Predator Free New Zealand

I’ve been reflecting on the idea of a predator free NZ. On first glance, this looks like a great idea – remove the introduced predators, save our native flora and fauna and the bush and our gardens will once again be filled with the majesty of our native birds and those on the edge of extinction will once again flourish.

I love the sound of the tūī and seeing them drink the nectar of the kōwhai & harakeke flowers. Seeing them weave and dart in their mating flights. Who can’t be moved by the antics of the kākā, and the joy of having kererū in your back yard?

With possums gone, I won’t have to keep trapping them out of my fruit trees.  The local rātā will flourish. No rats to eat the macadamia nuts before I get to them. No stoats to decimate the duck populations. Back to paradise NZ.

But wait – what did the original paradise NZ look like? Can it even exist in the very different NZ of 2018? Will killing off introduced predators (which is ecologically unlikely) save native birds from extinction? What are the other consequences of removing these predators from our New Zealand ecosystem?

I live in a valley surrounded by native bush. Our bush is often quiet – we have tūī & korimako when we have feed for them in the garden, 1 or two kererū fly overhead and occasionally stop when we’ve food plants that interest them. Fantails are around most of the year but not in the numbers I’ve seen in other bush sites. Kōkako became extinct locally in 1992. We hear ruru most nights. kōtare & pūkeko are always here. Kāhu (a predator) are around all year We often hear grey warbler & seasonally we sometimes have shining & long tailed cuckoo. I see more tūī and kererū in urban backyards and areas where they are fed sugar water than I see or hear in our bush covered land scape.

We do, however, have abundant sparrows, mynah, silvereyes, blackbirds, thrush, pheasants, quail, magpies & rosella. Yes, these are forest margin and pasture birds rather than bush birds but they are an integral part of New Zealand ecology today.

The bush here is not the bush early settlers would have seen, it has been cut over for mining and farming. There are no mature stands of any of the podocarps or kauri, although there are mature single trees and some regenerating kauri groves. We do have some mature tawa and kohekohe on more inaccessible sites. The bush is regenerating – in this phase, many of the trees and shrubs don’t flower & produce fruit every year, if at all. The slopes that have been grazed are still in the mānuka /kānuka or fern phases of succession. There are goats & pigs through the bush. This is not the climax forest from before Māori occupation or of 1769 that Cook would have seen. Mankind has been influencing the native ecosystem for 100s of years, there is no return to the pre-migration ecology.

We don’t know the consequences of predator management to invertebrate populations. Yes, we have tree wētā, cave wētā (in the old mine shafts), native moths and various borer beetles – the obvious but what about the more secretive insects, snails and other fauna? Logic would suggest the wētā at least would be better off with reduced predator populations, but if we don’t know what that ecosystem looks like now, how can we predict the consequence of such a massive change?

The introduced predators also feed on the introduced birds and rabbits. If there are no predators what will happen to these populations? What will happen to mice populations? Nature abhors a vacuum. Will flocks of sparrows, ducks and wax eyes prove an additional issue to horticulture? How do we address the issue of cats as a pet & cats as a predator?

Vivienne CruickshankComment