Patches that are larger, more species rich and less disturbed are likely to provide greater biodiversity value. Additionally, patches that are linked to other patches of the ecological community or other types of native vegetation, whether ecologically or by proximity, are particularly important as wildlife habitat and to the viability of those patches of the ecological community into the future, provided that threats are adequately managed.
Therefore, in the context of actions that may have ‘significant impacts’ and require approval under the EPBC Act, it is important to consider the environment surrounding patches that meet the condition thresholds. Some patches that meet the condition thresholds occur in isolation and require protection, as well as priority actions, to link them with other patches. Other patches that are interconnected with other native vegetation have additional conservation value. In these instances, the following indicators should be considered when assessing the impacts of actions or proposed actions under the EPBC Act, or when considering recovery, management and funding priorities for a particular patch:
Larger size and/or a large area to boundary ratio – patches with larger area/boundary ratios are less exposed and more resilient to edge effect disturbances such as weed invasion and human impacts;
Evidence of recruitment of key native plant species (where possible and including through successful assisted regeneration);
Good faunal habitat as indicated by patches containing a range of features such as diversity of landscape (e.g. pools), and that contribute to movement corridors;
High species richness, as shown by the variety of native plant species or high number of native fauna species;
Presence of listed threatened species or key functional species such as key pollinator and dispersal animals;
Areas of minimal weeds and feral animals or where these can be efficiently managed;
Evidence of low disturbance to natural soil structure and potential for good functional attributes such as nutrient cycling;
Connectivity to other native vegetation remnants or restoration works (e.g. native plantings) – in particular, a patch in an important position between (or linking) other patches in the landscape; and
Acknowledgement of the local value and regional representation of a patch, noting that these grasslands are better known in certain regions than others. For instance, most studies have centred on the Yarram and Western Port grasslands, while the Otway Plains, Port Phillip and Bass road occurrences remain poorly known.
1.8Areas critical to the survival of the ecological community
The areas considered critical to the survival of the South East Coastal Plain Grassland cover all patches that meet the key diagnostic characteristics and condition thresholds for the ecological community plus buffer zones around the patches. This is because the ecological community has a very restricted geographic extent, is highly fragmented and, therefore, is vulnerable to edge effects.
Areas of adjoining native non-grassland vegetation may be critical to the survival of the ecological community because they act as a buffer protecting the grassland edges, and provide linkages with other native vegetation across the landscape. The surrounding environment and broader landscape context should also be considered.
Grassy woodlands once occurred extensively across the plains in the south Gippsland region. They were interspersed with pockets of sparse tree cover that were effectively open grassland interspersed with seasonal wetland and swampy shrubland. However, much of the South Gippsland Plain has been heavily modified for agriculture while areas on the eastern fringe of Melbourne are increasingly subject to urban and peri-urban land uses.
The grasslands in the Clyde – Koo-Wee-Rup region may have arisen as a consequence of Aboriginal burning practices applied to the edges of dense swamp scrub to keep access open and increase the abundance of food plants and animals (Cook and Yugovic, 2003; Yugovic, 2011). Cook and Yugovic (2003) hypothesise that the burning regimes (which ceased after European colonisation) thinned out the shrub cover (predominantly Melaleuca) at the wetland margins and fostered development of an open, grassy ground layer. They note that the early European explorers of Western Port recorded that large areas of land were burnt, and Yugovic (2011) cites a report of one area having become scrubby since the land was no longer being periodically burned. He also notes that while Melaleuca can regenerate after fire, it is not tolerant of high fire frequency. As it reproduces by both root suckering and seedlings, it is able to spread rapidly under suitable conditions (such as absence of frequent fire).
However, Sinclair (2007) postulates that other factors may have been of greater importance in giving rise to grasslands at Safety Beach, Mornington Peninsula. He suggests that the former presence of blackwood indicates that fire may not have been of sufficient intensity to suppress swamp paperbark. He also cites evidence that most patches of Swamp Scrub ecological community at this location coincided with drainage lines and depressions and that some patches have maintained essentially the same boundaries for over 150 years. He hypothesises that relief and soil type have been more important factors than fire regimes in restricting Swamp Scrub in this area, though he notes that they are not mutually exclusive and may interact in their influence.
Essentially identical vegetation also occurs west of Port Phillip Bay (Yugovic pers. comm., 2014). Poa floodplain grassland with sparse Duma florulenta (tangled lignum) occurs beside the Barwon River on the Bellarine Peninsula, while glycophytic Poa labillardierei grassland (Plains Grassland) and/or Brackish Grassland also occur in the Painkalac Creek estuary, and at Curdies Inlet, Belfast Lough and Lake Yambuk. Yugovic (pers. comm., 2014) considers that the community is likely to have occurred on the floodplains of the lower tracts of major streams in south-west Victoria prior to European settlement. Remnants surviving from agricultural development may have been overrun by shrubs (particularly by Leptospermum lanigerum (woolly tea-tree) to form Swamp Scrub although such behaviour is not known from woolly tea-tree. Study of historical survey plans is required to determine their former extent.
The western occurrences were apparently more localised compared to the east where maximum development was reached at the Yallock Creek grassland on the southern edge of the Kooweerup Swamp. This may be related to relatively dense hinterland vegetation in Gippsland associated with the Kooweerup Swamp and Strzelecki Ranges and the corresponding greater need for Aboriginal inhabitants to maintain coastal pathways. Although the western occurrences may have been only a small part of the total extent they may now provide a higher proportion of surviving vegetation, with the eastern occurrences severely reduced.
The remaining total area of largely intact remnants on the South Gippsland Plain has been estimated at less than 15 ha, with perhaps a further 10 ha of degraded remnants (Frood, cited in DSE, 2004a). All known patches are under 10 ha in size. No more than 0.1% of the original distribution remains (Cook, cited in DSE, 2004a). Equivalent data have not been obtained for the Bass Coast, Port Phillip Bay and western Victorian occurrences, but these are generally very small and are unlikely to constitute a significantly higher proportion of the original extent. The goals of landscape-scale restoration of the ecological community should include maximising connectivity, increasing existing patch size and improving the ecological integrity of patches.