Beavers in Scotland: consultation on the strategic environmental assessment

A consultation on the policy to reintroduce beavers to Scotland and the strategic environmental assessment of this policy.

2. SEA Methodology

2.1 Scope of the Assessment

Following the feedback received from the Consultation Authorities ( CAs), the environmental topics considered to be in and out of the scope of the assessment process were finalised as detailed in the table below.

Table 2.1 - Environmental Topics in and out of the scope of the assessment process

SEA topic

Scope in/out


Biodiversity, flora and fauna


Beaver are considered to be ''ecosystem engineers.' They undertake various activities such as felling trees, creating dams/ponds, direct herbivory, which can result in changes to the structure and composition of their surrounding habitat. These changes can consequently impact on the species that depend on these habitats. Such changes may benefit some species (and habitats) but disadvantage others, although this will vary depending on scale and time.

Population and human health


The aspect of this environmental topic to be considered in this assessment relates to human health. Eurasian beavers host a number of external and internal parasites, some of which are already present in the UK and some are not. Many of these diseases and parasites have the potential to cause zoonotic diseases and maybe notifiable and/or reportable in the UK.

Soils and geomorphology


Soils and river processes: Beavers undertake various activities e.g. felling trees, creation of dams/ponds, foraging activities, which results in changes to standing and running water habitats and their associated hydrological and geomorphological processes. In relation to soils, burrowing into banks may cause localised bank erosion and soil being washed into rivers. However, the principal effect of beaver dams is to slow down river flow, causing sediment deposition behind the dam and the eventual creation of 'beaver meadows'. Reduced river flow will also result in slower rates of bank erosion in the area upstream of the dam. Beaver dams may also help attenuate flood flows, slowing the downstream passage of peak flood flows. Consequently any likely significant effects on soil interests are considered within the freshwater and biodiversity topics.

Geomorphological and geological conservation sites: Burrowing animals could locally impact on exposures of unconsolidated sediments in banks and cliffs, but there are a number of other burrowing riparian mammal species in Scotland already, like otters. Storage of branches and foliage, construction of beaver dams and consequent raised water levels could temporarily obscure rock outcrops and small scale landforms, such as river bars. This would be equivalent in scale and duration to fallen trees within water courses, and is similarly temporary and reversible. The visibility of rock outcrops or river geomorphology will eventually be restored after the dam has been abandoned and the woody and stony debris reworked by the river during subsequent floods.

Water quality, resource and ecological status


Beaver activity such as building dams and creating wetlands can influence water quality by reducing flushing times and increasing nutrient retention. Dam-building may also change water levels both upstream and downstream of structures. It is only the freshwater resource that is likely to be impacted upon by beavers. Marine waters or tidal waters are not significantly affected by beaver activity.



Beaver activity is unlikely to result in any significant changes to atmospheric emissions or air quality.

Climatic factors


The policy will not give rise to emissions or pollutants that might impact on climatic factors.

In terms of climate change adaptation, there may be positive impacts, for example, from flood alleviation and flow attenuation. However, this is considered in the assessment of the effects on freshwater, hydrology and associated geomorphological features.



The two beaver policy areas do include a number of National Scenic Areas ( NSAs) within their boundaries. However, any changes to habitat structure or composition as a result of beaver activity will be local in nature and are unlikely to have significant effects on the special qualities of the NSAs.

Cultural heritage


There are a number of sites of historic value that overlap with or are near to beaver habitat at Knapdale and in Tayside e.g. Crinan Canal for which certain beaver activities, such as burrowing, could have an adverse impact.

There are a number of sites in the Inventory of Gardens and Designed Landscapes that fall within the two beaver policy areas.

Material assets


Forestry - Since most of Scottish forestry relies on conifers, beavers are unlikely to have much direct impact through felling. However, there may be impacts on forest infrastructure (tracks, culverts), felling of planted riparian woodland and impacts arising from flooding.

Fisheries -Tayside supports significant recreational fisheries for Atlantic salmon and there is the potential for impact by beaver activity.

Agriculture - Impacts can arise from a range of activities, including burrowing and canal construction, dam-building, blocking culverts, direct foraging of crops and gnawing and felling of commercial trees.

Infrastructure - Infrastructure will be at risk only in proximity to beaver activity, in the immediate vicinity of running and standing water with associated riparian habitat. Impacted infrastructure could include roads and tracks, culverts, weirs, sluices and fish passes, canals, water treatment plants etc. Beavers may also cause impacts on drainage from households, affecting private waste water treatment works.

The focus of the assessment is on the environmental effects arising from the proposal to allow the beaver populations in the Knapdale and Tayside beaver policy areas to remain. Beaver activity is largely restricted to freshwater and associated riparian habitats, in particular broadleaved woodland which provides a key source of food and materials for building structures. Whilst this approximates to only 1.4% of the land area of the two Policy areas, the assessment also considers indirect impacts arising on land and infrastructure linked to areas used by beavers.

Although difficult to predict, recent research suggests that beavers may not expand far from Tayside or Knapdale over the next two or three decades, but may over time disperse into neighbouring catchments. Accordingly, this SEA will not include consideration of environmental effects arising from any subsequent releases outwith the beaver policy areas, and these should be the subject of further assessment.

Chapter 4 details the findings of the assessment process. Following feedback, the reporting structure varies slightly from that detailed in the scoping report, but the content covers the same receptors. Section 4.1 provides an overview of beaver ecology which provides the context for the interactions with the following receptors:

  • Biodiversity
    • Woodland
    • Bryophytes, fungi and lichens
    • Terrestrial vascular plants
    • Invertebrates
    • Amphibians and reptiles
    • Birds
    • Other mammals
  • Water
    • Freshwater - standing water, including aquatic macrophytes and wetlands
    • Freshwater - running water
    • Fish
  • Population and Human Health
  • Cultural Heritage
  • Material assets
    • Forestry
    • Fisheries
    • Agriculture
    • Infrastructure

Soils and geomorphology were initially considered within the scope of the assessment process. However consideration of any significant effects on soils and fluvial-geomorphology is captured within the sections on woodland, freshwater and material assets as these elements are too closely interconnected with these topics to separate out in any meaningful way.

Each receptor is detailed in a section which considers:

  • A summary of how beaver activity affects the receptor (i.e. broad scale)
  • A summary of positive and negative effects of beavers on receptor (i.e. broad scale)
  • The distribution of receptor within beaver policy area
  • An assessment of likely effects on important receptors within the beaver policy area, split into positive and negative (with link to mitigation / monitoring where appropriate).

Chapter 5 pulls together the relevant mitigation measures designed to address any potential adverse effects identified.

Chapter 6 considers the 4 policy alternatives below:

  • Scenario 1 - full removal of beavers from the wild in Scotland
  • Scenario 2 - restricted range. Allowing beavers to expand from their current range, but specific catchments would be managed to keep them free from beavers.
  • Scenario 3 - widespread recolonisation. The beaver population would be allowed to expand to its natural limits. Eventually this could include further releases outside the two current population areas.
  • Scenario 4 - accelerated widespread recolonisation. Proposals for new releases could be considered immediately.

The scenarios are broad and a number of sub-options were possible. As detailed in the scoping report, the preferred policy alternative draws from both scenarios 2 and 3.

Chapter 7 looks at opportunities to monitor the environmental effects arising from the reintroduction of beavers into both Knapdale and Tayside.

2.2 SEA Objectives

The following SEA objectives will form the basis against which the nature of the environmental effects on the receptors identified above will be considered:

  • Biodiversity, flora and fauna - to conserve and enhance the integrity of biodiversity interests in the two beaver policy areas
  • Population and human health - to protect human health and enhance well being
  • Soils and geomorphology - to maintain and improve soil quality and geomorphological features in the two beaver policy areas
  • Water quality, resource and ecological status - to maintain and enhance key ecological processes e.g. hydrology, water quality in the two beaver policy areas
  • Climatic factors - to reduce vulnerability to the effects of climate change - e.g. flooding in the two beaver policy areas
  • Material assets - to protect material assets and promote the sustainable use of natural resources in the two beaver policy areas
  • Cultural heritage including archaeology - to conserve and enhance the historic environment in the two beaver policy areas.

2.3 Limitations of assessment

Geographical extent

The geographical extent of this SEA is limited to two beaver policy areas in Scotland - Knapdale and Tayside. The Knapdale beaver policy area is 64,978 ha in size and Tayside comprises 1,140,075 ha. Within these policy areas the likely extent of habitat to accommodate the establishment of beaver territories was identified as 'potential core beaver woodland.' This comprises 970 hectares (ha) in Knapdale (less than 1.5% of the total Knapdale beaver policy area) and 14,717 ha in Tayside (less than 1.3%). This approach is consistent with the approach in the HRA of the Policy ( Annex 2).

Data collection

The two beaver policy areas by their nature do not correspond with local authority areas. This has resulted in some complications with data collection which is often available on a local authority basis. Where approximations have been necessary these has been recorded in the ER.

Assessment of the nature of likely significant effects on the environment

Difficulties in evidence to support long term effects will be examined as part of monitoring proposals. Monitoring and research will be driven by an adaptive management approach. The outcomes of trials and monitoring results will enable SNH to modify their conservation management and guidance for land, fisheries and infrastructure managers.

The assessment has focussed on significant positive and negative effects, and where there are cumulative effects these have been highlighted in individual sections. The assessment is complex as each beaver interaction can have more than one effect, both long term and short term. For example, in the short term a tree is felled but in medium term it may coppice and regrow which may result in a change in woodland diversity. However if there are herbivore impacts such as deer browsing there could be cumulative effects which in itself may open up the canopy and change the structure of the woodland.

Similarly, duration of effects is complex. For example beavers may temporarily exhaust the resources of an area and then move on. Beaver structures may degrade and new habitats such as 'beaver meadows' will form. In due course beavers may return to the site. The duration of these effects may vary according to local circumstances and environmental conditions influenced by weather events.

It is recognised that the nature of these effects and the difficulties with predicting wild animal behaviour and environmental events lead to uncertainty in the assessment and the need for a more generic approach in the ER.

Assessment approach

The SEA assessment particularly for biodiversity, flora and fauna and cultural heritage focusses on designated sites and focuses on the nationally and internationally important designations in the beaver policy areas, consistent with the approach of assessment of significant environmental effects. However, the wider importance of freshwater and riparian habitats should be recognised and that not all species of conservation interest are restricted to designated sites. For species and habitats of conservation interest in the wider countryside it is recognised that there will be an ongoing need to assess data derived from general surveillance and monitoring activities that are already in place, and intervene with management if and when necessary. This will be informed by a more strategic approach to management being developed in due course.

The necessarily precautionary nature of HRA for European sites should be noted throughout the assessment and this rigorous approach needs to be viewed in this context.

Recording of Positive effects

As a result of the precautionary approach of the HRA and the aim of keeping the reporting succinct, many of the positive effects may get lost on reading because of their generic and long-term nature. Positive effects have been identified in each of the assessment sections, but mainly in terms of a general overview.

Time Limitations

The HRA ( Annex 2) raises limitations in respect of validity of the timescale of the HRA assessment beyond 15 years. In particular, it states that "There should be a commitment to conduct an updated HRA after ten to twelve years, or at the point any new release site or other reinforcement is considered (whichever comes first). This should result in a new iteration of the HRA to take into account all relevant data acquired since the date of this HRA." Accordingly, this will require a refresh of the SEA within in a similar timescale.


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