Wolf reintroduction to Scotland could support substantial native woodland expansion and associated carbon sequestration

1. Large carnivores, including the grey wolf (Canis lupus), play an important role in the carbon cycle through modifying the behaviour and population of wild herbivores. Large carnivores have been eradicated from much of their former range and are now absent from the UK, contributing to increased herbivore populations, which can prevent natural regeneration of trees and woodland. A reintroduction of wolves to the UK could reduce deer populations and associated browsing of tree saplings, but the potential impacts on woodland expansion and carbon sequestration have not been assessed.

2. Here we estimate the impact of a wolf reintroduction in the Scottish Highlands on red deer populations, native woodland colonisation and carbon sequestration. We use a Markov predator–prey model to estimate that a reintroduction would lead to a population of 167 ± 23 wolves, sufficient to reduce red deer populations below 4 deer km−2, the threshold at which we assume browsing to be sufficiently suppressed to enable natural colonisation of trees.

3. Using a model of potential new native woodlands we estimate the subsequent expansion of native woodland would result in an average annual carbon sequestration of 1.0 ± 0.1 Mt CO2, with each wolf contributing an annual carbon sequestration of 6080 t CO2.

4. Practical Implication. Our analysis demonstrates the ecosystem benefit that wolves can provide through control of red deer numbers, leading to native woodland expansion. Large-scale expansion of woodlands, facilitated through the return of wolves, can contribute to national climate targets and could provide potential economic benefits to landowners and communities through carbon finance.