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 Rice grass (Spartina anglica) is a Northern Hemisphere intertidal saltmarsh plant that was deliberately introduced to Tasmania between the 1930s and the 1970s. Rice grass was introduced for its potential benefits to coastal engineering and agriculture but the spread of rice grass has emerged as a serious problem, degrading Tasmania's estuaries. It has become established in seven regions of the State's coastal zone including Australia's two largest infestations, which occur in the River Tamar and the Rubicon estuary. In 1997, rice grass occupied 590 ha of the State's intertidal zone, believed to be a very small percentage of its potential habitat. Rice grass has the potential to displace native plants, (such as seagrass and saltmarsh plants), fish species, and alter the habitat of birds and other wildlife. There has been growing concern that changes to water flows and estuary nutrient cycles caused by rice grass threaten the sustainability and expansion of Tasmania's aquaculture industry. Rice grass is also threatening Ramsar listed wetlands and has had a detrimental effect on recreation and tourism areas around the State. Rice grass is typical of an invasive weed species. Its dense growth habit and rhizome/root network act as a trap for sediments and debris altering the natural rate, magnitude and location of sediment deposition and erosion. These processes elevate shorelines and river banks to create terraces and marsh islands by promoting deposition and accretion which may have considerable impacts on the hydrodynamics and ecology of estuaries, aquaculture, wild fisheries, tourism and recreation. There is particular concern about the impact of rice grass on the biodiversity and integrity of native saltmarsh and seagrass communities, migratory birds and other near-shore marine fauna, such as estuarine invertebrates and fish. Several Ramsar listed wetlands are also threatened by the continued spread of rice grass including Moulting Lagoon, Great Oyster Bay and Pittwater. There is growing concern that changes to hydrodynamics and estuarine nutrient cycling caused by rice grass threatens the sustainability and expansion of Tasmania's aquaculture industry, particularly with respect to the intertidal leases (e.g. Little Swanport estuary, the Rubicon estuary and the Smithton region). The weed also threatens to destroy the habitats of juvenile fish and other marine species and therefore may seriously impact on adult fish populations that form valuable commercial and recreational fisheries, as well as the ecologically important non-commercial species. Tourism and recreation have also been impacted by the spread of rice grass. For example, in the River Tamar, well-established infestations inhibit public access to the shoreline, many private boat ramps and jetties have been rendered non-functional and several once popular sandy beaches have been transformed to muddy rice grass meadows. Thus, rice grass has reduced the utility value and aesthetic appeal of the River Tamar shoreline and has effectively reduced its attractiveness to residents and tourists. In the mid-1990s National Parks and Wildlife became aware of the problem of rice grass in the Derwent River and St Helens area and staff utilised early control techniques to reduce rice grass infestations in these areas. The community in Port Sorell was also aware of the problem of rice grass and received funding from Landcare to trial several control techniques. The Rice Grass Advisory Group (RGAG) was formed in 1995 to provide advice and direction on rice grass management for all infested regions in Tasmania. RGAG received funding from Coastcare and Fishcare Australia to research the ecology, impact and control of rice grass and to develop a management strategy. The Strategy for the Management of Rice Grass (Spartina anglica) in Tasmania Australia was completed in 1998 and identified the following points as vital in achieving the vision of the strategy, being to reduce the area of infestation of rice grass in Tasmania.
DPIWE received a comprehensive three year funding package from the Natural Heritage Trust Fisheries Action Program in 1998 to implement the management strategy and in 2002 a further one year funding from NHT was allocated for the project 'Habitat Restoration in Rice Grass Infested Estuaries in Tasmania'. A mobile and specialised team of three DPIWE staff was established and started work in Bridport, Little Swanport, St Helens and the Derwent River. Due to the isolated and hostile work environment, Hovercraft Survey was contracted to assist in surveys and have been awarded the contract each year since. As the methods developed and the team became adept at treating Rice Grass, larger areas in the Smithton area were treated in 2001-02. The team has also assisted the community of Port Sorell in maintaining a Rice Grass Free Zone. Contract sprayers (Beechworth PTY) were introduced in 2002 to assist in the Smithton region with larger infestations. Three successive control seasons have demonstrated unprecedented results in controlling and containing rice grass infestations with greater than 99.9% reduction of rice grass in 3 of 7 effected areas. This success has resulted in eradication of rice grass in Bridport, Little Swanport, St Helens and the Derwent river areas becoming a realistic management objective through the continued support of industry, community and the DPIWE.
Excellent results have also been achieved in the Smithton area with over 10 ha been treated to date. The management team and the contractors expected to treat large areas in Duck Bay and the Duck River during 2003. These results have seen a new outlook for the Smithton area with eradication becoming as long term objective if funding and stakeholder support is maintained. Rice grass infestation for each year of treatment and management objectives Area 1997 2000 2001 2002 % reduction Objective Bridport 3 ha 5 ha* 100 m
2
* 10 m
2
* 99.98% Eradicate Little Swanport 10 ha 10 ha* 250 m
2
* 30 m
2
* 99.98% Eradicate River Derwent 1 ha 1 ha* 10 m
2
* 1 m
2
* 99.99% Eradicate St Helens 1 m
2
1 m
2
* 1 m
2
* <1 m
2
* Eradicate * Represents Area of rice grass treated in that year. In recognition of the success of the programme and its contribution to the restoration of Tasmania's natural waterways, the project was awarded the prestigious Australian Water Association, Tasmanian Water Environment Merit Award 2000-01. The award is a reflection of the considerable commitment, cohesion and vision shared by all stakeholders. Strategy for the Management of Rice Grass (Spartina anglica) in Tasmania, Australia. 1998. |
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