Woodland expansion in the presence of deer: 30 years of evidence from the Cairngorms Connect landscape restoration partnership.
Abstract
Restoring native woodlands to areas where they have been lost is a key element for tackling the nature and climate crises. Natural regeneration offers the potential to achieve this cheaply and at scale, but browsing ungulates like deer can inhibit this or alter the pattern of regeneration. This issue is particularly pronounced in the Scottish Highlands, a heavily deforested region with high deer numbers. We describe the work of the 60,000 ha landscape restoration partnership, Cairngorms Connect, in speeding up natural woodland expansion. We use 30 years of regeneration monitoring to show a consistent, large-scale expansion of native woodland, largely through natural regeneration alongside deer culling, without the use of fences. This was achieved across the partnership, despite differing management histories and land-managing organisations (comprising two statutory agencies, one private landowner and one non-governmental organisation). During peak periods of woodland expansion, the area of new woodland (i.e. exceeding 100 trees per hectare) increased by 1.2%, 1.7%, 2.7% and 6.0% annually in the four landholdings' regeneration zones, equating to a total of approximately 164 ha annually of new woodland. Natural regeneration is however patchy and hard to predict. Higher levels of management intervention may be needed to increase species that are rarer, more palatable or further from seed sources; we recommend long-term field trials to inform this, such as those underway in Cairngorms Connect. Further research should develop techniques for remote sensing of woodland expansion, verified against field data and combined with the development of process-based models to enable us to predict the outcomes of different management scenarios. Synthesis and applications. We show that collaborative deer management across multiple adjoining landholdings can achieve rapid landscape-scale native woodland expansion with minimal need for planting or fencing. Our results show the power of monitoring regeneration directly, to inform deer management for an area. We demonstrate that by uniting over a shared vision, organisations with differing management approaches and histories can build understanding alongside landscape-scale ecological restoration.