3. Environmental Characteristics of the Beaver Policy Areas
The current state of the environment in the absence of the policy to allow the beaver populations in Argyll and Tayside to remain is considered in section 3.2. Implicit in this policy statement is the requirement for a level of reinforcement of the Argyll population which forms the premise for the beaver SEA policy.
Specific existing environmental issues which are relevant to the policy are presented in section 3.3.
3.1 Summary of the environmental characteristics of the beaver policy area
3.1.1 Geographical extent
The assessment has focussed on the geographical areas containing the two wild populations of beaver present at Knapdale in Argyll (map 2 below) and centred around Tayside (map 3).
Map 2 - Knapdale Beaver Policy Area
Map 3 - Tayside Beaver Policy Area
The extent of the beaver policy area is determined by the likely extent of habitat to accommodate the establishment of beaver territories - identified as 'potential core beaver woodland.' This is consistent with the approach in the HRA of the Policy ( Annex 2). The extent of the effects of this policy are limited to potential core beaver woodland which comprises 105,586 ha of suitable woodland in mainland Scotland.
The Knapdale beaver policy area is 64,978 ha in size and Tayside comprises 1,140,075 ha. In terms of the amount of potential core woodland in the beaver policy areas, this extends to 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%).
Map 4 - Potential core beaver woodland in Knapdale and Tayside beaver policy areas
3.1.2 Potential core beaver woodland characteristics
Potential beaver woodland can be identified by the following environmental characteristics:
- Broadleaf woodland and shrub - the main predictor of the presence or absence of beavers is the availability of food, in particular the abundance of suitable woodland. Hence, the datasets used categories of broadleaf woodland and shrub and native pinewood taken from the National Forest Inventory ( NFI) and Native Woodland Survey of Scotland ( NWSS)
- Within 50 m of freshwater edge - beavers prefer to feed in close proximity to water. In Denmark, 95% of foraging was within 5 m of the water's edge. As the distance from the water increases, the amount of beaver foraging declines. The great majority of activity will be constrained to within 50 m of a watercourse and this matches observations recorded during the Scottish Beaver Trial.
- Streams with less than 15% gradient - higher gradient streams are known to be sub-optimal habitat for beavers. Although stream gradient has a gradual rather than absolute effect on beaver presence, evidence shows that stream gradients greater than 15% are very unlikely to be occupied by beavers.
- Not in tidal sections - beavers are only rarely seen in salt/tidal water and do not establish territories in such habitats. Hence, coastal and tidal sections of rivers were excluded from the dataset.
Potential core beaver woodland
The 'potential core beaver woodland' dataset is a refinement of the 'potential beaver woodland' dataset described above. Beavers require a certain area of suitable woodland to set up a territory. The potential beaver woodland dataset contained all woodland that could be utilised by beavers, but many of these are small, isolated patches.
The minimum amount of woodland needed for a beaver to establish a long-term territory was estimated based on the literature. Any suitable woodland that could not be part of approximately 1.9 km of woodland within a 4-km territory (measured by river bank length) was rejected. If a small woodland patch was isolated, and could not form part of beaver territory with sufficient woodland, it was not included in the core beaver woodland dataset.
The potential core beaver woodland map consists of 105,586 ha of suitable woodland in mainland Scotland. It is anticipated that beavers would be more likely to set up long-term territories in proximity to these areas of potential core beaver woodland.
A previous mapping exercise identified four catchments as key woodland areas for beavers: Lomond, Tay, Spey and Ness. Analysis showed that the catchments with the most core beaver woodland were the Tay and Spey.
The potential core beaver woodland map attempted to predict which woodland fragments would be utilised as part of a territory. To test this prediction, the 2012 Tayside beaver survey data were used. The potential core beaver woodland dataset was created using an estimated minimum territory size of 4 km of bank, which equates to 2 km of watercourse length. Therefore, assuming the centre of a territory is within a core woodland patch, a beaver territory may extend 1 km upstream and downstream from these patches. All beaver signs that were within this area were identified as being predicted by the dataset. It was found that 82% of feeding signs and 84% of territory signs (e.g. burrows, dams, lodges and scent mounds) were predicted by the map. In particular, 91% of scent mounds were predicted. This is relevant as the abundance of scent mounds is likely to be correlated with the quality of a territory and the length of beaver occupancy. These results suggest that the dataset does seem to be a useful tool in predicting long-term beaver territories.
There are a number of limitations to these datasets and the associated maps. Many other parameters have the potential to affect the ability of beavers to utilise woodland, such as the steepness of river banks. However, they were not used here because either there was not a clear consensus in the literature or they could not be derived accurately enough at a national scale. In addition, in some specific areas of Tayside the map was a poor predictor of beaver signs. This was primarily thought to be due to thin strips of woodland along watercourses that were too narrow to be picked up within the baseline woodland datasets. So, whilst the map should provide a good overview of beaver woodland at the national scale, particular care is needed when using the datasets to examine local patterns. If necessary, the potential beaver woodland datasets can be refined at a regional or local scale to address some of these limitations.
3.1.3 Biodiversity, flora and fauna
Both Knapdale and Tayside core beaver policy areas contain significant and rich biodiversity interest, reflected in the high proportion of internationally and nationally important designations.
Relevant designations which overlap with potential core beaver woodland in both Knapdale and Tayside beaver policy areas are illustrated in the maps 5-11 in Appendix 1
- Special Protection Areas ( SPA)
- Special Areas of Conservation ( SAC)
- Sites of Special Scientific Interest ( SSSIs)
Section 4 provides comprehensive information on species and habitats within the core beaver woodland, including types and sites of riparian woodland, bryophytes, fungi and lichens, terrestrial vascular plants, invertebrates, fish, amphibians and reptiles, birds and other mammals. Please also see the HRA ( Annex 2) for full details of SACs and SPAs.
Further details on all designations can also be obtained from SNH's Site link : http://gateway.snh.gov.uk/sitelink/index.jsp
3.1.4 Water quality, resource and ecological status
Appendix 1 provides maps 12-15 illustrating water quality and flood risk in relation to potential core beaver woodland.
Section 4 provides further information on distribution of both suitable running and standing freshwater habitat, identification of important standing and running freshwater habitat types, wetland and aquatic macrophytes (plants that grows in or near water) within the potential beaver core habitat. Sites designated because of the presence of one of the habitat types and species of European importance associated with these habitats are identified.
- Knapdale - watercourses where recorded along potential core beaver woodland are primarily good status, and there are no areas of poor/bad status.
- Tayside - all classes of watercourses along potential core beaver woodland are recorded, ranging from high, good, moderate, poor and bad water quality status.
- Flood risk - As expected there is an overlap between flood risk areas and potential core beaver woodland in Tayside. The Tay catchment, and the five lochs within this, (Loch Ericht, L. Lyon, L. Rannoch, L. Tay, and L. Tummel) is a dominant characteristic of the Tayside beaver area. There is some overlap in the area between Lochgilphead and Kilmartin although the lower reaches of the River Add however have less potential core beaver woodland.
3.1.5 Population and human health
Appendix 1 provides maps 16-19 illustrating local authority boundaries and built up areas in relation to potential core beaver woodland.
- Knapdale - the population centres in the Knapdale beaver policy area are small and well scattered, and founded largely on forestry, tourism, agriculture, fishing and aquaculture. Many are dependent directly, or indirectly on the natural heritage. This area is sparsely populated in contrast to Tayside. The main settlements with a population of 500 or more are restricted to Lochgilphead and Ardrishaig on the shores of Loch Fyne.
Potential core beaver woodland primarily lies outwith these settlements apart from a small area of overlap.
- Tayside - the Tayside beaver policy area extends into the local authority areas of Highland Council, Perth and Kinross Council, Angus Council, Aberdeenshire Council, Dundee City Council, Stirling Council, Clackmannanshire Council and Fife Council areas. The area is predominantly rural but it is a far more populated area than Knapdale with a greater intensity of land uses. There are two significant areas of population in these areas (the cities of Dundee and Perth) and a number of medium sized settlements primarily in the lowlands of Tayside - such as Forfar, Blairgowrie, Crieff, Arbroath and Montrose. A proportion of the population reside in rural areas outwith these settlements. There is a significant projected population increase across Perth and Kinross in particular.
Potential core beaver woodland is located mainly outwith settlements with a population of over 500, but the dispersed rural nature of villages and hamlets along watercourses will result in some direct interaction between beavers and people's properties.
3.1.6 Cultural heritage
Maps 20-23 in Appendix 1 provide details of sites in the Inventory of Gardens and Designed Landscapes, and Scheduled Monuments and Battlefield sites in relation to potential core beaver woodland.
Inventory of Gardens and Designed Landscapes - there is only one Garden and Designed Landscape which interacts with potential core woodland habitat in Knapdale, and 54 sites in Tayside.
Scheduled Monuments - 9 sites are identified as overlapping with potential core beaver woodland in Knapdale, including the Crinan Canal, a historic and well used waterway, and Loch Coille-Bharr crannog - a submerged artificial island presumed to be the site of a late prehistoric-early historic period lake dwelling. Further details are provided in section 4.13 (beavers and cultural heritage). There are 97 sites in Tayside.
Battlefield sites - there are no sites overlapping with potential core beaver woodland in Knapdale, and 5 sites in Tayside.
3.1.7 Material Assets
National Forest Inventory cover in the Knapdale and Tayside beaver policy areas is provided in maps 24 and 25 in Appendix 1. Both areas comprise significant areas of forestry. However potential core beaver woodland is limited to those areas described under section 3.1.2 and broadleaved woodland and scrub rather than conifer species.
Knapdale - Taynish and Knapdale Woods SAC component of Knapdale is managed primarily for conservation.
Tayside - The National Inventory of Woodland and Trees' Tayside region, 2000 https://www.forestry.gov.uk/website/publications.nsf/DocsByUnique/3C2C5F7C1667BADE80257EBB0046FAFC estimated the total area of woodland in Forestry Commission (Scotland's) ( FCS) Tayside region as 12.9% of the land area. Conifer woodland is the dominant forest type representing 61% of all woodland. Broadleaved woodland represents 19%. The main broadleaved species is birch covering 8 572 hectares or 38% of all broadleaved species. It should be recognised that FCS's Tayside region is not consistent with the Tayside beaver policy area so these figures should be viewed only as a general guide. Broadleaved tree species are managed commercially in parts of the Tayside beaver policy area and, because of the flatter terrain, a greater proportion of the land is accessible to beavers.
Maps 26 and 27 in Appendix 1 provide the extent of salmon rivers within the beaver policy areas and their proximity to suitable beaver habitat.
Knapdale - streams in the Knapdale beaver policy area provide spawning habitat for those fish present in connected standing waters and lochs are popular trout fishing areas.
Tayside - the River Tay supports significant recreational fisheries for Atlantic salmon, trout (including sea trout) and grayling. It is one of the most iconic of the Scottish Atlantic salmon rivers and the number of rod-caught Atlantic salmon makes it one of the most important catchments for this species in the UK.
Knapdale - there is no prime agricultural land in the Knapdale area.
Tayside - the extent of prime agricultural land is illustrated in map 28 ( Appendix 1). This is exclusively located in the eastern lowlands of the study area. Areas of potential core beaver woodland are located along the watercourses in this area.
Infrastructure could include roads and tracks, bridges, culverts, weirs, sluices and fish passes, canals, water treatment plants etc. Tayside is a more populated area with a greater intensity of land use and major road infrastructure. The opportunities for beaver activity to impinge upon a range of land uses, and the associated infrastructure, are much higher. This is likely to be at risk only in proximity to areas where beavers may be most active, i.e. immediate vicinity of running and standing water bodies bordered by suitable riparian habitat.
3.2 The likely evolution of the environment in the absence of the policy
Current status of the two beaver populations
16 Eurasian beavers were released in Knapdale through the Scottish Beaver Trial; 11 animals in 2009 in three family groups followed by two pairs and single animals in 2010. Management surveys carried out post-trial in the autumn of 2016 indicated there were 8-10 animals still present in the Trial area, comprising two to three breeding pairs with an unknown number of kits, born earlier that year.
The Tayside beaver population was estimated to comprise 38-39 beaver occupied territories in 2012.
3.2.1 Future population viability of the two beaver populations
The Knapdale population was intended as a trial population, not a founder population. Population modelling was undertaken towards the end of the Trial to assess the likely fate of this population in the short, medium and long-term post-trial under a number of different scenarios (Beavers in Scotland Report (2015) Annex 1 (section 3.2).
Predictive population models were developed, informed by work at Knapdale and Tayside. These demonstrated that the longer term viability of the Knapdale population will benefit from reinforcement (i.e. supplementing the current population with new releases). Very recent surveys at Knapdale have shown that numbers are now very low (possibly around eight animals) and that reinforcement may be required urgently if the population is to remain.
Modelling carried out with respect to the Tay and Earn catchments have predicted the population to continue to expand positively.
3.2.2 Population implications for the two beaver populations in the absence of the policy
The policy reflects the desire to see the two current beaver populations remain with provision for natural expansion with suitable adaptive management processes including population reinforcement of the Knapdale site and legal protection afforded through the EU Habitats Directive. Without the policy and therefore the prospect of population reinforcement, the threat of extinction with respect to the Knapdale population cannot be ruled out.
3.2.3 Genetic status of the two beaver populations
The SBT was the first licensed release of a mammal species into unenclosed, 'wild' conditions in Britain. The licence application submitted by the RZSS and the SWT for the release of beavers at Knapdale proposed that, on the basis of work undertaken up to that point, Norwegian C. f. fiber animals should be used. This precautionary approach was accepted and a licence was issued in May 2008.
Subsequent genetic analysis of the current Knapdale population has confirmed that all are C. f. fiber. The Norwegian source population has low levels of genetic diversity. Reinforcement could therefore provide an opportunity to increase diversity and therefore reduce the risks that can arise from inbreeding.
The Tayside beaver population is likely to have arisen through either captive escapes or unlicensed releases. Genetic analysis of this population has shown that founder individuals were most likely to have originated from Bavaria, Germany.
3.2.4 Overview of current thinking with respect to genetic consideration for translocated species
The genetic diversity within populations of the Eurasian beaver today is low. This reflects previous hunting to near-extinction and the extensive reduction in size of individual populations. This creates two potential problems: inbreeding depression, which means decreased genetic viability and fitness of individuals in contemporary conditions, and a lack of adaptive potential, which means constraints on populations to further adapt genetically to new pressures such as emerging diseases or environmental change.
Outbreeding depression resulting in reduced fitness or viability can occur when highly divergent lineages are mixed. The apparent viability of populations with mixed eastern/western ancestry (such as in Bavaria) suggests that either there is little, if any, detectable reproductive isolation or genetic incompatibilities between these two genetic groups or outbreeding depression has already occurred but natural selection has eliminated unfit individuals.
It is not possible to identify which precise combination of beaver genes is ideal for long-term survival of the beaver populations in Britain, based on the available genetic and morphological data (they inform only on population relatedness). A reasonable assumption is that the beavers that are most closely related to those previously found in Britain will be the best adapted. For some morphological traits, historical Scottish beavers seem to have been most similar to those from Norway, although it is unclear whether this is due to genetic or environmental factors, or a combination of both. The survival of both Norwegian and Bavarian beavers has been successful in Scotland so far, and they have adapted to a range of environments.
The Beavers in Scotland Report (2015) highlights a number of implications that should be considered for beaver reintroductions in Scotland, those that have a particular bearing to Knapdale and Tayside, in the absence of the policy, have been reproduced below:
- Problems arising from inbreeding are viewed as the greater challenge to the viability of introduced beaver populations to Scotland/Britain. The risks of outbreeding depression are considered low if currently mixed populations and/or a mixture of different populations from the western lineage are used as donors.
- Inbreeding - individuals from genetic clusters, source populations and areas that have not been previously used in British releases are preferred, and hence close relatives of beavers already present are not preferred. Founder populations should be as large as possible and sourced from a diverse range of genetic sources (populations and families).
- Future genetic management - an increased number of wild founders is preferred to ensure genetic diversity. However, it is critical that any future releases (including within-country relocations) should be planned, co-ordinated, licensed and managed.
3.2.5 Genetic implications for the two beaver populations in the absence of the policy
The policy reflects the desire to see the two current beaver populations remain with provision for natural expansion with for suitable adaptive management processes including further population reinforcement and legal protection afforded through the EU Habitats Directive. Without the policy and therefore the prospect of further releases, genetic considerations to date suggest that the risk of inbreeding depression with respect to the Knapdale population cannot be ruled out. The population on Tayside did not come about as a founder population; uncertainty remains as to whether the population has sufficient genetic diversity to ensure long term viability.
In the absence of the policy, it is likely that the population in Knapdale face the threat of extinction, while modelling has shown that the population of beavers in the Tayside Beaver area is predicted to expand but the rate and distribution will be difficult to model because control of the population would be unregulated. The effects on the other environmental receptors will remain the same.
3.3 Existing environmental issues
Environmental issues which are relevant to the policy are presented in the table below.
Table 3.3 - Existing environmental issues
Biodiversity, flora and fauna
Indirect pressures such as sedimentation, nutrient enrichment in watercourses/waterbodies
Invasive non-native species, which can have long-term impacts on ecological communities, is an increasing issue both along the riparian zones and in watercourses themselves
Herbivore pressures, particularly lowland deer
Cumulative effect of other pressures on water-related designated sites and species, and on wider biodiversity in Tayside (e.g. .development, disturbance of species, habitat fragmentation, agricultural intensification, and herbivore pressures).
Population and Human Health
Eurasian beavers host a number of external and internal parasites, some of which are already present in the UK (such as Cryptosporidium parvum) and some are not.
Soils and geomorphology
Pressures such as soil loss through action of wind and water, soil organic matter depletion, soil contamination through surface and groundwater pollution.
For fluvial geomorphology, overwidening streams, canalising/realignment and culverting streams, hard bank/bed protection engineering, bank erosion and obstructions to migratory fish.
Irreversible loss of soil through development, contamination and erosion.
Water quality, resource and ecological status
Diffuse pollution (sediments and fertilizers), abstraction, oxygen depletion, invasive non-native plants, abstractions and discharges.
Consideration of pressures from flood risk to property, natural ageing of veteran/ancient trees including significant champion trees in Tayside, and invasive non-native species.
Climate change to weather patterns, storminess and pluvial/fluvial flood risk to transport infrastructure, property, public assets and economic facilities and infrastructure.
High proportion of high quality agricultural land. The need to retain and safeguard this high quality land is recognised in Scottish Planning Policy ( SPP).
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