Plans for less slash from forest harvest

The Kingsland forest harvest on the hills behind Richmond will be completed this month with the bulk of the slash removed to minimise any risk in major weather events.

PF Olsen regional manager Sam Nuske says the harvest of the Tasman District Council’s pine forest block goes beyond legal requirements in a bid to showcase good forestry practice in a high-risk area.

“We’re just making sure we’re doing the top job for everything. It’s a steep slope with moderate erosion risk, but the consequences below are extreme and if debris makes its way into a culvert in an urban area, it could flood houses and blow out roads. And everyone is looking at us.”

To avoid the risk of forestry slash (leftover forest debris) ending up in waterways, he says the harvest management plan has included a range of methods.

A fixed felling machine is being used to carefully lower trees so there are less branches lost when trees fall and all the debris can be collected at the skid site.

“That’s reducing the amount of slash on the hillside and maximising logs going out.”

All of the slash from the skid sites is being removed by local company Azwood to use as wood fuel to fire burners and also for landscaping.

“That means we don’t have big piles of slash to deal with that can combust into fires. It’s a win-win and environmentally a good outcome. It was going to biodegrade into the atmosphere, but now it’s been burnt in boilers instead of coal.”

A helicopter grapple is being used at the end of the harvest to extract any leftover wood that may be a risk if it is washed away in heavy rain.

Once the harvest is complete, Sam says the entire hillside will be sown with grass seed to get vegetation growing quickly, which will slow the impact of raindrops on the hill.

“It will slow down the raindrops that hit the soil and as water runs off the slope, the grass will slow it down. And it will stabilise the ground to reduce sediment and reduce slips.”

Native riparian vegetation in the gullies also help capture soil and debris that may make its way downhill.

Despite the extra steps being taken to reduce risks from the harvest, Sam says it still stacks up economically for ratepayers. Once the harvest is complete, the block will be retired from forestry and replanted in a mix of native and exotic trees.

In 15 years, the last block of pine trees in the Kingsland Forest Estate will be harvested and then the entire 100ha on the Richmond Hills will be retired from forestry.

He says the decision to retire the forestry block is not about economics, but rather other values that are important such as environment, visual and recreation aspects of the high-profile forest. The risk of fire and public safety during harvest are also factors.

While half of the public seem to be glad to see the end of the pine forest, Sam says the other half are sad to see the trees go because they like the shaded paths beneath them. The public should be allowed back onto the harvested hills by the end of May.

Tasman District Council communication officer Tim O’Connell says high-intensity weather events, including Cyclone Gabrielle, mean the council wishes to better understand the risk of woody debris and opportunities to reduce that risk.

He says a number of efforts have been undertaken to manage environmental risk throughout the harvest and council will continue to look at ways to mitigate the risk from forestry debris in the future.