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.
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Bellyache bush is one of a host of weeds now in
Kakadu
Photo: Greg Calvert
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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.
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Gamba Grass near Fogg Dam, east of Darwin
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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 .
