Australasian Plant Conservation
Originally published in Australasian Plant Conservation 18(1) June - August 2009, p 14-15
Protecting Swamp Sheoke: an endangered
species of Victoria’s Wimmera Woodlands
Trust for Nature—Wimmera, Longerenong, Vic.
Trust for Nature (Victoria) has been active
in recent years targeting vegetation types that traditional instruments of
permanent protection (including the National Reserve System) have struggled to
access, secure or significantly restore. Historically the factor determining
what was or wasn’t preserved was the real and perceived value and suitability
of the land for production, much as it is today.
This has resulted in a trend of choosing to
protect or not to protect based largely on soil type. The pattern that has
inevitably emerged is one where there is now an over-representation of certain
EVC’s (Ecological Vegetation Classes) protected on public and private land.
Historically, this has been at the expense of other EVC’s which have made way
for agricultural production and other forms of development. This pattern of
over- and under-representation of vegetation types is well illustrated in the
Wimmera Region of western and north-western Victoria.
The Bio Conservation Status of these EVC’s
now reflects this worrying historic pattern. Vegetation types traditionally
protected voluntarily on a large scale on private land, have been those on
poor, sandy or skeletal soils. Equally there has been less protection of Plains
Woodlands, Plains Grassy Woodland, Shallow Sands Woodlands, Plains Savannah,
Low Rises Woodland and other vegetation types that occur across the more arable
parts of the region on deeper, more fertile soils.
To complete the pattern, these same vegetation
types occur in only very small amounts in public reserves, having been
overlooked for reservation originally in favour of mountainous, forested and
less arable land. Required now is an accelerated effort to protect and restore
the best of what remains of the woodlands on private land and the various
endangered EVC’s they comprise. There is much less now to protect, what remains
is largely fragmented and the threats upon these ecosystems is, without any
long-term security, greater than ever.
Woodland with Swamp
Sheoke representing a secondary tree layer below Grey Box (Eucalyptus microcarpa) trees.
Photo: Adam Blake
Casuarina obesa (Swamp Sheoke) has endangered species status in Victoria and is
listed as threatened in the state under the Flora and Fauna
Guarantee Act 1988 (Vic.). Only nine known populations of this species
occur in Victoria, eight of them found in central parts of the Wimmera region,
west of Horsham. It also occurs naturally in south-west Western Australia where
it occupies a greater range, in places being common. There is also one known
population in south-west New South Wales.
All of the nine extant Victorian populations
occur on private land and none occurs in a conservation reserve—a situation
typical of other species on the agricultural Wimmera plains. But there is
another set of obstacles to confront if protection is
to result in the short- and long-term conservation of this species. Research
previously conducted indicates the extant, isolated populations in the Wimmera
are unisexual. This presents a problem for a wind pollinated species,
occurrences of which are separated by several kilometres. It is therefore clear
that permanent protection and rehabilitation is only a first (but fundamental)
step in conservation of the species. Because specimens from the Wimmera
populations are known to show considerable variability, this makes protection even
more urgent if we’re to discover more about this little known member of the Casuarinaceae family.
Recently in the Wimmera, using GIS
technology and by engaging with the landholder, a large population covering
about 30 ha and representing thousands of specimens was ‘re-discovered’, for
years known only to family members and more recently Trust for Nature staff. It
hasn’t yet been established whether or not it is one of the aforementioned
eight Victorian recorded occurrences. If so, it is possibly the largest, and
potentially the healthiest and least fragmented. It remains largely unmodified
as previous care and threat abatement activities by the landholder had
preserved habitat quality. Light grazing had kept the grassy ground cover open
and diverse, hardly reducing total cover in the areas providing habitat.
Sheoke provides the middle layer of small trees in
the vegetation, in some places densely beneath an open canopy of (in this case)
Grey Box (Eucalyptus microcarpa) and Black Box (E. largiflorens) trees. It grows on heavy soils at a
location slightly higher than, but fringing, a seasonally inundated area.
Preliminary bird surveys have turned up a number of important temperate
woodland birds indicating a level of ecological function. These include Jacky
Winter, White-browed Babbler, Diamond Firetail, Southern Whiteface and Brown
Treecreeper. Now protected on a 90 ha Trust for Nature Covenant, itself
connecting a large core area of public land, this represents the first Swamp
Sheoke population to be permanently protected on land title.
Protection with a Conservation Covenant
One of the stated objectives in the Action
Statement for this species (Walker 2003) is to protect existing populations
from threatening processes and encourage natural regeneration. Another
long-term objective is to ensure that single sex sites contain at least 100
plants of the opposite sex by 2010. It is hoped that with the long-term
security of a covenant in place, this can be achieved at this newly protected
site (if this population proves to be unisexual). Fencing of the area is the
first task to be undertaken. This will allow the immediate cessation of grazing
for an extended period of time and the more controlled use of grazing in the
covenant for conservation purposes over time.
Increasing Habitat Extent
In an effort to target areas where net gain
opportunities of endangered vegetation types occur, Trust for Nature
collaborated with Greening Australia. Those areas only lightly modified with
grazing and with reasonable tree density are seen as areas that could
cost-effectively be restored for conservation, particularly if they met other
key conservation significance criteria. It is
critical that opportunities to increase the total extent of some habitat are
sought if more ecological balance is to complement and be integrated into
Restoration of this Swamp Sheoke community
will be achieved with approximately 10 ha of revegetation by Greening Australia
in areas previously modified by grazing. Incentives are being provided by Trust
for Nature to the landholder as part of a Victorian Government funded
Department of Sustainability and Environment / Trust for Nature statewide
project, ensuring the permanent protection and ongoing management of this and other
significant habitat. These actions will help the Swamp Sheoke and also benefit
a range of other significant species, for example the endangered Red-tailed
Black-Cockatoo (also listed under the Flora and Fauna
Guarantee Act 1988), which this covenant assists by its position, and by
providing habitat and both of the cockatoo’s two critical food trees.
Trust for Nature plans to build upon these
partnerships in order to protect more endangered habitat. Identifying and
protecting the most valuable remaining vegetation in the endangered category is
fundamental to a landscape scale vision such as Habitat 1411, a
project that plans to restore ecological function across a large area of
temperate Australia from the ocean to the outback, south to north through
Walker, I. (2003). Action Statement No.133 Swamp Sheoke Casuarina obesa. Department of Sustainability
and Environment, Melbourne.
1 See also preceding article by Andrew Bradeyin this issue