1080 Use on the West Coast

Pest control operations on the West Coast are carried out by the Department of Conservation and the Animal Health Board and their contractors, to prevent damage to native trees and plants and to combat the livestock disease tuberculosis (TB) which is spread through wild possums. The Parliamentary Commissioner for the Environment has released a report which endorses the use of 1080 poison for possum control.

Possums are carriers of bovine tuberculosis (TB). A disease of cattle and deer, TB is highly contagious and poses a significant threat to New Zealand’s economy. A major outbreak of TB could put $10 billion per year of dairy, beef and venison export trade in jeopardy because our international customers for meat and dairy products would not buy our produce. Ferrets also carry TB. In the past, uncontrolled bovine TB has also posed a major human health risk.

Some 30% of New Zealand is in the conservation estate, but in only one-eighth of that estate is pest management carried out.

The management of the pest problem from an environmental perspective is the job of the Department of Conservation. The management of the pest problem from an animal health perspective is the job of TBfree New Zealand, the operating arm of the Animal Health Board.

Two organisations – one a Government department and the other a non-profit incorporated society, with differing objectives, tasks and funding, share a common enemy – the brush-tailed possum. Together, they spend around $66 million a year on possum control. Where possible, they work together to make sure the best value is obtained from their combined funds.

The West Coast accounts for about 35% of NZ’s total TB herd infection rate, because most of its farmland lies alongside large tracts of dense bush which is home to TB-infected wildlife.

The aerial application of the poison 1080 is widely used to target possums in bush-clad areas of the West Coast and it has become quite controversial, with a vocal minority opposed to the practice. Surveys have shown that about 40% of Coasters are not happy with the continued use of 1080.

In fact, 1080 is one of a range of tools and methods used to control possums, including other toxins, bait stations, hunters and traps. Some 75% of the control area on the West Coast will be treated using ground methods.

In Otira, DoC controls possums to protect the health of the mixed podocarp beech forest that occurs there. It picks the most palatable tree that exists in that forest and tailor the pest control to protect that species of tree – in the case of Otira it is the rata. At densities above a trap catch index (TCI) index of 15 possums trapped for every 100 traps per night , possums will be eating rata at a rate that is unsustainable for that species. This monitoring occurs at 30 or so sites in the Otira Operational Area . DoC authorises full scale aerial control when possum numbers are consistently high over all the monitoring sites – these full scale operations tend to occur every 4 to 7 years. These operations aim to reduce pest numbers to 5% TCI or less. A trickle feed operation is an interim control, and is a way of dealing to pockets of possums – areas where possum densities are higher – these areas tend to be around the bush margins , and river flats of the operational area . Possums are often in these areas making use of seasonal food sources – they are concentrated in these areas, so it is a good opportunity to control them. This is basic maintenance to slow the population build of possums in this area.

Trickle-feed sowing forest margins around farmland, roads and waterways using a helicopter, with a bucket slung underneath to deliver a low number of baits in a narrow swath along a flight line or at specific sites. The bucket works from a small electric motor and bait passes through a rolling drum. The rate of bait flow is adjustable and accurate. This method is useful for treating lowland forest margins when possums seek the early spring growth. Initially non toxic pre-feed would be used to increases possums acceptance of toxic baits followed by the application of 1080 cereal baits. Satellite navigation technology, slow flight speed and narrow swath width allows the pilot to be sure of the boundaries and to exclude important areas from being sown with baits such as huts or water intakes. This method will allow for effective coverage of the 1000ha area and require minimal bait to complete the task. The cereal baits used contain the pesticide sodium fluoroacetate with a 1080 content of 0.15% and are about 3 cm long, cylinder shaped pellets and are dyed green.

The Otira area is of high significance for conservation as it has a range of ecosystems including extensive and healthy forests of mixed podocarp, southern rata, totara, kamahi and broadleaf. The Otira is especially important as a key site for southern rata that has been badly damaged by possums elsewhere. The Otira area also holds populations of whio, kiwi and kaka; large birds that are becoming uncommon elsewhere. The full ranges of common forest birds are present throughout the area. Protection of forest habitat for these animals is vital to their long term survival.

Regular monitoring of tagged trees in the Otira area shows that the most vulnerable species in these forests, fuchsia and wineberry, are being maintained in good condition with very few browsed by possums.

The Parliamentary Commissioner for the Environment, Dr Jan Wright recently released a report investigating the use of 1080 – Evaluating the use of 1080: Predators, Poisons and Silent Forests. In the report Dr Wright recommends against a moratorium on 1080 citing the damage that would be done to native forests and animals if such a ban went ahead. “Possums, rats and stoats are chewing up our forests to the point that we are only a generation away from seeing regional extinctions of kiwis and other native species where no pest control is carried out. There are other pest control methods that are more suitable than 1080 in certain circumstances but on much of our conservation land there is currently nothing else that will effectively kill possums, rats and stoats. While there may be an alternative to 1080 one day, if we want to keep our forests for future generations we simply cannot afford to stop using 1080. Time is not a luxury we have. So many of our native forests, birds, reptiles and insects are unlike those found anywhere else in the world and form a distinct part of our identity. It would be a travesty to allow these to disappear.”

In practical terms, this means the continued use of aerial 1080 bait drops in forested regions. Ground control can’t be used over the vast tracts of native forest in rugged country where there is no control of possums, rats and stoats. In particular, in years when there is abundant seeding (masting) in forests you need to be able to knock down rats and stoats very quickly and effectively. This can’t be done with ground control.

Possums and to a lesser extent ferrets are thought to be the source of 80% of all new TB infections in dairy, beef and deer herds. The rest is caused by movement of infected cattle or deer from herd to herd. Controlling TB-infected wildlife is the key to eradicating bovine TB from New Zealand. Vector control operations aim to reduce the density of possum populations to numbers that are low enough to stave off the spread of TB and, ultimately, see the disease die out within those populations. The main form of vector control used around the country and on the West Coast is ground control. In the 2009/10 year over 300,000 ha on the West Coast was controlled using ground methods. Using either traps or toxins, ground control is useful for more accessible terrain, for follow-up control after an aerial operation and for areas where vector numbers are low.

Aerial control is used in selected areas where one of a range of factors might prevent or inhibit the ability to control the area effectively by ground methods. Aerial control is extremely efficient and this can be critical in some situations.

It usually takes three aerial operations over the same area to reduce and keep possum numbers at the low levels required to get rid of the disease.

There can be up to five-yearly intervals between each operation.

In areas with high possum numbers it is often more efficient to use 1080 baits to achieve the initial knockdown. Trapping is effective only once numbers have been reduced, because it is very labour intensive.

Despite the rugged nature of the West Coast terrain, aerial operations are only used on about 25% of the TB control area.

Aerial operations must use 1080 – it is the only toxin permitted by the Environmental Risk Management Authority for use this way – and have to meet stringent conditions.

Regulations covering the use of 1080 are specified and monitored by ERMA, but regionally many further regulations are applied to meet local council requirements. On the West Coast, these include resource consents issued by West Coast Regional Council and the approval of the independent Regional Medical Officer of Health.

Local consent from the Department of Conservation is required for operations on public conservation land and landowner agreements are required for work on private land. Buffer zones are used in sensitive areas and compliance with any conditions is regularly monitored by the consenting agencies.

Planning for possum control operations includes extensive communications. Neighbouring landowners are advised of operations well in advance and following this are visited to ensure that correct operational boundaries are clear and that any risks, such as to livestock and domestic animals are minimized and appropriately managed. Groups who use the outdoors such as hunting and tramping clubs are contacted and operations are often timed to avoid disrupting activities. Local schools are visited and the community is kept informed through fliers, meetings, media information and signposting.