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Carbon Dynamics
The Issue
About one third of Australia's terrestrial carbon stocks resides in the tropical savannas of northern Australia. The savannas offer great potential as a sink for carbon, to offset greenhouse emissions, but the size of the sink is highly dependent on land use. Grazing, clearing and fire all have the potential to affect the store of carbon in savanna landscapes, and the amount of carbon emitted to the atmosphere. Thus, there is a need to understand the size of the carbon pools, both above and below ground, the fluxes - the movement of carbon between soil, vegetation and the atmosphere - and the ways in which various land uses affect these stocks and fluxes. The world economy is becoming more carbon-constrained, and many businesses are seeking to offset their carbon emissions with activities that sequestor (store) carbon elsewhere. Such trade in carbon offset products is increasing rapidly, so there is a need to understand the nature of these products, and the institutional arrangements that may govern trade in carbon off-sets.
CSIRO Research
CSIRO research commenced in 2001 in partnership with Charles Darwin University, the Northern Territory Government and other agencies involved with the Tropical Savannas CRC. The key questions are:
- What are the stocks of carbon in the savannas, both above and below ground, in both mesic and semi-arid savannas?
- What methods are best used to estimate these stocks?
- Are the savannas a net source or sink of carbon?
- How does land use affect the stocks and fluxes of carbon?
- What is the role of carbon off-set products in the economy of the 21st Century?
The size of the various pools of carbon (trees, grasses, roots and soil organic carbon) has been estimated using direct harvest for sites in the Darwin, Katherine and Victoria River District regions in the Northern Territiory. Equations have been developed that relate carbon stocks to tree size and tree density. These data, and estimates of the fluxes of carbon between the landscape and the atmosphere, indicate that the savannas are a net sink for carbon. However, the size of the sink is affected by land uses such as tree clearing, grazing and fire.
Carbon trading may become a feature of the nation's economy in the coming years, and the results from this project will increase our understanding of how native ecosystems may contribute to the emerging carbon economy. Preliminary research indicates that national and global demand for carbon off-set products is substantial (millions of tonnes) and that demand of this nature could be met from off-set activities in northern Australia. Current research is also invesitigating the complex issue of how institutional factors (e.g. property rights) may govern trade in carbon off-sets in the savannas.
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Collaborators
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