Forestry industry tired of blame for hill erosion

By Shaan Te Kani of the Gisborne Herald

Photo / Duncan Brown
Photo / Duncan Brown

The forestry industry says it is tired of being labelled as the major culprit for hill country erosion and says other land uses and extreme weather events have played a part.

Despite the finger-pointing, Juken New Zealand's Gisborne forests general manager Sheldon Drummond believes the debate is one worth having and the industry is always looking at ways to improve practices.

"There is no doubt that forestry, like all land uses, needs to foster continuous improvement practice to minimise such effects," he said.

"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 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 RMA plans in respect of forestry practices might also be an option."

While a lot of debris came down during an extreme rainfall event in March, it was important to keep in mind that these types of weather events were a one-in-a-hundred-year occurrence, Mr van Kregten said.

"We inspect key waterways and beaches after major storm events.

"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."

Hikurangi Forests Farms (HFF) general manager forests Paul Ainsworth said extreme weather events had highlighted how quickly things can change.

"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," he said.

"These one-in-a-hundred-year events need to be kept in context, as they are ones most regions don't plan for."

Looking at ways to minimise soil disturbance during road construction to minimise sedimentation in the waterways was also a key focus, said Mr Ainsworth.

"It can be challenging, as we still need to build a safe road for logging truck access.

"Roading and harvesting practices our industry and GDC have been comfortable with for several years now require review and we need to modify practices in light of these issues.

"HFF and GDC staff communicate and work together well to identify issues and, where possible, find sensible solutions."

Outside of extreme weather events, the impact on waterways was not as great as public opinion suggested, Mr Drummond said.

"In moderation, woody debris in streams is beneficial for aquatic life," he 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 per cent 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."

The impact of other practices such as pastoral land use needed to be considered, 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.

"Other land uses, as can be seen almost annually in this region, are constantly at risk of soil erosion due to their lack of vegetative cover and root mass to hold the land together.

"The visual impacts of soil disappearing forever might be different to that of woody debris, but as custodians of the land we must look broader than the immediate impacts of the day."

- The Gisborne Herald

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