Key Points:

Dung beetles could be introduced within three years under a plan to improve the country's waterways and increase farming productivity.

The beetles would eat their way through the considerable piles of livestock dung that currently cover pasture, making it inedible to livestock, and run into waterways during rain, killing native fish and plant species.

The introduction is planned to begin in rural Rodney, and will be presented by Landcare Research scientists to the region's farmers at two meetings in the district next week.

Some animal imports have become ecological nightmares, with possums, rabbits and mustelids now multimillion-dollar problems. But the dung beetles are safe, Landcare Research biological control researcher Hugh Gourlay says.

Public fears are always high when any planned introduction is discussed, he says, but he has no fears of the beetle causing harm to New Zealand.

"We would look like complete idiots if it did. We'd never apply to introduce anything that had any risk associated with it," he said yesterday.

Even if the beetles chose to eat different dung, that would not harm the environment. The environmental benefits, though, would be significant.

The reduced runoff would leave waterways clearer, with fewer algal blooms and more native fish.

Greenhouse gas emissions would reduce, as livestock dung accounted for half of New Zealand's nitrogen oxide emissions, he said. About 80 per cent of the nitrogen content of dung was lost when it remained on the pasture surface. Only 10 per cent was lost following burial by dung beetles.

The beetles' tunnelling and depositing of rolled-up dung balls just beneath the soil surface helped fertilise the pasture, while their tiny tunnels allowed better aeration and water penetration of the soil.

Rodney was the ideal region to spearhead the planned introduction, Mr Gourlay said, as it was a leader in organic farming. Dung beetles were popular with organic farmers as they were a natural solution to the problems caused by intensive farming.