Conservationists in New Zealand say illegal cannabis growers are endangering native plants and animals.

The government's wildlife conservation department reports that the growers have been clearing large areas of woodland, particularly on North Island around Whangarei, a temperate area well suited to cultivation of the plant.

In some places, large indigenous trees have been felled to extend cannabis plots.

Other vegetation has been destroyed and potting mix used to cultivate crops has introduced weed seeds.

There is a risk from fire and litter, as growers frequently light campfires in the area.

Extinction struggle

The growers have also fenced off large areas with netting designed to camouflage and protect their crops. The netting disturbs and can trap local wildlife.

Among the native animals and birds threatened is the country's national emblem: the kiwi.

The kiwi is already under pressure from loss of habitat and non-native predators. It is estimated that its population is falling by 6% a year. Since 1991, the New Zealand Government has supported a number of initiatives to save the bird.

The North Island Brown Kiwi lives in a diverse range of vegetation types including the exotic forests and deep woodland also favoured by the cannabis growers. An estimated 35,000 birds remain.

Rangers working for the Department of Conservation say controlling the problem is difficult. Many of the habitats affected are in remote areas and the growers are armed.