‘It’s not necessarily about fishing, just knowing the salmon are there is what matters’, explains Anson Macauslan, estate manager at Braemore & Langwell Estate, as he drives me upstream along the Langwell Water near Berriedale in Caithness. I’ve come to see where Anson thinks the Garden’s Scottish Plant Recovery team could plant some special wych elm (Ulmus glabra) seedlings. The trees have been bred from the rare survivors of Dutch elm disease in southern Scotland and the story of how and why the Botanics started elm breeding is told in an earlier post called Next gen elms. But in short, the planting Anson and I are discussing will introduce trees that may have an edge over the disease that has been decimating the elm population since the late 1960s. The Langwell Water, like many other straths (broad valleys) in this part of Scotland, has elm as a natural component of mixed broadleaved woodland. The elms grow on the more fertile ground on lower slopes and river terraces where there is good drainage.
It’s not necessarily about fishing, just knowing the salmon are there is what matters
Anson’s passion is the Atlantic salmon (Salmo salar) that are an important part of the ecology of the Langwell Water, so it’s interesting to hear him speaking about why he wants to see the strath become more wooded. The river is designated a Special Area of Conservation (SAC) for its high-quality salmon habitat. But even here salmon numbers are in decline. The national picture is one of widespread and often steep decline in numbers. Unfortunately, salmon face a complex array of threats and there is no ‘silver bullet’ to reversing the decline. Being a migratory species, the salmon can be hit at various stages in their life cycle, both in their breeding and feeding grounds.
The thought that salmon might continue to decline is motivating Anson’s management of the land alongside the river to improve the habitat for the fish. Surprising as it may sound the salmon are intimately connected to the forests that should be growing on the banks of their rivers. The term ‘salmon forests’ comes from the scientific research that is revealing a two-way interaction – the fish need forests, and the forests need fish. Trees shade the river and keep the salmon safe from the harm caused by hot weather. The leaves and other ‘litter’ entering the river acts as food for a complex web of aquatic life that forms the prey of young salmon. What’s much less obvious is how the salmon benefits the forest. Research in the Pacific Northwest of North America is showing that the nutrients brought to the land by predators of the salmon, such as bears, is significant for the growth of trees and other plants. These predators catch and eat large amounts of salmon and this process transfers nutrients that originated in the sea onto the land next to the salmon rivers.
The treeless and bear-free hills around Scotland’s salmon rivers may seem a world away from the Pacific Northwest, but we need to remember that in the distant past the salmon spawning in Scotland’s rivers shared their environment with bears and the land was much more wooded. The ecology of the salmon in these two apparently different, and distant, places is essentially the same.
This is where an exciting synergy between Anson’s work and the Garden’s work on Scottish Plant Recovery becomes obvious. Both of us want to encourage appropriate native trees alongside upland rivers. In our case it is to benefit wych elm and some other threatened woodland plants like alpine blue-sow-thistle (Cicerbita alpina) and whorled Solomon’s seal (Polygonatum verticillatum) that are herbaceous plants found in this type of upland woodland. Restoring elms, and other native trees, recreates a habitat called ‘riparian woodland’ – woods that grow next to rivers and streams. Because the richest soils are near to rivers it is no surprise that people have preferentially cleared riparian woodland to make way for agriculture, as a result very little of this habitat survives today. The rarity and wider ecological value of this type of woodland means it is now recognised as a so-called ‘priority woodland’ in the Scottish Biodiversity Strategy.
Removal of the native forest in Scotland’s hills and lowlands took place so long ago it is hard to imagine there being more trees and woodlands. Despite the absence of trees over large parts of the Langwell Water’s catchement, this strath provides good evidence that the land ‘wants’ to be woodland again. In a few places along the lower reaches of the river there is good cover of mature native woodland, something that represents a rare and precious survival. More recently, in the last 20 years, some areas of treeless hillside near the river have been fenced against deer and planted with native trees, in particular downy birch (Betula pendula). The rapid recovery of woodland ground flora, and the natural regeneration of other trees alongside those planted, has been remarkable and very encouraging. It demonstrates the potential for woodland habitat restoration.
Simply by getting grazing levels down sufficiently the land will begin to revert to woodland without the need for any tree planting. In the case of the Langwell Water a complicated balance of hill sheep farming, wild deer management and woodland recovery is being managed. Anson’s vision is to increasingly tilt the balance towards woodland without the loss of the other traditional uses of the land.
The ancient elms of the Langwell Water’s surviving woodland fragments are now looking increasingly threatened by Dutch elm disease. There have been isolated cases of disease in the area, but for now the elms remain healthy. However, if you travel about 50 miles down the A9 heading south you will discover a very different picture. Here the elms have been hit hard by disease and most are now dead. Finding the rare survivors takes some effort.
The disease is advancing northwards, although possibly slowed down by cooler conditions in the north that don’t favour the beetles that spread the fungal pathogen. It’s impossible to know when it will arrive in the woods along the Langwell Water. What we do know is that when it does it will be devastating for the elms. The same pattern of severe losses plays out again and again. With the loss of mature elms comes the loss of those species that rely on old elms. Some of the Langwell Water elms have incredible leafy, green coverings of a lichen called lungwort (Lobaria pulmonaria) that favours the chemical makeup of elm bark and a few other tree species. It takes a long time for this lichen to spread, meaning it is not a good colonist of new habitat. By planting a new generation of potentially resilient elms into the landscape, before Dutch elm disease takes hold, we may be able to create habitat continuity for organisms, like the lungwort, that need old elms. Interestingly, lungwort is also a key part of the nutrient cycling of the woodland as it contains a microbial partner that not only captures energy from sunlight but also turns nitrogen gas from the air into plant food.
As we approach a flat expanse of river terrace that is covered in grass and a bit of bracken at one end, I’m pleased to hear Anson say he thinks it would be good for the elms. Being well above the level of the river it is well-drained ground that is obviously richer and more fertile. It will be ideal for the precious elm saplings. The position is south-facing and on a bend in the river next to a bridge. The steep north-facing slope on the far side of the river is covered by native woodland that even the deer and sheep can’t reach. A small waterfall runs down the slope and cascades into a pool of brown, peat-stained water that looks like tea. Apart from the soils being right for elm, the patch of flat ground is already almost entirely fenced to keep out the deer. A new section of fence will be installed to isolate the level ground from the slope above. There is also plenty of space for the intended 200 trees. Having agreed the suitability of the site, we move to discussing other practicalities like vole guards and when the planting will happen. We agree a team from the Garden is likely to be doing the planting in the next couple of months.
The wonderful thing about this collaboration with Anson and the Estate is that two threatened species are benefiting. In the process of riparian woodland restoration, we will improve the habitat for salmon in the Langwell Water, reestablishing a connection between the forest and the river that has been broken in too many places. We will also be adding to the gene pool of the local elm population with a diverse group of 200 trees that we hope have inherited beneficial qualities for survival in the face of Dutch elm disease. Each seedling is a unique genetic individual and the mix we plant will maximise the diversity coming from the 12 parent trees used for breeding.
The young elms will begin reproducing at about 20 years old and when this happens further genetic mixing will occur. Breeding between planted and indigenous elms will also be potentially beneficial. Natural selection will favour those combinations of genes that are best adapted to facing the challenges of the future, whether that is climate change, disease or some newly emerging threat we can’t currently foresee. Having briefly provided a little assistance, the recovery of the Langwell Water’s elms will be driven by natural processes.
For some people this is a radical approach to elm conservation, but the benefits to elm and the wider ecology of the Langwell Water, if our trees show resilience, cannot be overstated. The elms are as much an icon of these remote, wild places as the salmon. It is enormously encouraging, and a privilege, to work with people set on enabling nature to restore itself by providing opportunities and addressing the factors that are holding recovery back.
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