Trustees and friends view fish pass in fence at Tawharanui |
Geoff Pike, Trustee of the Bream Head Conservation Trust, and Chairperson of its Restoration Committee writes this article:
Remember the story of the boy who saved Holland by putting his finger into a leaking dike to avert a flood? Recently I attended an animal pest eradication workshop in Cambridge. Also there were eight representatives of the ten New Zealand conservation projects using predator proof fences. It focused on ‘best practice’ protocols for the eradication of pest species. One of these was “How do you deal with ‘leaks’ in your fence? How do you avert a flood of pests getting back into your conservation area once you have cleared it of pests?”
In the Waikato the Maungatautari Ecological Island Trust has NZ's longest predator proof fence (50 km) built at a cost of $13 million. Pests were cleared within the reserve by intensive trapping and poisoning. Post eradication there were 4 rats, 2 pockets of mice, some rabbits, hares and goat still surviving. All of these have since been eliminated (except the last mouse which they are still after - and hopeful of nailing!)
There is a constant “pressure” of pests attempting to reinvade a cleared area and monitoring at Maungatautari has revealed some interesting statistics which have direct relevance to achieving a pest free Whangarei Heads.
It has been determined that if a “leak” or breach occurs in the fence (such as a rip in the mesh or a fallen tree forming a bridge) within an average of 90 minutes some pest animal will discover it and reinvade. And the most likely transgressor (in order) will be a stoat, or a mouse, or a rat. The researcher cut experimental holes in the fence. In summer over a 24 hour period 95% of these holes were discovered by pests, 72.5% of which entered the reserve.
This illustrates the intensity of pest pressure all around us in rural areas. Most of us are probably unaware of this except when we find evidence of mice or rats inside our homes!
Over the past 2 years at Maungatautari they have had 111 actual breach events, such as tree fall, 82% of which were detected immediately by an electronic surveillance system. The result - only 4 animals got back inside, and all were subsequently caught.
Trying to achieve this highest level of pest control in urban areas without installing a predator proof fence is well nigh impossible. It is unlikely that public support and funding would be there for the level of ongoing intensive poisoning needed, especially around people’s houses.
We need to utilise all the tools in the pest control tool box - they are complementary.
Lower levels of pest control, especially in regenerating and forested areas, is happening right now, thanks to the excellent work of various land care groups. This, surrounding and supporting a smaller fenced area, reduces the pest pressure and helps achieve the highest level of pest control within. Consequently the out flow of endangered species to surrounding areas increases.
It sort of puts a finger in the dike. The net result is a win-win for the ecology for the whole area, which must surely be our aim.
|
