Forest Modelling: Exploring the Future of Scottish Forests under Diverse Restoration Actions
Restoration Story by Louisa Bouri-Saouter
Have you ever wondered what it would be like to look into the future? With climate change on the horizon, many hope to understand what we are walking into. So, what if we could get a glimpse of tomorrow’s forests? What if we could see what this vital ecosystem is becoming or could become? When it comes to Scottish forests, that’s exactly what six researchers have explored*.
By using forest resource modelling, researchers have projected what would happen to forests in Scotland when different forest restoration activities are applied. In total, 1,411,958 hectares of forests were simulated, within which the forest restoration activities were carried out on 33% of this total area (approximately 463,536 hectares). Forest development under a « Business-As-Usual » scenario and two different restoration scenarios were projected over the next 30 years, until 2055.
Map of initialized NFI plots in Scotland, in total 15 523 plots. Colour of the bar represents the initial dominant species or species group per plot, and height of the bar shows the initial growing stock volume.
Here’s what the projections reveal about these two restoration scenarios:
Following current Scottish Government regulations on sanitation felling in larch forests infested with pathogen Phytophthora ramorum, the first scenario focused on the implication of Larch removal on 65,007 hectares (5% of Scotland’s forest area). This large-scale sanitation felling, including the removal of larch trees near infested areas to prevent the spread of pathogen, was followed by the replanting of a mix of future-suitable species such as Sitka spruce, birch, and rowan.
Projection results show a clear increase in harvested volumes during the first five years as a direct result of the larch removal. However, this short-term rise gradually declines and stabilizes over time, aligning with the harvested volumes observed in Business-As-Usual scenario. Replanting with a diverse mix of future-suitable species also supports faster forest recovery and has a positive long-term effect on soil carbon stocks.
Since the primary constraint to the management of productive forests in Scotland is the risk of wing damage, the second scenario meant to support the conversion of 28% of Sitka spruce forests located in high-risk wind areas to coniferous continuous cover forest (CCF), creating more complex and diverse forest structures. Despite an overall decline in growing stock and harvested volumes, forest structure began to shift: after 30 years, more medium- to large-sized Sitka spruce trees (20–50 cm in diameter) were present.
This structural diversification is expected to result in higher growing stock volumes and greater structural diversity in Sitka spruce forest stands in wind-prone areas, potentially contributing to improved resilience over the next three decades.
Growing stock (m3/ha) development per species over diameter classes (cm) from 2025 till 2055 for the three different scenarios.
Today, monocultures of Sitka spruce cover 45% of Scottish forests. But recent shifts in UK forest policies are set to transform this landscape, reducing these vast monocultures to create room for more structurally diverse forests. These changes hold great promise for improving biodiversity, flood mitigation, and the recreational value of these forests.
These scenarios, brought to life through advanced forest resource modelling, give us the chance to better understand the trajectories and consequences of applied restoration measures. A glimpse into tomorrow’s forests that could significantly change their course.
*Projections of Scottish forest restoration activities are part of SUPERB project’s deliverable D6.5 on the projected ecosystem data and were carried out by Sara Filipek, Silke Jacobs, Tom Locatelli, Bruce Nicoll, Daniele Ferraretto and Gert-Jan Nabuurs.
