Large old trees

The site is notable for the presence of fourteen identified River Red Gums (Eucalyptus camaldulensis) that qualify as large old trees according to the Department of Sustainability & Environment’s criterion for Floodplain Riparian Woodland (i.e. trunk diameters of at least 0·8 m). These are marked with cyan crosses on the aerial photograph on page 95. The maximum diameter was 1·45 metres, which makes it one of the largest indigenous trees in Boroondara, hundreds of years old. The health of all but two of the trees was rated by the author as good. The exceptions were one in very good health and one in fair to good health.

Fauna of special significance

The significant fauna species in the list below have been observed in the Burke Road Billabong site. The conservation status ratings (e.g. endangered or vulnerable) are explained in Section 2.5.2 (page 18).

Full fauna list

The following list includes all fauna species recorded at the site. The names of species not detected in the present study are accompanied by the date of the most recent record. Asterisks indicate introduced species and obelisks (†) indicate that breeding was confirmed.

Site significance rating

This site is part of the Department of Sustainability & Environment’s BioSite number 5063, which extends along the Yarra River from Burke Rd to Chandler Hwy, on both sides of the river. The significance level given in the BioSites database is ‘Regional’, but this was based on information and criteria from the 1990s that are now obsolete. The following is an assessment against the current BioSites criteria of the Department of Sustainability & Environment (Amos 2004).

Ecological integrity & viability

BioSites criterion 1.1.1 attributes Local significance to ‘All parts of riparian systems with riparian vegetation present’, which applies to this site.

BioSites criterion 1.1.2 attributes Local significance to ‘Areas of 100 ha or more of contiguous native vegetation in a heavily fragmented landscape’, which applies to the corridor of vegetation along the banks of the Yarra River (extending upstream and downstream of this site).

BioSites criterion 1.2.6 attributes Regional significance to links of regional-scale ecological corridors, which applies to this site because its vegetation represents a component of the Yarra River corridor.

Regionally threatened Ecological Vegetation Class

According to the criteria of ‘Victoria’s Native Vegetation Management – A Framework for Action’ (NRE 2002a), even quite degraded native vegetation belonging to an endangered EVC (including both EVCs on this site) has a conservation significance rating of High. The conservation significance rises to Very High where the habitat score is at least 40% within an area of an endangered EVC, and the habitat score for part of the Burke Road Billabong site was found to be 51%.

According to BioSites criterion 3.2.3, State significance applies to any site with a ‘remnant patch’ whose conservation significance is High or Very High due to the presence of a threatened EVC. This applies to the present site, noting that the area and native understorey cover of the native vegetation easily meets any reasonable definition of a remnant patch.

Rare or threatened plants

The site has a modest population (approximately one dozen plants) of Lepidium pseudohyssopifolium, which is listed by DSE (2005a) as suspected (but not confirmed) to be rare or threatened. BioSites criterion 3.1.2 attributes Regional significance to such a site, taking into account that the species is not endemic to Victoria.

The site also supports ten other species of plants that are threatened in Boroondara, some of them in abundance. Each one of the species with viable populations gives the site Local significance according to BioSites criterion 3.1.5.

Rare or threatened fauna

It is not clear how many of the significant fauna species recorded in this site have viable populations that rely to a substantial degree on the site’s habitat, other than the Victorian Smooth Froglet (which has been recorded repeatedly from the billabong). However, it only takes one such species for the site to qualify for Local significance according to BioSites criterion 3.1.5.

Waterway protection

All riparian vegetation has a Very High hazard rating for waterway protection according to Appendix 1 of Victoria’s Native Vegetation Framework (NRE 2002a). This is separate from conservation significance, and indicates the level of importance that should be placed on protecting, restoring and revegetating riparian vegetation such as in the present site.

Threats

The following threats to the site’s ecological values are presented in a form to suit the Department of Sustainability & Environment’s ‘BioSites’ database.

Past management and revegetation

The site appears to have been historically managed as a grazing property. Old drums and other metal waste have beendumped by the billabong. The drums may have had farm chemicals in them, and leakage into the billabong may explain the apparent paucity of aquatic life.

In recent years, there has been a small amount of revegetation in the southeast of the site, comprising only tree species.

Expanses of pasture grass and weeds in the ‘pastoral woodland’ area had grown rank at the time of the inspection for this study (March 2005). Other serious but tractable weeds, such as Blackberry and Hawthorn (Crataegus monogyna), were also rampant. The exception was Gorse (Ulex europaeus), which had been sprayed recently with a reasonable degree of success.

Overall, the site is not receiving the level of management effort required.

Priority actions

1. Very important and urgent: Devise and implement a staged program to control blackberry and Hawthorn, and follow up the recent control of Gorse. (These species are all declared noxious weeds.) Use chemical(s) that do not pose a serious threat to the herbaceous rare plant, Lepidium pseudohyssopifolium, which grows among some of the blackberries. Near the billabong, use a chemical or method that presents low risk to the aquatic environment. Aim to remove these weeds over several years, synchronised with a program to plant indigenous shrubs (particularly Coprosma quadrifida, Melicytus dentatus, Melaleuca ericifolia and Callistemon sieberi) to provide substitute habitat for small birds such as wrens. These actions probably require cooperation between the organisations responsible for the Crown land and VicRoads property.

2. Destruction of the weeds, Sweet Pittosporum (Pittosporum undulatum) and Box Elder (Acer negundo), is not quite as urgent as the noxious weeds just discussed. However, depending on the method employed for removing the Hawthorn, it may be economical to do so in conjunction with the Sweet Pittosporums and Box Elders. The importance and urgency are both moderate.

3. Spray the needle-grass (Nassella/Stipa ?neesiana) on and beside the slashed vehicle route to the Melbourne Water sewer inspection point in the northwest of the site. This weed species appears to have been spread by the slashing or use of this route. Spraying should be done in November, when it can be readily identified, with follow-up in subsequent Novembers. The importance is moderate and the urgency is high.

4. Arrange testing for chemical contamination of water and sediment in the billabong. This is because of the unexpectedly low aquatic life (other than algal bloom) that was seen during the inspection of the site for this report. This should be done urgently and is of high importance. Carp should be considered as an alternative explanation.

5. Collect a small proportion of the seed of each plant of Lepidium pseudohyssopifolium and Rapanea howittiana, to allow propagation for planting within the site or in secure locations elsewhere along the Yarra River (e.g. Yarra Bend Park or Freeway Golf Course).

Future revegetation

Development of a program of future revegetation would require knowledge of plans for the future of the Crown land, the VicRoads property and the part of the golf club land that lies within the site. A landscape plan would be highly desirable.

Some recommendations for revegetation are expressed in Priority Actions 1 and 5 above. The western bank of the billabong, where the Main Yarra Trail passes close to the billabong, could be a high priority for bushland rehabilitation and creation of a safe, attractive access to the billabong.

Species of plants that are growing in the site and would be suitable for collection of seed or cuttings are underlined in the full flora list above.

If it becomes possible to obtain plants of Calystegia sepium that are known not to be genetically contaminated by the serious weed, Calystegia silvatica, they would be ideal for planting by the river and billabong. A single plant of this species (or another indigenous scrambler or climber, such as Calystegia marginata) next to the billabong would be enough to raise the habitat score by ten percentage points.

Records should be kept of any planting done in this (or any other) site, including species, numbers and locations.

Monitoring

Prior to this study, the only pre-existing data suitable for ecological monitoring were the meticulous records of frogs by Ewen McGilp in 1994. The present study could not inspect the billabong during a suitable season to provide complementary frog data to allow a comparison with McGilp’s data, other than to confirm that the Victorian Smooth Froglet remains.

The following items have been gathered to provide a baseline for future monitoring:

• Photographs 1, 3, 4, 5 and 6 as displayed on pages 97 & 104, with locations and orientations shown on the aerial photograph on page 95. All were taken on 30th March 2005. Original digital images are available separately. Repeat the photographs about every two years. Check tree foliage density, the abundance of weeds and structural changes in the vegetation.

• The flora lists for the various parts of the site, as provided beneath the heading ‘Full flora list’ above.

• Ratings of weed severity within each part of the site, stored in the database of this study.

• Population sizes of scarce plant species, as indicated beneath the heading ‘Flora of special significance’ above.

• Tree health ratings, as stored in the geographic information system data from this study and summarised above.

• The habitat score determination for the zone around the billabong, as marked with a dashed line on the aerial photograph.

The original field data sheets are available separately. Repeat every two to four years. Check the abundance of weeds, structural changes in vegetation, changes in habitat score and the species present.

Monitoring photographs for the Burke Road Billabong, taken on 30th March 2005

The locations and orientations of the photographs are shown by numbered arrows on the aerial photograph on page 95. Site 6, Photo 3. A large River Red Gum in good health at the north of the billabong. The purpose of the photograph is to show the tree's overall condition and the luxuriance of its crown. The leaves of Box Elders are turning yellow for autumn.	Site 6, Photo 4. A westward view of the northeastern shore of the billabong, taken from 2 m south of an extremely large River Red Gum. The ground is bare due to a record flood seven weeks prior. Coprosma quadrifida plants have died from waterlogging.
Site 6, Photo 5. Looking east over the southern part of the billabong, from a pile of metal rubbish in the billabong's southwestern corner. The large tree on the righthand edge is marked on the aerial photograph on p. 95. The River Red Gums in the eastern end of the billabong had been flooded for at least seven weeks (and probably rather longer) when this photograph was taken.	Site 6, Photo 6. Looking southeast between the billabong and the Main Yarra Trail, taken at the intersection of two informal, well-worn footpaths. The purpose of the photograph is to show the present weedy state of an area that should be rehabilitated by weed control, revegetation and possibly an improved path to the billabong.

Information sources used in this assessment

• A vegetation and habitat survey by Dr Lorimer for one hour and forty minutes on 8th March 2005 and eight hours, fortyfive minutes on 30th March 2005, using this study’s standard approach described in Section 2.3. This included:

° Compilation of lists of indigenous and introduced plant species in each of four parts of the site, including the species’ abundances and the threat level of all weed species in each area;

° Mapping, assessment and documentation of populations of plant species that are rare or threatened in the site or more generally;

° Weed mapping;

° Assessment of habitat score;

° Individual assessment of all large old trees;

° Photography for monitoring;

° Incidental fauna observations; and

° Checks for fauna habitat, ecological threats and management issues;

• Information from the Department of Sustainability & Environment’s flora, fauna and BioSites databases;

• The Department of Sustainability & Environment’s BioMaps of the area;

• Aerial photography from August 2004;

• Maps of geology and topography produced by agencies of the Victorian government.

Recommended further investigation

• It would be desirable to investigate the vegetation of the Burke Road Billabong when it dries out. All nearby billabongs were found to support rare flora, and the same is likely in the Burke Road Billabong. Particular attention should be paid to the possibility that Amphibromus fluitans occurs in the billabong, which would represent National significance as the type locality for that species.

• A survey of frogs in the billabong would be desirable in spring. It would also be desirable to check for the nationally threatened Warty Bell Frog (or Growling Grass Frog) in hot summer weather.

• As noted above, tests should be conducted for pollution of water or sediment in the billabong, prompted by the unexpected paucity of aquatic life observed in the inspection of the site for this study. Carp should be considered as an alternative explanation.

• This site would be one of the most promising in Boroondara for any survey of reptiles or bats.