7. Summary
New Zealand uses more 1080 each year than any other country. The major users of 1080 are the Animal Health Board, to control Tb vectors (mainly possums), and the Department of Conservation, to protect conservation values from mammalian pests (again, mostly possums). This situation is a consequence of our unique evolutionary history. We are trying to rectify the mistakes of the early European settlers who, in the absence of native land mammals, imported a great variety of “replacement mammals”. Unfortunately, some of these have had disastrous impacts on our native plants and animals. As a vertebrate toxin, 1080 can be used here to control pest mammals without putting at risk a wide range of native mammals, as would be the case in most other countries.
As 1080 use has increased in New Zealand, it has been necessary to find out how 1080 behaves in the environment, what risks it poses to native and domestic species, and whether it affects human health. Over the past 30 years, the possible risks of 1080 in the New Zealand environment have been studied intensively. Researchers have also studied the benefits of using 1080 for the reduction of Tb in cattle and deer herds, and the benefits for the native animals (especially birds) and ecosystems that have proved to be so vulnerable to introduced species. A third line of related research has been into improving management techniques for pest control, seeking ways to increase effectiveness, lower costs and reduce risks to pest control workers, non-target species, and the environment in general.
For the major user of 1080, the AHB, the benefits of 1080 as the primary tool to reduce the incidence of Tb in cattle and deer herds are clear. There are currently no effective and affordable alternatives. The present approach of ground and aerial operations, and combining 1080 use with other poisons, is effectively reducing the incidence of Tb. While the trends are encouraging, the goal of Tb eradication is still some years away. The costly mistake, made during the 1980s, of relaxing the control effort cannot be repeated if Tb is to be eliminated.
Studies of native forests and birds have shown the widespread benefits of using 1080 to control mammal pests. Although only 15 –18 % of conservation lands are under sustained management for possums, DOC research and monitoring show significant gains are being achieved. These gains are essential if we are to achieve the goals of the New Zealand Biodiversity Strategy54 which outlines the threats causing the decline in our indigenous biodiversity. Where no control occurs, predators (including possums) are annually killing about 95% of kiwi chicks, about 85% of kokako chicks, and similarly high numbers of chicks and nestlings of other endangered birds, including kaka and mohua (yellowhead). 1080, used in bait stations or in aerial drops, and in combination with other toxins, is helping to “stem the slide” to extinction faced by a number of our bird species.
Research on management techniques has led to steady reductions in the aerial sowing rates of 1080 bait, from a high of 20 kg per hectare in the 1970s, down to current rates of 2–5 kg per hectare. These current sowing rates represent the application of 3- 7.5 grams of 1080 per hectare, about 1-2 teaspoonfuls, respectively. Monitoring shows that these low sowing rates appear to have little or no deleterious impact on the bird species most at risk, that is the small insectivorous species such as robins and tomtits. Instead, populations of these species benefit from fewer predator and possum numbers, despite the occasional deaths of some individuals. Similarly, many insect species benefit from low possum numbers as they make up an important part of possum diets.
Other studies summarised here have shown how plant species such as northern and southern rata, mistletoe, fuchsia, tawa, kohekohe and others have recovered after possum populations have been reduced to low densities and maintained through follow-up 1080 operations. The non-target deaths of deer in aerial operations also assist forest recovery, although deer numbers generally recover within a few years through annual breeding.
The concerns people have held over possible contamination of water supplies have led to extensive water sampling after aerial 1080 operations since 1990. The results show that 96.5% of 1649 samples contained no traces of 1080. Only 0.3% of the samples had 1080 levels of between two and four parts per billion. An adult would need to drink an impossibly large amount of water from such a source, over a period of weeks, to suffer any health risk. Research has shown that common bacteria and fungi rapidly break down 1080 in both water and soil, but less quickly at low temperatures. The high solubility of 1080 in water and the breakdown action of common bacteria mean that 1080 has only a short-lived presence in water bodies if pellets do get into water systems.
1080 has never been detected in rural or city water supplies following 230 aerial 1080 operations between 1990 to 2003. Continuing strict adherence to all the specified operational features to protect human health should maintain this safety record.
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