Our latest field research in the Top End's wetlands has revealed a critical and escalating threat: the invasive African Gamba Grass (Andropogon gayanus). This tall, fast-growing perennial grass is fundamentally altering the fire ecology of sensitive wetland fringes and adjacent savannas.

Gamba Grass grows in dense stands up to 4 meters tall, accumulating up to ten times more fuel load than native grasses. This creates conditions for fires of unprecedented intensity and height. Where native fires might reach 1-2 meters, Gamba-fueled fires can exceed 4 meters, generating extreme heat that kills mature trees, destroys seed banks, and sterilizes the soil. This intense heat penetrates into the edges of monsoon vine thickets and mangrove ecotones, habitats that are not fire-adapted.

Dense stands of invasive grass create a high fuel load.

The impact on wetland filtration is severe. The loss of tree canopy increases runoff and sedimentation into waterways. Post-fire erosion from bare soil washes excess nutrients and ash into wetlands, overwhelming their natural filtration capacity and leading to algal blooms and reduced water quality in systems like the Adelaide River catchment.

Our team is collaborating with Indigenous Ranger groups on a dual-strategy management plan: targeted herbicide application followed by immediate reseeding with native species. Early results from controlled burn plots show that reducing Gamba biomass can help restore a lower-intensity, mosaic burning pattern, crucial for the health of the entire wetland ecosystem.

Controlling Gamba Grass is not just about land management; it's a frontline defense for protecting the biodiversity and water-purifying functions of our northern wetlands.