Willow control in Jerrabomberra Creek
What is the Jerrabomberra creek restoration project?
The Jerrabomberra Creek restoration project aims to remove willows and alder species from the creek within Jerrabomberra Wetlands Nature Reserve. The work complements the ACT Government's existing Waterways Restoration Program which aims to improve the health of the ACT's river systems through replacing exotic and invasive weeds with native species.
The Jerrabomberra Creek restoration project will maximise the habitat value of the shoreline and develop a more natural environment in Jerrabomberra Wetlands Nature Reserve.
Where and when will the work take place?
This project has been ongoing since 2012. Considerable work has already been done along Jerrabomberra Wetlands Nature Reserve between the silt trap and Lake Burley Griffin.
More recently, work has commenced on the small islands and the cut trees have been dragged by boat to the shore for chipping and removal. Replanting of native species will follow and these will begin to provide habitat for more native species. Follow-up maintenance and revegetation will be ongoing.
Why are willows and alder considered to be a serious weed?
Jerrabomberra Creek is currently dominated by Crack Willow, a highly invasive Weed of National Significance, and Black Alder, a declared pest plant. Together these weed species are among the worst in Australia due to their invasiveness, potential for spread and economic and environmental impacts.
Willows have a direct negative impact on the ecosystem influencing both flora and fauna species biodiversity. For example, Willows provide few habitat opportunities for mammals, birds or fish; they are not known to provide a food source for birds or insects; and fallen leaves from Willows can affect water quality through increasing nutrient content.
Studies of bird biodiversity along waterways in South Eastern Australia show there are almost twice as many birds in native vegetation areas than in either willow invaded or cleared areas (Holland Clift et al 2011). Less invasive willows, for example Weeping Willow, will not be removed immediately.
How will the willows and alder be removed?
Willows and alders along Jerrabomberra Creek will be poisoned using glyphosate herbicide. In some cases, axe cuts will be placed around the trunks of each tree and poison injected into the cuts. After six weeks (around mid to late June) the trees will felled and removed. In other cases, poisoning will occur as the trees are cut. A small number of dead trunks will be left standing to provide roosting spots for birds.
Removed trees will be chipped and removed or used to mulch future native tree and shrub plantings within Jerrabomberra Wetlands Nature Reserve.
Will waterbirds and other riparian/aquatic species be affected?
Recent inspections by the Canberra Ornithologist Group and ACT Parks and Conservation Service have confirmed there are no current nest sites in trees marked for removal. The establishment of reed beds and other vegetation will provide future nesting and breeding habitat for a number of native wetlands birds, amphibians and insects. This has already been highly successful on the peninsula where new reed beds have proven a favourite habitat of the Lathams Snipe.
What will happen after the willows and alder are removed?
Following removal, Jerrabomberra Creek will be planted with common reed (Phragmites australis) seedlings adjacent to the water and with other native species, including trees and shrubs, where the ground is not so wet. Phragmites reed beds are a natural vegetation community in Australian wetlands that will stabilise the shoreline and help create habitat.
Where can I get more information?
For enquiries call Access Canberra on 13 22 81.
1 Holland Clift S., O'Dowd J., MacNally R. (2011) Impacts of an invasive willow (Salix x rubens) on riparian bird assemblages in south-eastern Australia. Austral Ecology. 36, 511-520.