In the “Ecosystem restoration on Mainland New Zealand

Mapara

 

Until very recently our attitude to mainland sites resembled that for islands three decades ago: the pervasive effects of pests and weeds could not be overcome, we were faced by the imminent collapse of millions of hectares of forest browsed by possums, goats, pigs and deer, and species sensitive to these effects on the mainland had a dubious future - unless they could be translocated to islands. The Mapara experience turned that perception on its head.

Mapara is a 1400 ha Crown reserve "island" of cut over podocarp/hardwood forest in a "sea" of central North Island farmland and introduced pine plantations. The forest inhabitants included 65 kokako, an endangered wattlebird rapidly declining in abundance in the North Island. Until the late 1980s the forest was periodically entered by stock from neighbouring farms, the understorey was eaten out by wild goats, and the canopy was browsed by introduced possums. The native wildlife was preyed on by ship rats, Norway rats, wild cats and introduced mustelids (stoats, weasels and ferrets).

In 1989 the bold decision was taken by Department of Conservation staff to upgrade the fences, cull the goats, and then attack the possums and introduced predators with vigour. The campaign against possums assumed added urgency when remote video cameras indicated that this "herbivore" was devouring kokako eggs and chicks.

Trials indicated that baits laid against possums also reduced numbers of rats. But rats were the main food for mustelids; removal of rats led mustelids to eat more birds. The solution has been to hit everything at once. Mapara has been trapped, laced with baits from the air and dosed with others in bait stations on the ground. As ground based operations using bait stations became increasingly cost-effective, possum catch rates declined to near zero and rat densities fell from encounter rates of 70% to (in some areas) below 10%. The responses by forest inhabitants have been correspondingly spectacular.

By 1989 the kokako population had declined to 52 birds, 90% of which were males due to predation of females on nests. Following intensive management, the 1996 census identified at least 86, and possibly 100 kokako, of which females comprised 40%. Other monitoring indicated increased numbers of insects, long-tailed bats, and forest birds such as tui, bellbird, kereru, whiteheads and fernbirds. The increased abundance of kereru is particularly significant because these are a fruit pigeon with a vital role in forest regeneration through the spread of large seeds. Consequently, protection of the kokako has reactivated ecological processes that can have an influence on succession of the entire forest block and these will have positive effects on a wide range of its inhabitants (Bradfield and Flux 1996).

There have been other benefits: the easy access of this mainland site and its spectacular recovery mean that it is increasingly visited by school groups, outdoors clubs, nature societies, university classes, community possum control groups, Maori groups and local farmers.

The Mapara success has encouraged the development of a network of intensively managed mainland restoration projects scattered through the North and South Islands. These include projects on public and private land (Simpson 1995).

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