Summary
Terms of Reference
Aims and Scope of This Report
Declaration
Basis of This Report
Structure of This Report
The Issues
A. Appraisal of Issues Identified by MAF from Public Submission
The Rabbit Problem
-Effects on agriculture
-Ecological Impact
Flora
Fauna
-Current Rabbit
Control
Epidemiology of RCD
RCV as a Biocontrol Agent
Effects of
Introduction on NZ Flora and Fauna
Programme to Release the Virus
B.
Appraisal of Additional Issues listed in
'MATTERS TO BE CONSIDERED'
C. Other Issues
APPENDIX A
Areas of Expertise - Glenn Iason
INTRODUCTION OF RABBIT CALICIVIRUS INTO NEW ZEALAND
ISSUES REPORT
REPORT TO MAF CHIEF VETERINARY OFFICER
by
Glenn R. Iason
Macaulay Land Use Research Institute
Craigiebuckler
Aberdeen AB15 2QH
UK
10 February 1997
Rabbits are a pest species particularly of pastoral agriculture, which is the main land use in the most rabbit prone parts of New Zealand. They compete directly with domestic stock for food and in high numbers can contribute to denudation of vegetation and cause breakdown of soil structure in areas of intense burrowing.
The economic impact due to the necessary costs of control can be locally severe. The seriousness of the rabbit pest problem declines as the scale over which the problem is viewed is increased from local to regional to national, although rabbits still impact on agricultural production at these higher scales.
Rabbits have a very high impact on natural ecosystems through the high grazing pressures they exert resulting in low biomass grassland communities. Plant and animal species of short grasslands probably benefit from the presence of rabbits and vice versa. They are also key prey species for many predators and hence influence the predator guild structure. Some of the rabbit's predators, but particularly the ferret, carry Bovine Tb.
The over-riding impression of the effectiveness of RCD as a biocontrol agent is one of uncertainty. This is due mainly to the current lack of hard data concerning how the disease is spread, its likely reservoirs, and the effects of climate and host density on disease epidemiology. In the absence of disease resistance in New Zealand, the initial mortality of rabbits is likely to be high, especially in high density areas. However the extent and timing of subsequent waves of the disease cannot be predicted with any certainty.
The introduction of RCD will result in some positive effects on native flora, but also some negative effects, such as the spread of scrub communities of potentially low species and structural diversity. This particular negative effect would need to be mitigated with scrub control program, or adjustment of grazing strategy using domestic stock. The positive effects of large scale rabbit removal on native vegetation are unlikely to be realised if the rabbit grazing is simply replaced with grazing by more domestic stock.
Reductions in rabbit numbers due to RCD would effect changes on native fauna via increased vegetation biomass and structural diversity which would be more similar to the original environment in which many native species evolved. However, species of invertebrate, reptile and bird which require short grass habitats for any part of their life-cycle are likely to decline. An important and likely negative influence of reduction in rabbit numbers due to RCD, on native fauna is the effect this might have on prey switching to native species, by the usual predators of rabbits including cats and mustelids. Although this will be important in the period immediately after RCD affects rabbits in a particular locality, the effect may attenuate with time, recur sporadically with new disease epidemics and/or continue for a longer period, depending on the way in which the disease interacts with the rabbit populations. This very undesirable effect could be mitigated with a very large predator trapping program which would need to be targetted both geographically and temporally, to protect threatened native animal populations. An effective trapping program would need to be well resourced and organised and potentially remain in place if necessary for a period of several years or longer. There remains a question as to the trapability of predators during times of abundance of their prey items.
The program to release the virus has been planned to achieve good geographical coverage with the disease whilst permitting some environmental monitoring and feedback from specifically chosen sites. It also minimises the effect of prey switching by predators to ground-nesting native birds. Such a high impact, nationally important ecological event as the introduction of RCD, requires the formation of a body of responsible parties and experts to oversee the process at the national level. The previous devolution of responsibilty for rabbit control to the regions is not conducive to achieving the level of integration necessary to ensure success of mitigation measures and maximise the benefits from RCD.
Although unpalatable, the threat of illegal introduction of RCD is real. Instead of a simple yes or no answer to the introduction of RCD, other decision options including provisos regarding the timing of the introduction and implementation of mitigation measures, should be considered.
As per letter dated 23 December 1996, from Barry O'Neil, The Chief Veterinary Officer, namely
'- identify and address any new significant issues, and
their impact on the application; and
- address the identified issues and any others that you think should be taken into account.'
To provide a review and opinion on the ecological issues in my area of expertise, connected with the introduction of RCD. The review has been kept intentionally brief as requested in the terms of reference letter. Only the main issues are covered; exhaustive coverage of all issues raised in the public submissions is not attempted. I have not worked on New Zealand wildlife and hence restrict this report to the relevant general principles, rather than include a detailed consideration of all species and habitats. The report is not intended to be an abbrieviated impact assessment, which I believe to be the responsibility of the applicant group. Nor is it a critique of the 'Application to Introduce RCD and Import Impact Assessment' - this was provided in a previous report of 18 July 1996, and by the other members of the original peer review group. Since this report aims to synthesise the pros and cons of taking a particular action viz the introduction of RCD, the selective quotation of parts of it, taken out of context, are of no value.
Neither Glenn Iason nor the Macaulay Land Use Research Institute has had any prior connection with the issue of RCD in Australia or New Zealand, other than as a member of the peer review group.
This report was prepared from a biological stand-point, on the basis of the previous experience of my own research and reading, plus information obtained from reading the IIA and its appendices, the other peer reviewers comments on the Application and IIA, the analysis of public submissions and the public submissions that were made available to me (those covering ecological and process issues).
A. An appraisal of the issues identified by MAF as having been raised by the submitters.
I address sections 1,3,4,8 and 9 which are within my area of expertise. These are cross-refernced to the list of 'MATTERS TO BE CONSIDERED FOR DECISION MAKING' (MCDM).
B. An appraisal of the issues listed in 'MATTERS TO BE CONSIDERED FOR DECISION MAKING' which were not considered in section A.
I address only those issues that I consider to be within my area of expertise.
C. Other issues that I consider should be taken into account.
A. An appraisal of the issues identified by MAF as having been raised by the submitters.
nature, source and effects of the rabbit problem
current control, effectiveness, costs and alternatives (MCDM 5.1)
Nature of the rabbit problem - Effects on Agriculture:
The negative effect of the large numbers of rabbits in New Zealand which attracts most attention is the effect on pastoral agriculture. The main type of animal production enterprise affected is sheep farming. Although other forms of livestock production and other land uses including forestry, horticulture, viticulture are affected by rabbits, the effects on these may be locally severe but are are generally less widespread.
Pastoral agriculture is affected primarily by rabbits eating vegetation that would otherwise be eaten by domestic livestock, resulting in financial costs by reducing stock performance and requiring financial input for control operations. The expenditure required for control of rabbits using current techniques, in rabbit-prone areas is large in proportion to income in these areas; the high financial impact of rabbits on particular farms is persuasively argued in the public submissions. Where former grazing land is denuded of vegetation, remaining ground cover is sparse or land has been colonised by plant species not compatible with pastoralism, this has often been attributed in whole or in part to the presence of rabbits. The result is that stock numbers have to be reduced.
The magnitude of the rabbit problems outlined above vary strongly between geographic areas, ranging from a very high impact in some localities mainly in the South Island, compared to no problem at all in some other areas. Perceptions of the problem are related to the scale at which it is viewed; the magnitude of the problem declines, as the scale over which it is considered is increased, eg from a local scale to regional to national. In comparison to the total human population of New Zealand, relatively few people and a small area are adversely affected by rabbits. However those that suffer, form part of an industry which is the major contributor to the NZ GNP.
Since the introduction of RCD cannot be definitely contained in any one locality, it must be assumed that its consequences will be borne nationally. The decision maker will need to decide if the magnitude of the problem at the national scale warrants any possible ill-effects of RCD being borne at the national scale.
The precise proportion of the negative effects described that is attributable to rabbits cannot be ascertained. However I accept that at they are at least a contributory factor to the problem. From my own current experiments and from published literature (Myers and Poole 1963; J Ecol,51,435), I am in no doubt that they compete significantly with domestic stock in New Zealand as in other countries, although the degree depends on the density of both.
Nature of the rabbit problem - Ecological Impact:
It is important to remember that the most effective way to assess the impact of rabbits, and the effects of their removal, is to analyse their impact on individual species as well as on the communities in which they live. This affords quantification of conservation value in terms of the both the species and the habitat's status and distribution, and facilitates the specification of mitigating measures if a change is imposed. However, several factors preclude very accurate prediction of the impacts of rabbits and their removal, on other animal and plant species and communities:
(i) the specific and complex nature of ecological interactions means that effects observed elsewhere are unlikely to be exactly repeated in New Zealand, where different species and combinations of species are involved.
(ii) lack of data in New Zealand on the abundance and distribution of species likely to be influenced, particularly of the invertebtrate species, whose conservation profile is much lower than that of birds.
(iii) unwillingness or inability on the part of the applicant group to collate available information into a comprehensive impact assessment.
These same factors also limit the confidence with which mitigating measures can be suggested. In the absence of a comprehensive species and community level impact assessment, I am only able to synthesize the issues at a fairly general level.
Rabbits have a high impact on natural vegetation via:
(i) the direct defoliation of plants.
Individual rabbits feed selectively and can reduce the abundance of preferred plants, particularly if they are intolerant to grazing. Conversely, plants which remain uneaten by rabbits can become relatively abundant. When rabbits are at high density then usually unpreferred species are defoliated. Some species notably the introduced grasses in New Zealand are tolerant to grazing and are likely to be enhanced in the presence of rabbits, whilst grazing-intolerant species are more likely to disappear under rabbit grazing.
(ii) the modification to the communities due to alteration of the competitive relationships between the communities' component plants.
As a general rule, but particularly in nutrient rich areas, a few species, notably grasses, can dominate the vegetation community. The grazing activity of rabbits can reduce this dominance and promote species diversity.
(iii) destruction of soil structure due to their burrowing and scraping activities. If this leads to vegetation loss and soil erosion then these effects are not easily reversed.
Due to this broad range of effects, it is likely that some native plant species and communities benefit from the presence of rabbits whilst others are negatively influenced.
Rabbits are an important component of most systems of which they are a part because of the link they form between primary production and a range of predators and scavengers which consume them. Their high reproductive rate allows them to respond quite rapidly to changes in environmental conditions reaching high densities which in turn have a high impact on the environment. Rabbits affect other fauna by (i) modification of the habitat and (ii) more directly as they are a key prey species.
(i) modification of the habitat
In that rabbits maintain areas of grassland in a short growth form, this impacts negatively on all other animal species whose habitat preference would be for longer vegetation. Conversely their presence probably has a positve influence on those requiring short grassland habitat. Although in some circumstances the latter may occur naturally in New Zealand,
in the main, the evolution of New Zealand native fauna has been in the absence of high impact ruminant and lagomorph herbivores such as the rabbit. It is hence likely that most native fauna, with the exception of specialist short grassland species would be negatively affected by the type of habitat modification effected by rabbits.
(ii) as a key prey species
In many areas rabbits form the main dietary item of several predators including the introduced stoats, ferrets and cats as well as for the raptors such as the New Zealand Harrier. There are several examples in the scientific literature, in which the densities of a key prey species influence the numbers of a predator species (and vice versa) and it is likely that the populations of the above predators are linked in some way to the rabbit populations in New Zealand. Causality in this linkage is difficult to prove, but it is likely that the large numbers of rabbits sustain greater population sizes of the predators than would occur in the absence of rabbits. Rabbits have an important role in shaping the population sizes and the composition of guilds of predator species. As well as affecting predation on other wildlife, this has implications for the spread of Bovine Tuberculosis as correlative evidence suggests that the disease can be spread by ferrets and possibly stoats.
Current Rabbit Control, Effectiveness, Costs and Alternatives
(MCDM 5.2)
The main techniques currently used in New Zealand for controlling rabbit numbers are poisoning, shooting, trapping and gassing. A long-term strategy for reduction of rabbit numbers involves modification of the habitat to make it less favourable to rabbits. Shooting, trapping and gassing can limit rabbit numbers where they are already fairly low but only poisoning can reduce numbers from very high levels in a cost-effective manner. Even so, poisoning only appears to be cost effective in some circumstances. The magnitude of these costs are often appraised relative to the income from the land-use on the property. They should however properly be appraised relative to the additional incomes generated on the land as a result of the control operation, but this quantification is difficult to achieve. Poisoning has a questionable long-term future due to the possible future development of aversion by rabbits to either the baits used, or to the toxins themselves. The poisoning techniques confer environmental disadvantages of affecting non-target species by direct ingestion or by secondarily poisoning predators or scavengers which eat affected rabbits or rabbit carcasses. Alternative methods of rabbit control involving sexually transmitted fertility control are currently being developed, but these require refinement and are likely to encounter opposition from the public due to general wariness concerning biotechnological products.
It is likely that in the most rabbit-prone or most rabbit affected localities, the costs of rabbit control by currently conventional methods cannot be financially justified by the returns that reduced rabbit numbers bring. This leads to the conclusion that under current economic circumstances, either the purely ruminant production land-use is innappropriate for these areas, that it is appropriate as long as some form of subsidisation from elsewhere is supplied, or that alternative cheaper rabbit control methods are required. Several sources have raised the issue of commercial harvesting of rabbits as an alternative form of animal production from these areas. The commercial viability and sustainability of this alternative is questionable in the absence of a full analysis. It would be likely to require effort and financial input to establish large enough overseas markets for rabbit products.
adequacy of knowledge about the the methods of transmission of the virus and behaviour of RCV in New Zealand (MCDM 5.7)
Attempts to predict the behaviour of the virus in New Zealand are based on the limited knowledge of its effects and spread elsewhere. These limited data derive mainly from Spain and the earliest observations now available as personal comments from Australian scientists on their experiences in Australia. Statements regarding the means of transmission of the virus appear to be mainly speculative. Information on transmission of RCD is an important ommission from our knowledge since it is germane to the persistence of the virus and its frequency, pattern and season of future recurrence, if any (see 4. below).
assessment of effectiveness and suitability of RCV as a biological control agent - its ability to maintain stated pastoral and environment goals over time (MCDM 5.3).
Estimates of the mortality of rabbits attributed to initial epizootics of RCV vary from none at all, 20% to 95%, all in Australia. In Spain the disease is reported to have caused local extinction of rabbits although this claim is not well substantiated. Given the absence of antibodies to RCV of tested rabbits in New Zealand, it is likely that large initial knockdowns will occur, and that young rabbits upto a few weeks old will not suffer mortality on infection, due to a resistance at this age - very young rabbits would die if their mothers die during early lactation. The subsequent behaviour of the disease and its effects on the rabbit populations is an area of far greater dispute. The presence and the nature of disease reservoirs and the involvement or otherwise of vectors of the disease, are among the as yet unknown factors that would lead to contrasting patterns of disease spread and long-term behaviour. The preliminary models produced by Barlow (1996, Modelling the likely impacts of RCD, Report to MAF Policy) make predictions which I consider to be too speculative on which to base any firm decisions regarding introduction of RCD. The call for further data made by Barlow himself (1996) implicitly endorses this conclusion. The refinement of the models to include more of the data emerging from the spread and effects of the disease, including the development of immunity, in populations in Australia, would be most valuable. It should be noted though that this course of action would not guarantee error-free predictions for the disease effects in New Zealand, where climatic factors, vectors and the effects of predators will all be unique. In addition, these factors will vary locally within New Zealand. However, despite these specificities, I believe their effects could be fruitfully modelled and used constructively in decision making.
A further area of uncertainty is the population density of rabbits on which RCD will act. One of Barlow's models suggests that there is a threshold population density of rabbits required before the disease will spread and result in significant mortality. This prediction is at odds with the findings in Spain, where the disease has recurred in low density populations.
The possible medium and long-term effects range from rapid recovery of the rabbit populations to their pre-RCD sizes, recurrence of the disease in a cyclic fashion as in Spain where it is reported to occur at two-year intevals, or irregular and unpredictable epidemic events. Any of these scenarios could result in initially smaller rabbit populations which tend to return to original sizes after varying time periods. It is not out of the question that RCD would reduce rabbit populations in the long term and maintain them at low levels, but I think this a most unlikely outcome, given the liklihood of acquired disease resistance by the rabbit populations.
A secondary benefit of RCD may lie in the possible longer-term reduction of numbers of predators of rabbits, notably ferrets, which are probably vectors of Bovine Tb.
Clearly very little certainty can be attached to the ability of RCV to maintain any stated pastoral and environment goals over time in NZ. The safest assumption on which the decision-maker could operate in the light of current information, is that RCD will spread rapidly, causing a very high mortality of rabbits and that chaotic population fluctuations which are unpredictable in both time and space will ensue. This would be the worst-case scenario and the most difficult and testing conditions under which any mitigating measures would need to be imposed.
8. Effects of introduction on New Zealand flora and fauna
the prey switching problem and the need for predator control (MCDM 5.5)
It should be noted that despite having identified a negative effect due to the presence of rabbits, it does not necessarily follow that simply to remove them will solve the problem.
Effects of introduction of RCD on flora:
Despite the paucity of information available, some generalities concerning the effects of reduction of rabbit numbers on communities can be concluded.
Rabbit grazing results in lower standing crops of vegetation and intense grazing can lead to reduction of ground cover of vegetation. Reduced rabbit grazing pressure is likely to lead to higher standing crops and re-vegetation of these areas although the exact time course of the re-colonisation will depend on the extent of denudation. Where soil degradation has taken place recovery is likely to be very slow, if at all.
The reduction of rabbit numbers in areas that might support native tussock grasslands is likely to facilitate the re-establishment of these valued communities. In contrast where rabbit grazing holds in check the highly competitive grasses, facilitating the persistence of more diverse communities of herbaceous plants, a reduction in rabbit numbers is likely to lead to reduced species diversity. Where particular species that are favoured by the current grazing regime are of high conservation value, there is a danger of a change that is detrimental to conservation values, if these are lost due to a reduction in rabbit numbers.
Woody plants are generally less tolerant to grazing than grasses and hence reduction in rabbit numbers is likely to favour survival of woody species, which would be advantagous if the species was a conservation issue, such as species of native broom. A related negative aspect of the introduction would be the occurrence of similar experiences as in the UK following myxomatosis. Invasion of grasslands by species of woody shrub formed dense communities of low species and structural diversity; this is a likely outcome of reductions of rabbit populations in New Zealand, and would need to be mitigated by scrub control or alteration of the grazing strategy with domestic stock.
Effects of introduction of RCD on fauna:
Effects due to likely habitat modifications
If greater standing crops of plants follow reductions in rabbit numbers after introduction of RCD then this may in turn lead to greater numbers of rats using the cover of the taller vegetation. The increased vertical component of vegetation will probably facilitate the occupation of the habitat by more species of insect and other invertebrates, such as grasshoppers and spiders. The increased structure of the vegetation is also likely to favour some of the species of skink. These factors appear to sum to a net gain for conservation of the introduction of RCD. However, a critical final analysis would need to evaluate the current status of those species that would probably be positively benefitted by the introduction of RCD and balance these up against those that are likely to be negatively affected by the introduction, such as dung-feeders or those with a specialist requirement for short vegetation. I do not believe that this analysis has yet been performed. For example if 10 species that were already common were to benefit from a predicted habitat change but one already threatened species were to go extinct, one would hesitate to impose the change. Indeed the opposite may be true, in that already threatened species may benefit from the putative habitat modification.
Effects due to prey switching by predators
There is a strong probability that under a regime of reduced rabbit populations due to RCD, then the predators of rabbits will switch to alternative prey sources. This statement is based on observed effects of other disease introductions such as myxomatosis and on the effects of RCD in Europe and Australia, as well as on the generally good understanding of predator-prey relationships in other well-studied ecosystems. The focus of the debate concerning this effect in New Zealand has been likely influence of ferrets, stoats and cats on the ground nesting native birds. This effect could be mitigated to some extent by an intensive program of predator control prior to the release or arrival of RCD in the well known areas occupied by these species which are at risk. The financial costs and implementation plan for these measures are not documented in the IIA, but in public submission 795 the Deptartment of Conservation provides estimates. The possibility of occurrence of similar effects of prey switching on other species such as skinks and large insects has not been thoroughly assessed.
Although the likelihood of occurrence of prey switching is high, the extent, time course and geographical distribution of the effects are all less clear. The reason for these uncertainties are that they are dependent on the way in which the disease might spread and persist throughout New Zealand, and our ability to predict these characteristics is currently poor (see section 4 above). Prey switching is widely held to be a short term effect which will be associated with initial knock-downs of rabbits populations. However, it is by no means certain that the effect will be only short-lived. The magnitude of the effect will probably diminish if the predator numbers decline with time, as is likely to occur if there is a long-term sustained reduction in rabbit population sizes. But depending on the resultant predator population sizes, the final predation rates on native prey species may still be higher than the pre-RCD situation. Additionally, both short and long-term changes in the proportions of the individual predator species which comprise the total predator population, are likely. This will depend on the extent to which the population sizes of the predator species are differentially affected by the reduction of rabbits, as well as on competitive and direct interactions between predators. If the composition of the resultant predator population favours a predator of a particular native species in a particular area, then that species will undoubtedly suffer. It is crucial to obtain as much information as possible from the Australian RCD release in order to increase the certainty of the predictions of the effects of RCD in New Zealand. This may take several years.
The indirect effects on native fauna due to prey switching by predators would probably overall be negative. However, in contrast, the same conclusion applies to the direct effects on both flora and fauna of habitat modification by reduced rabbit numbers due to RCD. These direct effects are likely to be negative for some native species but positive for a greater number. In my opinion this bias does not, on its own, provide an arguement in favour of the introduction. Rather, although the nature of the formal impact assessment has been superficial, the evidence points to the potential of RCD to have positive ecological effects. However, it is clear that if any benefits are to be realised and the possible serious negative consequences on native plants and animals are to be avoided, mitigation of the negative effects is imperative. The decision maker must be satisfied that mitigation measures can be successfully implemented, prior to making the decision. A full assurance of this should include that the proposals are technologically practicable, such as the ability to control predators or invading scrub, and that the resources and organization exists to undertake such measures for a long or indefinite period.
9. Programme to release the virus (MCDM 5.4)
RCD alone is not likely to solve the long-term problem that pastoral agriculture in New Zealand has experienced due to competition with rabbits. If it used injudiciously in the form of an ill-prepared introduction (or an ad-hoc illegal introduction) then the maximisation of its potential benefits to agriculture and the natural environment, will not be realised. At worst an ill thought out introduction will cause only a short-term drop in rabbit numbers and a return to the
staus quo, simultaneously causing untold damage to native fauna as a result of predation being displaced from rabbits to native fauna.
The proposed strategy of release attempts to maximize the impact of RCD on rabbit populations, whilst with its timing it tries to minimise the effects of switching to alternative prey (in the form of native birds) by the predators of rabbits.
Post-introduction monitoring of effectiveness of RCD, and implementation of mitigation measures, particularly scrub and predator control, are essential. The proposed RCD release strategy would permit a degree of implementation of feedback from the monitoring operations into subsequent viral relases.
However, although the IIA identifies the responsibilties of the different organizations, little formal provision has been made across the responsible bodies, to coordinate the implementation of release, monitoring, predator control, vegetation management and subsequent rabbit control measures. The integration of these actions would be required at a national level, at sites additional to those being monitored by Landcare.
B. An appraisal of the issues listed in 'MATTERS TO BE CONSIDERED BY THE DECISION MAKER'.
This section includes only those items in the list of 'MATTERS' which were not considered in section A and which are within my area of expertise.
One point of view expressed commonly in the public submissions is that any method which implements large scale culling of the European rabbit is unacceptible. The appealing appearance of rabbits has considerable impact on the overall public perception of them. Rabbits in New Zealand did not co-evolve with a naturally occurring suite of predators and many of the diseases which may also exert control over their numbers are absent. Under these circumstances, the need to control rabbits to some extent is inescapable.
In comparison with other methods of rabbit control, RCD is relatively humane. The time from infection to a relatively painless death is short. If RCD were to be released or were to spread to populations during the time that young rabbits were in their burrows or breeding stops, then the resistance of the young whose mother was killed by the disease may lead them to die of starvation. This is a most inhumane consequence of RCD introduction. Since the climatic conditions and season in which RCD is likely to spread or secondarily reappear in the rabbit populations in New Zealand is unknown, the probability of this occurrence cannot be ascertained. Data from the spread of the disease in Australia would help resolve this deficiency.
C. Other issues that I consider should be taken into account.
1. Haste in preparation of the application and the possibility of illegal introduction.
One of the main factors hampering a more quantitative and careful consideration of the issues relevant to the introduction of RCD into New Zealand is the haste with which the process has been conducted. The origin of this haste is not completely clear to me, but it appears to stem from the assertion of the applicants that the disease will be introduced illegally into New Zealand. This may take place in a manner or at time when mitigating predator control measures could not be mobilised or when native fauna was at high risk from prey switching.
I agree that a realistic assesment of the situation is that an illegal introduction would take place eventually. However, I do not think that this should be used as a lever to force a rapid legal introduction of RCD. A counter arguemnt is that in order to derive full and lasting benefit from RCD, New Zealand must carefully consider its impacts and strategy for its implementation and integration into other control methods. I submit that as well as the two options of either
1. legal introduction of RCD
2. reject the application to introduce RCD,
further options should be considered. These include:
3. reconsider the application in four or more years time, after the data from the Australian experience are known.
4. accept the application now but defer the introduction until after the data from the Australian experience are known.
5. accept the application provisional to the assurance that mitigation measures can be effectively implemented.
These aspects are clearly outwith my area of expertise. However, it appears that several objections to the legality of the application and the consequences of RCD have been raised in the public consultation process. It would be advisable for MAF regulatory authority to satisfy themselves on all counts at this stage before proceeding further with the assessment of the application.
Of potential importance is the objection raised for example in submission 236, concerning the effects of rabbit carcasses generated by the disease on public health and "nuisance" covered by the Health Act 1956. If such nuisance coincides with human habitation, access or water supply, then the introduction of RCD may contravene this act.
3. Land management and grazing strategy of domestic stock
One suggested way to deal with the problem of rabbits as a pest is to adopt an integrated land management strategy (eg Rabbit and Land Management Program). Despite references in the Application and IIA document to the integration of RCD with other methods of rabbit control, there is little sign that this ethos has been taken on board in the context of integration of the effects of RCD with land management in general.
No consideration has been given as to how strategies of land management, including grazing by domestic stock, could be used to maximise the benefits of RCD and ameliorate the undesirable effects of rabbit control such as scrub development. Provision should be made to provide restrictions or at least guidelines to farmers concerning limitation of stock numbers to facilitate vegetation recovery which would in turn facilitate gains for conservation or subsequent agricultural use of land. Implementation of grazing livestock on the conservation estate should be considered if benefits would accrue to retaining open short grassland habitats.
Relevant Areas of Experience and Expertise
Glenn R. Iason
This report was prepared by Glenn R Iason, a biologist with 17 years of post graduate research experience covering a range of aspects of the ecology, reproduction and behaviour of wild mammals including mountain hares, European rabbits, European hares, red deer and roe deer. This research experience has been gained in several natural environments including upland moorlands of the UK, Boreal forests and Arctic woodlands of Scandinavia, and East African savannah where I studied the antipredator behaviour of the African buffalo. My main expertise is in the area of plant herbivore interactions and includes studies of the nutritional ecology and feeding ecology of lagomorphs, sheep, goats and deer. Recent work includes the impacts of changes in land use, notably afforestation and changes in sheep stocking, on the feeding ecology and distribution of mountain hares and European rabbits.
I have published over 40 scientific papers in refereed international journals, covering these subjects.
Scientific career:
1977-80 University of East Anglia
BSc hons Biological sciences
1980-83 Research Assistant - University of Cambridge
Rum Red Deer project
1983-86 PhD Student - University of Aberdeen
Seasonal reproduction of mountain hares
1987 NERC post-doc fellowship - Aberdeen
Effect of plant tannins on lagomorph feeding ecology
1987-88 Royal Society European Exchange Fellowship - Sweden
Comparative nutritional ecology of hares
1988- Research ecologist - MLURI
1990- Associate - Northern Ecological Consultants
1993- Honorary Lecturer - University of Aberdeen
Contact for Enquiries
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NEW ZEALAND
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