Reintroducing Wolves to Boost Scotland’s Carbon Sequestration

The number of red deer in Scotland has increased tremendously over the last five decades. The surge is attributed to the disappearance of one of their main predators, wolves, from Britain.

According to folklore, the last wild wolf in Scotland was killed in 1680, and since then, cervids have roamed the country unthreatened by predators. If undisturbed, a herd of 300 can grow to 3,000 in 13 years (Flyn, 2018).

In controlled numbers, deer help shape ecosystems. Light grazing by deer keeps competitive plant species in check, allowing a greater diversity of plants to thrive. However, too many deer can become a problem. In uncontrolled numbers, deers switch from gentle gardeners like bulldozers to vegetation.  

The 2020 report of the independent Deer Working Group recommended that there should be no more than five deer in every one-kilometre square of land for natural woodland regeneration. However, many places in Scotland today far exceed this number, and woodland regeneration is quite impossible without the protection of deer-proof fencing (The Problem, 2020).

A study from the University of Leeds, “Wolf reintroduction to Scotland could support substantial native woodland expansion and associated carbon sequestration”, has found that reintroducing wolves to the Scottish Highlands could contribute to an expansion of native woodland that would sequester up to one million tons of CO2 annually.

Researchers emphasise the crucial role that large carnivores, such as wolves, play in regulating ecosystems by influencing their prey’s abundance and behaviour. Recent studies indicate that grey wolves could enhance the carbon capture of Northern Hemisphere forests by approximately 260 million tons of CO2 each year. This impact occurs because wolves help manage herbivore populations and their behaviours.

Reintroducing wolves to regions where they have been absent could further boost carbon sequestration, which is vital for addressing climate change and keeping global warming below 2°C. Wolves were removed from Scotland around 250 years ago, significantly increasing the red deer population. Despite attempts to control deer numbers, the population in Scotland is still on the rise, with estimates ranging from 360,000 to 400,000 red deer today.

The overpopulation of deer, along with the presence of sheep in certain regions, poses significant challenges to tree regeneration throughout Scotland. In the winter of 2019, the density of red deer in some areas of the Scottish Highlands reached approximately nine individuals per square kilometre, exceeding the capacity for natural tree growth.

As a result, native woodlands have declined, making up less than 4% of Scotland’s total land area. However, initiatives aimed at controlling deer populations have led to improved tree regeneration, with an increase in seedlings noted when deer densities decreased to below 3.5 per square kilometre.

In the Cairngorms region, reducing deer numbers below 6 per square kilometre over a large area has allowed natural woodland to grow, adding about 164 hectares of new forest each year over 30 years. If deer numbers were reduced across a more significant part of the Highlands, it’s estimated that more than 39,000 square kilometres could be suitable for new native woodlands.

Large carnivores such as wolves have started to re-establish across mainland Europe. Wolve numbers even thrive in human-dominant areas in Central Europe, demonstrating their ability to coexist with humans. The study notes that the wolf population in Western Europe now exceeds 12,000. However, due to the sea acting as a natural barrier, reintroduction in the UK will be necessary to re-establish them.

Studies have shown that expanding native woodlands across the Scottish uplands could remove nearly 700 million tons of CO2 and contribute to national climate targets. Achieving this would require reintroducing wolves back to the Scottish woodlands.

The authors of this study point out that wolf reintroduction to reduce red deer populations in the Scottish Highlands has already been demonstrated. Still, the impacts on woodland establishment and carbon sequestration have not been assessed.

The study used a Markov predator-prey model to estimate the impact of wolf reintroduction in the Scottish Highlands on the red deer population, native woodland establishment, and carbon sequestration.  The model shows that a population of around 167 wolves would reduce red deer numbers below 4 per square kilometre, enough to allow trees to grow naturally. This new woodland could capture around 1.0 Mt CO2 each year, with each wolf contributing an annual carbon sequestration of 6080 t CO2.

However, researchers also anticipate the considerable conflict between hunters and farmers that would come with the reintroduction of deer. They believe that a substantial and wide-ranging engagement with stakeholders and the public will need to happen before the reintroduction of wolves can be considered.

Researchers also aim to provide new information to inform these ongoing and future discussions around human-wolf conflict and wolf reintroductions in the UK and elsewhere.

Research findings show that wolves can help control deer populations, allowing woodlands to grow and expand. This could help Scotland meet its national climate goals and provide economic benefits to landowners and local communities through carbon credits.