The Problem
Olive hymenachne (Hymenachne amplexicaulis) is one of the worst semi-aquatic invasive weeds in Australia, which inhabits northern Queensland wetlands and currently covers around 1,200ha in the Hinchinbrook Shire. Infestations are spread rapidly as it reproduces from both robust seedlings and stem fragments which makes physical removal and grazing control ineffective.
The lower Herbert floodplain has already lost 75% of palustrine and 60% of riverine wetlands that were present pre-European settlement. Fortunately the weeds have not extended into the Melaleuca woodlands which would alter fire regimes, water flow and cause significant degradation. |
Hymenachne forms in dense patches which blocks waterways, affects water quality, reduces plant diversity and available habitat for native animals. Consequently local industries, especially sugarcane farmers and wetland tourism potential are negatively impacted.
In addition, feral pigs (Sus scrofa) are also a problem in the area which cause significant habitat degradation and increase competition, predation and disease transmission. Management of feral pigs is difficult as they are intelligent, highly adaptable and robust creatures and often require a variety of pest control techniques.
Insulator Creek is partially infested with hymenachne and leads into the Hinchinbrook Wetlands which are listed as "of concern". The project aims to control feral pigs and stop the invasive weeds from spreading further upstream to protect the wetlands from contamination. |
The Solution
Currently the hymenachne is being subjected to regular, controlled burns along with continued pig trapping, which are conducted by the Nywaigi traditional owners and land owners.
The research component aims to survey the area before and after the burns to determine the success of the weed control and any effects on the native biodiversity.
The research component aims to survey the area before and after the burns to determine the success of the weed control and any effects on the native biodiversity.
The possible benefits of this project include:
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Current Research
Benthic Invertebrates & Dissolved Oxygen
Benthic aquatic invertebrate fauna was assessed from sediment samples from 4 pools in Insulator Creek. Sediment was sampled using a soil scoop and sieved through mesh to separate out invertebrates. A probe was lowered into each pool for 10 second intervals to measure dissolved oxygen. |
Vegetation Surveys
Vegetation was recorded along a 160m transect, beginning in the forest where hymenachne was thick and finishing at the upper edge of the wetland. Vegetation was recorded every 10m included species present, percentage cover, species composition and height of dominant species. |
Fish Surveys
Fish assemblages were assessed in Insulator Creek using un-baited underwater video surveys. Cameras were deployed underwater along the creek across 8 sites for 15 minutes. |
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