Australasia's home for timber news and information

Forestry not bad guys in NZ soil erosion

Forestry leaders are tired of being labelled as the major culprits for hill country erosion in New Zealand and say other land uses and extreme weather events have played a part. Source: The Gisborne Herald New Zealand

“There is no doubt that forestry, like all land uses, needs to foster continuous improvement practice to minimise such effects,” said Juken New Zealand forests general manager Sheldon Drummond.

“This is a topic our community needs to fully understand for the greater benefit of future generations.”

The industry is working with local government to embrace the issues around hill country erosion, particularly logging slash — a major concern throughout the district.

“The District Council is working with the forestry industry towards changing management practices and tightening up consent conditions,” said Gisborne District Council (GDC) environment and policy manager Hans van Kregten.

“It has been signalled to the council that a change to the council’s Resource Management Plan (RMA) in respect of forestry practices might also be an option.”

“A lot of the debris is poplar and willow that is often planted along waterways in forests and on farmland for erosion control.

“Generally, little driftwood shows direct evidence of being logging slash (cut ends and processing machinery marks), but it is likely some trees and woody material along waterways is carried out by logging debris flows.”

“Slash in waterways is a major concern and how we handle logging debris around landings is being modified, given some failures that have occurred as a result of these extreme weather events,” Hikurangi Forests Farms general manager forests Paul Ainsworth said.

“In moderation, woody debris in streams is beneficial for aquatic life,” Mr Drummond said. “It provides habitat and, together with the forest itself, becomes shade for life to flourish.

“Logs left after the forest harvest, comprising dead trees and offcuts, are at risk of being caught up in earth slides as an ‘avalanche of debris’ during a period of two to five years after harvest.

“In perspective, that’s just 15 percent of the rotation time of 30 years. This is a risky time for forestry and we are somewhat at the mercy of the changing climate for this period.

“Once the trees pass five years, the risk dramatically reduces and in older plantation forest the risk of slipping is minimal,” said Mr Drummond.

“Plantation forests provide for a far greater degree of soil protection and enhancement (through decades of forest organic litter layer) than any other current economic land use.”