Scientists say emu and ostriches could be used to replace the extinct moa as grazing animals in today's native forests.
The popular theory is that moa munching New Zealand's native plants over tens of thousands of years caused many to become twiggy shrubs less suited to moa "grazing."
Ecologists now suggest regular"mowing" of such shrubs by big birds might aid forest health.
"If we want to return these wiry plants to native ecosystems ... should we introduce emus and ostriches to some protected natural forest or scrubland areas?" Landcare Research scientist Dr Bill Lee said yesterday.
New Zealand has many small-leafed "divaricating" shrubs with more than 10 per cent of their branches at angles greater than 90 degrees, often in a tangled mass.
Dr Lee, a New Zealand ecologist, has teamed up with a South African botanist to feed native shrubbery to imported emus and ostriches in a bid to show that some native plants adopted their twisted forms to protect themselves from hungry moa.
The two men said yesterday that their findings could have significant conservation implications.
The divaricating plants, such as some small coprosmas, have small, widely spaced leaves on wiry interlaced branches that grow in zig-zags.
Some of the divaricate plants, such as lowland ribbonwood and kowhai, change form as they mature, starting life with tough, shrubby divaricate growth, and then swapping to straighter branches and bigger leaves when they reach about 2.5m in height.
Dr Lee and co-researcher Professor William Bond from Cape Town University said the very strong branches and small leaves were defences against browsing moa.
They believed the birds fed by plucking or stripping leaves and clamping and tugging shoots.
The thin convoluted branches also created a zig-zag pattern that produced a spring-like recoil when tugged.
All of these features reduced the moa's ability to remove plant material.
The larger leaves and easier-to-snap branches appeared from about 2.5m up the tree, above the reach of most browsing moa.
Eleven species of moa are thought to have been hunted to extinction.
