NSW Bitou Bush Threat Abatement Plan - Department of ...

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54 Threat Abatement Plan - Invasion of native plant communities by Chrysanthemoides monilifera following removal of bitou bush therefore indicating they were limited by bitou bush invasion. < years of bitou bush control have not provided information on which species are affected by bitou bush invasions. An integrated approach to broad-scale weed management that incorporates plant conservation is long overdue. Such an approach is needed in order to deliver conservation outcomes from weed management (Downey 2003a, b, submitted). Thus, the ‘no change in current management’ control option would be a retrograde step which will not benefit biodiversity conservation. The cost of ‘doing nothing’ in terms of controlling bitou bush for biodiversity conservation can be assessed using the estimated cost of losing a species due to weed invasion, being $86,700 per species per year (see Sinden et al. 2004) and the number of species identified here as being at risk (158). Thus, the cost of ‘doing nothing’ equates to $13.7 million per year. Lastly, given the scale of the problem the cost of doing nothing at sites where species are threatened far outweighs the economic benefits of controlling new or isolated infestations. Arguments have also been made that control for biodiversity should also address potential or future impacts. Again, given the scale of the problem, the limited nature of resources, and the aims of a threat abatement plan, the current impacts to biodiversity are so great and immediate that they outweigh any potential or future impacts to un-infested areas. Such control programs are thus outside the scope of this plan and should be addressed in other plans (i.e. regional strategies). 7.9 Roles and responsibilities with respect to bitou bush control The declaration of bitou bush as a noxious weed under the Noxious Weeds Act requires land managers to control bitou bush (a list of all the local control authorities in New South Wales, in which bitou bush or boneseed is declared noxious, is presented in Appendix 1). In addition, the control of bitou bush and boneseed in areas containing threatened species may require a licence (see Chapter 2 for further details). 7.9.1 The role of the Bitou TAP in bitou bush management in NSW The role of the Bitou TAP is to prioritise the control of bitou bush in New South Wales for species, populations and ecological communities at risk and their locations where control will have the greatest biodiversity outcomes (see Chapters 4 and 6 and Appendices 3, 5 and 8). While the TAP aims to address the highest priorities, lower priorities (both threatened biodiversity and sites) should be used to establish regional and local priorities for bitou bush control. The priority lists are not definitive and other species and ecological communities in New South Wales threatened by bitou bush invasion may be identified in the future. The control of bitou bush other than for the priorities established here is outside the scope of this TAP, except for the species that co-occur at control category 1 sites. Control of bitou bush at lower priority sites (i.e. Category 2, 3, 4 and 5 sites) is the responsibility of local land managers and other strategies e.g. regional bitou bush strategies. Other funding sources should be maintained to combat bitou bush where programs are already in place or in other important areas.
Threat Abatement Plan - Invasion of native plant communities by Chrysanthemoides monilifera 8 Monitoring the recovery of priority biodiversity and the control of bitou bush 8.1 Developing a monitoring system for control category 1 sites To determine the effectiveness of any weed control program, a monitoring program must be developed and implemented. Monitoring programs must take measures from both controlled and uncontrolled areas in order to detect any changes in bitou bush attributed to the control program. In addition, given that this plan is focused on biodiversity at risk, monitoring must be tailored to those entities identified as being at risk. Many variables can be measured and a number of monitoring techniques can be used. The following measures must be addressed at control category 1 sites described in the TAP: < the response of bitou bush (adults and seedlings) to the control program, measured by detailed and frequent assessments of plant abundance and vigour, as well as through regular observations from photo points both prior to and post control < the response of the high priority plant species, populations and ecological communities to the control program, measured by a similar range of measures as described for bitou bush above < the response of other weed species to the control program, measured by regular surveys of the other weed species along with their relative abundance. More detailed measures can be obtained using similar response variables as described for measuring the response of bitou bush above (e.g. plant vigour). Additional measures can help to determine the effectiveness of control programs with respect to the broader invaded community and should be collected where resources are available: < the response of a broader suite of native species (both plants and animals), populations and ecological communities to the control program, measured by similar range of measures as described for other weed species above < the response of biocontrol agents following the control program, measured by the rate of attack and density of the agents taken at regular intervals following control. Measuring these variables is difficult and sampling methods need to consider several factors: < the timeframe required to measure a response, for example, to determine bitou bush recruitment/seed bank depletion rates accurately a timeframe of at least five years is required to account for seed dormancy < differences between controlled areas and non-controlled areas, or before and after control need to be accounted for < the timing of individual measures or samples (e.g. summer) and interval between them < the level of replication needed to provide credible results < how the data will be analysed/presented < a balance between too simplified and too complicated data collection techniques < a standard and consistent way of collecting data < experimental non-treatment and control sites < commitment to maintaining the integrity of the sampling design and regime over the course of the monitoring program. A more detailed discussion on monitoring bitou bush, the biodiversity at risk and other weeds is presented below, followed by a proposed monitoring system for this plan. 55
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