Irenepharsus trypherus (Illawarra Irene) Recovery Plan
NSW Department of Environment and Conservation, 2005
ISBN: 1 7412 2145 5
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 I. trypherus 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 program and ex- situ conservation program; and
- Consideration of the species ability to recover.
The level of information that is known about I. trypherus (as detailed in Sections 5 and 6) is limited and only broad assumptions can be made regarding its biology and ecology. An enhanced knowledge of key aspects of the 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.
A quantitative assessment of the impact of grazing by feral and native animals at I. trypherus sites is required. This assessment could involve a comparison of herbivory rates inside and outside animal exclosures constructed at selected sites.
A recent observation of an introduced Cabbage White butterfly (Pieris rapae rapae) visiting an I. trypherus plant and appearing to leave an egg sac (M. Robinson, pers. comm.) raises some interesting questions. Investigations are required to confirm whether the Cabbage White is capable of laying eggs on I. trypherus, and if so, determine the extent to which its larvae are capable of consuming the foliage of I. trypherus.
Investigation of the presence and nature of the I. trypherus soil seed bank is required. Of particular importance is investigation of the period for which the soil seed bank remains viable. Other aspects of the seed biology of the species requiring investigation include seed dormancy mechanisms and the role of fauna in seed dispersal.
Monitoring of tagged individuals is required to provide an insight into the population dynamics of the species. Seedling survivorship, longevity and age to reproductive maturity are considered important aspects of population dynamics requiring investigation.
A quantitative assessment of the response of the soil seed bank to different fire intensities is required.
While not considered essential to the practical management of the species, genetic investigation of the species across its range would greatly improve our knowledge of the population structure of the species and would inform land-use and recovery planning decisions, including the implementation of an ex-situ conservation program.
The cryptic nature of I. trypherus and its preference for difficult to access locations indicates that our knowledge of the distribution of the species is likely to be incomplete. A program of targeted survey is required to determine the current distribution of the species.
8.3.1 Loss and fragmentation of habitat
Habitat loss is considered to be a relatively minor threat to I. trypherus because the majority of known sites occur within conservation reserves, in 'secure' zonings (ie in areas zoned for environmental protection), or on steep slopes that are unsuitable for development. The threat of habitat clearance does exist however, and clearing associated with the construction of an access track has disturbed at least one Stockyard Mountain site (NCC 1999).
The only confirmed I. trypherus sites in non-secure zonings occur at Stockyard Mountain where six sites are zoned for rural land-uses. The draft Shellharbour Rural LEP 2001 proposes a more secure zoning of 7(n) Nature Conservation in these areas and designates them “Areas of High Conservation Value”. The increased controls on the clearing of native vegetation under this proposed rezoning should assist the conservation of these I. trypherus sites and proximate habitats.
Liaison with private landholders is required to ensure that the inadvertent clearing of I. trypherus habitat does not occur. 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 around sites to maintain the integrity of the 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 latters influence on drainage patterns) and the proposed adjacent landuse.
8.3.2 Habitat modification and disturbance
The greatest threat to I. trypherus is believed to relate to the modification of its habitat and the physical disturbance of plants, rather than the removal of its habitat. Threatening processes that degrade the habitat of I. trypherus sites or physically disturb the species include:
- Weed invasion;
- Grazing and trampling by feral and native animals;
- Grazing and trampling by livestock; and
- Soil erosion.
Weed invasion is the most commonly recorded threat at I. trypherus sites. Lantana (Lantana camara), Cape Ivy (Delairea odorata) and Mistflower (Ageratina riparia) were the most frequently observed, and often the only, weed species present at the sub-sites surveyed during the preparation of this plan. Weed densities in the immediate vicinity of I. trypherus plants is highly variable, ranging from 0 to 80 per cent projected canopy cover (M. Bremner, DEC, pers. comm.).
|Grazing/trampling by feral or native animals||3||8|
|Grazing/trampling by livestock||0||6|
Field observations of I. trypherus indicate that the species is unlikely to germinate under a dense canopy and consequently, dense weed growth threatens the species by inhibiting recruitment. In the absence of information regarding the presence and longevity of the I. trypherus soil seed-bank, the length of time that the species can persist at a site once the canopy cover reaches a density that prevents recruitment is not known.
The management of weeds at I. trypherus sites will require targeted bush regeneration efforts. These efforts should aim to restore, maintain and expand suitable habitat for the species at extant sites. Given the erosion-prone nature of I. trypherus sites, bush regeneration works must aim to minimise unnecessary disturbance. Guidelines for threat abatement works at I. trypherus sites will be prepared to minimise the potential for such activities to adversely impact upon the species.
It should be noted that Lantana prevents livestock from accessing a small number of sites. The removal of Lantana from the perimeter of these sites must only proceed following the construction of fencing or other measures to exclude livestock.
Grazing and trampling by feral and native animals
Grazing and trampling by feral and/or native animals is a potential threat at a high number of I. trypherus sites. In addition to physically damaging I. trypherus, animals may also exacerbate soil erosion at affected sites. The presence of feral goats or deer has been confirmed at three I. trypherus sites (Ir1, Ir3 and Ir12) through the direct observation of tracks and scats, or from discussions with landholders. Evidence of herbivory (possibly from native fauna) has been observed at a number of other sites.
The control of feral animals is a complex problem requiring a regional solution. At present there are no established programs to cull or trap feral goats or deer in the Illawarra area outside of Royal National Park (A. Glover, Rural Lands Protection Board, pers. comm.). Under current legislation landholders are allowed to shoot goats that are found on their property but not deer. Consequently, landholders in or adjacent to I. trypherus habitat should be encouraged to control feral goats found on their property and to report sightings of feral goats and deer to Rural Lands Protection Board rangers.
The NSW Scientific Committee made a preliminary determination to list “Herbivory and environmental degradation caused by feral deer” as a key threatening process (KTP) in October 2003. If a final determination is made to proceed with the listing of this KTP, a threat abatement plan will be required to be prepared by the DEC. The threat abatement plan will outline the actions required to manage this threatening process and the authorities responsible for carrying them out.
In the interim, the construction of exclosures may be required to safeguard I. trypherus plants at some sites. This is considered necessary because, as a consequence of the small number of extant I. trypherus plants that are present at many sites, just a few feral or native animals could have a significant impact on the species.
It should be noted however that the exclusion of fauna has the potential to influence aspects of the ecology of I. trypherus that are poorly understood at present (eg seed dispersal, recruitment following disturbance etc). For this reason, exclosures should initially be constructed to contain a proportion of the plants that are present at a site. This proportion will vary between sites, but as a general rule exclosures should be constructed to contain no more than 50 per cent of extant plants at a site.
The monitoring of subsequent recruitment and survivorship levels, both inside and outside of these exclosures, should be undertaken to determine the success (or otherwise) of this threat abatement measure.
Ir12, located in the Kangaroo Valley section of Budderoo NP, is considered to be a priority site for the construction of exclosures, as large numbers of goats have been observed visiting the site. Regular monitoring is required at the other sites where grazing and trampling by feral and/or native animals has been identified as a potential threat, to identify other priority sites for the construction of exclosures.
Grazing and trampling by livestock
Grazing and trampling by livestock is a potential threat at three I. trypherus sites (Ir4, Ir6 and Ir8) that are located on freehold land at Stockyard Mountain. Liaison with the owners of these properties is required to secure their cooperation and involvement in the recovery program.
If livestock are confirmed to be impacting upon I. trypherus plants at these sites, opportunities for the implementation of protection measures for the species (including the installation of protective fencing) will require investigation. As I. trypherus sites generally occupy a very small area, potential impacts on the landholder in terms of the loss of grazing land is expected to be minimal. Costs associated with the construction and the provision of materials will be sourced from grant funding.
A number of other I. trypherus sites are presently protected from livestock by boundary fences or dense stands of Lantana. These barriers to access should be maintained and monitored regularly.
The movement of people and fauna on the steep slopes that characterise many I. trypherus sites has the potential to create erosion problems. While small- scale erosion events on these slopes may assist recruitment of the species (see Section 6.4), large- scale erosion is undesirable as it will degrade the site and move topsoil (and any associated soil seedbank) downslope into potentially unsuitable habitat.
The movement of people along a steep informal track between two waterfalls in Macquarie Pass NP is creating significant erosion problems at site Ir2. The extent of erosion at the site has increased significantly in recent years (M. Robinson, pers. comm.). Strategies to reduce the extent of erosion at this site may include signage advising that the track is closed, barriers to discourage access and/or the provision of a formal alternative access track between the waterfalls.
Increased activity at all I. trypherus sites during the implementation of this recovery plan has the potential to create or exacerbate erosion problems at these sites. Guidelines for the implementation of threat abatement works at I. trypherus sites will be prepared to minimise the potential for such activities to adversely impact upon the species.
8.3.3 Bush Fire Hazard Reduction
To enable the conservation requirements of I. trypherus to be considered by public authorities when planning bush fire hazard reduction work (prescribed burning and mechanical vegetation clearance) or when issuing Bush Fire Hazard Reduction Certificates, I. trypherus has been 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.
As a consequence of our limited knowledge of the fire ecology of the species (see Section 6.5), the conditions in the TSHRL that relate to hazard reduction burns at I. trypherus sites are based upon the vegetation formations that are present at each site. Sites that occupy rainforest habitats are not to be burned, while those that occupy sclerophyll forests are not to be burned at a frequency greater than once every 25 years. Conditions in the TSHRL that relate to mechanical hazard reduction at I. trypherus sites include restrictions on slashing, trittering and tree removal.
Notwithstanding the above, until the fire response of I. trypherus and its soil seedbank has been determined, habitat that is known to contain the species should be managed to exclude fire wherever possible.
An increased awareness of I. trypherus 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 I. trypherus 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 encourage such support.
Public authorities with consent, determining or environmental planning responsibilities under the EP&A Act require an improved 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 I. trypherus sites.
Initiatives to assist these authorities in meeting their statutory obligations in relation to the consideration of I. trypherus in environmental impact assessment and land-use planning processes include:
- The preparation and distribution of updated 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 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.
An increased community awareness and capacity to recognise I. trypherus (particularly amongst bush regeneration contractors and volunteers) may assist the species by preventing inadvertent clearing of plants (through confusion with the common weed species, Mistflower) and may contribute to the opportunistic discovery of new sites.
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 currently not considered necessary for the survival of I. trypherus although this recovery plan does recommend that an ex-situ seed collection be established as a contingency measure to protect against the loss of genetic material that may result from any future local extinctions (see Section 8.6.2).
It should be noted that, 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).
8.5.2 Ex-situ collection
While there is no clear evidence that I. trypherus populations are in immediate danger of extinction, the species is considered to be at a moderate risk of suffering one or more local extinctions during the five-year period of this recovery plan. This conclusion is based on the following factors:
- Extant populations are small and fluctuating in size;
- The extent and intensity of threats at extant sites remain poorly understood; and
- Recent surveys failed to locate the species at three sites.
Consequently, the implementation of an ex-situ conservation program is recommended to safeguard I. trypherus against the potential loss of genetic material. This program will involve the collection and storage of genetically representative samples of germplasm from each extant I. trypherus population in a state suitable for re-establishing a self-sustaining wild population at that site following local extinction. The collection and storage of germplasm will be undertaken in accordance with the “Germplasm Conservation Guidelines for Australia” (ANPC 1997).
Recovery in the context of this plan, is to maintain the current endangered status of I. trypherus 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 in this context is not known as the extent and intensity of the threatening processes operating at extant I. trypherus sites remain poorly understood.