Organic food on rise - but birds not so keen

The Otago University report found organic farms here and abroad were often better for birds and earthworms. Photo / Paul Estcourt

New Zealanders are eating organic produce at a growing rate - but garden birds may not be so keen, two new reports reveal.

The 2010 New Zealand Organic Sector Report by Otago University found land dedicated to certified organic food production had risen 94 per cent since 2007, and the sector was worth between $450 million and $530 million.

It also showed organic farms had several environmental benefits over other forms of farming, including making better homes for earthworms and insect-eating birds.

But a British study released at the same time last week questioned nutritional claims that birds and animals preferred to eat organic food.

University of Newcastle biologists found wild garden birds, given the choice, ate more conventional than organic wheat - probably because of its higher protein levels.

The authors said the findings suggested the "dogma" that the animal kingdom preferred eating organic food might not always be true, but stressed the study did not take into account factors such as the long-term health effects of pesticides or the environmental effects of conventional farming.

The Otago University report found organic farms here and abroad were often better for birds and earthworms, could produce less nitrogen run-off, and had the potential to soak up harmful greenhouse gases.

Otago University's Dr Chris Rosin said though it was too early to say whether organic food had any added nutritional value, comparisons of conventional and organic kiwifruit farms had found organic farms had more carbon in the soil and significantly more earthworms and birds.

The next step was to discover whether organic soils could lower greenhouse gases in the atmosphere by accumulating carbon, he said.

"Earthworms and birds are very good indicators of biodiversity. By doing the sprays [on conventional farms] you are removing the food source [of insects from birds]."

Bigger numbers of earthworms in organic farms made the ground more nutritious for plants and cut the need for artificial fertilisers, Dr Rosin said.

"The worms help make the nutrients more accessible to plants and they also mix it through the soil."

The Otago report - prepared for Organics Aotearoa New Zealand - said streams on organic farms had more insects and other creatures living in them than ordinary farms.

"This is likely to be partly due to lower nitrate leaching from organic dairy farms, with Massey University suggesting that leaching into waterways is reduced by 58 per cent with the adoption of organic practices," said OANZ chairman Derek Broadmore.

One with nature:

* 43 per cent more earthworms (on organic dairy farms).

* Leach 58 per cent less nitrate to waterways.

* Store 28 per cent more carbon storage in the soils.

* More biodiversity in streams.

- Source: 2010 New Zealand Organic Sector Report, Otago University.