Coastal Saltmarsh Recovery Project - Robbins Passage and Surrounds update June 2022

UPDATE | JUNE 2022

Coastal Saltmarsh Recovery Project Robbins Passage and Surrounds

What and where are coastal saltmarshes?

Coastal saltmarsh wetlands are found in a narrow margin around the coastline of Tasmania in “low energy” and shallow, sheltered intertidal zones. Saltmarsh plants grow from the low tide mark up to the inland areas occasionally flooded by storm tides.

The coastal saltmarsh wetlands in the Circular Head area form the largest coastal wetland system in Tasmania, extending from Shoal Inlet at Woolnorth to East Inlet near Stanley and covering more than 1,300 ha.

Sarcocornia quinqueflora and Juncus kraussi in the tidal zone with bordering Melaleuca ericifolia swamp forest, grading into Eucalyptus forest behind.

Saltmarsh wetlands are unique habitats where salt-tolerant plants such as succulents, herbs, grasses and low shrubs grow. They provide a nursery for many fish species, are an important filter for surface runoff, and are vital summer feeding habitats for migratory birds. Saltmarsh wetlands often display distinct vegetation zoning depending on tidal flooding frequency. In the Circular Head area, the low marsh is inundated by every tide and is characterised by pioneer saltmarsh plants such as Sarcocornia species, and in areas where enough freshwater inputs are available, reed and tussock species such as Juncus kraussi occur.

The mid marsh, which is inundated less frequently, has longer lived shrubs and sedges. The high marsh, which is rarely inundated, is dominated by grasses and rushes and is bordered by Melaleuca swamp forests.

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This project is supported by Cradle Coast Authority, through funding from the Australian Government.

Good gradation and buffer from saltmarsh species such as Sarcocornia quinqueflora through to paperbark fringe (Melaleuca ericifolia swamp forest) and Eucalyptus ovata forest and woodland.

Coastal saltmarsh is listed as a threatened ecological community under the Australian Government’s Environment Protection and Biodiversity Conservation Act 1999.

Coastal saltmarsh areas: stabilise and buffer the coast from storms are an important food source for migratory birds and marine species Bar-tailed Godwit (Limosa lapponica).

Risks to saltmarsh

provide nursery habitat and shelter for fish support highly specialised plants adjusted to salinity and waterlogging act as “buffer strips” to agricultural land and

There are a number of serious threats to

help reduce sediment and nutrients in run-off

coastal saltmarsh areas including:

are an important carbon capture and storage area which may help landholders reach

Weed invasion, particularly by Rice Grass

carbon neutrality in their farming enterprises.

(Spartina anglica). Other significant weed threats include Gorse and Sea Spurge.

Earthworks such as drains and levees that form tidal barriers and impact saltwater and freshwater movement.

Livestock trampling and grazing.

Burning, which changes the species composition and can leave bare soil prone to

Drain earthworks impact saline and freshwater flows, as well as damaging natural vegetation.

erosion and weed invasion.

Rubbish – both dumped and washed-up rubbish.

Nutrients from adjacent farming and industrial land.

Damage from cattle grazing and pugging.

Project update Cradle Coast NRM has funding from the Australian Government up to June 2023.

This project has two main aims: to improve saltmarsh vegetation condition by reducing the presence of Rice Grass, a serious weed threat in the Robbins Passage-Boullanger Bay area, and protecting existing coastal saltmarsh by establishing conservation covenants on saltmarsh ecosystem areas under private ownership.

Rice Grass (Spartina anglica) is an aggressive and troublesome weed continuing to spread in the Robbins Passage-Boullanger Bay area. This highly invasive weed has the potential to impact on boating, aquaculture, community recreation and the estuarine environment. It out-completes the threatened native saltmarsh community and reduces the area of mud flats that provide food and habitat for fish, migratory and resident wader birds, shellfish and crabs.

Rice Grass is a perennial grass which grows 30-130 cm tall. Its green or greyish-green leaves (10-45 cm long) are long and narrow with flat or in-rolled edges. Rice Grass partially dies back in winter, becoming yellowish. The flower head is distinctive: a long erect spike with small yellowish-green flowers. If left unmanaged, individual Rice Grass plants can form clumps that can expand to extensive meadows within a short period of time.

Rice Grass can sometimes be confused with the native grass, Southern Reed (Phragmites australis). Southern Reed is noticeably taller (up to 300 cm) and has a feathery flower head, compared to the narrow spike of Rice Grass.

Above: Rice Grass meadow in Duck Bay with flower head (inset).

Right: Native Southern Reed, Phragmites australis.

The third season of Rice Grass treatment was completed in May 2022. The season was a success with 846 hectares (ha) receiving follow-up treatment (i.e. second treatment or more) while 20 ha received their first treatment. This huge amount of work was only possible because of the dedicated Rice Grass battlers from Circular Head Landcare Group, who contributed a massive 282 volunteer hours this season alone!

To date, nearly 900 ha of Rice Grass infestation have been treated during this project. Rice Grass is treated with Fusilade Forte, a selective herbicide that does not affect native saltmarsh species or seagrasses, quickly breaks down and has very low toxicity to marine animals.

More than twenty private landholders were contacted who had small or large areas of saltmarsh on their land.

As a result, two landholders have entered into a conservation covenant to protect 46 ha of coastal saltmarsh.

The landholder continues to use, own and live on the land but will conserve the natural values of the saltmarsh areas. Both landholders will receive stewardship payments to help them protect and manage the areas and one of the landholders will also receive additional funding to undertake fencing and revegetation along the saline/freshwater margin.

Although the majority of saltmarsh landholders did not wish to enter into a conservation covenant, they did benefit from identifying the mapped saltmarsh areas on their land and receiving technical advice about how to manage or improve the areas long-term.

Get in touch For more infomation and to get involved in the project: Fiona Marshall Agriculture Project Coordinator Phone: 03 6433 8433 Email: fmarshall@cradlecoast.com Website: www.cradlecoast.com

Nick Jamson NRM Project Coordinator Phone: 03 6433 8423 Email: njamson@cradlecoast.com