A smoke plume rises above a tropical savanna fire.

Carbon dynamics in Australia’s tropical north

We are measuring carbon stocks and fluxes to investigate a future role for tropical savannas in greenhouse gas offsets and potential carbon trading.

• 4 December 2007 | Updated 14 October 2011

Overview

• The burning issues
• Carbon source or sink?
• Fuel dynamics, emissions and fires
• Estimating carbon stocks in savannas
• Partners

The burning issues

With the growing demand for carbon-offset products in Australia and internationally, the tropical savannas of northern Australia are likely to play a key role in an emerging carbon economy.

Frequent burning of savanna landscapes is a considerable source of greenhouse gases, accounting for about 50 per cent of the Northern Territory’s emissions, which is three per cent of Australia’s total human-driven emissions.

However, the tropical savannas of northern Australia also represent about one third of Australia’s terrestrial carbon stocks, and are therefore potential sinks (stores) for carbon.

Carbon source or sink?

Present indications are that tropical savannas of northern Australia are net carbon sinks, even if burnt frequently. To maximise their sink potential, CSIRO and partners are seeking more knowledge of the long-term potential sink strength, and how sensitive this is to land use, particularly tree-clearing, grazing and fire.

Research is aiming to determine how the carbon sink capacity can be optimised, for example by reducing the area burnt, especially by hot late dry season fires.

We are also investigating the complex issue of how institutional factors, such as property rights, may govern trade in carbon off-sets in the savannas on aboriginal land.

Current activities:

Fuel dynamics, emissions and fires

Savanna greenhouse gas emissions can be reduced by decreasing fire frequency, but a greater understanding of fuel dynamics is necessary to produce accurate estimates of emissions.

With funding from the Australian Greenhouse Office through the Tropical Savannas Management Cooperative Research Centre (CRC), CSIRO researchers are contributing to the West Arnhem Land Fire Abatement (WALFA) project. The project aims to improve the estimates of greenhouse gas emissions from savanna burning. It is also focussed on engaging Aboriginal landowners to manage land to decrease these emissions.

CSIRO’s role is to improve the understanding of fuel dynamics and the ability to manage greenhouse gas emissions by manipulating fire frequency.

The WALFA project draws on many different case studies and data sources to estimate sink strength. These include:

• estimates of tree mortality and recruitment from the Kapalga Fire Experiment
• data on Net Ecosystem Productivity (NEP) and Net Biome Productivity (NBP) from a flux tower at Howard Springs (managed by Dr Lindsay Hutley of Charles Darwin University and Associate Professor Jason Beringer of Monash University)
• estimates of variation in fuel mass, and consumption during fire (working through the Tropical Savannas CRC).

Estimating carbon stocks in savannas

Dr Dick Williams and his team are exploring ways of estimating carbon stocks in savanna ecosystems at the Territory Wildlife Park, Howard Springs, Katherine, and Kidman Springs, both before and after fire.

Carbon exists in four main components of the landscape:

• trees
• grasses and litter
• roots
• soil organic carbon.

Researchers are estimating biomass according to the National Carbon Accounting System Technical Report No 31.

Coarse woody debris is measured by collecting and weighing woody litter, trees and roots in a known area. From this data the research team developed equations to estimate carbon stocks from tree trunk diameter and tree density, which are readily measured.

Importantly, the team found that all eucalypt species fit the same allometric equation for estimating carbon stocks.

The use of radar to estimate carbon stocks at a landscape scale was successfully trialled in the Mary River catchment near Darwin in the Northern Territory (NT).

Partners

This work is being completed under a number of project partnerships with:

• Tropical Savannas Management Cooperative Research Centre (CRC)
• Bushfire CRC
• Bushfires NT
• Australian Greenhouse Office
• Northern Land Council
• Aboriginal traditional owners in Arnhem Land.

Read about Dr Dick Williams: investigating the carbon dynamics of Top End tropical savannas.