National recovery plan for the Downy Wattle (Acacia pubescens)
NSW National Parks and Wildlife Service
Environment Australia, February 2003
ISBN 0 7313 6504 6
9. Management Issues
The following sections identify our current understanding and/or limitations of the biology and ecology of A. pubescens, the threats operating on populations and a consideration of the social and economic factors that affect the success of the recovery program. A discussion is also included on translocation, which is another issue that is often raised in relation to the management of threatened species.
The object of a recovery plan is to promote the recovery of a threatened species to a position of viability in nature. A. pubescens is listed as vulnerable, so the objective will be to ensure the viability of sites and prevent its status from becoming endangered. As the species occurs at a number of sites which are largely outside of conservation reserves, and as there are a number of threats acting on the sites where it occurs, further reductions in its distribution are likely if current management practices continue. To prevent the species from becoming endangered, actions are needed to maximise the protection and security of sites of the species. On-site actions should occur at least at the most significant sites of the species. However, due to the lack of information about the genetic diversity of the species, it is difficult at this stage to identify which sites are the most significant. Small sites in highly disturbed areas, that may appear to be insignificant to some land managers, may hold quite significant genetic diversity. The lack of information on the genetic diversity within and between populations also complicates the possibility of any translocation programs that might be attempted.
Other aspects of the biology and ecology of A. pubescens are also not well understood. An increased understanding of these aspects of A. pubescens will improve the finer scale approach to the recovery of the species. A greater understanding of its habitat requirements and its lifecycle processes will increase the likelihood of the successful recovery of A. pubescens and our ability to manage the species in the future. The recovery actions listed in Section 13.3 aim at investigating these essential aspects.
Some of these management issues are discussed in more detail below.
The threats and reasons for the decline of A. pubescens can be separated into two categories - those that are leading to the loss of habitat, and those that are leading to degradation of existing sites.
Habitat loss is a major issue in Western Sydney. Over 90% of the original distribution of vegetation in the region has been cleared (NSW NPWS 1997). Eleven of the sites recorded on the Atlas for NSW Wildlife (NSW NPWS 1998) no longer contain A. pubescens (see Appendix 2). Most of these sites have been lost due to residential development. Many old records indicate that the species occurred in locations that have now been developed, such as Georges Hall, Belmore, Cabramatta, Chester Hill and Warwick Farm.
As well as reducing the numbers of individuals, loss of habitat also fragments populations. The distributional information in section 5 of this plan demonstrates this fragmentation. Fragmentation creates sub-populations of species, isolates those sub-populations from one another and often disrupts ecological processes, such as pollination, dispersal and gene flow. In doing so it increases the risk of extinction. Smaller populations are more likely to suffer local extinction and more isolated habitat fragments are less likely to be re-colonised if local extinction does occur (Margules et al. 1993).
A potential threat at some sites is the planned development of those sites. A large percentage of sites occur on lands zoned for residential and industrial uses. The species may be lost from these sites due to development for these uses, or developments may introduce impacts onto the site which degrade the habitat.
Several threats are acting on existing sites of A. pubescens which are likely to be reducing the capacity of these sites to be self-sustaining. These threats were recorded at sites during surveys for the preparation of this Recovery Plan and during the Urban Bushland Biodiversity Surveys (NSW NPWS 1997), and include weed invasion, mechanical damage, rubbish dumping, illegal track creation, arson, horses and hybridisation. The percentage of sites where such threats were recorded is summarised below:
|Threat recorded at site||Percentage of sites|
|Illegal track creation||21%|
- Weed invasion::
Weeds recorded at sites include African Lovegrass (Eragrostis curvula), Whisky Grass (Andropogon virginicus), Paddy's lucerne (Sida rhombifolia), Prickly Pear (Opuntia spp.), Mother-of-millions (Bryophyllum delagoense), Paspalum (Paspalum dilatatum), Kikuyu (Pennisetum clandestinum), Blackberry (Rubus fruticosus sp. agg.), Honeysuckle (Lonicera japonica) and African Olive (Olea europea ssp. africana). Since large numbers of sites are threatened by weed invasion, developing a careful bush regeneration strategy at sites to remove and control weeds will be a high priority.
- Mechanical damage:
Mechanical damage includes damage from mowing, whippersnippering, slashing, and so on. As A. pubescens occurs in many areas that are mown, such as reserves and roadsides, the likelihood of this threat occurring is high. This threat was also noted by the Urban Bushland Biodiversity Survey (NSW NPWS 1997) as a particular problem along railway lines. The species has the ability to tolerate some level of disturbance but may not be able to tolerate repeated damage. Also, the ability of the species to regenerate may be reduced as its temporary removal allows access for other species, especially weeds. Mowing gangs need to be able to identify the species and leave an unmown buffer around where it occurs. Other strategies may be needed where contractors that maintain sites are constantly changing. This is currently an issue with the sites within railway corridors, and is likely to also be a problem in Council reserves, as local government moves increasingly towards using private contractors for park maintenance. Where this problem can be addressed, it should become less of a threat over time, as areas that are unmown start to regenerate and become established and more obvious.
- Rubbish dumping:
Dumped rubbish can degrade sites through mechanical damage. It can also lead to the introduction of weeds and increase rates of arson if the dumped material is set alight. This problem is likely to increase as government restrictions are placed on the amount of green waste that can be taken to landfill. This is a community problem that is difficult to police. The most effective methods currently available to address the problem appear to be the removal of rubbish as it appears and the erection of barriers to prevent further access. Many Councils have implemented such measures at some sites, but dumping continues to be a problem in other areas.
- Illegal track creation and impacts from horses:
The use of illegally created tracks by walkers, bicycles (particularly BMX bikes) and horses can also degrade sites. These activities lead to mechanical damage of plants, compaction of the soil, introduction of weeds and they increase edge effects. Tracks can also encourage dumping and arson. This problem should be addressed through an education campaign, negotiation with horse riding clubs and by the erection of barriers.
There is no known natural hybridisation for A. pubescens, but the species is known to hybridise with some bipinnate wattles such as A. baileyana, A. jonesii and A. cardiophylla which occur outside the range of A. pubescens. Hybrids can be a major threat through reduction of the genetic integrity of the species. Hybrids and any bipinnate Acacia species that are not native to the area and that are in proximity to A. pubescens sites need to be removed. Council officers and others who may be planting such Acacia species in or near bushland, need to be informed about hybridisation - that it occurs and what the consequences may be. It should be noted that A. baileyana has been listed as a bushland weed by the Australian Association for Bush Regenerators.
- Inappropriate fire regimes:
Arson was also observed to have occurred at a number of sites. If arson is occurring repeatedly at sites, this may diminish the seedbank, as seedlings and suckers may not get the opportunity to develop and set seed in the interval between fires. Until research has been carried out on the fire requirements of the species, fire should be suppressed at those sites that are subject to arson so that the seed bank may be replenished.
In areas where arson is not occurring, lack of fire may be a threat to the continued survival of the species. As A. pubescens occurs largely in developed areas where fires are generally suppressed, this is likely to be an issue at a number of sites. Fire intervals which are too long have the potential to reduce seedling recruitment. The most appropriate fire regime for A. pubescens is currently unknown (see section 7.4). Studies of the fire ecology of the species are needed before the appropriate fire management strategies can be implemented.
A large proportion of individuals appear to be suffering from an unknown disease which affects the leaves of plants (T. James, consultant pers. comm.). The number of sites where this was occurring has not been recorded. Investigating the nature and the extent of impact of this disease should be seen as a high priority. Actions have been included in this Recovery Plan which deal with the researching and reporting of this threat.
The NPWS recognises that actions within this plan may have impacts on the public authorities and private individuals, who own or manage land on which the species occurs. Some landholders (both public and private) are reluctant to conserve habitat and view the recovery effort as an intrusion on their rights to manage their land. While these opinions are in the minority they certainly constitute a challenge for the recovery effort. Personal and regular contact with landholders is a key strategy in encouraging awareness and involvement in the recovery effort.
It is considered that the plan will also result in some positive impacts on sections of the community. For example, implementation of the plan will result in increased preservation of habitats, which will improve the aesthetic value and recreational and educational potential for residents in areas where A. pubescens occurs. This is especially beneficial for Western Sydney, where there are a limited number of opportunities for local residents to access and experience the flora and fauna of the region. However, preservation of habitats may also require that public access is restricted at some sites. As this would not occur without public consultation (eg. through the public exhibition of draft Plans of Management for sites), any negative social consequences of restricted access should be minimised.
The NPWS recognises that the implementation of the actions of this Recovery Plan will result in some degree of economic impact. The proposed recovery strategy seeks to minimise these impacts through the prioritisation and targeting of recovery efforts to those populations on private land. Without a strategic approach to managing this vulnerable species, and with the continuation of current practices, it is likely that the species will be reduced to a level where it is at risk of becoming endangered or possibly extinct at many localities, given current rates of loss and degradation of habitat.
The negative economic consequences of the recovery of A. pubescens are those costs associated with the implementation of this plan. One of the main actions of the plan is to increase security of tenure of sites (see section 11). This may reduce development potential of some sites, and therefore result in financial losses. The exact value of these losses are difficult to estimate, due to the number of sites where the species occurs. However, an attempt has been made to minimise any direct impacts on individuals by concentrating efforts on preservation of land in public ownership, which is not zoned for development.
Actions involving on-ground management programs and the long-term monitoring of sites will also have economic consequences for land managers. However, it is considered that these management programs involve recurrent activities which are required for the normal management of the land, such as weed control and rubbish removal. Costs can be minimised by seeking funding from external sources and by adopting a co-operative approach to management, which involves the NPWS, other relevant landholders and the community.
It is considered that some positive economic consequences will also result from the implementation of the plan. For example, it will result in more efficient resource use, as management of the species will be more co-ordinated and strategic. In addition, economic benefits should also be gained by consent and determining authorities, as the information contained in the Recovery Plan should assist in their decision making processes in relation to A. pubescens.
Translocation is defined as the deliberate transfer of plants or animals from one place to another, including existing or new sites or where the species is now extinct (Australian Network for Plant Conservation (ANPC) 1997).
The booklet 'Guidelines for the Translocation of Threatened Plants in Australia', (ANPC 1997) provides a discussion of the issues involved in translocation. This booklet also discusses several reasons why attempts to translocate often fail, such as not removing the original threats affecting the habitat, not properly considering the biological and ecological requirements of the species, neglecting to assess the genetic variability and not providing an ongoing commitment to monitoring and maintenance.
At this stage, translocation of A. pubescens is not considered necessary for the continued existence of the species in the wild, given the distribution and abundance of A. pubescens. In addition, the clonal nature of A. pubescens makes it difficult to assess the impact of any translocations on the genetic integrity of populations. The collection of genetic information is included as a recovery action of this plan. At the review of the Recovery Plan, these data should be examined to assess whether translocation trials are necessary for the persistence of the species in the wild. If appropriate, translocation guidelines should be prepared for the species.
For those land managers and organisations interested in improving the conservation status of A. pubescens, there are two alternatives to translocation that should be attempted - ensuring conservation of areas where the species currently exists, and in situ regeneration of the species. These alternatives are likely to be more successful than translocation programs and will not affect the genetic integrity of the species.
'Recovery' in the context of this plan will be targeted towards maintaining the current vulnerable status of A. pubescens and preventing it from becoming endangered. It will not be possible to recover the species to its former distribution, given the degree of development and the small number of conservation reserves within its distribution. In fact, unless actions are taken to reduce threats, it is likely that reductions will continue to occur in the current number of sites and the species will become locally extinct in some areas. The likelihood of local extinctions are quite high for this species given the large percentage of sites that are very small and fragmented, and the number of threats acting on sites (see section 9.2).
Despite the current status of the species, actions can be employed to halt local extinctions and improve the quality of habitat. The threats identified in section 9.2 are manageable and solutions are straightforward. Implementation of on-ground works will slow down the current rate of habitat loss and will lead to the enhancement of existing populations. However, the majority of sites occur on lands outside of NPWS estate. Thus the NPWS will need to negotiate with relevant landholders over implementation of appropriate on-ground works. If negotiations could be successful in protecting a majority of sites of A. pubescens, this would greatly improve the conservation status of the species. Given that a large number of sites are on land that is in public ownership, there is a high likelihood that successful negotiations could occur in relation to a large percentage of sites. Negotiation over management of sites is included as an action in this plan (see section 11).