It is essential that vegetation management of the reserve does not conflict with the recommendations given to protect Aboriginal heritage values. The Aboriginal Heritage Assessment found that there are no significant sites remaining within the study area; the midden material having been significantly degraded by urban development. The midden site at the Taroona High School point (TASI 7729), just to the north of the study area, is of great significance as one of the largest and least disturbed midden sites along the Derwent estuary.
The recommendations of the Aboriginal heritage assessment are for a precautionary approach to future management practices. Any excavation works which reveal shell layers should cease immediately and further advice from an Aboriginal Heritage Officer should be sought1.
3.2 Environmental Weeds
Appendix 2 identifies all naturalised non-native species which includes all weed species. Short summaries of the key species are given in Table 4.
A consequence of the disturbances associated with previous management and the proximity to varied sources has been the proliferation of various environmental weeds within the study area. The close proximity of environmental weeds in some neighbouring private gardens maintains an ongoing source for future infestation.
Recent management activities have done much to reverse this trend by targeting the ‘worst offenders’. It is important in weed management planning to recognise the futility of eliminating all non-native species but instead to focus on key species that are having, or have the potential to have, a negative impact upon the native flora but are also manageable.
There are intensive infestations of some herbs such as Kikuyu Pennisetum clandestinum, Panic veldt grass Ehrharta erecta and oxeye daisy Leucanthemum vulgare for examplethat are only effectively tackled by a committed and costly program that would require continuous follow up to be effective in the long term. It is important to acknowledge the ongoing exposure to outside sources of weeds and it is worth considering the most significant of them for attention eg boneseed at Crayfish Point and Illawong Reserve.
Abundant infestations of annual and herbaceous weeds exist along the main track of the foreshore. Although it is a priority to treat declared and woody weeds initially, annual and herbaceous weeds are continuously being spread along the pathway and pose a threat to the core areas of remnant vegetation. It is worth attempting to contain the annual and herbaceous weeds within certain areas of the reserve and aim to eradicate them from bushland in Taroona Park, Illawong Reserve and the remnant vegetation from the sewage treatment plant to the planting area below TAFI. This may involve spraying the track edges to reduce the spread of seed and also to maintain the edges of the remnant bushland.
Table 4: Notable environmental weeds
Widespread and occasional.
Bird spread. Proliferates after fire from long-lived woody seed in soil. Has been significantly reduced through cut and paste and hand pulling. Will require annual monitoring during spring flowering. Significant infestations found below bowling green and within Illawong Reserve.
Widespread and occasional.
Bird spread. Potential to infest drainage lines. Control by hand removal, cut and poison or spraying of larger infestations.
Large leaf cotoneaster
Widespread. Most abundant along the boundaries of residential properties.
Bird spread. Widespread source from neighbouring gardens. Minimal control efforts for this species – often located within private areas.
Cut and poison with woody herbicide.
Widespread with patchy infestations along the foreshore, including planting areas and extensive infestations below sewage treatment works in land slide area.
Small seed spread by animals and machinery. Generally proliferates in disturbed areas but limited spread into intact native vegetation. Best controlled by herbicidal spraying.
Occasional with infestation east of Kelvedon Oval.
Vigorously smothers other vegetation. Wind disperses seed. Best control is to cut climbing stems when in the canopy and leave aerial plant parts to dry out, dig out small roots and stems and re-spray the regrowth.
Several patches below residential properties. Found within planting areas along foreshore and below Seaview Avenue properties.
Spread from illicit garden dumping and in contaminated soil. Infestations smother all other ground covers. Difficult to eliminate. Requires timely use of herbicide cocktail.
Occasional with several patches along the foreshore at Illawong Reserve, Niree Parade and Crayfish Point.
Controlled by herbicidal spraying.
Bird spread. Difficult to eliminate. Requires timely use of appropriate woody herbicide – spraying or cut/paste.
Occasional behind boatsheds and waterfront.
Bird spread. Difficult plant to tackle with its large spines. Best controlled at this site through cut and paint with woody herbicide.
Widespread and occasional along the foreshore and along residential properties.
Several mature trees on foreshore reserve resulting in localised establishment of wildlings.
Investigate gradual replacement of mature trees with native plants. Hand pull wildlings.
Widespread and occasional. Very bad infestation in Passionfruit Gully and occasional along waterfront.
Spread by birds and animals. Smothers or collapses other vegetation. Remove all fruit and either dig out or cut and paint stems, ensuring all stems are treated
Occasional within small infestations along edges of Taroona Park.
Seeds are long lived, spread by water, vehicles, in contaminated soil and dumped garden waste. The seed pods are explosive and can spread up to 3 metres from the parent plant. Methods of control for canary broom include slashing, hand pulling, and chemical control.
6 – ‘D’ – declared weed –Tasmanian Weed Management Act, WONS - Weed of national significance
Declared weeds are listed under the Tasmanian Weed Management Act 1999. Each of these has a statutory weed management plan which includes requirements for control or eradication which is characterised by municipality. Declared weeds include environmental as well as agricultural and silvicultural weeds. Environmental weeds are species which readily naturalise into native vegetation thus presenting a management hazard to the maintenance of natural areas.
Weeds of National Significance (WONS) include 20 key species across Australia. These are identified as ones for which financial assistance for management is linked to strategic regional programmes administered by the Commonwealth.
3.3 Tree Decline
There have been notable deaths of various tree and shrub species in recent years. These have been scattered along the foreshore. Most deaths are of drooping sheoak Allocasuarina verticillata, andnative hop Dodonaea viscosa, below the track in zone 7. These cannot be attributed to disease. Most plants are mature specimens. The most likely cause is from drought stress which has impacted on mature and over mature plants. The age structure of the vegetation is such that these plants have reached late maturity. Death is inevitable and natural. However in a small area when it occurs in such a widespread manner it is visually confronting. Although at the landscape level it is preferable to allow for dead shrubs to remain in situ as habitat, where the visual impact is greatest, or there are safety concerns, there may be a case for their removal. There is also a fire hazard associated with a mass of dead twigs and branches close to walking tracks. There may be incidences where active planting could supplement this process following the removal of larger dead trees.
3.4 Planted Trees
There is evidence of planting of both exotic and native Tasmanian trees within the foreshore reserve. Non-native trees include radiata pine Pinus radiata, macrocarpa Cupressus macrocarpa and Norfolk Island pine Araucaria excelsa. Some inappropriate natives have also been planted within the foreshore area. The ecological impact of such introductions needs to be taken into consideration. It is important to note that the bushland is far from pristine and has been significantly altered by management practices. Therefore it is recommended that where the exotic species is having a negative impact on bushland values, its removal is recommended. In other instances, the parent plants could be retained and monitored.
Several planted trees and shrubs are now spreading or have the potential to spread through seedling establishment in Zone 8 (as shown on the weed map). These include non Tasmanian species such as mainland species of eucalypt Eucalyptus sp., Melaleuca armillaris, Melaleuca nesophila, Acacia saliciformis and Acacia pycnantha at Belhaven Reserve. Several mature Pinus radiata are also found within the study area sporting occasional seedlings beneath their canopy.
3.5 Fire Management
The native vegetation is adapted to fire. Some plant species and forest types require fire for their maintenance and to trigger regeneration. The fire ecology of dry sclerophyll forest which characterises the area is such that it is typically maintained through a fire frequency between 10 and 25 year intervals. Biodiversity is maximised by having a range of fire histories at the landscape level. Where small pocket remnants of vegetation occur fire is considered less relevant as a management tool. In the urban situation burning is controversial and is also hazardous where there is a large number of assets. Fire management planning for small urban bushland reserves is more about protecting these assets through adequate firebreaks and suitable access for fire fighting purposes.
There have been no substantial fires since 1967 when all bushland areas are understood to have been affected by the Tasmanian ‘black Tuesday’ wildfire. A significant fire in 1998 which burnt large areas of forest above Taroona and Albion Heights extended into the gully near the southern boundary of Illawong Reserve.
Biomass reduction can be achieved by means other than fire.
Recruitment of fire dependent species can be artificially achieved through active planting.
Fire risks killing newly planted trees and shrubs and reducing young forest cohorts. The eucalypts present within the study area can regenerate in the absence of fire.
The largest forest remnants at Illawong Reserve and Taroona Park may be considered suitable candidates for active burning. Key determinants would be whether or not there is a lack of regeneration, or over abundance of dead and rank understory species. There is little evidence of either which cannot be more easily attended to through direct clearing and planting. Consequently the use of fire as a management tool is not recommended.
3.6 Threatened Species Habitat
3.6.1 Swift Parrot Habitat
The blue gums in the area are known to be utilized for their foraging resource by swift parrots Lathamus discolor. Blue gum is the prime foraging tree for the swift parrot Black gums provide secondary foraging resource which is understood to be significant in years where blue gums fail to flower or in the early spring prior to blue gums coming in to flower.
Swift parrots are protected under both Tasmanian and Federal threatened species legislation and categorized as endangered with an estimated breeding population of less than 1000 pairs2.
There are mature blue gums throughout the entire study area at Taroona. TEN has been planting replacement blue gums and black gums where possible to ensure a continuous supply of adequate food for swift parrots. The study area between Taroona Park and Illawong Reserve is well catered for with a mix of large scattered blue gums along the foreshore between these two areas, with adequate numbers of regenerating saplings.
Planting of blue gums and black gums in other areas should occur where possible to maintain food source. It is important that the planting of such large gums are well planned, so as not to interfere with services, established lookouts or nearby residential properties.
Birds utilise direct routes to fly between prime foraging trees. Although they will generally fly high above the houses there are situations where their flight path leads them below the canopy. Certain structures that these fast flying birds fail to notice include chain link fences and expansive glass windows (especially where they are see-through, such as on corners of buildings, or are reflective of trees or sky). These structures represent the greatest hazard for collision which is a significant factor in mortality rates of swift parrots.
3.6.2 Eastern-barred Bandicoot
The eastern–barred bandicoot Perameles gunnii, a small pale tan marsupial with dark dorsal stripes, inhabits grassland and grassy woodland, bushland/pasture interfaces and larger suburban gardens. Bandicoots forage in open grassy areas but for shelter and nesting they require a dense ground cover of native tussock grasses, sedges, shrubs and even garden plantings. They forage after dusk and seek shelter during the day in grass-lined nests where the cover is thick.
This species is not listed under Tasmanian threatened species legislation. The national listing, however, classifies it as endangered on the mainland and vulnerable in Tasmania. It is widespread across Tasmania, particularly in the eastern and northern lowland regions. Although subject to predation from domestic pets (cats and dogs) it persists in many peri-urban situations. It is perhaps most at risk from the potential expansion of the European fox in Tasmania.
Avoidance of an over tidy approach to bushland management is important to ensure suitable shelter is maintained. This includes the retention of dense thickets and gradual, phased replacement of weedy herbage which may be providing the only local habitat. Revegetation planning should include provision of adequate ground cover species for habitat purposes.
In areas where native vegetation exists, natural regeneration can occur with appropriate management. Furthermore plant establishment and survival is usually much greater with naturally seeded plants. Within the study area, there are some instances where replanting is required to support natural regeneration:
To enhance the range of species and supplement some of the less common species.
To replace weeds in specific sites.
To establish new plantings in areas currently managed as grass.
3.8 Water runoff
At numerous sites along the foreshore there are drainage areas flowing into the River Derwent. These areas are often associated with erosion and weed outbreaks. Some areas remain permanently damp. Stormwater management is beyond the scope of any bushcare group, however it is recommended that such areas are targeted for weed control.
3.9 Adjacent Land Impacts
The best endeavours for controlling weeds within the reserve can be partially undone if sources outside the site remain unmanaged. There are many adjacent properties which have a bearing on this.
Illawong Reserve, for example, has some dense infestations of broom which are spreading from adjacent private properties and from upper areas of the drainage line. In order to control the weed, work will require a combined approach with TEN and the private land owners. This will require liaison with the properties in upper areas of the drainage line and with those properties directly backing onto the reserve.
‘Passionfruit Gully’ is an area of private land adjoining the coastal foreshore, so named by TEN for the proliferation of banana passionfruit vines. Some of the gully owners support conservation and restoration works of the gully habitat. Work within this area has been undertaken in the lower areas above Hinsby Beach. In order for work to be successful the weed issues in the upper areas of the gully will need to be addressed. Some work is already being undertaken by a local resident which has been extremely successful, however above these areas there are major problems with banana passionfruit and cape ivy which will require work in the future. For control of these weeds to be successful liaison with the adjacent land owners will be required.