Where is the link between aquaculture and blanket bog in Shetland? Well, about half of Shetland is covered in peat (although Scottish Natural Heritage (SNH) has estimated that 70% of Shetland’s blanket bog is damaged). Meanwhile, the fishing industry is Shetland’s biggest sector with about 25,000 tonnes of farmed salmon produced each year.
Shipping materials or equipment for peatland restoration to Shetland is costly in both £s and carbon, leading the Shetland Amenity Trust to take an innovative and resourceful approach to sourcing materials and techniques by using waste materials from the aquaculture industry to build dams and stabilise bare peat. Not only have these techniques proved remarkably successful but have also reduced the cost and carbon footprint of the projects.
Local contractors were used throughout, developing a local skill base for peatland restoration in Shetland and local windfarm developer Viking Energy have been taking a big interest in the results.
Peatland restoration in Shetland has been kick started over the last two years by funding from SNH’s Peatland ACTION Fund. This funded a Peatland Restoration Project Officer and three peatland restoration projects resulting in the construction of over 1,000 dams benefitting about 150 hectares of blanket bog, all from a “standing start”. The projects appeared daunting at first: many hectares of filigree-like networks of erosion gullies take water off the hill and dry out the bog. Large bare areas of peat get washed away all winter; during brief dry spells in the summer it literally blows away. Projects on the mainland where diggers block long straight ditches with peat dams were viewed enviously. The digger driver on Shetland spent much of his time just trying to navigate the maze of erosion gullies, not a straight edge in sight.
Whilst the same priniciples of peatland restoration apply on Shetland as mainland Scotland, the methods and materials used were not always useful. From the outset transport costs of materials or equipment (Shetland being 200 miles from Aberdeen) in terms of money and carbon were a considerable obstacle.
So, the team set about finding their own locally applicable solutions for peatland restoration. An important part of this was through sourcing and making use of abundant locally available waste materials from the salmon farming industry. They also wanted to build the peatland restoration skills of locally based contractors and trial methods that anyone could tackle on a small “crofter scale” without needing to hire in machinery.
A Shetland Amenity Trust ‘peatland team’ undertook practical manual work, along with a local digger driver (with some experience of Scottish mainland restoration work) for more traditional peat dam construction.
The main issues on Shetland in addition to a harsh climate and exposed sites are erosion gullies, extensive areas of bare eroding peat and peat hags.
New Materials for Blocking Erosion Gullies
Salmon farm polar circle pipes
Salmon farm cages are constructed from thick black plastic pipes about 50cms diameter. There is a large amount of this material available locally from redundant cages which would have to be shipped off Shetland for disposal/ chipping and recycling. Shipping costs and freight for importing plastic piling into Shetland are high, not to mention the carbon footprint of transporting this bulky, heavy material. The waste salmon farm pipes make an effective alternative to plastic piling. Local recycling firm Augean cut up the pipes and sliced them in half for us. Upright half pipes were arranged in two interlocking rows to build dams. The material is much sturdier than commercial piling and with peat behind it this creates a really strong and effective dam. Half pipes laid flat on the ground were also used to allow water to flow over them and spread rather than causing erosion on slopes where water cannot be held back entirely.
Salmon Smolt net
Redundant salmon smolt net has turned out to be a fantastic locally available resource for peatland restoration (see use for stabilising bare peat below). It is a waste product from salmon farms, it needs to be replaced every 2-3 years and would otherwise end up in landfill. The nets come in huge irregular shaped pieces that need to be cut to size but once rolled up tight and positioned it works well where a low dam is sufficient. The net soon gets clogged with peat particles, peat silt builds up behind it and vegetation starts to establish naturally.
Not a locally available material (it comes from a Fair Trade source in Tanzania) but new to use for peatland restoration. The sisal tubes were cut to size, filled with catotelm peat from the gulley and keyed into the gulley. Once covered with turf from an adjacent eroding overhang these “sausage” dams worked well and could be used where there was too little peat for piling dams.
Innovative approaches to repairing extensive areas of bare eroding peat
The waste salmon farm smolt net described above has also turned out to be an incredibly cost effective alternative to commercial geo-textiles commonly used to stabilise bare peat. Again the Shetland Amenity Trust worked with Augean who cut up the net into manageable sized pieces. These were spread out over the bare peat and held in place with small wire pins (the method has worked even on our exposed wind swept hills). There is already a difference of several centimetres of peat at the edge of net laid in 2015 and cotton grass soon re-establishes naturally adjacent to existing vegetation. During dry weather the peat under the net cracks less than the surrounding bare peat.
Revegetating bare peat
Seed for re-seeding bare peat was sourced from the local spinning mill- the material (seeds, soil, bits of sheep muck and wool fibres that are shaken out of the sheep fleeces before they are washed) was collected and spread on some of the bare peat areas that were then covered with salmon smolt nets.
Sphagnum moss was collected by hand from nearby donor areas and spread around newly created pools and rewetted bare peat, a very low tech but successful method. Plugs of bog vegetation and locally collected/grown cotton grass seed/plants were also used.
The Shetland Peatland Project has restored about 100 hectares of blanket bog but more importantly has demonstrated that even bog in exposed conditions in a highly degraded condition can be restored using straightforward techniques and locally available materials. It is particularly exciting and gratifying that the methods that have been tried out are now being used to inform local windfarm Habitat Management Plans.
Erosion gullies have become chains of pools full of sphagnum mosses, bare peat has been flooded or stabilised with nets and vegetation has started to recover. Dunlin and golden plover are on the hills that have been restored and red throated divers have returned to breed on a hill top lochan.
Climate change savings have been made several times over. Not only have we restored blanket bog to a state where it can actively sequester carbon, we have also used locally available waste products, diverting these from the waste stream and doing away with the need to freight materials such as plastic piling into Shetland. A “win win” for nature.
Sue White, Peatland Restoration Officer, Shetland Amenity Trust