Restoring British Salmon Forests - A Lesson from Canada and Yarner Woods

Written By Julia Comerford - Digg & Co

Canopy after management to open light levels for tree regeneration and epiphyte diversification

It has been fascinating to stumble into the world of rainforest restoration in the UK, at what feels like a very pivotal time for cultural identity; as the lichen and fern-clad, rain-sodden woodlands of coastal UK are increasingly being reimagined as Atlantic Temperate Rainforests. Having moved over from Vancouver Island, Canada, I’ll admit that the last thing I expected to encounter in the UK was rainforest. Rather, I had pictured wind-battered coastal cliffs, rolling meadows with the occasional craggy old oak, and Heathcliffe emerging from the mist of a heather-clad moorland.

I had been in the vicinity of rainforest restoration for some time in Canada, where I learnt of incredible work being done by Coastal First Nations and organisations such as Reddfish Restoration. This work was being carried out throughout Nuu-Chah-Nulth territories on the West Coast of Vancouver Island. One key thing that stood out for me on the Island was the focus on restoring ecosystems at scale. In these ‘salmon forests’, it seems that one of the most crucial elements for rainforest integrity is river and intertidal restoration, and vice-versa. In the forests of the Pacific Northwest, the connection between ocean and rainforest, maintained through the thread of the river, forms the backbone of these vital habitats. So, restoration of any one habitat really must focus on them all. To illustrate this, studies have found that marine-derived nitrogen is transported hundreds of kilometres upstream in the bodies of the salmon, where bald eagles, bears, and wolves transport this vital nutrition further into the forest and even high up into the tree canopy.

Back on this side of the Atlantic, when I hear these conversations about stewarding, enhancing, and expanding the fragmented and vital Atlantic temperate rainforests, I can’t help but be struck with the feeling that the thread of how vital our rivers and coasts are to rainforests is missing, or at least underrepresented, from the conversation over here. The state of Atlantic Salmon, a distant relative of the Pacific Salmon, is dire. Now listed as endangered in the UK, populations are in crisis and have declined 70% in the last 25 years, with returns of just 50 fish counted on the River Dart in 2023 for example, according to the Fishtek Totnes Weir.

But what to do about our Salmon? Well, perhaps a good place to start is to think about the linkages between the rainforests that line the river valleys of salmon runs to the river themselves, and in turn their ocean-going fish. The question in my mind is how can we better manage our rivers - crucial riparian arteries between land and sea - alongside their linked rainforest habitats with our critically endangered Atlantic salmon in mind?

This past week I was lucky to snag a spot at a Rainforest Management Day offered by the Woodland Trust in partnership with Plantlife and Natural England at Yarner Wood in East Dartmoor.

We saw an incredible example of this sort of riparian-based rainforest management playing out at Yarner Wood. The felling works that have been done have created biogenic (any natural feature that helps to slow the flow of water, such as woody debris) interventions to help slow and spread the flow of the river coursing through the site.

Felling trees along the river channel to create leaky damns to help slow and spread the flow of the river coursing through the site.

The next step, we’re told by The Woodland Trust team, will be to plant willow along the river bank, helping to provide appropriate shading to keep river temperatures optimal for salmon. Water temperature is another vital component to consider, as water temperatures beyond 16°C may result in salmon run declines; as warm temperatures cause salmon to become stressed and unable to spawn and eggs also cannot persist in higher temperatures. Beyond temperature regulation, riparian willow planting will also help stabilise river banks thereby supporting runoff mitigation, and will also gradually add more biogenic woody material from the willow into the mix.  

Water spreading outside of the channelised river bed thanks to the woody debris. 

Salmon require cool, clean, oxygen-rich fast-flowing water with extensive gravel beds to spawn in. They are very vulnerable to changes in river water quality, temperature, and flow. By adding woody debris into the watercourse at Yarner Wood, sediment is caught and filtered, thereby improving water clarity and quality. Gravel is also trapped and filtered which optimises the rivers for salmon, as they require larger, smooth cobbles for spawning.

The next step, we’re told by The Woodland Trust team, will be to plant willow along the river bank, helping to provide appropriate shading to keep river temperatures optimal for salmon. Water temperatures beyond 16°C may result in salmon run declines; as warming temperatures cause salmon to become stressed and unable to spawn, and eggs also cannot persist in higher temperatures. Alongside providing shading, the saturated, humid sponginess of intact, functional temperate rainforests helps to moderate humidity and in turn, helps to optimise salmon stream temperatures. In addition to temperature regulation, riparian willow planting will also help to stabilise river banks thereby supporting runoff mitigation, and will also gradually add more biogenic woody material from the willow into the mix.

Canopy before management work

Canopy after management to open light levels for tree regeneration and epiphyte diversification

Overall, this filtering, slowing of flow, and re-connecting of rivers with their floodplains also provides the invaluable benefit of flood control for downstream communities and increases the resilience not only of the rainforests but the people around them.

At the event, we learned from Sam Manning at the Woodland Trust that the three key components for functional temperate rainforests are good air quality (which bryophytes - lichen, mosses and liverworts rely on), light reaching through a somewhat open canopy (which bryophytes also require to photosynthesise), and ample water and rainfall to create appropriate humidity level within rainforests. The water bit is key. Centuries of drainage remove and rearrange the way water flows through the land and has resulted in drier habitats, including our rainforests. Therefore, the key to restoring rainforest function is rewetting them; removing drainage, the addition of biogenic material, and allowing water to flow freely across floodplains, all to help raise the water table. This moistening of the whole forest has benefits not only for humidity regulation but also for the control of over-dominant plants such as bracken, which thrive in drier soils and don’t like soggy feet.

Rainforest Recovery is the South West strand of The Rainforest Restoration Project. It is being led by the Woodland Trust in partnership with Plantlife. This project is funded as part of the Government's Species Survival Fund. The fund was developed by Defra and its Arm's-Length Bodies. It is being delivered on behalf of Defra by The National Lottery Heritage Fund.