The Mountain Birch Project

The fading ‘birch belt’

The vast open landscapes of the Scottish Highlands provide an awe-inspiring image of nature for many people. However, it’s increasingly recognised that all is not well ecologically. Centuries of human-induced pressures and neglect have gradually diminished the diversity of habitats with some entirely disappearing. One of these habitats is known as the ‘birch belt’ (or perhaps ‘birk belt’ in Scots), which should sit at around 650-800 metres above sea level in Scotland. This band of montane woodland, largely dominated by mountain birch, should occupy the space above the line of Scots pine woodlands and below the higher zone covered in montane willows. In this ecotone (a region between two biological communities), biodiversity can often be rich.

Mountain birch woodland in Norway provides a good example of such diversity. In the southwest of the country, a variety of broadleaved tree species exist in a relatively open canopy. Where the climate, geology, topography and ecology are similar to that of Scotland, species such as birch, rowan, aspen and willows thrive. Among them patches of tall shrubs like downy willow, juniper and dwarf birch are interspersed with boggy glades and wind-clipped heath. This offers habitats for mountain birds, mammals, herbs, ferns, mosses, lichens and other species that currently have to occupy other niches in Scotland. Iconic birds like the red and black grouse would seek food and shelter here from the brunt of the harsh weather at higher altitudes.

Why target this high-altitude species? 

This habitat is functionally extinct in Scotland. Due to shifting baseline syndrome, this issue is practically unknown in the Scottish upland conservation/ecology sector. A lack of awareness of the role of mountain birch in the Scottish uplands is, in some cases, hindering its return.

The importance of mountain birch as a montane tree species becomes more apparent considering its adaptation to high altitudes. Low-ground provenance birches have not fared well trying to establish when used in mountain woodland restoration efforts thus far. Experience from organisations such as the Borders Forest Trust indicate that low-altitude downy birch fail to grow at higher elevations. As such, mountain birch has an important role in mountain woodland restoration in Scotland and its scarcity means locating and propagating remaining fragments is a priority.

Another benefit of restoring mountain birch is that with a more complete montane habitat there would be an opportunity for currently extinct species to recolonise or be reintroduced, such as bluethroat and alpine blue-sow-thistle. Restoring mountain birch woodlands contributes to the overall restoration of Scotland's upland landscapes. It’s part of the effort to address the loss of native forest cover that, if restored, would promote a more diverse and healthy ecosystem.

Addressing the risks, challenges and uncertainties

There is little to no experience of growing this high-altitude species of birch in Scottish nurseries which raises some important questions for our attempts: Do the trees need to start life at high altitude? How do we guarantee the best germination rates? Will genetic impoverishment from wild trees be an issue? Will seedling/sapling mortality be high for these trees in the harsh upland environment? How to mitigate the impacts of the deer density problem?

Our approach will involve an element of trial and error to help navigate these challenges. However, we will also look to examples from Norway and draw on the knowledge and experience from the Norwegian Institute for Nature Research. From their experience, viable mountain birch seed can grow like a weed, not needing to begin life at high altitude. To reduce the risk of mortality from harsh upland weather, planting will be undertaken in relatively sheltered locations as we build up mutual shelter from established trees, and we could potentially plant willows to act as nurse trees (larger, faster-growing trees that shelter smaller, slower-growing ones). We will facilitate discussions between Scottish tree nursery managers and practitioners in Norway to address any additional challenges that may arise. In regards to the issue of deer densities, we will prioritise distributing seeds to sites where densities are low or fencing is able to protect young saplings.

We would like to thank Mossy Earth members for making this project possible. With their support, we have a chance to bring back the birch belt, and enhance Scotland’s uplands with more intact, diverse woodlands.