One man's work to restore native bush on Karaponga Reserve over the past 20 years is being undone by inadequate fencing.

Retired dairy farmers Steve and Lesley McCann have taken enormous pleasure in the recovery of native wildlife on and around their McIvor Road property, next door to the reserve in the Eastern Bay of Plenty.

Even finding the occasional gigantic centipede in the bathtub is a small price to pay.

The McCann's see it as a sign of the resurgence of native biodiversity, due to pest control and planting.

They have done this almost single-handedly since they moved to the 40-hectare block, 80 per cent of which they have put into a QEII National Trust covenant to protect it in perpetuity.

Tui, bellbirds, kereru, fantails, grey warblers and silvereye are just a few of the birds that flit though the trees. 'We've been seeing lots of robins recently, too,” says Steve.

As well as his own land, the fit 73-year-old also runs bait lines and traps and plants native trees in the neighbouring Whakatāne District Council-owned Karaponga Reserve, often at his own expense, but says the council needs to do more to make sure this area is protected from neighbouring farm stock.

Over the past 18 months, Steve has had a running battle with entire herds of cows wandering over inadequate fencing from the neighbouring farm, smashing through the understory of the forest and eating the native plants.

'They eat anything palatable – ferns, tawa, mahoe - the only thing they won't touch is the kawakawa. They don't seem to like the taste.”

There have been at least four occasions when this has happened over the past year and Steve says the result has been devastating to the forest.

The most recent occasion was two weeks ago when somewhere between 200 and 400 cows found their way into the park.

'It's difficult to tell how many there are when they are spread though the forest.

'All the lower greenery has gone.”

He complained to the council about the issue last year and, together with the farmer, they replaced some of the fencing.

Now the cows just need to find their way around the new fencing to the parts where it is still broken down.

'I don't understand why they stopped and left the rest unfinished,” he says.

The reserve is 177 hectares of hilly native bushland, which also contains a historic hydro dam built in 1922 and which still generates power, a waterfall and walking tracks.

Steve has between 100 and 150 bait stations in the reserve, which the council pays him to fill once a year.

However, off his own bat, he does so at least four times a year, keeping pest species such as rats, stoats and mice under control and eradicating possum and wallaby, almost single-handedly.

Steve McCann shows an area where forest has been trampled by stock.

The council's open spaces operations manager Ian Molony says the council was made aware of cows entering the reserve last year and worked with the neighbouring farmer to share the replacement of 615 metres of stock fencing, which was completed during May.

'Since this time the council has not received any further reports of stock entering the reserve until last week,” he says.

'Council immediately followed up with the neighbouring farmer who reported a tree had fallen across the fence during the recent cyclone, which enabled the cows to gain access. They were removed from the reserve as soon as the farmer became aware.

Ian says the council will continue to work with the neighbouring farm to prevent any further incursions into the reserve.

Steve says he knows the reserve like the back of his hand and is aware of several places the fencing is inadequate.

He says it's not just an issue that is due to one storm event, but a progressive deterioration of fencing due to neglect.

-Local Democracy Reporting is Public Interest Journalism funded through NZ On Air