National Carbon Accounting System
Australia’s National Carbon Accounting System (NCAS) provides world-leading accounting for greenhouse gas emissions from land based activities.
Land based emissions (sources) and removals (sinks) of greenhouse gases form a major part of Australia’s emissions profile. Around 27 per cent of Australia’s human-induced greenhouse gas emissions come from activities such as livestock and crop production, land clearing and forestry.
Land management such as soil preparation, fertiliser use, harvesting and burning all affect emissions of greenhouse gases. A significant proportion of Australia’s land based emissions occur as non-carbon dioxide gases, in particular methane from livestock production and nitrous oxide from fertiliser application.
Actively growing forest systems remove carbon dioxide from the atmosphere through photosynthesis. Growing forests act as a long-term carbon sink by storing carbon in the trees, debris and soils. In 2007, removals associated with reforestation activities were estimated to be approximately 21 Mt of carbon dioxide (based on forests planted since 1990), effectively reducing national emissions by almost 4 per cent.
Land activity accounting
Accurate accounting of the emissions and removals of greenhouse gases from the land requires knowledge of the dynamics of carbon (for carbon dioxide and methane emissions) and nitrogen (for nitrous oxide emissions) in the landscape. The growth and life cycles of forests and agricultural crops, climate, soils, land cover change and land management are all important components of a comprehensive emissions accounting system.
The NCAS estimates emissions through a system that combines:
- thousands of satellite images to monitor land use and land use change across Australia since 1972 that are updated annually,
- monthly maps of climate information, such as rainfall, temperature and humidity,
- maps of soil type and soil carbon,
- databases containing information on plant species, land management, and changes in land management over time, and
- ecosystem modelling - the Full Carbon Accounting Model (FullCAM).
NCAS development
The Australian Government established the NCAS in 1998 to provide a complete accounting and forecasting system for human-induced sources and sinks of greenhouse gas emissions from Australian land-based activities.
The NCAS is continuing to be developed over several phases. These phases are driven by reporting priorities. This reporting capability includes:
- land use, land use change and forestry categories for both the United Nations Framework Convention on Climate Change National Greenhouse Gas Inventories and the Kyoto Protocol Greenhouse Gas Inventory, and
- projections of future emissions for these same categories.
These reporting categories include changes to emissions and removals of carbon dioxide in the major carbon pools – soil, litter, debris, and both above ground and below ground biomass from agriculture and forest systems.
Derived from the NCAS, the National Carbon Accounting Toolbox (NCAT) is available free of charge and allows users to track emissions and removals of greenhouse gases at specific locations and to input information about their specific management activities.
Progress
Ongoing development of the NCAS is focused on improving the estimates of non-carbon dioxide emissions such as methane and nitrous oxide. Enhancing the spatial information in the NCAS is also continuing, with particular focus on reforestation, management of native forests, mapping of sparse woody vegetation and fire extent.