First steps to deal with woody debris

A109 Light Utility Helicopter flight with mayor Gisborne City from the air in November 2023.

Opinion

A pilot bioenergy plant alongside research into woody biomass market options and forestry slash recovery, transportation and processing methods are encouraging first steps for dealing with our slash problem by making productive use of it.

Prime Minister Chris Hipkins visited Uawa Tolaga Bay with East Coast MP Kiri Allan yesterday to announce investments in a “more sustainable, lower impact forestry industry”, including $10.4m for this effort to clear and use slash as woody biomass.

Another project aims to develop business models for “continuous cover forestry” in New Zealand — ie, harvesting trees on a rotation instead of cutting them down all at once.

Minister of Forestry Peeni Henare’s statement on these initiatives noted the Ministerial Inquiry into Land Use had recommended this for some areas, especially steep country with highly erodible soils. New models needed to be developed to ensure it was a viable alternative, he said.

The inquiry panel’s report actually recommended an immediate halt to large-scale clear-fell harvesting within the Tairāwhiti and Wairoa districts, and the adoption of staged coupe harvesting as an alternative.

This was in a section headed “Loss of social licence” — for forestry, because of its activities — which said: “Nowhere is this more evident than the Uawa catchment, particularly the Hikuwai River. We heard that, in this catchment, clear-felling of 4500 hectares of forest over a three- to five-year period led to sediment and woody material forming debris flows that caused devasting damage downstream.”

Existing regulations were “too permissive” in not preventing large areas of a catchment being felled at once: “This needs an urgent response.”

Stressing this was for Tairāwhiti and Wairoa only, the report suggested that felling within a catchment be limited to 5 percent of the total area each year and “an appropriate maximum staged coupe size is 40 hectares”. Also, “A minimum ‘green-up’ period of five years between staged harvest coupes will minimise the risk of large-scale erosion events.”

It said this should happen alongside the immediate clean-up of woody debris (which the Government has already put $10m towards). The report recommended a Woody Debris Taskforce be established to lead the planning and delivery for current and future clean-up activities, with independent leadership, involvement from the three councils of the wider region and the forestry sector, and mostly funded by forest owners.

The removal of woody debris should be on a risk-priority basis, “for reuse as biomass wherever practicable or otherwise mulched and spread where the wood chips cannot enter waterways to cause further problems”.