires and pest outbreaks; and
• deforestation and conversion to other uses is prevented.

In addition to reducing the volume of GHGs emitted into the atmosphere, Malmsheimer et al examine the role forests can play in sequestering carbon. Trees sequester large volumes of carbon when:

• they are managed on relatively fast-growing rotations, since the majority of carbon sequestration occurs in the early years of growth; and
• wood products are produced, which remain as carbon stores for periods up to 100 years.

Malmsheimer et al (2008, 121) conclude their review in dramatic fashion:

The challenge is clear, the situation is urgent, and opportunities for the future are great. History has repeatedly demonstrated that the health and welfare of human society are fundamentally dependent on the health and welfare of a nation’s forests. Society at large, the US Congress, state legislators, and policy analysts at international, federal and state levels must not only appreciate this fact but also recognize that the sustainable management of forests can, to a substantial degree, mitigate the dire effects of atmospheric pollution and global climate change. The time to act is now.

Malmsheimer et al’s analysis is compelling but they oversell the benefits of forests as carbon sinks and fail to spell out what they mean by sustainable forestry management (SFM). In forestry circles, SFM is a highly elastic concept that can justify all manner of unacceptable practices from an ecosystem perspective. The approach adopted by Malmsheimer et al requires a more thorough going embedding in an ecosystem-based approach to forests and forestry.

Undervaluing the global warming threat

In contrast to Malmsheimer et al’s analysis, a recent report from the Australian National University’s Fenner School of Environment & Society promotes the benefits of wilderness as carbon sinks.

Mackey et al argue in their report Green Carbon: The Role of Natural Forests in Carbon Storage that natural forests “are more resilient to climate change and disturbances than plantations because of their genetic, taxonomic and functional biodiversity” with a high capacity for “regeneration after fire, resistance to and recovery from pests and diseases, and adaptation to changes in radiation, temperature and water availability” (2008, 5).

Moreover, the authors found that intact natural forests in south-eastern Australia, including Tasmania, store on average three times more carbon than conventional estimates. For example, while the default value for carbon sequestration for temperate forests used by the Intergovernmental Panel on Climate Change (IPCC) is 217 tC ha-1, the average stock of carbon found by Mackey et al was 640 tC ha-1.

These authors conclude: “From a scientific perspective, green carbon accounting and protection of the natural forests in all nations should become part of a comprehensive approach to solving the climate change problem” (Mackey et al 2008, 8).

To do this, they argue that two core definitions need to change: