Gamba grass effects on savanna carbon and fire

Leading researchers in invasive grass management, carbon accounting and savannah ecology determined the quality of baseline carbon stocks in native vegetation and how these are affected by gamba grass invasion.

Before this project, there was no information on how gamba grass infestations and fires affect carbon stocks, particularly soil carbon, which is the largest store of carbon in ecosystems. By understanding the impact and risk to carbon stores, policy and land managers will be in a better position to allocate resources effectively.

The Australian Government’s carbon farming initiative excludes land with gamba grass (or other invasive grasses). Many properties across northern Australia contain only small infestations. The research findings can assist policy and land managers to prioritise areas for gamba control, based on the risk of invasion to biodiversity assets, economic and social assets, and the cost of management activities.

The team mapped gamba invasion within priority areas and determined the rate of invasion and effectiveness of current management. They used new techniques to determine the baseline quantity of carbon stocks in native vegetation and the change following invasion. The data was integrated in a decision-support tool to guide the most cost-effective management of gamba grass at a regional scale.

This research delivered an improved understanding of the impact of gamba grass on savanna carbon stores. It also improved understanding of the relative costs and benefits of managing gamba grass.

Research outputs include:

• maps of the current distribution of gamba grass in the Coomalie/Litchfield National Park region;
• estimates of the rate of spread of gamba grass by comparing current mapping to maps of past distribution;
• quantification of carbon stocks in selected sites and the estimated change to stocks following gamba grass invasions;
• a predictive spread model for gamba grass; and
• a decision-support tool to identify high priority areas for management.

Evidence-based recommendations on accounting for gamba grass invasion in the Carbon Farming Initiative savanna burning methodology.

The team undertook field work in the Top End’s tropical savannas, particularly Darwin and the Daly region.