Unravelling mimosa

Location:	Daly, Moyle and Fitzmaurice Catchments, Northern Territory
National priority area:	Biodiversity and natural icons Coastal environments and critical aquatic habitats Sustainable farm practices Community skills, knowledge and engagement
Funding:	$690,000 (2009-10) $730 000 (2010-11) $1 420 000 (Total)
Partners:	Northern Land Council together with three Ranger Groups Wangamaty Landcare Group Thamarrurr Ranger Group Department of Natural Resources, Environment, The Arts and Sport (NT) Tipperary Group of Stations Jindare Station

Coordinated response to on-ground control of Mimosa pigra in the Daly and Moyle Catchments

Through a partnership between Indigenous and non-Indigenous land managers this project is tackling an infestation of the weed Mimosa over 20 000 hectares within the Daly and Moyle catchments of the Northern Territory.

In the tropics south-west of Darwin, stretched out across 70 750 square kilometres (about the size of Tasmania), are the catchments of the Daly, Moyle and Fitzmaurice Rivers. More than 60 000 hectares of this area is infested with the weed Mimosa pigra. While some areas may only have one or two plants, others are wall-to-wall monocultures.

Of further concern is protection of the aquatic ecosystem at Anson Bay, within the Daly Catchment, which supports internationally-significant numbers of waterbirds. Ten threatened species live in these catchments, including the endangered northern quoll, the vulnerable water mouse, and flatback turtle.

The vast problem demands a strategic approach by prioritising management of upstream outliers (weed patches situated away from main infestation). This is the aim of a $1.4 million project driven by Territory Natural Resource Management (NRM) and funded by the Australian Government’s Caring for our Country initiative. It marries with the national priorities: biodiversity and natural icons, coastal environments and critical aquatic habitats, sustainable farm practices, and community skills, knowledge and engagement.

Building on from five years of previous work, funds are helping to manage more than 16 500 hectares of mimosa. To date, much of the infestation has been mapped, 1800 hectares of outliers have been controlled by chemical, biological and mechanical means, 3000 hectares of containment lines have been managed and 13 000 hectares of core infestation are under management control. This containment of core infestations can largely be attributed to four Tipperary land managers in the Douglas Daly region.

Funding is also equipping traditional owners and Indigenous ranger groups to engage in project planning, decision making, ground and aerial treatment, surveying of mimosa and management and protection of cultural sites. The ranger groups include: Asyrikkarrak Kirim at Peppimenarti, Yantjarrwu at Woodycupaldiya, Thamarrurr at Wadeye (Port Keats) and Malak Malak at the Daly River.

Project manager Caroline Biggs says mimosa delivers devastating environmental and economic impacts due to its invasive nature. The insidious weed forms dense prickly stands and grows up to six metres high, reproducing rapidly with infestations capable of doubling in size annually to form large monocultures.

“Anson Bay and the associated coastal floodplains support activities such as pastoralism, fisheries, wild harvest and tourism,” she says. “With nearly 200,000 hectares of floodplains potentially under threat from mimosa infestation, the cost of not managing this invasive species in these catchments is likely to far outweigh the cost of on-going control.”

While protecting native floodplain habitat, the land’s productivity and access to culturally significant sites is improved. And with more non-infested waterholes the pressure on existing clear waterholes when harvesting bush tucker is reduced.

“By managing and protecting culturally significant sites at risk of or isolated by mimosa infestations, traditional owners are able to maintain and re-establish cultural connections with country while reducing bush tucker pressure placed on non-infested areas in the region,” Caroline says.

Controlling re-infestations to enable regrowth of existing native vegetation is ongoing. The short-term benefits are local employment, improved knowledge and skills and the development of a strategic control and management plan for mimosa within the catchments. The longer-term benefits are the capacity building of the groups and their collaboration in the containment of mimosa.