Deer impacts

Deer impacts on designated sites


The aim of the guide is to provide a general overview of deer impacts, how deer impacts may be assessed and what that means on designated sites.


Wild deer are an important component of Scotland’s wildlife and have a significant ecological role as the largest undomesticated grazers. They are an integral part of the Scottish countryside and at appropriate density can contribute to maintaining the natural heritage value of many habitats.
However, deer can cause damage to woodland and the natural heritage through:

  • Grazing, browsing, bark stripping and trampling, which result in damage to plants; reduction in the extent of plant cover; alterations to the composition of plant communities; knock on effects on dependent species; or direct effect on other species, such as trampling of bird nests.

When determining whether “damage” or “serious damage” to woodlands or the natural heritage is occurring,  SNH will take account of the nature and extent of the impact of deer and other herbivores on the woodland or natural heritage features, the importance assigned to these features by national and international legislation, government policy and the wider interests of society.

Assessing Deer Impacts

Some broad indications of grazing impacts can be seen at a distance. For example, woods with virtually no understorey of the appropriate type, or patches of heather (Calluna vulgaris) which appear greyish (rather than brown or purple) when viewed from a distance, are heavily grazed. A high grass to heather ratio in areas most likely to be grazed (for example, around supplementary feeding areas) can indicate heavy grazing. Spring and flush habitats are sensitive to trampling by hoofed animals, giving rise to visible poaching. Dung on the ground indicates the species of grazing animal.

Beyond these broad indications of grazing impacts, individual habitats need to be examined more closely. Not all impacts will occur in any one situation. Some impacts are best seen at certain times of year, for example, browsing on dwarf shrubs (heather, blaeberry etc.) is best seen in early spring, after winter browsing has taken place, but before the current year’s growth has started. More detail on how to assess deer impacts on different habitats can be found in the BPG Habitat Impact Assessment guides.

Evaluating Damage to Woodland & the Natural Heritage

It is important to distinguish between impacts and damage. Impacts can be measured, and taken collectively can be evaluated against the woodland or natural heritage importance of the features being impacted, in order to assess whether damage is occurring. Damage involves a judgement, based on clear evidence, that the impacts are deleterious in a particular location. Damage to woodland and the natural heritage arises when natural and semi-natural habitats are prevented from regenerating to sustain their ground cover and the diversity of plant species; or where local populations of important species (animal or plant) are in decline; or where important earth science features are being eroded by deer.

Issues which have a bearing on the nature of Damage & Serious Damage

In the context of the natural heritage, damage is more likely to be considered serious by the SNH when a nationally or internationally important feature is being changed, or is likely to be changed for the worse, or habitats that have been enhanced with public money are being damaged (eg WGS and SFGS). The most important cases of serious damage are likely to relate to the natural heritage interests of statutory designated sites and tackling these cases is a priority for SNH, FCS and SGRPID. More detail on designated sites can be found in the SNH Natural Heritage Statutory Designations.
In the context of commercial woodlands damage is more likely to be considered serious when the landowner is effectively unable to control the deer when they are on their property.
SNH advises government on the condition of statutory designated sites. On those sites where there are concerns that deer may be causing damage to natural heritage interests, the agencies will work with landowners to collect more detailed information on the nature and scale of impacts in order to find appropriate solutions and the right balance between incentives and regulation. More detail on this process is provided in SNH Deer Impacts on Designated sites.


Identifying sites for action

Sites recommended for action are identified through either an SNH-led audit on the state of designated sites (Site Condition Monitoring) or via expression of concern from 3rd parties.
In summary there is a 3 stage process of:

I. Natural heritage site audit

The condition of designated sites is monitored on a 6 year cycle to provide an overview of all sites affected by deer and livestock. Site Condition Monitoring (SCM) results are compiled in to an audit list which records the following:

  • Whether features are in unfavourable condition because of grazing and types of grazers present.
  • Whether deer are a potential contributor to unfavourable condition.

II. Assessing Priority

Sets out criteria for prioritisation and includes weightings for:

  • importance in terms of international obligations
  • significant of impacts (in terms of extent or degree)
  • sites with impacts regarded as critical in terms of timescale requirements

And when taking action:

  • Cost effectiveness of early action
  • Positive opportunity

The main aims of this stage are to:

  • Bring forward those sites in most need of attention
  • Make the best use of tax payers monies

III. Work programming

The work programme details sites where agencies are working jointly to address grazing and trampling impacts. This includes sites where:

  • Action is underway on sites agreed as the highest priority
  • There is additional monitoring ( to provide more information on the nature and scale of impacts)
  • There are positive opportunities for enhancement through voluntary approaches and incentive schemes.

Managing deer on designated sites

The assessment of current impacts provides an early indication that positive or negative changes in habitat condition are likely to occur (see BP Habitat Impact Assessment Guides)
If current herbivore impacts are considered to be negative, when assessed against the conservation objectives for the site, then agencies will work with owners/occupiers and look to what mix of incentives or regulation may be appropriate to secure more effective management of grazing.
The process highlighting the incentive and regulatory options open to agencies and land managers is summarised below: