Rest and Be Thankful landslide: Trees could be 15ft by now

The talk was titled: “The A83, an Off Road: The Role of Forestry To Stabilise the Slopes Surrounding it.”  

Their proposal was that trees should be planted to help prevent erosion and landslides – and that the strategy should be one of first planting willow and later “suckering” trees like Sitka alder, a North American species which is used in land restoration projects, to help stabilise the slopes.   

The basic principle of planting trees, Mr Pretswell said, was not rejected at that meeting. “They said, he recalled, "that in three years time, they were going to have trees.”  

The meeting led to another with Scottish Natural Heritage and the Forestry Commission.

Speaking last week, his colleague, Ron Greer, added: “We had that meeting in 2014, so if the trees we recommended had been planted then, some of them would be 10-15ft high by now.”  

Tree planting began only last year on the slopes above the Rest and Be Thankful. Following purchase of the land, Forestry and Land Scotland (FLS) started planting trees on the steep southwestern flanks of Ben Luibhean above the A83 trunk road.

The project has involved novel techniques, including the trialing of scattering of 20 million birch seeds on the hillside by drone. 

According to its website, FLS is “planting a mix of native woodland species at the western end of the hillside and will, over the course of the next two years, work their way steadily eastwards.” Species being planted are locally sourced and include “downy birch, aspen, oak, blackthorn, hawthorn, hazel, juniper and Scot pine.”  

But Mr Pretswell criticised not just the delay, but also the initial use of birch.  “Birch trees are not the species you need to put in there to stop the erosions straight away. They could just have easily started scattering Sitka Alder seeds as Birch. In the part of Alaska that is the origin of Argyll Sitka Spruce, Sitka Alder grow up to 800 metres on the hillside. Do we really require a huge leap of imagination to believe they would do equally well on 850 metre hill”?

Derek Pretswell, ecologist

Pretswell and Greer’s plan for the slopes of Beinn Luibhean had been based on the groundbreaking work these two ecologists had done with the Loch Garry Tree Group.  

“What we did at Loch Garry,” he said, “was a technique called successional planting. We put plants in – broom and Alaskan lupin – to change the quality of soil. Then we planted trees through it. Because you’ve got a more enriched soil because of the broom and the lupins, they grow well. In the case of Glen Croe, lupins would not be needed.”  

At Loch Garry, the group also fenced off areas to prevent grazing by sheep and deer – and the result is that there are now thriving patches of woodland around the loch.   

The A83 has been plagued by landslides, and the threat of them, for many years (Photo - BEAR Scotland)

The first stage for the A83, the ecologists recommended, would be to plant willow, by sticking cuttings into the ground, along the streamlines. This would be followed by Sitka alder planting.    

“It’s about planting trees that sucker," said Mr Pretswell, "because they create then a natural gradient. They have a network that hold the soil in place, and the easiest way rather than waiting for seeds to grow is to just take cuttings and plant them all the way along where you can see in the photographs water is running through. It stabilises it and then you put it out onto the shoulder to stop the erosion, and you’ve got light canopy plants, so you’ve got an understorey that is good, you use suckering species and that’s your first stages.   

“Then you can also use plants like Juniper and Holly, which are evergreen, and they take the energy out of the rain, slow the passage of water through the land and reduce compaction.”

Mr Pretswell refers to this kind of planting as “not rewilding but biological engineering”.  

The pair are not alone in having advised tree planting. A report by Bill Rayner and Bruce Nicoll in 2012 titled ‘Potential for woodland restoration above the A83 in Glen Croe to reduce the  incidence of water erosion and debris flows’. It was produced by Forestry Research for the Forestry Commission Scotland a full decade before planting actually began on the hill.   

“Transport Scotland,” it said, “has already commenced a programme of installing engineered catch fencing and improved drainage to counteract the immediate potential effects of debris flows toward the A83.”  

It cited planting as an option that “could form part of a future package of measures being discussed for the wider area around the problem section of the A83.”  

The description it gave of the site was of a hillside over which the then landowner was running over 200 sheep, with further cattle put out to the hill in the summer months, and also a transient deer population which “have a significant influence upon the hill”.   

The soil, it suggested was fertile, with the presence of indicator plant flowering bluebell and occasional seedlings could be spotted: including downy birch, eared willow and some rowan. 

“These had been heavily grazed and only the occasional  rowan was seen growing from a rock fissure, or other inaccessible site, where it had avoided being browsed or burnt [by muirburn]."   It noted that “at present” there were “no extensive binding root systems extending to greater than ~30cm depth across the hillside and this is exacerbating the inherent soil properties to erode and flow downhill”.  

The plan suggested by the report was to restore a cover of native broadleaf species. But it noted: “the site has considerable browsing pressure from a combination of deer, sheep and cattle that must be addressed in any management scheme.” It  recommended less than four deer per square kilometre.  

 The A83 at Butterbridge, north of Rest and Be Thankful

Similar to Pretswell and Greer, it also advised planting willow "on the banks of both disturbed and undisturbed gullies, willow... to provide a potentially rapid improvement to soil cohesion.”  Restoration, it said, “would take thirty years or more across the site where climatic conditions are most severe.”  

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Mr Pretswell said he believes “institutional inertia” is the problem. He observed: “You have civil servants who sit behind a desk, are risk averse and thus promote stasis conservation, and advise politicians. Or politicians will go to an institutional source, like a university, for advice to validate their political position.

“Why is the messenger more important than the message, have we lost faith in the public to understand a simple argument”?

He also believes such delay has resulted in a profound waste of public money. Already over £90 million has been spent on repairs and prevention measures, and a further £470 million looks set to be invested in the creation of a debris-flow shelter to protect the road. 

“I said at a public meeting, for £90 million you could buy the estate, give it to the local community, reforest it and still have money left over to do the road." 

One element of this has happened: Forestry and Land Scotland bought 736 hectares of land above the Rest and be Thankful, according to their acquisitions record, for £600k in 2017/18.  

According to Transport Scotland, one of the reasons tree-planting did not occur sooner was that the previous landowner did not have any obligation to plant trees on the hillside used for livestock farming. It was the opportunity to purchase the hillside that shifted the strategy to the next stage.

A Forestry and Land Scotland spokesperson said: “We worked with Transport Scotland from around 2012 in their development of a resilience plan, preparing a planting plan and agreeing funding arrangements for the planting programme.

“Unfortunately, land ownership issues and protracted sale negotiations meant that no work could begin for several years.

“Once the sale concluded in 2019, a planting plan was formally approved that year and deer fencing work – the preliminary stages of the plan – took place in 2020/’21.

“Tree planting began in April 2022.”