Motutapu Pest Free Farm

A $3 million operation targeting seven animal pest species has been operational for one year on Department of Conservation-managed Motutapu and Rangitoto Islands, in Auckland’s Hauraki Gulf. “At its conclusion, Motutapu may be the only pest-free farm in New Zealand and possibly the world”, says farmer Rick Braddock who grazes sheep and cattle on this DoC recreation reserve. The challenge is how the ongoing pastoral farming aspects of the island tie into the rapidly changing/enhanced ecological landscape.

The 1509 hectare Motutapu Island is joined by a causeway to Rangitoto Island in the Hauraki Gulf, a short ferry-ride from Auckland City.

Motutapu is a Department of Conservation recreation reserve, managed to protect natural and historic values. Much of the island is taken up by a 1340 hectare pastoral farm, capable of supporting around 3500 breeding ewes and 1000 beef cattle.

Motutapu Farm Limited is managed by the company’s shareholder and director, Rick Braddock. Rick is also a trustee of the Motutapu Restoration Trust who took on the lease in 1992 after a public tender process.

With its deep, rich soils from the Rangitoto eruption, Motutapu is more fertile than other Gulf islands and has a reputation for producing very good livestock. The long-term aim is to integrate pastoral farming with other values on the island. These include the ecological restoration being carried out by the Motutapu Restoration Trust, pest eradication, recreational uses including the Home Bay Camping Ground and the outdoor education camp at Administration Bay and events like the “Dual” multi-sport event day held in March.

Grazing management is designed around preventing historic sites – including Maori campsites, pa and artefacts as well as defence installations built during World War II – from being overgrown and damaged by tree roots. Only sheep and light cattle are grazed in these areas, especially during the winter months when some more sensitive sites are fenced off.

The farm also represents a funding source, contributing to maintenance of the island’s infrastructure.

Rick Braddock is keen that DoC gets credit for its commitment to managing these types of public/private partnerships. It is in effect the glue that keeps the whole operation ticking over and pointed in the right direction. It has come under quite a bit of flack over pest eradication projects and the associated poisoning programme. The way in which the Rangitoto/Motutapu project was engineered and executed and how DoC continues to maintain an active monitoring and biosecurity programme, is very impressive, Rick says.

Attached: Excerpts from Motutapu Restoration Programme.

PEST ERADICATION

Seven introduced predators – Norway rats, ship rats, mice, feral cats, rabbits, stoats and hedgehogs – were targeted in an eradication operation covering both Motutapu and neighbouring Rangitoto Island; a total 3842 hectares. Wallabies and possums were eliminated during the late eighties and early nineties, using a combination of 1080 poison, ground hunting and trapping.

Over three days in June 2009, three helicopters spread 85 tonnes of cereal pellets containing the toxin brodificoum over the islands’ entire area. Pellets of the rodent-specific poison were also hand-placed in nearly 340 structures including farm and military buildings, sheds and power boxes.

Further aerial bait drops were done in July and August. The winter timing coincided with the period when little food is available and so pests were most likely to eat the bait. The excellent coverage achieved, coupled with near perfect weather conditions during and after each drop, meant that rodents on Motutapu and Rangitoto were exposed to bait right through the harshest period of the winter, ensuring that the chances of operational success were maximised. An intensive search effort aimed at locating surviving rabbits began following the second bait drop. The four person rabbit team encountered just one live rabbit in two weeks of spotlighting, a spectacular and entirely unexpected result.

Two weeks after the last application of bait, the islands’ stoat and hedgehog trap network was activated. All 1,050 traps have been checked multiple times with no stoats detected, providing an earlier than expected indicator that the islands’ stoat population may be non existent. Surveillance across the stoat/hedgehog trap grid has failed to detect any mice or rats, providing an early indication that the islands are now free of rodents, although two years of monitoring is required before success can be truly confirmed. Some small numbers of cats and hedgehogs may still be present.

The bellbird has recently been rediscovered on the island after more than 100 years’ absence. Kakariki (parakeets) began breeding on Motutapu in December, and pateke (brown teal) were spotted on the island in early February. These native birds have repopulated Motutapu of their own accord, in advance of plans to release birds like takehe and kiwi.

FARMING

Rick Braddock and his farm manager John Duggan have restocked Motutapu with cattle following the three-month pest eradication, during which time livestock were absent. They are running 1,300 cattle, both boner cows and steers, to get on top of the growth that occurred during destocking. They also had 2,500 10-month old lambs for finishing on contract, the last of which has now left the island for slaughter (November 15).

Restocking with ewes will be planned when the summer rainfall pattern is known. The pastures have kikuyu dominance and after the driest autumn ever recorded, there is not a lot of non-kikuyu pasture around. Olsen P and pH levels on Motutapu are good and Rick is considering a switch from phosphate fertilizer to calcium-based fertilizer. Pasture quality is not adequate and expenditure is needed for stock yards, woolshed, water system and fencing. The property is capable of carrying 10,000 to 12,000 stock units, along with an ecological improvement programme, carried out by the Motutapu Restoration Trust. The trust plans to plant 30,000 to 40,000 native trees and shrubs each year. They have already achieved some 500,000 trees, which are to provide feed for native birds as they are re-introduced. At the present rate of planting it will take 20-30 years to retire perhaps one-third of the grazing, but that will still leave two-thirds or 1,000ha of pasture. Motutapu has been farmed since 1840 and will continue to be farmed for at least 50 years in the future, says Rick.

Rick’s ambition is to sustainably farm Motutapu to provide an accessible large-scale farm right on Auckland’s doorstep, so people can visit and connect with agriculture and conservation at the same time. Significant opportunities exist for iwi involvement, as Maori inhabited the island for hundreds of years and there are many remains of settlement.

POWER GENERATION

Motutapu Island now has New Zealand’s largest off-grid solar power system, with solar panels erected on top of the defence stations. The $715,000 Motutapu solar project is expected to generate at least 65,000kwh per year, providing up to 70% of the island’s energy requirements and saving 800 litres of diesel a week. As DoC moves to renewable energy generation on the islands under its control, money previously spent on diesel and the hours spent maintaining and running generators, will now go directly to conservation work. Power generated on the island supplies a number of DoC houses where staff and contractors live while carrying out conservation work. It also supplies the Motutapu Outdoor Education Camp (MOEC), which hosts 12,000 guests each year, and the Motutapu Farm.

Motutapu is the ninth Department of Conservation-managed island to have renewable energy solutions installed as part of the ongoing Sustainability Programme, which aims to boost renewable energy use and halve off-grid diesel fuel bills.

Now the renewable power generation system is complete, the power and water distribution networks on the island will also be upgraded. Cost savings associated with replacing the current system are estimated to be $188,000 per year.