map

Weeds and conservation

Conservation concerns

The invasion of native vegetation by weeds is one of the major conservation threats in northern Australia. Although areas such as Kakadu contain a low proportion of weed species relative to parks in southern Australia, there is no room for complacency. Weeds have the potential to displace native vegetation and the animals that rely on it from very large areas, especially in the wetlands.

Bellyache bush

Bellyache bush is one of a host of weeds now in Kakadu
Photo: Greg Calvert

Weeds in Kakadu

In Kakadu, emphasis has been placed on controlling mimosa and salvinia. There are also coordinated efforts to control other major weeds such as para grass, gamba grass (Andropogon gayanus), mission grass (Pennisetum polystachion) and annual pennisetum (P. pedicillatum), bellyache bush (Jatropha gossypifolia), wild cotton, rubber bush (Calotropis procera), candle bush (Senna alata), coffee bush (Leucaena leucocephala), and calopo (Calopogonium mucunoides).

Gambia pea (Crotalaria goreensis) is causing concern because it is invading undisturbed areas, especially after wet season burning. This and other hard-seeded legumes may cause very serious problems in the future.

Gamba grass

Gamba Grass near Fogg Dam, east of Darwin

Exotic grasses

Vigorous exotic grasses such as gamba grass and mission grass have the potential to irreversibly degrade large areas of savanna because they produce large quantities of fuel and increase fire intensities. These grasses are also taller than native grasses, and dry off later in the season, when fires are hotter and more difficult to control. The trees that are so characteristic of Top End savannas are therefore more likely to be killed or seriously damaged by fires that these exotic grasses fuel. There is concern that they may irreversibly damage many Top End savannas. The landscape could be transformed from biologically diverse open forest and woodland to impenetrable grassland with little native flora and fauna. To see a recent list of research findings on gamba grass click here .