MONITORING WEED FOR COORDINATED CONTROL DISTRIBUTION IN THE REMOTE GULF SAVANNAH STEP 1
Gulf Savannah Natural Resource Management (GSNRM) contains: Cape York Einasleigh Upland Gulf Plains Wet Tropics bioregions Gilbert, Mitchell, Norman and Staaten River Catchments
Each participant was given five, A3 size property maps, overlain with ~100 ha hexagons, which differs from the current Queensland Weed Distribution data which uses ~1700 ha squares.
STEP 2 Of the 175 landholders we communicated with, 44 were unable to fully participate due to varied reasons.
The Region is Dominated By: Tropical Savannah Rangelands 200km of coastline in the Gulf of Carpentaria
It is noteworthy that the region was impacted by Cyclone Jasper when this project commenced, with unprecedented rainfall, flooding and the highest 1 24-hour total rainfall (975mm) ever reliably measured in Australia .
STEP 3
19.61 million ha 84% Beef Cattle Grazing
131 individual property maps were distributed in person, electronically or via post, spanning ~8.87 million ha. Participants used a density mapping guide (Figure 1) and scored the presence of up to five top priority plants of concern across their property, with each map dedicated to one species only.
11% Private Refuges & State Conservation
36 PLANT SPECIES
100ha was the smallest reportable infestation size. 2
Figure 2: Most Frequently Reported Plants by area
Chinee apple (Ziziphus mauritiana) 181,946 ha
Rubber Vine (Cryptostegia grandiflora) 358,069 ha
mapped across 2.96 million ha
Between March 2024 and April 2025, 52% of the maps were returned by 68 landholders, covering 2.96 million ha.
IMPACTS
Breadfruit (Gardenia vilhelmii) 64,685 ha
Breadfruit (Gardenia vilhelmii), Conkerberry (Carissa lanceolata & C.ovata), Rubber vine (Cryptostegia grandiflora) Soap bush and Turpentine (Acacia holosericea & A.chisholmii) were raised due to their contribution to woody thickening and subsequent impacts on pastoral production4. Accidental introduction of weed species was raised through contaminated hay bales, turf and transiting machinery (externally owned).
OUTCOMES
Figure 3: Plant Species by Catchment Plant Species Recorded
Catchment
0
10
20 28
Gilberton 15
Mitchell Norman Staaten
14 0
FOOTNOTES
Plant Density Score
Map Example of ‘Abundant and Widespread’
0 = Unknown 1 = Absent 2 = Occasional & Localised 3 = Occasional & Widespread 4 = Common & Localised 5 = Common & Widespread 6 = Abundant & Localised 7 = Abundant & Widespread
Figure 1: For each plant species, density varied across the properties. Density scores were dominated by occasional (score 2-3) (41.4%), followed by common (score 4-5) (33.6%) and abundant (score 6-7) (25%).
RESULTS
Native Heart Leaf Poison Bush (Gastrolobium grandiflorum) was noted due to its toxic effect on stock.
The number of species recorded by landholders in each catchment can be viewed in Figure 3. The higher reporting rate from Gilberton catchment (Etheridge shire) may be explained by the fact that (1) 8.5% of the GSNRM region’s population resides in this location, and (2) GSNRM has a stronger history of community engagement with this catchment’s area.
Data points and density scores recorded in this project will be shared with Local, State and Regional organisations, such as Far North Queensland Regional Councils to support planning and future management actions.
Horehound (Mesosphaerum suavelons) 94,158 ha
Grader grass (Themeda quadrivalvis) 202,047 ha
36 plant species were mapped. The most frequently reported plants by area are listed in Figure 2. Categorically, shrubs were the most common (16 spp.), followed by trees (9 spp.), grasses (4 spp.), herbs (3 spp.), sedges (2 spp.) and one vine species. One tree still remains unidentified, but has been tentatively labelled Single Thorn Prickly Bush (Dichrostachys spicata). Additionally, ten Category 3 Restricted Invasive Plants under the Biosecurity Act 2014 were reported3.
Infestations of category three restricted invasive species that are an extension to their mapped range and additional to the Queensland Spatial Catalogue (28/10/2024) are Chinee apple (Ziziphus mauritiana) 31,983 ha (Etheridge shire) and Prickly Acacia (Vachellia nilotica) - 2,999 ha (Carpentaria shire). GSNRM will prioritise control work in this area in the future as funds become available.
PROJECT SUMMARY
OUR REGION
During 2024, GSNRM conducted six workshops across the region to showcase the project to local landholders.
1 Prasad V. 2024. Bureau of Meteorology. Severe Tropical Cyclone Jasper (02U) 2 - 17 December 2023. Tropical Cyclone Environmental Prediction Services.
2 Figure 1. PHOTOS: Most Frequently Reported Plants. Franklin, D. 2025.
3Category 3 Restricted Invasive Plants under the Biosecurity Act 2014 are: Rubber Vine (Cryptostegia grandiflora), Chinee apple (Ziziphus mauritiana), Bellyache bush (Jatropha gossypiifolia),
Prickly Acacia (Vachellia nilotica), Parkinsonia (Parkinsonia aculeata), Captain Cook tree (Cascabela thevetia), Lantana (Lantana camara), Rats tail grass (Sporobolus), Siam (Chromolaena odorata), Parthenium (Parthenium hysterophorus) and Gamba Grass (Andropogon gayanus). (Biosecurity Act 2014 (Qld). https://www.legislation.qld.gov.au/view/html/inforce/current/act-2014-007) 4The drivers of thickening are uncertain but are likely due to increasing atmospheric CO2 concentration and water availability, plus changes to fire management which can either increase or decrease rates of woody thickening. Murphy B, Lehmann C, Russell-Smith J, Lawes M. 2014. Fire regimes and woody biomass dynamics in Australian Savannahs. Journal of Biogeography. 41(1):133-144 Contact: Scott Morrison, Gulf Savannah NRM, scott.morrison@gulfsavannahnrm.org
Acknowledgements: Thank you to all landholders that participated in the project, both through formal and informal discussions and completing property maps; GSNRM staff M. Tadese (GIS Officer) and T. Taylor (Project Officer). Funded by the Queensland Government as part of the Queensland Feral Pest Initiative.