Northern Ireland

Northern Ireland biosecurity: Clearing infected forests

Brown diseased trees amid the greenery of healthy forest
Image caption The brown trees amid the greenery are infected with P. ramorum, popularly known as Sudden Oak Death

Following the discovery of P. ramorum, popularly known as Sudden Oak Death, at Glenariff Forest Park in County Antrim, the Northern Ireland Forest Service has begun implementing its biosecurity procedures to prevent the infection spreading.

The disease was discovered in several Japanese larch trees in the park following an aerial survey of Northern Ireland forests.

It is the seventh location where the disease has been discovered in Northern Ireland.

With many thousands of tons of timber to be cleared from over 270 hectares across part of Northern Ireland, the process will take months.

The infected trees have to be felled to prevent the fungal spores that cause the disease from spreading to other areas.

The timber, Japanese larch, is still valuable and can be sold to licensed sawmills provided the correct biosecurity measures are followed. A task that is not as easy as it sounds.

Protection

The number of trees to be felled is considerable, up to 150,000. A team equipped only with chainsaws would take a long time to achieve that.

Instead the Forest Service have brought in specialist equipment that can fell, log and clean up to 50 trees an hour.

It works so fast that the operator needs special protection - bullet-proof glass. The special hydraulic chainsaw it uses to fell and log the trees works at such a speed, that if the chain were to break, it would be as dangerous as shrapnel.

Image caption The number of trees to be felled is could be up to 150,000

Using a machine like this aids biosecurity. It means just one person and one vehicle in the area. This means fewer feet and vehicle wheels to sterilise.

Once cut, the logs are then moved by mechanical grab to a clean area clear of the ground.

They are stored beside a high-quality roadway where there is little or no leaf or needle litter.

Licensed lorries then use their own mechanical grab to load the logs at the sterile location. They don't enter the contaminated area so don't need as much cleaning.

Once loaded, they set off on a designated route to a specially-licensed sawmill in County Fermanagh.

At the mill, the logs will be unloaded and stored. When enough wood has been gathered, a special production line will be set up to cut the wood into planks.

Deadline

The planks themselves are free of disease and can go into the normal timber supply. All the offcuts, sawdust and bark will be incinerated in case they harbour any infection spores.

The need for this biosecurity puts a considerable strain on the sawmill which has to dedicate a separate area and equipment and keep them sterile while the process takes place.

Image caption The operator of the logging machine is protected by bullet-proof glass

It also means that those working in the contaminated areas have to wash vehicles, equipment and their footwear every time they leave the area.

The Forestry Service face a deadline to fell and clear contaminated trees by May 2011.

After that, the trees then start to produce infected needles and can begin to spread the fungal spores again, even though the trees may already be dying.

While the biosecurity and mass felling will have some effect on the local habitat, these trees were grown as a commercial crop and were always destined to be cut down. But some of their value will be lost because of the considerable expense of the task ahead.

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