Dairy conversions of plantation forests threaten native species

5 November 2007

Land conversion to dairy farming could threaten some of New Zealand’s native plants and birds if it isn’t done carefully, says a biodiversity scientist.

Ensis senior scientist, Dr Eckehard Brockerhoff, has led a decade long biodiversity project looking at New Zealand’s plantation forests.

Ensis is the collaboration between New Zealand Crown Research Institute Scion and Australia’s CSIRO.

“The boom in the dairy industry and a temporary slowdown in forestry is leading to increasing land-use conversion from plantation forest to dairy. But what most people don’t realise is that plantation forests often provide an important home for our native biodiversity, even for some of our most precious and endangered species,” he says.

Dr Brockerhoff says that conservation in New Zealand traditionally focused on native forests in National Parks and other natural areas, which now remain primarily in the high country and in remote areas.

“But there is a world-wide trend of including production land in conservation strategies and towards sustainable management that is sympathetic to native biodiversity,” says Dr Brockerhoff.

“There is the perception that there isn’t much biodiversity of interest in plantation forests. But our research has found many native plants and animals – including rare and endangered ones – are thriving in plantation forests.

“There are 1.8 million hectares of plantation forest in New Zealand, but already 100,000 to 200,000 hectares have been or are about to be converted – mainly to dairy farming. If this isn’t done in a careful way, we could potentially increase the threat to some of our rare species,” he says.

Native species living in plantation forests around the country include 36 native orchid species, birds such as native robin (or toutouwai), kakapo, kiwi, kokako, an endangered ground beetle, and hundreds of other insects, plants and fungi.

“For many of these forest species – such as the endangered ground beetle, several orchids and the robin – plantation forests seem to be as suitable as native habitats. It’s just a coincidence that introduced trees provide the perfect habitat, but in any case, such forest species cannot survive in pure pasture or grassland.”

Dr Brockerhoff says irrigation and an improved understanding of fertiliser requirements mean that land which was once unsuitable for dairy, and therefore used for plantation forestry, can now be converted to farming.

“Dairy conversions of plantation forests should not be done without providing at least some forest habitat to ensure that populations of forest species are not entirely wiped out. This could be done by either keeping some areas in plantation forests or by restoring native forest areas, for example, along riparian areas, to ensure that the homes of native species aren’t entirely lost. Ideally, surveys for rare and endangered species should be done before such conversions go ahead. This is something that has to be done now, before it’s too late,” he says.

“For example, the Canterbury Plains and the central North Island are areas where dairy conversions are becoming common place. If Eyrewell Forest was to be converted entirely to pasture, that would effectively remove the only remaining habitat of a critically endangered ground beetle that occurs only in this part of the Canterbury Plains, and it is only found in plantation forest. Similar situations apply to several birds in forests in the North Island that are territorial and have nowhere else to go to,” he says.

“Apparently there is nothing that can be done to stop landowners converting plantation land to dairy, because plantation forests are not protected.”

Dr Brockerhoff and his team began researching biodiversity in plantation forests in 1998.

“Our work started because of the international demand for plantation forests to be managed sustainably, and until then there was not much information about the effects on biodiversity of plantation forestry in New Zealand. This coincided with the release of the Government’s Biodiversity Strategy, which supports similar aims.

”Until recently there was a perception In New Zealand that there was little concern about biodiversity in pine forests because they were thought to be poor habitat for native species.”

“But over the past decade we’ve found the plantation forests are actually rich in biodiversity and can provide important forest habitat in regions where little native forest remains. It is unfortunate that some of this habitat is now being lost to a land use that is less suitable for supporting our natural heritage.”

The research has been funded by Scion and the New Zealand Government through the Foundation for Research, Science and Technology.