Gamba grass: Controlling the nightmare

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In Denise Goodfellow

/ Published on 03 June 2020

Gamba grass (Andropogon gayanus) is a tall (4 metres high), multi-stemmed plant introduced to Australia in the 1930s as cattle fodder (Csurhes, 2005).   The potential danger this grass posed was recognised early on, but despite assurances that it could be safely contained within paddocks heavily grazed by stock, gamba quickly escaped into surrounding savannah woodland (Petty, 2013) and elsewhere via “wind, water, animals and vehicles” (Beaumont, Keily & Kennedy, 2018).    Now a weed of national significance gamba infests more than 1.5 million hectares of the Top End.  The Top End is fast becoming a monoculture of gamba, and a ‘field of nightmares’ (Petty, 2013) for all concerned.

Gamba devastated the flora of woodland and even wetlands by crowding out trees and other plants, changing the nutrient status of the soil so that it better suits gamba than native vegetation, and fuelling wildfire so hot that even trees cannot survive - one study from Adelaide River 120 kms south of Darwin found 140 dead trees per hectare (Brooks, Setterfield & Douglas., 2010).  A property near us lost 50-60% of it mature trees in one fire.

Gamba carries high-intensity crown fires more like those seen down south than the cool low fires once typical of the north.  But unlike southern fires these Top End conflagrations can occur annually or ever more often (Kurucz, 2019).  Every year our property southwest of DarwinGamba won’t grow under these trees because of the saponins in their leaves is threatened at least once.    Landholders have expressed both despair and fear at the amount of gamba grass infesting their land.  We’re actually putting in a firegate at the east end of our property so that neighbours have an escape route should their property go up in flames.  Tourists and locals alike have nearly died in gamba-fuelled fires.

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