Overview
The gulf region contains great variation in land types and
intensity of land use. Given that weed invasion tends to be
directly related to either human traffic or to intensity of land
use, there is a parallel variance in weed presence across the
region. Limited financial and human resources on the ground has
severely constrained the amount of weed survey work carried out in
the Gulf region. The NT Department of Primary Industries and
Fisheries has recently begun a survey of weeds throughout the
Northern Territory's portion of the Gulf.
Major weeds
The major weed threatening the biodiversity and productivity of
riparain systems on the Queensland side of the border (Morgan 1999:
2/9) is rubber vine (Cryptostegia grandiflora), which now
infests areas of most river systems, and has had a particular
strangle hold on the Mitchell-Gilbert system in the far north-east
of the region. It also infests dunes and scrubs along the coastal
zone in the east of the region. It has currently advanced as far
west as the Nicholson River system in the Northern Territory,
although it has since been eradicated from the area.
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Rubber vine is a serious weed of the riverbanks
of north Queensland
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In the south of the region between the Leichardt and Flinders
catchments are areas of black soil plains. In this part of the gulf
region, weed problems are distinct and include encroachment of
woody natives such as coolibah (E. microtheca), whitewood
(Endospermum medullosum) and gutta percha (Excoecaria
parvifolia) . Exotics such as Parkinsonia (Parkinsonia
aculeata) and, in the most southerly reaches, prickly acacia
(Acacia nilotica) also are becoming problems. These areas
are considered prime grazing country and as such are often
protected from fire. This may be a major factor in the weedy
invasion.
Noogoora burr (Canthium pungens) and hyptis (Hyptis
sauveolens) are also considered high priority weeds throughout
the region. They reduce the value of pastoral land and are a threat
to native plant communities. Mesquite (Prosopis spp.)
occurs, sometimes as dense infestations, throughout the southern
parts of the Gulf Country around Cloncurry, the southern Nicholson
River and on northern sectors of the Barkly Tableland.
Salvina (Salvina molesta), water hyacinth ( Eichhornia
crassipes) and callotropie (Calotropis procera) are also
locally significant.
Introductions
Plants currently being introduced to the area which have been
identified as having significant potential to become weeds include
neem trees (Azadirachta indica) which are being planted
around, and to the north east, of Cloncurry. The concern is that if
these trees were to spread to the marine floodplains, they could
become unmanagable.
Ponded pasture species which are being planted on the fan of the
Mitchell-Gilbert system and along coastal floodplains to the west
of this system are also of conern. These plants have the potential
to invade native wetlands and displace local plants and
animals.
Other invaders
Mexican poppy (Argemone ochroleuca) occurs in some river
catchments including the McArthur, the Calvert and Settlement
Creek. Khaki weed (Alternanthera pungens) and Star burr
(Acanthospermum hispidum) are two nuisance plants that occur
in settled areas throughout the Gulf region. Similarly, chinee
apple (Zizyphus mauritiana) is not a major concern at
present, but has potential to become a problem on sandy
country.
Weeds on Aboriginal lands
There are significant areas of Aboriginal land in the gulf
region, especially on the Northern Territory side of the border.
While weed problems are known to exist on many of these lands,
there is limited knowledge of the extent of the weed problem in
many of these areas (Smith 2001).
Overall Aboriginal lands have less weeds than other areas,
mostly by virtue of their isolation and lack of infrastracture. In
addition, the requirement for permits to enter these areas may
further decrease the traffic. In general, those catchments on
Aboriginal lands with the greatest number of weeds are those
traversed by major roads, those with significant agricultural or
pastoral activities and those containing large settlements.
It is important that traditional owners be kept informed of new
weeds which may threaten their country, and be informed of control
methods. Aboriginal lands close to the Queensland border, for
example on the Nicholson River, may be under threat from rubber
vine in adjacent catchments. These areas are extremely strategic in
ensuring that weeds from Queensland do not advance further to the
west.
References
Morgan, G. (1999). Gulf Plains. In: Sattler, P. & Williams,
R. (eds), The Conservation Status of Queensland’s Bioregional
Ecosystems, page 9, Chapter 2. Environmental Protection Agency,
Brisbane.
Smith, N.M. (2001) Not from here: Plant invasions in
Aboriginal lands of the Top End, TS–CRC, Townsville,
Qld.
