Department of Environment and Conservation (NSW), 2005
ISBN: 1 7412 2144 7
8 Management Issues
- 8.1 Introduction
- 8.2 Limits to current knowledge
- 8.3 Threatening Processes
- 8.4 Community awareness of the species
- 8.5 Translocation and ex-situ conservation
- 8.6 Ability to recover
The following section identifies the management issues affecting D. sp. C Illawarra including:
- Our limited knowledge of the species biology, ecology and distribution;
- The threats operating on the species;
- Community awareness of the species;
- Consideration of a translocation and ex-situ conservation program; and
- Consideration of the species ability to recover.
The level of information that is known about D. sp. C Illawarra (as detailed in Sections 5 and 6) is limited and only broad assumptions can be made regarding its ecology and biology. An enhanced knowledge of key aspects of species biology and ecology is clearly required if land managers and consent/determining authorities are to make informed judgements regarding its conservation requirements.
Future research should target aspects that are relevant to the practical management of the species and its habitat. High priority research projects for the species (as identified in Section 6) are described below.
- Investigation of the extent of seed production at individual sites, with an emphasis on identifying sites where seed is produced
- Investigation of pollination mechanisms
- Investigation of the perceived low levels of seed production and the potential causes of this (seed predation, pollen sterility, self-incompatibility, loss of pollinator etc)
- Investigation of seed dispersal, dormancy and germination mechanisms
- Investigation of seed viability and longevity.
While not essential to the practical management of the species, genetic investigations to determine population size and structure would greatly improve our understanding of the species and would inform land-use and recovery planning decisions.
- 8.3.1 Clearing for agriculture
- 8.3.2 Hard rock quarrying
- 8.3.3 Residential development
- 8.3.4 Road construction
- 8.3.5 Weed invasion
- 8.3.6 Grazing by livestock and feral deer
- 8.3.7 Rubbish dumping
- 8.3.8 Bush fire hazard reduction activities
The threats operating at D. sp. C Illawarra sites are described below and an assessment of the threat level at each site is included at Appendix 5.
The clearing of vegetation for agriculture (primarily cattle grazing and dairying) is a potential threat to D. sp. C Illawarra on a number of rural properties. Liaison with the owners of these properties is required to prevent the inadvertent clearing of habitat for the species.
Where clearing approvals are required, access to accurate site location records will assist consent and determining authorities in considering the conservation requirements of the species. Sufficient vegetated buffers should be retained in the vicinity of site that contain D. sp. C Illawarra to maintain the integrity of its rainforest habitat. The extent and design of the buffers required to achieve this will be site specific, depending on factors including aspect and slope (and their influence on a sites exposure to insolation and wind and the laters influence on drainage patterns) and the adjacent landuse.
Five D. sp. C Illawarra sites in the Dunmore Hills area are potentially threatened (either directly or indirectly) by hard rock (latite) quarrying activities. Two of these sites (Dc14 and Dc20) lie within 100 metres of land that has been identified by the Department of Mineral Resources as containing a state significant latite resource.
Four sites (Dc12, Dc14, Dc16 and Dc20) are owned by mining interests and two (Dc16 and Dc20) of these are zoned 1(a) under Shellharbour LEP 2000. Mineral extraction is permitted with development consent within this zone. The other three sites are zoned 7(e) Environmental Protection (Scenic).
In addition to the threat of further habitat loss and fragmentation as a consequence of quarrying, the five known sites within the Dunmore Hills area lie within catchments where hydrological conditions may be effected by upstream quarrying activities. Reductions in water quality and altered surface and groundwater flows have the potential to directly impact upon the species and to affect the viability of its rainforest habitat.
Quarrying activity upstream of one site (Dc14) has potentially altered hydrological conditions in the gully where it is located. The impact that this may have on the long-term viability of D. sp. C Illawarra at the site (the only site confirmed to produce viable seed) and its rainforest habitat is not known.
It is expected that all of the D. sp. C Illawarra sites in the Dunmore Hills area will come under increasing pressure from the direct and indirect impacts (altered hydrological conditions, dust etc) of quarrying activities as the mineral resource in the currently identified extraction areas becomes depleted.
Shellharbour Council is to commence preparation of a Local Environmental Plan and Local Environment Study that reviews the mineral extraction boundaries in the Dunmore Hills area. The preparation of these documents provides an opportunity to protect D. sp. C Illawarra from the direct and indirect impacts of quarrying through the rezoning process. Targeted survey as part of this process will be necessary to ensure that all locations of the species within the study area are identified and considered in the preparation of these documents.
Population growth in the Illawarra area is likely to place D. sp. C Illawarra sites under increasing pressure from residential development. Such development, in addition to directly impacting upon the species through habitat loss and fragmentation, can indirectly affect sites in proximate or downslope locations by modifying environmental conditions and contributing to habitat degradation.
These impacts can result from factors including:
- Altered hydrological flows (and associated problems with sedimentation and erosion);
- Altered soil pH and nutrient levels;
- Weed infestations;
- Increased pedestrian/vehicular access to sites;
- Rubbish and green waste dumping;
- Bush fire hazard reduction works;
- Inappropriate landscaping activities; and
Accurate and readily accessible site location records will assist consent and determining authorities in considering the conservation requirements of the species during the assessment of rezoning and development applications. Strategies to mitigate direct and indirect impacts on the species should be incorporated into the design of developments that are constructed upslope of, or proximate to, D. sp. C Illawarra sites.
Three D. sp. C Illawarra sites (Dc37, Dc38 and Dc39) were identified during the route selection study for the proposed upgrade of the Gerringong to Berry section of the Princes Highway (Muston & Associates 1991). One of the five proposed routes investigated during that study (the North Saddle Corridor) would result in the removal of one of these sites (Dc39). However, the RTA is yet to determine its preferred route for the upgrade (Chris Cleary, RTA, pers. comm.).
Under statutory environmental impact assessment processes, the RTA is required to consider the direct and indirect impacts of the proposed road upgrade on D. sp C Illawarra, in addition to Zieria granulata, Illawarra Subtropical Rainforest and any other threatened species, populations or ecological communities that occur in the study area.
Weed invasion is a threat at the majority of sites surveyed during the preparation of this plan. Lantana (Lantana camara) was the most commonly recorded weed species at these sites, occurring in densities of between five and 100 per cent projected cover at all but one surveyed site. Mistflower (Ageratina riparia), Crofton Weed (Ageratina adenophora) and Cape Ivy (Delairea odorata) are also present in high densities (>60 per cent projected cover) at a small number of sites. These weeds will potentially impact upon D. sp. C Illawarra by inhibiting recruitment.
Madeira Vine (Anredera cordifolia) is in the early stages of infestation at one site (Dc14) and is established immediately upstream of this site. This weed species has the ability to establish under an intact canopy and could potentially smother mature D. sp. C Illawarra plants, in addition to inhibiting recruitment. For this reason, Madeira Vine is considered to be a more immediate threat to D. sp. C Illawarra than the other weed species that were recorded at the surveyed sites.
The management of weeds at D. sp. C Illawarra sites requires targeted bush regeneration efforts. These efforts should aim to restore, maintain and expand the rainforest habitat of the species. The targeted removal of Madeira Vine (and any other weed species with the potential to smother mature D. sp. C Illawarra plants) is considered to be a high priority.
Grazing and rubbing of D. sp. C Illawarra stems by cattle has been observed at a number of sites that are located on rural properties. Grazing and rubbing by feral deer is also suspected at a number sites, and substantial damage resulting from the grazing of feral deer has been observed at one site (Dc28) (M. Hindmarsh, pers. comm.).
Grazing has the potential to prevent recruitment of the species, while bark damage (and subsequent infections) can affect mature individuals. General habitat degradation resulting from the presence of livestock and feral deer (including soil compaction and weed invasion) will also impact upon the species.
Liaison with landholders is required to facilitate the installation of fences where livestock or feral deer are accessing D. sp. C Illawarra sites.
Dumped rubbish (including old cars and corrugated iron sheets) has been observed at two D. sp. C Illawarra sites (Dc11 and Dc13). The dumping of rubbish has the potential to damage D. sp. C Illawarra and degrade its habitat through burial, physical damage and soil compaction. Liaison with landholders is considered to be the key to managing this threat.
In the absence of specific evidence to the contrary, it is assumed that D. sp. C Illawarra would be adversely affected by prescribed burning or mechanical vegetation clearance for bush fire hazard reduction purposes (see discussion in Sections 6.4 and 6.5). Consequently, such activities should be excluded from habitat that contains the species.
To enable the conservation requirements of the species to be considered by public authorities when planning bush fire hazard reduction work or issuing Bush Fire Hazard Reduction Certificates, the species should be placed on the Threatened Species Hazard Reduction List (TSHRL). This list has been prepared as part of the Bush Fire Environmental Assessment Code established by the Rural Fires and Environmental Assessment Amendment Act 2002. The provision of accurate location records (ie within 100 m accuracy) to public authorities is required to ensure that the impact of managed bush fire hazard reduction activities on the species is minimised.
An increased awareness of D. sp. C Illawarra is required to ensure that the species is appropriately considered in statutory environmental planning and impact assessment processes and to facilitate the implementation of threat abatement works. The target groups for awareness raising initiatives are:
- Private landholders;
- Public authorities; and
- The general community
The informed support of the private landholders whose land contains D. sp. C Illawarra is essential to the success of the recovery program. Regular liaison with affected landholders and the publication of an annual newsletter detailing progress of the recovery program are two initiatives that will be implemented through this recovery plan to facilitate such support.
Public authorities with consent, determining or environmental planning responsibilities under the EP&A Act require an understanding of the species, particularly regarding its known locations, habitat requirements and sensitivity to impacts. Some public authorities also have an operational role (Rural Fire Service, Transgrid) in potential habitat for the species and as such, may inadvertently impact upon D. sp. C Illawarra sites.
Initiatives to assist these authorities in meeting their statutory obligations in relation to the consideration of D. sp. C Illawarra in environmental impact assessment and land-use planning processes include:
- The preparation and distribution of a species profile and environmental impact assessment guidelines; and
- The verification and registration of site records on the DEC Atlas of NSW Wildlife.
The third target audience for awareness raising initiatives is the general community. The initiatives targeting this group aim to enhance the social benefits of the recovery program amongst this target group and include:
- The preparation of an annual newsletter detailing the progress of the recovery program, which will be distributed to affected landholders, public authorities, community groups and interested individuals;
- The preparation of press releases to highlight key recovery actions; and
- The involvement of community members in the implementation of recovery actions.
Translocation, defined as the deliberate transfer of plants or regenerative plant material from an ex-situ collection or natural population to a location in the wild, including existing or new sites or those where the taxon is now locally extinct (Vallee et al. 2004), is often raised as a possible method of conserving threatened flora. However, given the high cost and risk associated with the technique, translocation should only be considered as a last resort when all other management options are deemed inappropriate or have failed. As stated by Vallee et al. (2004), where possible, resources will be more effective when directed towards conserving existing populations in-situ through habitat protection and/or habitat rehabilitation measures and through the control of threatening processes.
Translocation is not considered to be necessary for the survival of D. sp. C Illawarra as the in-situ conservation measures proposed in this recovery plan are expected to meet the conservation needs of the species. Further, primarily due to the uncertainty of success and the risks associated with translocation, the technique should not be considered by consent or determining authorities to be an appropriate means of ameliorating the impact of a proposal on the species (Vallee et al. 2004).
While not considered necessary for the survival of the species, it would be prudent to maintain an ex- situ collection of D. sp. C Illawarra seed from those sites that are found to produce viable seed. Such a collection will provide some protection against the loss of genetic material that may result from unexpected local extinctions.
It is not known whether D. sp. C Illawarra is naturally uncommon or whether it has suffered minor or substantial declines in population size and/or distribution. It can be reasonably assumed however, that the extensive clearing of the Illawarras lowland rainforests since European settlement has had a substantial impact on the distribution and population size of D. sp. C Illawarra. The high number of threats operating at extant sites indicate that the species is likely to still be in decline.
The viability of a species can be broadly defined as the ability of that species to be self-replacing in nature. There is currently little information as to the viability of the D. sp. C Illawarra populations identified in this recovery plan. Seed production has been reported from just two sites (only one of which has been confirmed to produce viable seed) and the extent to which this seed is capable of surviving in the wild is unknown. However, it has been reported that many clonal plant species do not show signs of senescence and are capable of surviving indefinitely, or at least as long as the surrounding environment remains compatible (Nooden & Leopold 1988; Eriksson 1993). All populations of D. sp. C Illawarra should therefore be assumed to be viable unless there is clear evidence to the contrary.
Recovery in the context of this plan, is to maintain the current endangered status of D. sp. C Illawarra and prevent the taxon from moving to a less desirable conservation status (ie TSC Act Schedule 1, Part 4, presumed extinct). The likelihood of recovery of D. sp. C Illawarra in this context is high provided that the recovery actions outlined in this recovery plan are implemented, monitored and amended as required.