5 minute read
Salty efforts
RIVERS, WETLANDS, COASTS AND OCEANS
ABOVE: Healthy coastal saltmarsh contains a large variety of species and along with Paperbark (Melaleuca ericifolia) fringe vegetation provides a great buffer for agricultural areas inland.
RIGHT: Rice Grass infestation on a mud-flat near Eagle Point, north of the containment line. This area will be treated as part of the upcoming control season.
S A L T Y E F F O R T S
What many think of as tidal mudflats along our northwestern coastline and inlets, may in fact contain unique and valuable saltmarsh wetlands. These saltmarsh environments contain salt tolerant plants such as succulents, herbs, grasses and low shrubs. They are flooded regularly or occasionally and provide important food sources for migratory birds, a nursery for many of our commercial fish species, and are an important buffer and carbon storage. They are threatened by weed invasion, drainage works, off-road vehicles, rubbish and stock access.
Cradle Coast Authority is working with local community groups, Landcare groups, Tasmanian Land Conservancy and private landholders to improve the condition and protect these threatened saltmarsh areas.
Planning for the Rice Grass control season (December to April) is in full swing. Planning days, reference committee meetings and site inspections with contractors have taken place to determine target areas and the appropriate control strategy.
The control work in the Rubicon estuary will focus on maintaining a “Rice Grass free” zone, north of a “containment line” (between Squeaking Point and Eagle Point), as well as control in strategic areas south of the containment line. Similarly, in the Robbins Passage area, the aim will be for follow-up control of all areas treated in the last few years, as well as some select sites for a first treatment.
The greatest weed threat to the saltmarsh environment is Spartina anglica, or Rice Grass. Rice Grass outcompetes native saltmarsh and invades sand and mud-flats which provide food and habitat for native animals. Rice Grass can also impact boat access, aquaculture production and community recreation.
Negotiations continue with a number of private landholders to establish conservation covenants over their saltmarsh areas and undertake works such as fencing or revegetation to enhance and protect the saltmarsh. A healthy saltmarsh and the adjoining fringe vegetation, which is often the threatened Melaleuca ericifolia Swamp Forest, provide really important coastal stability and buffers against storm surges.
Get in touch with Project Officer, Nick Jamson for more information: njamson@cradlecoast.com
Sea Spurge infesting Pardoe Beach
S E A S P U R G E B I O C O N T R O L R E L E A S E D I N T A S S I E
Sea Spurge (Euphorbia paralias) is one of the most prolific coastal weeds in Tasmania and is a serious threat to coastline biodiversity. It came to Australia from the coastal regions of France and swiftly took over the coastline from Geraldton in Western Australia, south and around the coast towards Sydney. Sea Spurge can reach densities of 150 000 to 180 000 plants per hectare. Long distance dispersal of the plant occurs when the buoyant and saltwater-resistant seeds are carried by ocean currents to new areas of coastline.
The weed invades habitat for some shorebirds, including the threatened Hooded Plover. Sea Spurge also outcompetes native plant species, which can affect coastline stability. The CSIRO has been testing a new method of controlling Sea Spurge – a fungus called Venturia paralias from the weed’s native habitat in France. The fungus initially infects the leaves, which can create a lesion on the leaf, then it can move into the stem. Once in the stem, it produces a characteristic dark lesion on the stem, which makes it very difficult for the plant to transport water up and down the stem.
Venturia paralias has been released on three separate beaches so far in Tasmania (Duck Creek on the west coast, Bakers Beach and Low Head), as part of the pilot program to test if it will spread and thrive in Australian conditions. This CSIRO project has been overseen locally by Jon Marsden-Smedley with his extensive experience in fighting Sea Spurge across remote south-west Tasmania with the Wildcare Group SPRATS.
CSIRO is working with the Tasmanian Parks and Wildlife Service and local councils to extend approval of the release program through local volunteer groups.
S E A S O N A L D U N G B E E T L E A C T I V I T Y
Over recent years, the Cradle Coast Authority NRM team have been involved with bringing a new species of spring-active dung beetle to Tasmania, Onthophagus vacca. The idea has been to establish nursery colonies on beef and dairy farms, allow them to breed for a generation in a protective nursery cage, and then release the new generation of young beetle progeny into the environment.
Six such nursery colonies have been established so far, across the districts of Oldina, Mooreville, Mawbanna and Cressy. To determine whether these nursery colonies have been successful, and to identify activity of any other dung beetle species out there in the region during spring, a modest dung beetle monitoring program was started this spring. Monitoring involves setting up a number of pitfall traps on farms where the new spring-active dung beetle nursery colonies have been established. The traps need to be set and checked for 2-3 days in succession, to allow for varying weather conditions which may affect dung beetle foraging behaviour patterns (i.e. if it is very windy and wet, not many beetles will be out and about!).
The first round of spring monitoring was undertaken in mid-October, with seasonal conditions at this time not particularly conducive to dung beetle activity. October 2021 was the 10th wettest October on record, with rainfall 69% above average for Tasmania for this month! Burnie recorded its highest daily total rainfall across all years on October the 15th of 38.4 mm, with 135.8 mm reported for the monthly total. Oldina reported 192.2 mm of rainfall across the month of October, with five rainfall events of 20 mm or more.
Small numbers of the dung pad dwelling Aphodius femetarius were observed at Mooreville and Oldina during October, but little else. This species of beetle doesn’t tunnel through the dung pad and bury a proportion in the soil but resides in it. English in origin, this species will consume a notable quantity of dung when in sufficient numbers.
November monitoring proved more fruitful, with much higher numbers of A. femetarius observed at Oldina and Mooreville. Moderate numbers of Onthophagus binodis were observed at one site at Oldina and Mooreville, with a couple of the native Australian species Onthophagus australis observed at Oldina. None of the recently introduced spring active O. vacca have been observed during monitoring as yet, but hopes are high for December as higher temperatures finally arrive.
