An aerial survey for declared weeds was undertaken in June 2017 in targeted sections of the West Pilbara to assess the effectiveness of control work.
The helicopter survey, which took two days and 17 flying hours, was conducted by the Pilbara Mesquite Management Committee (PMMC), who undertake the regional coordination of declared weed programs across the Pilbara region with particular focus on threatened species habitats.
The work was supported by Rangelands NRM through funding from the Australian Government’s National Landcare Programme.
PMMC Project Manager Jo Kuiper said previous aerial surveillance efforts in 2004, 2010 and 2014, were undertaken by the PMMC to detect the presence of declared weeds, particularly Mesquite and Parkinsonia.
The 2017 survey covered multiple tenures including sections of the Ngurrawaana Lease, Yalleen Station, Mardie Station, Karratha Station, DPaW Conservation Estate, City of Karratha recreational estate, Yarraloola Station, major highways, roads and access tracks.
“The survey was designed to verify the presence of key declared weed infestations, collect information on their density and provide data to the PMMC and stakeholders to assist in evaluating weed control management efforts to date and informing future priorities,” Ms Kuiper said.
Habitats surveyed included Roebourne grass plains (a Priority ecological community), a variety of river, creek line and riparian habitats, flood plains, a wide range of shrub lands including Snake wood (Acaccia xiphophylla) shrublands, Gilgai cracking clay grasslands, and various ecotones and mixed habitats.
Ms Kuiper said two people were used as spotters on each side of the helicopter, and recorded plants found using a multichannel data logger hooked to a GPS.
“Distinction between weed species, single plants and thickets of plants was achieved using different GPS markers,” she said.
At all locations where on-going weed control is undertaken a reduction in the density of those infestations was recorded.
“The evaluation of the effectiveness of the PMMC coordinated declared weed program allows the continued refinement of the integrated program, particularly in terms of spatial priorities,” Ms Kuiper said.
“This data and information also provides invaluable motivation and positive feedback to those land managers that are committed to this effort which is expensive, time consuming and laborious.”
She said knowledge gained from this survey has been incorporated into future prioritisation and control technique selection.
The survey also enabled the assessment of an extensive range of habitats that are within, or adjacent to, the known infestations of the declared weeds.
“This information will be used to specifically target single plants and low density infestations during the 2017 control season before they establish or spread further through the habitats.”
“This has also been discussed with the relevant land managers with review of (and support to improve) biosecurity hygiene and seed dispersal risks,” Ms Kuiper said.
Ms Kuiper said the PMMC and its partners will continue to deliver integrated declared weed management in the Pilbara region to support sustainability of our Pastoral industry, conservation of our biodiversity and the protection of cultural values.
“On-going evaluation and critique of the control methods employed is an integral component of the work; this aerial survey has added extensive understanding to the current status of declared weeds in the West Pilbara Region.”
The PMMC continues to develop strategic control programs, as well as seeking complimentary funding to assist delivering key on-ground activities and evaluating the achievements of the program.
Special thanks the volunteer-observers, Mardie Station Management and Willimabry Helicopters for their support during the program.