Sheoak Grassy Woodlands Recovery

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Sheoak Grassy Woodlands were once widespread on Eyre Peninsula, but largely due to clearance and intensive grazing, they are now a threatened ecological community.

More formally known as Drooping Sheoak Allocasuarina verticillata Grassy Low Woodland, the ecosystem is listed as Vulnerable in South Australia where it occurs on clay loams of low hills (DEH, unpublished). It is not rated where it occurs on sandy coastal plains.

A nomination has been made under the Environment Protection and Biodiversity Conservation (EPBC) Act 1999 for listing Calcarenite Dune Woodland of South Eastern Australia as Endangered. This nomination encompasses particular areas of Sheoak Grassy Woodlands on lower Eyre Peninsula and is currently being considered.

Decline of Sheoak Grassy Woodlands

Since European settlement there has been a significant decline in the condition and extent of Sheoak Grassy Woodlands on Eyre Peninsula. The reasons for this decline include:

• grazing by sheep, cattle, horses, rabbits and kangaroos
• clearance (particularly of the dominant overstorey species, Drooping Sheoak)
• invasive weeds
• changed fire patterns.

Sheoak Grassy Woodlands have declined significantly, largely due to grazing and clearance

The following maps show how the distribution of Sheoak Grassy Woodlands on Eyre Peninsula has changed over time, with only small areas of the once extensive Sheoak Grassy Woodlands remaining on Eyre Peninsula.

• see 1800s map
• see 2000 map.

The decline of Sheoak Grassy Woodlands, and the presence of introduced cats and foxes, has contributed to the decline of numerous native animals on Eyre Peninsula. These include the Greater Bilby (150Kb PDF), Brush-tailed Bettong (150Kb PDF), Tammar Wallaby, Common Brushtail Possum, Bush Stone-curlew (150Kb PDF) and Diamond Firetail.

Grazing

To the early settlers, the open nature of Sheoak Grassy Woodlands made the grassy woodlands ideal for running sheep. But intensive stock-grazing, combined with the short-lived nature of sheoaks, was a main factor in the vegetation community's decline. Overgrazing prevented the regeneration of sheoaks for the whole reproductive lifespan of existing trees. These existing sheoak trees eventually died of old age, having not recruited any new seedlings. The population was all but wiped out, with invasive weeds and soil erosion also impacting grazed areas.

High grazing pressure is still preventing the growth of sheoak seedlings and preventing native grasses from producing seed and forming tussocks. This has reduced food and habitat availability for many small animals that use sheoaks and tussock grasses for food and shelter.

Recovery

Although Sheoak Grassy Woodlands are poorly conserved on Eyre Peninsula, some patches with good understorey remain and others are being restored. Areas of protected sheoak woodlands occur in some of the large reserves, such as Lincoln and Coffin Bay national parks and Hincks Conservation Park, as well as in a number of smaller reserves. In addition, a number of Heritage Agreements contain Sheoak Grassy Woodland.

Grasses are regenerating in the understorey of Sheoak Grassy Woodland

We are working with the community, including Friends of Parks Groups, Green Corps, the Eyre Peninsula 4WD Club and other interested individuals, to restore Sheoak Grassy Woodlands in our region. Recovery actions to address threats include:

• revegetation by direct seeding and planting tube stock - Drooping Sheoaks are easy to propagate from seed and grow rapidly if grazing pressure is low.
• monitoring vegetation response - Fenced exclusion areas have been erected in Coffin Bay National Park to determine the grazing impact of various herbivore species and how the vegetation responds to lower grazing pressure. This monitoring is supported by field observations and scat analysis. Herbivore grazing and seed availability appear to be the main factors limiting the survival and growth of new sheoaks.
• reducing grazing pressure - Many native plant species that were once present in Sheoak Grassy Woodlands, including native grasses, will recover if herbivores are controlled and grazing pressure is low over a number of years. In Coffin Bay National Park, grazing pressure has been reduced by the removal of horses and cattle, and the ongoing control of rabbits and Western Grey Kangaroos. The closure of artificial water sources has also helped to maintain low numbers of kangaroos. Browsing damage has been reduced in the area with high herbivore control.
• controlling introduced predators - Since fox baiting was commenced in Coffin Bay National Park, Heath Goannas are more abundant and Fairy Terns have begun nesting on Seven Mile Beach.

Green Corps team planting sheoak seedlings		Direct seeding sheoaks		Grid for monitoring sheoak seedling response

More information

• Sheoak Grassy Woodlands on Eyre Peninsula brochure (400Kb PDF)
• Restoring Sheoak Grassy Woodlands on Lower Eyre Peninsula report (1.6Mb PDF)