Assessment of environmental effects of beaver translocation to the River Leven (Loch Lomond) and River Forth catchments

Background

An update to the Beavers in Scotland Strategic Environmental Assessment (SEA) produced in 2017 has been produced as an Addendum to the 2017 Environmental Report (ER). The ER brings up to date to our knowledge of beavers in Scotland, their impacts and management since the 2017 report was produced. The ER Addendum supports the new policy position announced by Scottish Ministers in November 2021 to enable the proactive movement of beavers to new areas of Scotland. It provides a national overview of the environmental effects that are likely to be important in informing where beaver translocation benefits are likely to out-weigh the risks. Socio-economic impacts are not part of the SEA process, but socio-economic costs and benefits are also recognised. We set how we will assess the effects of beaver releases into new areas at a catchment scale. The assessment of catchments will be subject to prioritisation based on their suitability for beavers and other factors including where there is an interest in beaver translocations.

By assessing effects at a catchment scale, ecologically this is the logical extent that beavers will disperse to in the medium-long term if released into a particular catchment. A previous analysis of catchment permeability (Stringer et al., 2015) suggests most catchments are likely to be permeable to beaver dispersal.^[1] This analysis indicated that 50-60% of the catchment boundary for both the River Leven (Loch Lomond) and Forth catchments is likely to be permeable to beaver movement to adjacent catchments. This analysis did not account for colonisation of freshwater via coastal routes. The 2017 ER for Tayside and Knapdale applied a buffer zone based on the anticipated rate of dispersal. Defining assessment areas based on buffer zones requires assumptions to be made about release sites or existing populations and may not realistically reflect the most likely routes of colonisation into new catchments. Instead, in the approach set out here, we plan to make assessments on a catchment by catchment basis and will assess the likely routes of movement to other catchments and the need for impacts in other catchments to also be assessed. The proposed catchment by catchment approach does not incorporate any population modelling to assess the likely time taken to colonise different parts of the catchment, but assumes that all areas that are ecologically accessible could be colonised by beavers in due course and aims to assess the likelihood and significance of effects.

^[1] The model applied a cost distance from watercourses up to a maximum of 300m, with overland movements limited by urban areas and steep ground.

In this report we have assessed the environmental effects for the River Leven (Loch Lomond) catchment and also the River Forth catchment. Parts of the River Forth catchment were included in the Tayside ER in 2017. The beaver population is well established in the Forth catchment already and remaining areas will likely be colonised by natural dispersal. However, an accelerated programme of dispersal assisted through translocation could increase the resilience and genetic make-up of the beaver population. The catchment also provides an extensive area of suitable habitat and hence provides opportunities for moving beavers from conflict sites, where they could potentially bring wider environmental and socio-economic benefits.

Loch Lomond has not been subject to previous ER, but beavers already have a presence in the catchment again through natural dispersal from both the east (Forth catchment) and presumably from the north (River Dochart). Both catchments are illustrated in Figure 1 along with the Tayside Detailed Zone of Appraisal from the 2017 SEA.

The potential routes of beaver movement to other catchments from the River Leven catchment are via Glen Falloch to Glen Dochart in the Tay catchment where beavers are already present; to the Forth potentially via Loch Arklet and via the tributaries of the Endrick Water. It is assumed that the beavers that have made their way to Loch Lomond to date, have taken an overland route from the tributaries of the Endrick Water. The upper reaches of the Endrick Water run within 100m of Carron Valley reservoir which feeds the river Carron catchment. There is very little suitable habitat predicted around the reservoir, although there is potential beaver habitat lower down the Carron Glen. Dispersal into the Carron catchment is also possible via a coastal route from the Firth of Forth, but neither route into the Carron valley are considered likely in the short-term. Further population modelling could inform a rough timescale for colonisation.

There is potential for beavers to make the short journey from the Tarbet burn into Loch Long, although suitable habitat beyond the head of the loch is limited to Glen Croe and Glen Loin. Hence there would appear to be limited scope for onward dispersal into Cowal by this seaward route.

The potential for onward dispersal seems greatest via the River Leven, with existing reports of beavers and their signs in the River Leven and River Clyde. The inner Clyde lacks suitable habitat, but upstream there is potential habitat in the Clyde catchment and the River Kelvin catchment.

The River Forth catchment has potential linkage with the River Leven catchment via the Forth tributaries and already has established connections with the Tay via the Earn/ Allan water and Lochearnhead. The catchment links directly with the Forth Coastal Catchment. Although the catchment is contiguous with the River Forth, the route for colonisation is via the tidal sections of the estuary; although there are short distances overland from parts of the Forth catchment to some of the tributaries feeding the Forth estuary. In the same way as there has been estuarine colonisation in the Firth of Tay into the Carse of Gowrie, Dundee and the North coast of Fife, there is potential for colonisation of the coastal catchment from the Firth of Forth from Bannockburn to Cramond to the south and into Fife to the north. We have not included these other catchments in the current assessment.

The long-term monitoring of the beaver population is an action in Scotland’s Beaver Strategy 2022-2045. Post-release monitoring of the beaver population is likely to be a condition of a licence to allow the release of beavers into new catchments for a specified time period. Hence the likely spread of beavers into new catchments could be used to trigger the assessment of effects in new catchments where they have not already been assessed. Habitats Regulations Assessment will need to continue as the beaver population expands for as long as a licence is required for beaver releases.

Environmental characteristics of the River Leven (Loch Lomond) and River Forth catchments.

River Leven (Loch Lomond)

General description of the catchment

The catchment is divided into two main parts, on either side of the Highland Boundary Fault which runs through both catchments from Callander in the north-east, through Conic Hill to Helensburgh in the south-west. The north side is mountainous and rocky, with exposed rock and bare ground and at higher elevation, though there is increasing forest cover; while the south-east around the Endrick Water is lowland/rural with gentle slopes and rolling valleys.

The south shore of Loch Lomond (around Balloch) is the main tourist destination in the Loch Lomond and the Trossachs National Park (LLTNP), with planned new development potentially increasing this further. Outdoor tourism and recreation is the largest activity in the National Park and surrounds, followed by agriculture and forestry. There are existing pressures from tourism in the National Park associated with informal camping. It receives the most visits to a rural area in Scotland.

The LLTNP area comprises 30% woodland cover, which includes coniferous (22.5%) and native woodlands (7.5%). The National Park Trees and Woodland Strategy is aiming to increase the woodland resource. Productive conifer forests comprise large areas to north of the Highland Boundary Fault. These also double as tourist points as most contain footpath networks. Loch Lomond itself is the main water based recreation hub in the catchment. Around Loch Lomond Atlantic oak woodland is found, much of which is designated as a Special Area of Conservation. There is ancient Caledonian pinewood in Glen Falloch, with new planting and natural regeneration to extend this.

Above the Highland Boundary fault, most farming is based on livestock grazing; mainly sheep and cattle.  Hill farming is carried out over the largest proportion of the catchment by land area, however there is a current trend away from unprofitable sheep farming towards forestry.

The Rivers Leven, Endrick/Blane, Fruin and Loch Lomond are the main sites for angling. Loch Lomond is extensively used for water sports, based at Balloch, Luss, Inverarnan and Rowardennan. There are also sea plane rides arriving / leaving form here. There are a number of golf courses around the south end of Loch Lomond. The West Highland Way is an extremely popular long-distance path that runs right the way along the east shore of Loch Lomond, through Invereran and up towards Tyndrum. People often wild camp along this route, with lochshore camping and subject to seasonal controls under byelaws. The John Muir Way starts at Helensburgh and goes through Balloch, south to Strathblane and out of the River Leven Catchment towards Kilsyth. This is also a popular walking route, but sees less wild camping associated. All accessible parts of the Loch Lomond shoreline are used extensively for a range of recreational activities.

Potential for beavers and beaver activity

The River Leven catchment has a total watercourse length of 2931km and ranks 8^th in Scotland in terms of the extent of potential beaver habitat with 2649 ha of ‘Potential Core Beaver Woodland’. Potential Core Beaver Woodland (Map1) is distributed throughout the catchment from Glen Falloch and Gleann nan Caorann, down both sides of Loch Lomond with near contiguous cover and around the islands; extending into the reaches of Glen Douglas, Glen Luss, Finlas water, Glen Fruin to the west of the Loch and along the Endrick Water to the headwaters and into Strathblane to the east.  Hence much of the catchment has the potential for beaver colonisation with some burns likely to be too steep or rocky to be colonised. Similarly much of the loch-side may not be suitable for establishing territories where the shores are rocky and exposed to waves from the considerable fetch on the loch. The preferred habitat is likely to be in the sheltered bays and water-courses with a gentle gradient feeding into and exiting the loch. Note that in addition to the ‘Potential Core Beaver Woodland’ there are also other areas of habitat that beavers may use on a more temporary basis.

The Potential Core Beaver Woodland data layer is comprised of largely broadleaved woodland. Broadleaved woodland makes up a large proportion of the woodland resource in this catchment. Map 2 illustrates the National Forest Inventory classes of all woodland in the catchment and also the considerable extent of land managed by Forestry and Land Scotland.

There are falls on the River Falloch around NN337208 and several further to the north east. These are not vastly high and the banks are sloped and wooded so may not present an impassable barrier to beaver. There are several hydro intakes in Glen Falloch, however, they are small run-of-river intakes rather than impoundment schemes and can be easily bypassed. There is a long section of waterfall on the Strath Dubh Usige to the north west of Loch Lomond, these are low rocky rapids, rather than a drop and again likely to be navigable. There are run-of–river hydro schemes on the Luss Water and tributaries; again which are not impoundment schemes and are relatively small scale. There is a hydro intake on the Douglas Water at NS32829774. This is slightly larger than the Luss and Glen Falloch intakes, it could not be passed in stream, but the south bank is wooded so it is likely it could be bypassed. Beyond this the Douglas Water reaches almost all the way to Loch Long. Loch Sloy is dammed at the east end, this is the largest dam in Scotland and would be impassable in the river and the surrounding habitat is steep, with rocky slopes and likely to be a significant barrier. There are no significant falls or hydro schemes around the Endrick Water. The lowland section of the Leven catchment to the south of the Highland boundary fault is largely too flat for falls or hydro schemes to present a barrier to beaver movement. From earlier evidence of downstream movements it is assumed the Scottish water barrage on the River Leven is passable by beavers overland if not by water.

Loch Lomond and the main tributaries in the catchment are unlikely to be subject to beaver damming, with damming most likely on the smaller burns where there is a shallower gradient around the Endrick mouth, Gartocharn, Fruin, Rossdhu and Rowardennan. See Map 3 for the Beaver Dam Capacity (BDC) modelling outputs for the two catchments. Table 1 provides a summary of the Beaver Dam Capacity modelling outputs for the catchment.

Table 1 Beaver Dam Capacity model predictions for the River Leven catchment [2]

Beaver Dam Capacity class	Length of watercourse in catchment (km)
None	1030
Rare	895
Occasional	383
Frequent	203
Pervasive	450

²From Graham et al. 2020 and Graham et al. 2021

Were beavers at their maximum capacity, 34% of the River Leven (total watercourse length) is predicted to be liable to ‘occasional’ or ‘pervasive’ damming.

There is 8689 ha of land in the catchment within public ownership of which 305 ha is Potential Core Beaver Woodland. The catchment ranks 10^th nationally in terms of the extent of Potential Core Beaver Woodland in public ownership, most of which is managed by Forestry and Land Scotland. The catchment also has one of the highest proportions of designations, with nearly 5% of designated land having the potential for beavers to establish (567 ha of Potential Core Beaver Woodland overlap).

The 2020-2021 Tayside beaver survey noted the presence of what the authors assessed to be a single resident beaver on the Endrick Water (south Loch Lomond) approximately two km upstream of the mouth, with public reports of a beaver at that location beginning in autumn 2019. In May 2019, there were also public sightings of an individual beaver swimming during daylight on the River Leven in Alexandria (south Loch Lomond), and a public report of a road-killed beaver in Alexandria the following September. These were followed by public daylight sightings of an individual beaver in Govan (Clyde Catchment) in May 2020 and later, beaver foraging signs further upstream on the Clyde at Strathclyde Country Park beginning in February 2021. In addition, beaver foraging signs were recorded around Inverarnan on the River Falloch (north Loch Lomond) in June 2021. The Falloch was not surveyed during the 2020-2021 Tayside survey and therefore beavers could have been on that river before this date. Overall, it is likely that beavers have been present within the Lomond catchment since at least 2019, possibly arriving via different routes, with at least one animal probably moving from there into the Clyde catchment. Such long-distance movements may be occurring because early dispersing individuals are failing to find mates in these vacant river systems. To date there is no knowledge of a pair establishing a territory within the catchment. Reinforcing this nascent population would hasten the establishment of territories that would otherwise establish naturally within just a few years. Beavers are likely to colonise the River Leven catchment naturally from the existing populations in the Tay from the north and from the Forth the south east. Hence the decision to allow the translocation of beavers will largely dictate the speed of colonisation. Reinforcement brings the additional benefit of providing a larger initial founder population, with greater genetic diversity.

Hence the environmental effects explored in this assessment are likely to happen whether or not there are translocations of beavers via the natural expansion of the beaver population.  However, translocation would speed up the process of beaver re-colonisation, and consequently of beaver-related environmental effects. The ongoing trend in land use within the National Park of moving away from hill farming towards afforestation and developing infrastructure for the enjoyment of nature, will likely continue independent of any beaver translocations. However, the presence of beavers has the potential to bring new ecotourism opportunities from the running of beaver tours, wildlife photography operations and the multiplier effect to the local economy through support services, transport, catering, accommodation etc. The opportunities missed if a beaver translocation were not to go ahead include the potential environmental benefits explored in more detail in the following sections.

The LLTNPA is developing a delivery plan for elements of the Future Nature Route Map, and has published the overarching Vision document. Specific reference to beavers has been made in National Park Authority Board papers in developing this vision.

River Forth

General description of the catchment

The uplands are similar to the River Leven catchment. Surrounding Loch Katrine the land is rough grassland/ heather with some afforestation to the east. The land is largely managed for sheep grazing and has typically held higher red deer densities. Loch Chon to the south is an area of coniferous forest and moorland, changing to unforested blanket peat moor around Loch Tinker. A trend of moving from sheep farming to forestry is also occurring in Forth uplands.

The Great Trossachs Forest (the largest National Nature Reserve (NNR) in Scotland) is currently coniferous dominated, however, there work is ongoing for it to become the largest area of broadleaved woodland in the UK. This surrounds Loch Katrine, Loch Arklet, Glen Finglas Reservoir, and has significant riparian habitat along the adjoining rivers. The Queen Elizabeth Forest Park intersects the NNR and extends southwards from Loch Lomond up to Strathyre.

To the south of the Highland boundary fault there are shallow river valleys surrounded by mainly enclosed and improved farmland, with a mosaic of parkland, pasture and semi-natural woodland, with grasslands and wetlands including raised bogs. This is better agricultural land, however also contains several peat bogs such as Flanders, Ochtertyre, Offerance, Shirgarton mosses, all of which are Sites of Special Scientific Interest (SSSI)/Special Areas of Conservation (SAC) sites. Historically, much of the Carse of Stirling was wetland and bog that was drained in the 16^th and 17^th centuries giving rise to productive agricultural land.

The Lake of Menteith is kept well stocked for sport fishing. Loch Katrine is a very popular tourist destination, with the steamship running the length and a footpath along the north side, extremely well used by walkers and cyclists. Loch Earn also has a water sports centre, while Loch Venachar is popular for paddle boarding and swimming and has a small sailing club.

Figure 1 illustrates the River Forth catchment boundary and the boundary of the Detailed Zone of Appraisal from the 2017 ER. Parts of the catchment not included in the 2017 assessment; include, the River Forth floodplain and upper reaches including the Menteith hills, Loch Katrine, Loch Ard Forest Block and Achray Forest within the LLTNP. Although part of the catchment has previously been subject to SEA, we have included the whole catchment in the maps and figures reported in this assessment for completeness and comparability with other catchments, rather than extracting the part of the catchment not already subject to SEA. However, we draw on many of the findings of the 2017 report.

Potential for beavers and beaver activity

The River Forth catchment has 2651 ha of Potential Core Beaver Woodland making it the 7^th ranked catchment nationally in terms of habitat suitability. See Map 1 for the extent and distribution of Potential Core Beaver Woodland. Potential beaver habitat is widely distributed particularly within the LLTNP, along the Forth from the Port of Menteith to Loch Con and into Loch Ard Forest and from Lochs Venachar, Drunkie and Achray (where beavers are already established), to the head of Loch Katrine. Note that in addition to the ‘Potential Core Beaver Woodland’ there are also other areas of habitat that beavers may use on a more temporary basis.

Loch Arklet is dammed at the west end so dispersal would need to occur over land into the River Leven catchment from here. Loch Katrine is dammed at the south end at the start of the Achray Water, in an area of wooded hills, so although the river is unlikely to be passable in the river, the overland routes are likely to be passable.  Loch Venachar is dammed, however there is a wide overflow weir, and the land either side is open and flat so unlikely to present a barrier to upstream travel. There is a large waterfall on the Keltie Water at Bracklinn Falls which would be impassable from the river, however, with wooded banks on both side it is potentially passable over land.

The total watercourse length in the catchment is 3475 km. Beaver Dam Capacity analysis indicates that much of the Forth and Teith would not be dammed, but a larger area would be subject to ‘occasional’ damming in the Forth valley, with the potential for ‘pervasive’ damming in the tributaries of the Teith, in Loch Ard Forest, the Kelty Water, Duchray Water and the burns to the south of Flanders Moss. As a proportion of the total watercourse length, the Forth has 43% potentially liable to ‘occasional’ or ‘pervasive’ damming. See Map 3 and Table 2 for the Beaver Dam Capacity outputs for the River Forth catchment.

Table 2 Beaver Dam Capacity model predictions for the River Forth catchment

Beaver Dam Capacity class	Length of watercourse in catchment (km)
None	1009
Rare	969
Occasional	681
Frequent	332
Pervasive	496

 

There is a large area of land in public ownership within the catchment at 36338 ha between Forestry and Land Scotland, NatureScot and Scottish Water, with the major share of 28319 ha being on the National Forest Estate (Map 2). The Forth is the highest ranking catchment nationally in terms of having the largest area of public land that overlaps with Potential Core Beaver Woodland with >1000 ha. Potential Core Beaver Woodland in the River Forth catchment makes up 5.1% of the designated area (at 335 ha).

Beavers were first recorded in the Forth catchment on the River Leny in July 2012 (immediately following the 2012 Tayside survey), possibly having dispersed over the headwaters from Loch Earn. By the 2017-2018 Tayside beaver survey, beavers had become well established, with 10 territories recorded. By the 2020-2021 survey, this number had increased to 25 (a greater rate of increase than was recorded in the Tay and Earn catchments).This increase is expected to continue. The population in the Forth has potentially undergone a further genetic bottleneck after dispersing from the Tay and therefore reinforcement though translocations will improve both the genetic diversity and the population robustness in the Forth.

Again further beaver spread is likely to happen in the Forth whether or not there are further translocations. Translocations present the opportunity to improve the conservation status of the population, whilst accelerating the potential environmental benefits anticipated from beaver’s activities as ecosystem engineers.

As noted for the River Leven catchment, the LLTNPA Future Nature Route Map, Vision document reflects the ambition for a nature-rich environment that benefits communities within the National Park.

Key environmental issues to consider in the River Leven (Loch Lomond) and Forth catchments

This section includes an assessment of the potential environmental effects that may arise in each of the catchments with a focus on receptors (interests) identified in the national spatial analysis (in the ER Addendum) and drawing on the 2017 ER, those effects that are considered to be the most important within each catchment. An updated review of beaver mitigation approaches is included in the 2022 ER Addendum.

Biodiversity, flora and fauna

An appropriate assessment (HRA) of potential effects on Natura sites (Special Protection Areas (SPAs) and Special Areas of Conservation (SACs)) is being completed by NatureScot and will be made available when completed. The conclusions regarding the likely significant effects and effects on site integrity will be considered by making an appropriate assessment for each of the Natura sites in these catchments (Five sites in River Leven Catchment and three sites in River Forth catchment) and will outline the need for mitigation and management.

A comprehensive assessment of biodiversity impacts is included in the ‘Beavers in Scotland’ report, which covered each major habitat type and each major taxonomic group. This emphasises that on balance beaver cumulative effects are expected to be largely positive for biodiversity. We have sought not to repeat this evidence here and hence the information presented is somewhat biased towards where there is the potential for negative effects. In highlighting these potential effects it should be noted that there are many potentially positive effects not repeated here for brevity.

The key Natura features where it could not be ascertained that there is no adverse effect on the site integrity and where mitigation and management is likely to be necessary based on the 2017 SEA ), are included here as habitat and species accounts rather than site specific (SAC) assessments. The potential impacts on Sites of Special Scientific Interest (SSSIs) features (not already covered by HRA or equivalent interests) is included as Annex 1. In assessing impacts on SSSIs, we have scoped out those where beavers are unlikely to have an effect due to a lack of ecological connectivity or geographical overlap. The narrative also relates to notable conservation interests in the wider countryside.

River Leven (Loch Lomond)

See Annex 1 for the list of SSSI interests and the scoping of likely beaver effects. The introduction of or release into the site of any wild, feral or domestic animal, plant or seed is an Operation Requiring Consent (ORC) for many of the SSSIs.  Many of the feature types in the catchment are reflected in the summary of conservation interests below. The hydrology of raised bog interests are likely to be independent of beaver effects. Lochs and fen features are most likely to benefit from beaver presence through improvements to water quality, although changes in plant communities should be assessed.

Riparian woodlands

The catchment sits within the ‘assumed rainforest’ zone (scroll down to map) and the broader category of ‘potential rainforest’ (see ER Addendum, Annex 2 for definitions).  A high proportion of the large Potential Core Beaver Woodland resource in the catchment is classed as rainforest, highlighting the oceanic character of the woodlands. Thirty percent of the ‘assumed rainforest’ within catchment is Potential Core Beaver Woodland and 41% of the ‘potential’ rainforest is Potential Core Beaver Woodland. The following is an extract from the data form for the Loch Lomond Woods SAC.

Loch Lomond Woods is one of three sites representing old sessile oak woods in the most bryophyte-rich zone in the UK, the south-west Highlands zone. This extensive block of woodland in western Scotland comprises a mosaic of woodland types, including ash Fraxinus excelsior, elm Ulmus spp. and alder Alnus glutinosa woodland, which adds to the ecological variation of the site. Pedunculate oak Quercus robur, rather than sessile oak Quercus petraea, is locally abundant, and the oak stands intergrade in places with ash-elm stands, and with alder at flushed sites by the loch. The stands on the islands include areas that have been less subject to grazing than many other examples of this type of woodland.

The lichen and bryophyte interests are part of the typical species of the SAC and have the potential to be impacted by tree felling activity by beavers. There is 1008ha of qualifying old sessile oakwood habitat in the SAC, of which only a proportion will be in the riparian zone. Detailed assessment could identify which stands of trees or individual trees are likely to host important lichen assemblages and if there are specific locations for notable rare species. This is particularly the case for ancient or veteran trees in parkland. This approach was taken in Knapdale where, as a precautionary measure, a few trees that hosted a particularly rare lichen were protected.

Some of the woodland interests may benefit from increased structural diversity, light levels to the field layer and increased deadwood.

The Native Woodland Survey of Scotland data is now over 10 years old, but provides an assessment of herbivore impacts in native woodlands. The national spatial analysis recorded that herbivore impacts in the catchment as a whole, were classed as Moderate to High in 97% of the Potential Core Beaver Woodland. Hence much of the woodland is already subject to the negative pressure of herbivore impacts. Beavers could present an additional pressure on woodland regeneration, structure, extent and continuity. Again for the SAC interests in particular, it would be recommended that a programme of monitoring be implemented if beavers are to be released to ensure that herbivore impacts continue to be assessed and steps are taken to ensure the management of other herbivores is sufficient to support the presence of beavers. Beaver impacts on individual trees and woodlands, will be spatially and temporally patchy. The large extent of broadleaved woodland in the catchment provides a large resource within which beaver effects can more easily be accommodated.

Vascular plants

The national scale analysis of vascular plant records included Botanical Society of Britain and Ireland (BSBI) records from the last 30 years for those species of vascular plants on the Scottish Biodiversity List which are assessed as red or amber in relation to potential risk from beavers. The grid references are at varying scales (10m-100m) and all have been buffered by 50m to allow potential overlap with PCBW. This is one of only six catchments nationally where there is potential overlap with vascular plant species assessed as red. There are 50 records of species assessed as red within 50m of Potential Core Beaver Woodland and two records of species assessed as amber within 50m of Potential Core Beaver Woodland. The two species assessed as being red are narrow-fruited water-starwort (Callitriche palustris) (two within 50m of PCBW) and Scottish dock (Rumex aquatics; 48 within 50m of Potential Core Beaver Woodland). Both species are located around the south of Loch Lomond from Balmaha to Portnellan and to the west around Ross Park.  Assessed as being amber is marsh clubmoss (Lycopodiella inundata), located near Inverarnan, north of Loch Lomond.

When assessed in relation to Potential Core Beaver Woodland the risk to the two populations of narrow-fruited water-starwort beside Loch Lomond is assessed as low. The Great Britain threat status of narrow-fruited water-starwort is assessed as “Vulnerable”.

All recorded locations (BSBI) for Scottish dock are within 7km of the southern shores of Loch Lomond.  Twelve records are within Potential Core Beaver Woodland and the others are within 50m. It is possible that Scottish dock could benefit from habitat creation by beaver.  However, due to the potential for Scottish dock to be palatable to beaver, the limited range of Scottish dock and the proportion of sites within Potential Core Beaver Woodland, the overall risk to Scottish populations of Scottish dock from beaver is assessed as high. It is recommended that surveillance be established for Scottish dock should beavers become established.  The Great Britain threat status of Scottish dock is assessed as “Vulnerable”.

Marsh clubmoss is associated with open water margins which fluctuate in height and which allow the clubmoss to grow in muddy substrate. A key threat to the marsh clubmoss would be from rapid changes in water levels or permanently elevated water levels. Gradual changes in water level may result in displacement rather than local extinction. Hence on larger lochs (not subject to rapid draw-down) the indirect impacts from beavers may be reversible and the site specific threat in the River Leven catchment is considered low.  Due to the declining number of sites at which it is recorded, the threat status of marsh clubmoss is assessed as “Endangered” in Great Britain.   Although marsh clubmoss is assessed as an amber species with regards to potential risk from beavers and the site specific risk assessment is low, due to the ‘Endangered’ threat level status across Great Britain it is recommended that surveillance be established for marsh clubmoss should beavers become established.

The palatability of vascular plant species on the Scottish Biodiversity List has not been published with regards to Eurasian beaver.  As the locations of the vascular plant species are well known it should be possible for the most susceptible species to be monitored and where necessary implement appropriate mitigation on a site by site basis.  Where beaver range overlaps with the recorded distribution of Scottish Biodiversity List vascular plant species assessed as either red (high) or amber (moderate) with regards to potential risk from beavers it is recommended that impacts are monitored and if necessary mitigation is put in place. Potential risk is based upon the plant species habitat preferences and published information about beaver ecology. 

Atlantic salmon/fish

The Endrick Water is of national and international nature conservation importance for the populations of river lamprey (Lampetra fluviatilis) and brook lamprey (Lampetra planeri). Both species are listed in Annex II of the European Habitats and Species Directive. The distribution of lamprey within catchments differs according to species. River and Brook lamprey are more closely associated with the middle and upper catchment. However, it is recognised that much is still not known about the biology and distribution of all three lamprey species. Current understanding has some limitations associated with sampling methods, for example, the difficulty of distinguishing between Brook and River lamprey in the field means the species are reported as Lampetra. The river lamprey found on the Endrick Water are of particular interest because some do not migrate to sea as do other populations. Instead, they remain in freshwater as adults feeding in Loch Lomond on fish species. This is the only instance of this unusual behavioural trait recorded in the UK. Both lamprey species are in favourable maintained condition (2010).

The Atlantic salmon (Salmo salar) feature of the Endrick Water SAC/ SSSI (Map 4) was assessed (Site Condition Monitoring 2011) to be in ‘Unfavourable Recovering condition’, with agricultural operations, game/fisheries management, non-native invasive species (giant hogweed (Heracleum mantegazzianum), Himalayan balsam (Impatiens glandulifera) and Japanese Knotweed (Fallopia japonica)) and water management being listed as negative pressures. The Endrick Water is the main spawning ground for salmon and sea trout in the Loch Lomond catchment. The salmon feature is in an unfavourable condition as indicated from the lower fish catches, occasionally poor water quality, damaged habitat, and the possibility of damage due to competition from introduced species of fish. The salmon population is considered to be recovering following action carried out through the EU Life and UK Rivers Project.

The complex evidence around the potential effects on fish populations is reviewed extensively elsewhere (‘Beavers in Scotland’ see 3.4.7, CREW report), and highlights the potential for positive as well as potentially negative effects. For example the variability of damming effects on migration depending on flow regimes, the spatially variable effects on temperatures, and predation risks, the beneficial effects of an increase in woody debris and for sediments, water quality and invertebrate populations.

The River Leven catchment has a watercourse length of 2931 km. Of this extent there is predicted to be an overlap between assumed salmon presence and a potential for damming (‘occasional’ to ‘pervasive’) over 126 km of this length. Map 5 illustrates where these sections are located.  In this catchment these are principally on the Fruin Water, the Luss Water, the River Falloch and the tributaries of the Endrick Water.

The mapping of salmon interest is used as an illustration of potential impacts on all migratory fish, with the real impacts likely to be species/site, and time specific.

There is no predicted overlap between adult/juvenile freshwater pearl mussel occurrence and damming potential in this catchment, although it should be noted that their larval/glochidial stage is parasitic on salmonids.

Although there are recognised to be potential benefits to fish populations from beaver activity as reviewed in Beavers in Scotland and the recent CREW report. The HRA assessment for the Endrick Water will as it did (for the River Teith SAC) in 2017) likely conclude that ‘it cannot be ascertained that there is no adverse effect on the site integrity of SACs designated for Atlantic salmon and lampreys through dam-building activities and other related activities. Mitigation to avoid these impacts is necessary’.

The same precautionary approach with mitigating measures would likely be required as for the Forth, in relation to the Teith SAC. A monitoring plan could be developed to risk assess and target locations that are predicted to be have a higher likelihood of damming and where beavers are present. Monitoring would need to be sufficiently regular to detect any dams that presented a potential and possibly temporal barrier to fish passage, such that it could be expediently mitigated or removed. Conversely the potential benefits of beaver dam presence on such systems also need to be taken account of during decision making.

River Forth

See Annex 1 for the list of SSSI interests and scoping of the relevance of beaver impacts in the River Forth catchment. In summary, the main feature types on which beavers are likely to impact are woodlands; marshes, fens and meadows and lochs. The interaction with other herbivore impacts is likely to be a key issue for many woodland interests, whilst some beaver effects may be positive. Impacts on wetland features and lochs are likely to be largely positive, although the effects of herbivory on plant species composition should be kept under review on some sites.

Riparian woodland

This catchment lies on the edge of the rainforest zone with no ‘assumed rainforest’ and a small area of ‘potential rainforest’; indicating the woodlands have less oceanic influence than the adjacent River Leven catchment. However, there may still be individual trees with notable lichen and bryophyte species that would benefit from tree protection.

Similar to the River Leven catchment, herbivore impacts were assessed (by NWSS) to have been moderate or high in 90% of the Potential Core Beaver Woodlands in the catchment. Hence beavers may present an additional pressure and woodland management would need to take account of all herbivores.

Vascular plants

The national scale analysis of vascular plant records with potential overlap with Potential Core Beaver Woodland indicates there is one record for a Scottish Biodiversity List species with an amber risk and with potential overlap. This record is for marsh clubmoss (Lycopodiella inundata) near Loch Katrine. As for this species in the River Leven catchment, the site specific risk from beaver impacts is considered to be low.  Due to the threat status of marsh clubmoss in Great Britain being Endangered it is recommended that surveillance be established for this species should beavers become established.

Atlantic salmon/fish

The Forth has one of the more significant extents of river where salmon are present nationally, with salmon being a notified feature on the River Teith SAC (Map 6). The total water course of 3475 km length, has 203 km where salmon are assumed to be present and where there is a Beaver Dam Capacity from ‘occasional’ to ‘pervasive’. Map 5 illustrates the potential for damming to present a challenge/benefit to salmon by modifying the river character or presenting a potential challenge to fish passage.

The 2017 HRA included an appropriate assessment of impacts on the River Teith SAC for qualifying interests Atlantic salmon, Sea lamprey, River lamprey and Brook lamprey.

The assessment was as follows:

We advise that it cannot be ascertained that there is no adverse effect on the site integrity of SACs designated for Atlantic salmon and lampreys through dam-building activities and other related activities. Mitigation to avoid these impacts is necessary. It is important to ensure that the passage of fish past any barrier is assured such as by the use of flow devices; this precautionary approach is currently needed due to the existing lack of understanding of the full details of any potential impacts on the SACs. Mitigation to ensure passage may be achieved through the easement or removal of barriers at certain times of year important for salmon (i.e during spawning and smolt emigration) or through the installation of flow control devices. However; it is unclear at this time whether such devices could be used to assist the upstream migration of large Atlantic salmon (which is typical of ‘Spring’ fish). If a beaver dam might cause an adverse effect on the integrity of the SAC and a fish pass might not allow passage upstream, then alternative mitigation measures which will allow passage must be put in place. These mitigation measures should be included in a Beaver Management Plan for the individual SACs, which should also set out in what circumstances there could be an adverse effect on site integrity, and a framework through which to implement any mitigation measures should they become necessary.

As yet a Beaver Management Plan has not been developed for the River Teith SAC. However, NatureScot is not aware of any dams that have caused concerns for fishery interests in the Forth catchment to date. This may be in part because fishery managers are removing dams as soon as they are formed without the need for licensed intervention, or simply that the number and location of beavers has yet to result in dams in tributaries that are considered to be potentially significant for fisheries. However, a monitoring and management plan for the catchment would be a necessary means of ensuring there are no adverse effects on Atlantic salmon interests.

Freshwater pearl mussel

There is a short length of river where adult/juvenile freshwater pearl mussel are assumed to be present in the catchment, but neither this nor the downstream section have any predicted potential for ‘occasional’ to ‘pervasive’ damming. Note that the larval/glochidial stage of freshwater pearl mussel is parasitic on salmonids.

Water quality, resource and ecological status

River Leven (Loch Lomond)

The catchment has water courses that fall into all of the classifications of Scottish river types and characteristics from mountain streams, to meandering reaches to modified rivers in agricultural and urban settings.

The Site Management Statement of the Endrick Water SSSI has important context for the features of interest and management pressures on the river.

SMS extracts as follows:

In its lower reaches, near Buchanan Castle, the river is of considerable geomorphological interest. Here the river provides an excellent example of an unmodified and highly sinuous lowland river with irregular to tortuous meanders. At present, the channel is actively migrating across the valley floor, generating a floodplain in which are preserved excellent examples of relict landforms such as meander scrolls, oxbow lakes and sections of abandoned channel. A recent cut-off provides an insight into how such channel adjustment develops and into the processes of fine overbank sedimentation into a former channel. This natural feature continues to be in favourable condition as the extent, visibility and accessibility of key land forms has been maintained…

In some areas, farming practices such as growing crops to near the edge of the river or allowing sheep and cattle unrestricted access to the riverbank have contributed to bankside erosion. Overgrazing of 

the river bank has inhibited the natural regeneration of riparian woodland, scrub and tall herb vegetation types in places, while trampling has also exposed the banks to erosion in places. However, in recent years, a number of farms have used support from schemes such as the Scottish Rural Development Programme (SRDP) to put up fencing to create riparian buffer zones to help the riverbanks recover….

Nutrient input to the river from point and diffuse sources has an adverse effect on water quality and could affect the fish populations, other species and habitats. Eleven sewage treatment works and an unknown number of privately owned septic tanks discharge into the river and its tributaries. Although several of the sewage works in the catchment are upgraded, there is some unregulated runoff from agricultural fields of fertilisers and slurry. The creation of more buffer strips of bankside habitat together with best practice in use of fertilisers and placement of middens could help to reduce runoff……

There is a long history of gravel extraction from the river bed, mainly for agricultural use. Extracting gravel can damage the natural sediment cycle within the river system, which directly affects the fish and lamprey interests of the river because they need a range of sediment available in their habitat to allow them to spawn successfully. ….Artificial reinforcement of the river banks for stabilisation is likely to have caused habitat loss for those species that utilise natural sand and earth banks, and may cause increased downstream erosion. Breakwaters and weirs (for angling purposes) alter the nature of the river and may harm spawning/breeding grounds for fish. The long-term channel migration in the lower reaches of the river could influence future management as the habitat in this location changes.

Hence the SMS highlights the natural dynamic of the river, the geology and seasonal inundation as part of the basis for the interests on the designated sites. The narrative also highlights some of the existing pressures on the rivers where beavers could have a beneficial role e.g. water purification, but also the potential for conflict by exacerbating erosion through burrowing where erosion processes are already prevailing as a result of historical and ongoing land management practices.

Some impacts are likely to be complex such as the impact of beaver presence, dam building and collapse; burrowing and digging canals, on river sediments and morphology – as illustrated in the review of beaver activity on the functioning of rivers and streams and water resource management in Scotland commissioned by CREW. CREW have also produced a shortened policy note version of this report). However, beavers are a natural component of riverine ecosystems across Europe and North America, and have the potential to contribute to the restoration of natural processes in such systems.

River Leven catchment hydro schemes that overlap with Potential Core Beaver Woodland are as follows:

• Auchengaich
• Burncrooks Reservoir
• Carmar Reservoir
• Carron Valley Reservoir
• Deil's Craig Dam
• Dumbrock Loch
• Loch Lomond
• Loch Sloy
• Finlas Water
• Loch Walton (Upper)
• Loch Walton
• Muir Park Reservoir

The catchment has 539 km of watercourse listed as High flood risk and 557 km as Medium risk and is listed as a Potentially Vulnerable Area (SEPA classification). Given the large river system and the potential indicated by the BDC (Beaver Dam Capacity) modelling, it ranks in the top 20 catchments nationally where beaver dams could have a role in ameliorating flood risk. This is equivalent to potential damming across 34% of the Medium/High flood risk areas. The analysis is pretty crude in terms of assessing the likely effect, but indicates there is potential for beaver damming (‘occasional’ to ‘pervasive’) along 372 km of High or Medium flood risk watercourse. In the case of this catchment this is partly a feature of the large catchment with significant length of watercourse rather than a particularly high density of predicted damming capacity per river length as indicated by the BDC mapping Map 3. Map 7 illustrates the flood risk areas, where beavers could locally contribute to the flood risk or hold water back, reducing downstream flood events. Loch Lomond could also benefit from beaver dams reducing the severity of drought with 796 km of Moderate or High ‘drought risk’ river lengths with the potential for beaver damming (‘occasional’ to ‘pervasive’). A water scarcity warning was issued by SEPA for the River Leven in summer 2022.

The flood risk maps can be viewed in combination with the Land Capability for Agriculture maps to indicate the potential for flooding of agricultural land (Map 8) or with commercial forestry (NFI Map 2). These potential impacts are discussed further under material assets. The flood risk map highlights the existing pressures on land and infrastructure, with beaver effects being potentially positive (at a local and cumulative scale) and negative (at a local scale).

River Forth

A SEPA catchment profile from 2011 provides much of the background to water resources and existing pressures in the catchment, a number of which are relevant to beavers e.g.   where there are opportunities to enhance water quality, existing barriers to fish passage and control programmes for invasive non-native plant species.

River Forth hydro schemes with Potential Core Beaver Woodland overlap are as follows:

• Glen Finglas Reservoir
• Loch Arklet
• Loch Drunkie
• Loch Katrine
• Loch Rusky
• Loch Venachar
• Lochan a' Ghleannain
• Touch No.2
• Touch No.3
• Touch No.4

As one of the larger catchments in Scotland the Forth has 750 km of water course classed as having a High flood risk and 800 km a Medium risk. (Trossachs Potentially Vulnerable Area, Gargunnock Potentially Vulnerable Area). Of these flood risk categories, a total 685 km has a predicted BDC class of ‘occasional’ to ‘pervasive’. The potential for damming could be interpreted as indicative of the potential for the amelioration of flood events and conversely the potential for exacerbating local flooding depending on the surrounding land use. The Forth also ranks highly in terms of the length of watercourse subject to drought risk (Moderate or High >1200km) where beaver dams (‘occasional’ to ‘pervasive’) may have a role in reducing the severity of drought events. Again flood risk categories are illustrated in Map 7 and BDC in Map 3. The Land Capability for Agriculture map can be compared with the potential for flooding again discussed under material assets.

Population and human health

River Leven (Loch Lomond)

The catchment has 75ha of built up area that is adjacent to Potential Core Beaver Woodland with the potential for impacts on built assets and hence is one of the catchments with a greater area mapped as built-up that overlaps with potential beaver habitat nationally. The overlap of built-up areas with Potential Core Beaver Woodland is principally around Alexandria and Balloch, but also extending to Drymen, Tarbet and smaller settlements along the loch-side.

The Local Authority boundaries fall along the length of the loch, with the west shore within Argyll and Bute Council, the east and to the north in Stirling and to the south in West Dumbartonshire. All is within the Loch Lomond and Trossachs National Park.

The ground water quality (superficial and bedrock) is classed as entirely good quality.

The national spatial analysis highlights there is 847 ha of reservoir (with 50m buffer) in the catchment of which 447 ha overlaps with Potential Core Beaver Woodland (Table 3).

Table 3 Overlap of Potential Core Beaver Woodland with reservoirs in the River Leven catchment

Name	Area (ha)
Loch Lomond	439.2
Finlas Water	0.2
Carron Valley Reservoir	0.9
Deil's Craig Dam	0.8
Dumbrock Loch	2.6
Carmar Reservoir	2.9

 

A detailed review of the potential effects of beavers on human health was included in the 2017 SEA report (section 4.12.2). This included the potential for beavers to be involved in the transfer of diseases and parasites in three ways:

1. Beavers acting as a mechanism for the introduction of new or eradicated diseases and parasites, and acting as potential transmission routes for the infection of humans, domesticated livestock and existing wildlife.
2. Diseases and parasite transfer from existing wildlife populations to translocated and wild beavers.
3. Beavers acting as a reservoir host for infectious diseases and parasites already present in Scotland, with potential transmission routes for infection of humans, domesticated livestock and existing wildlife.

The potential for beavers to introduce any parasites or pathogens is addressed by all beavers being sourced from the wild in Scotland (release from captive populations has a separate risk assessment) and the application of health screening protocols on all translocated beavers. A disease risk protocol is in development which will be used for all beaver translocations going forward. It includes testing and if necessary treatment for Cryptosporidium spp and Giardia prior to release.

NatureScot is the not the lead specialist organisation for public health issues, but the Centre of Expertise on Animal Disease Outbreaks (EPIC) undertook a public health risk assessment of Cryptosporidium and Giardia posed by beavers in Scotland in 2015. EPIC considered the likelihood of beavers acting as an important source of contamination of Giardia to water supplies as ‘very low to low (high uncertainty)’ in the context of other sources of contamination, such as humans, livestock, other wildlife and domestic animals. However, as a precaution, and to provide further reassurance, it was recommended that there is enhanced surveillance of human cases for a set period; further reintroduction proposals should be discussed with local authority environmental health teams and Scottish Water to allow levels of risk to be evaluated; and best practice in relation to public and private water supplies should continue to be promoted.

Campbell-Palmer et al. 2020 published the findings of health screening of beavers from Tayside (56 live from live-trapping in 2012-204 and 2017-2019, and 25 post mortem) and Knapdale (9 live and 7 post mortem). The authors concluded none of the beavers tested harboured any non-native disease or parasites of concern and demonstrated remarkably low levels of any disease or parasite exposure. The authors detail the results of 122 animals subject to testing with no animals being positive for Giardia or Leptospira.

The 2017 ER reviewed that Leptospira bacteria are widespread, with people most commonly acquiring leptospirosis through occupational, recreational or domestic contact with the urine of carrier animals either directly or via contaminated water or soil. Hence it is likely that beavers present a minimal additional risk to existing wildlife populations.

It was noted any significant increase in beaver numbers across Scotland in the longer term could conceivably lead to a greater overlap of human recreational activity in areas inhabited by beavers. However, the risk of acquiring leptospirosis appears to be highest among farmers, veterinarians and sewer workers, who all work around animals, rather than among those engaged in recreational activity.

Both catchments have many lochs and rivers that are used recreationally for fishing, water sports and wild swimming. There are human health risks associated from these activities, but there is no evidence to suggest that beavers would present a significant additional risk. Where translocations are approved, disease screening of translocated animals and additional public health surveillance are recommended.

Beaver burrowing has the potential to impact on paths used by a variety of recreational users. The catchment has some significant core paths, many loch and riverside paths and informal access as noted in section 2.1. There are examples of paths, cycle paths and fisheries access that has been locally impacted by beavers in Tayside through tree felling, collapse of burrows and flooding. Such impacts could incur additional costs, however, there are established techniques to address these impacts.

River Forth

The Forth catchment has 40 ha of built up area that is adjacent to Potential Core Beaver Woodland mostly in Doune, Callander and Aberfoyle. The catchment falls entirely within Stirling council boundaries. More than half of the catchment lies within the Loch Lomond and Trossachs National Park, with the area to the north west of the Port of Menteith, Flanders Moss and Callendar all lying within the Park.

Loch Katrine and tributaries are owned by the West of Scotland Water Authority. They control all water activities in that area. There is a hydro network with water from Loch Arklet and Finglas Reservoir piped into Loch Katrine which supplies drinking water for Glasgow area. The Forth has a large extent of reservoir boundary (394 ha in catchment) that overlaps with Potential Core Beaver Woodland 155 ha (Table 4).

Table 4 Overlap of Potential Core Beaver Woodland with reservoirs in the River Forth catchment

Name	Area_ha
Glen Finglas Reservoir	9.0
Loch Arklet	1.0
Loch Drunkie	12.4
Loch Katrine	97.4
Loch Rusky	1.3
Loch Venachar	33.2
Lochan a' Ghleannain	0.7

 

Impacts on human health and recreation are as discussed for Loch Lomond, noting the Trossachs is also an important area for public recreation and access.  

Cultural heritage

We have identified some of the key cultural features within catchments where there is predicted potential for overlap with Potential Core Beaver Woodland, indicating that at some point, beavers may occur close to these features with the potential for beaver activity to impact on these features (Tables 5 and 6, Figure 2). Established mitigation measures will be adaptable to suit heritage sites, however, some specialist mitigation, pro-active mitigation or monitoring may be appropriate.

Scheduled Ancient Monuments

Table 5 Scheduled Ancient Monuments that intersect with Potential Core Beaver Woodland in the River Leven and River Forth catchments

River Leven catchment	River Forth catchment
Rossdhu Castle	Dasher, fort 600m ENE of Doune Primary School
Rossdhu Chapel	Leckie Burn,bridge 230m WSW of Watson House
Island I Vow, castle and settlement, Loch Lomond	Bochastle Roman fort, temporary camp and prehistoric enclosures
Strathcashell Point, Cashel	Keir Hill of Dasher,earthwork
Balloch Castle,earthwork, Loch Lomond Park	Mill of Torr,fort
Luss,  churchyard surrounding Luss Parish Church	Auchenlaich, fort
-	Inchmahome Priory
-	Wester Arngibbon,earthwork
-	Keir Knowe of Drum,motte
-	Keir of Cashley,motte
-	Doune Castle
-	Doune Roman Fort, fort 60m S of Doune Primary School
-	Broch, rock shelter and cup marked rocks, 165m W of Leckie House

 

Gardens and Designed Landscapes

Table 6 Gardens and Designed Landscapes that intersect with Potential Core Beaver Woodland in the River Leven and Forth catchments

River Leven catchment	River Forth catchment
Rossdhu	The Roman Camp
Duntreath Castle	Cardross House
Ross Priory	Inchmahome Priory
Balloch Castle	Doune Park
-	Rednock House
-	Blair Drummond
-	Keir
-	Gargunnock House
-	Touch

 

Ancient Trees

Material assets

River Leven (Loch Lomond)

Fisheries

Loch Lomond is famed for sea trout and Atlantic salmon. The Loch Lomond Angling Improvements Association owns or leases much of the fishing rights alongside other private riparian owners, notably Glen Falloch Estate. The Loch Lomond Fisheries Trust (LLFT) was established in 2001 through a partnership between riparian owners, the Loch Lomond Angling Improvement Association (LLAIA) and the Scottish Federation of Coarse Anglers (SFCA). This is a charitable organisation with a remit to undertake research intended to underpin the management of the fish and fisheries.

Forestry

The extent of Potential Core Beaver Woodland is discussed in section 2.1.  The extent of conifer/ productive and woodland in the catchment is illustrated in Map 2. A large proportion of the productive woodland is managed by Forestry and Land Scotland. There are many smaller parcels of broadleaved woodland along the Endrick valley and Strathblane. Beavers have the potential to impact on established and new riparian planting schemes. Whilst there are mitigation approaches to individual tree protection and it would be possible to use beaver exclusion fencing for small stands of high value crops, neither approach lend themselves to more extensive riparian woodland or planting. Where planting is grant aided, further discussions are required with Scottish Forestry to establish tolerance around beaver impacts, prescriptions for planting in the presence of beavers and how management relates to other herbivore impacts. Further discussion of how future riparian planting strategies can be designed to support wider beaver restoration would also help to maximise the opportunities from beaver presence.

Agriculture

The overlap between Potential Core Beaver Woodland and Land Capability for Agriculture (LCA) classes in the River Leven and River Forth catchments is illustrated in Map 1. This highlights that most of the land that overlaps with Potential Core Beaver Woodland in the River Leven catchment is not agricultural land or is classed as rough grazing or improved grassland.

The Prime Agricultural Land (PAL - defined as LCA classes 1 - 3.1) is all in the southern end of the loch from Alexandria to Balfron and extending along the Endrick from the mouth to Strathblane. The River Leven catchment has 17 ha of PAL land capable of arable production that is adjacent to Potential Core Beaver Woodland and 311 ha of LCA class 3.2 (mixed agriculture).The more productive LCA classes (1 - 3.2) is all found towards the southern end of the loch.

The most significant extent of flood risk land in the catchment is around the Endrick mouth due to the topography elsewhere in catchment. The surrounding land is mostly classed at LCA 4.1 or less productive LCA classes, however, there is some flood-prone land (LCA 3.1) around Strathblane. Elsewhere in catchments the areas highlighted as a flood risk (and Potential Core Beaver Woodland) are around Inverarnan, and the lower reaches of the Luss Water, Fruin Water and Finlas Water. These are all classed as LCA 4.1 or less productive LCA classes and may benefit from any upstream damming by reducing the flashiness of the run off.

River Forth

Fisheries

The Forth District Salmon Fisheries Board represents the fishery proprietors throughout the Forth catchment and have statutory duties to protect salmon and sea trout fishing interests. The Forth Rivers Trust was set up in 2009 to protect, conserve and enhance freshwater fish, within the Forth District and are also working to achieve wider environmental and wildlife improvement and work with communities within the river catchments. 

Forestry

As noted in section 2.1, there is 28319 ha of forest within Forestry and Land ownership in the Forth catchment, with forestry being the main land use in the west of the catchment. Map 2 illustrates the total extent of forest in the catchment. The Forth floodplain is sparsely wooded, with more broadleaved woodland in the foothills of the Gargunnock Hills and Braes of Doune. The Trossachs lochs have a high proportion of broadleaved woodland and are well connected by wooded networks. There are some commercially grown broadleaves in this catchment although the proportion of commercial stands that would be accessible to beavers is not known. The Trossachs forests provide an extensive recreational asset with existing infrastructure for supporting ecotourism and wildlife watching.

Agriculture

There is 11 ha of PAL land in the catchment that overlaps with Potential Core Beaver Woodland and 357 ha of LCA class 3.2 (mixed agriculture). This proportion of PAL land is 3% of the PAL land in the catchment. This compares with 587 ha of potential overlap with Potential Core Beaver Woodland of PAL land (LCA 1 - 3.1) and 861.1 ha of LCA 3.2 in Tayside.

The LCA 1 - 3.2 land in the Forth is largely in a triangular parcel between the River Teith and the Forth heading westward to the National Park and skirting Flanders Moss and in a corridor along the B8037 to Balfron. The PAL overlap is limited to the Forth floodplain between Bridge of Allan and Doune. See MAP 8 Potential Core Beaver Woodland by Land Capability for Agriculture class in the River Leven and River Forth catchments.

Map 7 illustrates the areas of significant flood risk in the catchment. This includes much of the Carse of Stirling which is classed as LCA 3.2. The Goodie Water has areas of LCA 3.1, 4.1 and 4.2 land that is classed as flood risk around which there is a network of drainage channels. Around Callendar, Aberfoyle and Gartmore the flood risk land is of generally lower agricultural capability (largely 4.1).

As an overview it is likely that beaver activity will sometimes have a varying negative impact on some individual farms in the catchment. From experience in Tayside the impacts are most likely to be from the damming of burns and drainage ditches and to a lesser extent from burrowing impacts into river banks and embankments. However, the extent of farmland potentially affected in the Forth catchment would appear to be much smaller than in Tayside, with impacts likely to be most significant on areas of flat productive land that is reliant on field drainage.

The economic significance to individual farms will vary depending on the type of farming, the extent of land that is available to them to farm and the extent to which they are able to switch areas of production away from areas that may be affected by beaver activity. The Beaver Management Framework provides an existing framework for addressing such negative impacts, although will inevitably incur some additional time costs and inconvenience for those affected. Some farms with diversified interests may also benefit from visitor/guest accommodation where beaver presence may be attractive to visitors. 

There are existing measures in agricultural support that could be used to provide a range of environmental benefits one of which could be to reduce beaver conflicts. Work is ongoing to see support for the delivery of habitat restoration and ecosystem services in future rural support payments, which could include where these services are provided by beaver activity.

The national spatial analysis indicates there is around 7 km of recorded embankment (SEPA data) in catchment, of which 2.3 km overlaps with Potential Core Beaver Woodland. This compares with 89 km of recorded embankment within Tayside with 15 km adjacent to Potential Core Beaver Woodland. The presence of woodland on embankments has a stabilising effect on the bank, but is likely to increase the likelihood of a beaver territory being established. Again the Beaver Management Framework can be used where there is a risk of burrowing impacting on adjacent land use. To date this has tended to follow a licensing approach within limited options currently available to address these impacts through mitigation. There are however, approaches that involve setting productive land back from the watercourse that could reduce conflicts, and result in wider environmental and socio-economic benefits. There is currently work ongoing to develop tools that will enable better assessment of the risks posed by burrowing impacts.

Infrastructure

River Leven (Loch Lomond)

The catchment has 30 km of trunk roads that are adjacent to Potential Core Beaver Woodland, 17 km of A and B roads and 94 km of minor road.

Of the 36 km of railway within the catchment, there is 7.3 km of overlap between railways and Potential Core Beaver Woodland (with 10m buffer). The rail line runs from Dumbarton to Balloch and the West Highland Line, crosses from Loch Long to Loch Lomond at Tarbet and runs on the upper side of the road to Glen Falloch and then onward to Crianlarich.

There are no canals in either catchment and the reservoirs are listed under section 3.3, Population and human health. 

River Forth

There is a 10 km of trunk road that overlaps with Potential Core Beaver Woodland, 25 km of A and B road and 110 km of minor road.

There is no railway or canals in the catchment and reservoirs are listed under section 3.3.

Summary of key report findings

River Leven (Loch Lomond) catchment

The catchment is highly suitable for beavers in terms of habitat availability and suitability. Table 7 provides a summary of the most likely and most significant effects that may arise in the River Leven catchment from the translocation of beavers. Beavers already have a presence in the catchment and their re-colonisation by natural dispersal seems likely.

The overall benefits to biodiversity from beaver activity are well established in the literature, as is the potential for beaver activity to contribute to a wide range of ecosystem services including water supply and purification, the moderation of flood and drought events, nutrient cycling and river restoration. The magnitude of such beaver activity effects on physical processes at catchment scales are less clear, but have been identified as a priority for further investigation.  Releases into new catchments presents an opportunity to undertake research to further assess areas of uncertainty, and to enable mitigation/management to be adapted accordingly. Beavers may also act as a catalyst for riparian woodland creation and management, for the better management of other herbivore impacts, and provide a range of socio-economic and socio-cultural benefits including ecotourism provision.

The biodiversity interests in the catchment require that as a precautionary measure considerable additional monitoring would be needed to ensure that there are no adverse effects on Natura interests should a licence for beaver release be granted. Such monitoring could be risk assessed and targeted at locations where beavers are present and are more likely to have effects. This would include specific fish interests where there remain some uncertainties, and a need for further research to inform management.  A management plan would also be required to detail what actions are to be taken if beaver activity is considered to have the potential to have an adverse effect. In the case of dams this may require the use of species licensing to permit their removal or mitigation to be installed. For negative herbivore impacts, it may require the review of a herbivore management plan or further measures to reduce other herbivore impacts. Further modelling work could be carried out to establish the likely rate of beaver’s spread from modelled release scenarios. This could be used to inform a surveillance strategy. The Endrick Water SAC has relatively few tributaries where salmon are present, but there is greater uncertainty around the distribution of lamprey species and hence a more extensive monitoring programme may be needed on the Endrick Water SAC than in other rivers in the catchment. A management plan could also be used to identify opportunities for beneficial effects and wider ecosystem restoration to assist planning and to ensure potential benefits are realised.

The impacts on infrastructure, material assets and possibly cultural assets are those where there is more established experience from Tayside and where licensing or mitigation approaches can be applied.

Whilst the evidence points to their being low additional risks to human health, the recognised public health specialists have already highlighted the need to ensure the disease risk protocols are in place with recommendations for additional monitoring of public health to provide public assurances on these effects.

Table 7 Summary of likely significant effects within the River Leven (Loch Lomond) catchment

SEA category	Receptor or interest potentially affected	Effect	Likelihood of impacts	Significance in absence of mitigation	Specific mitigation/ actions proposed should a licence for release be issued
Biodiversity	Other interests comprehensively reviewed in Beavers in Scotland Report and 2017 SEA – not repeated here for brevity	+	High	NA	Largely positive
Biodiversity	Riparian woodland	+/-	High	High	Risk assessment and monitoring of SAC woodlands. Management of herbivore impacts at a level that can support beaver presence. Exploration of using beavers as a means of further promoting the restoration of riparian woodlands.
Biodiversity	bryophytes and lichens	+/-	Low	High	Risk assessment and implementation of monitoring and proactive protection of specific trees where appropriate. Exploration of using beavers as a means of further promoting the restoration of riparian woodlands.
Biodiversity	Highlighted vascular plants	Neutral/-	Low	High	Surveillance of known populations of species of conservation interest for beaver impacts.
Biodiversity	Salmon and lamprey	+/-	Medium	High	Risk assessment and implementation of dam surveillance programme and development of a management plan for the SAC to ensure timely intervention to ensure unimpeded fish passage. Aligned with monitoring there is a need for research to determine the pass-ability of beaver dams by adult salmon (upstream) and smolts (downstream), into the wider effects (positive and negative) of beaver on salmonid/fish populations, and into the effectiveness of flow devices incorporating fish passage.
Water quality, resource and ecological status.	-	+	Reflecting the conclusions of the CREW report the effects of beaver activity on water quality, flood amelioration, mitigation of drought likely difficult are likely to be positive at a catchment scale. Benefits will be tempered where dam removal is required to ensure fish passage, until such a time as effects are better known. Localised flooding and bank erosion may require use of Beaver management Framework.	High	-
Population and human health	-	Neutral	Low	High	Disease screening protocol and additional public health surveillance.
Cultural heritage	-	Neutral/-	Low	High	Site specific mitigation
Material assets	Forestry	+/-	Low	Medium	Exploration of impacts on forestry grants and herbivore management requirements and opportunities for beavers to promote riparian woodland restoration.
Material assets	Fisheries	+/-	Medium	High	As for salmon and lamprey.
Material assets	Agriculture	+/-	Low	Low	Existing measures through the Beaver Management Framework to mitigate or consider the use of licensing approaches. Opportunity to work with farming interests to deliver environmental benefits that are supported by rural support mechanisms.
Infrastructure	Railways	Neutral/-	Medium	High	Existing measures through the Beaver Management Framework to mitigate or consider the use of licensing approaches.
Infrastructure	Roads	Neutral/-	Medium	High	Existing measures through the Beaver Management Framework to mitigate or consider the use of licensing approaches.

 

River Forth catchment

There is already an established beaver population present in the Forth with 25 territories recorded in the 2020/21 survey. The beaver population is likely to expand into unoccupied parts of the catchment over the coming years. The catchment presents a large expanse of suitable habitat particularly within Loch Lomond and Trossachs National Park. The large area of land within public ownership also provides the opportunity for wide public access to and interpretation of beaver activity.

The potential for conflicts within the catchment are relatively few, with impacts on fish, riparian woodland and agriculture likely to be the most likely and or significant. It may be anticipated that within the extensive area of suitable habitat in the National Park there would be relatively limited negative effects on agriculture and forestry due to the topography and land use and greatest potential for benefits.

The 2017 SEA which included parts of the Forth catchment, concluded that there is sufficient evidence that the majority of the adverse effects identified can be satisfactorily and straight forwardly mitigated to avoid significant effects.  As for the River Leven catchment, this is likely to be the case if impacts arise in relation to infrastructure, material assets and possibly some cultural assets. There is potential for conflict between beaver activity and agriculture, particularly in the Carse of Stirling where the higher LCA classes are found and the land is also more prone to flooding. Whilst beavers may have localised impacts in terms of flooding, there is also the potential that beavers will reduce the severity of flood events in the Carse by holding water further up the catchment. There may be some anticipated need for beaver licensing to prevent serious agricultural impacts, but these would be expected to be far more restricted than in Tayside. There may also be opportunities for farm businesses to benefit from beaver presence through ecotourism provision and support services.

The biodiversity effects of greatest significance are likely to be on fish (positive and potentially negative) and riparian woodlands (likely). As for the River Leven catchment, a programme of surveillance/ monitoring and further research would be required to ensure that the beaver activity does not have an adverse impact on Natura interests. Again this surveillance can be risk assessed and targeted to areas of beaver presence, but in this catchment where the river Teith SAC in particular, includes a very extensive network of tributaries, the programme could be significant (Map 6). As yet a management plan has not been developed for the River Teith SAC and that would remain a recommendation if further beaver releases are to be considered. Again a management plan could be viewed as an opportunity to explore opportunities for habitat restoration that would support beaver restoration and wider environmental and socioeconomic benefits.

NatureScot are not public health specialists and further discussions with Local Authority Environmental Health Teams are recommended where further release licences are considered as recommended by EPIC.  Report: Public health risk of Giardia and Cryptosporidium posed by reintroduction of beavers into Scotland

The extensive network of watercourses in the Forth and the potential for beaver dams presents a significant opportunity for beavers to deliver a range of ecosystem services. At the same time the extensive nature of the network and likely beaver presence presents a challenge for the effective monitoring of effects. Re-colonisation of beavers in the catchment, aided by translocation, provides an opportunity for further research to be carried out and the effect of beaver dams on fish passage (and fish populations at a wider scale), to be better understood. Further research could also assess the extent to which flow devices that incorporate fish passage can be effective in mitigating any negative impacts.

Table 8 Summary of likely significant effects within the River Forth catchment

SEA category	Receptor or interest potentially affected	Effect	Likelihood	Significance in absence of mitigation	Specific mitigation proposed should a licence for release be issued
Biodiversity	Other interests comprehensively reviewed in Beavers in Scotland Report and 2017 SEA – not repeated here for brevity	+	High	NA	Largely positive
Biodiversity	Riparian woodland	+/-	High	High	Risk assessment and monitoring of SAC woodlands. Management of herbivore impacts at a level that supports beaver presence. Exploration of using beavers as a means of further promoting the restoration of riparian woodlands
Biodiversity	Salmon and lamprey	+/-	-	-	Risk assessment and implementation of dam surveillance programme and development of a management plan for the SAC to ensure timely intervention to ensure unimpeded fish passage. Aligned with monitoring there is a need for research to determine the pass-ability of beaver dams by adult salmon (upstream) and smolts (downstream), into the wider effects (positive and negative) of beaver on salmonid/fish populations, and into the effectiveness of flow devices incorporating fish passage.
Water quality, resource and ecological status.	-	+	Reflecting the conclusions of the CREW report the effects of beaver activity on water quality, flood amelioration, mitigation of drought likely difficult are likely to be positive at a catchment scale. Benefits will be tempered where dam removal is required to ensure fish passage, until such a time as effects are better known. Localised flooding and bank erosion may require use of Beaver management Framework.	High	-
Population and human health	-	Neutral	Low	High	Disease screening protocol and additional public health surveillance.
Cultural heritage	-	Neutral/-	Low		Site specific mitigation.
Material assets	Forestry	+/-	Low	Low	Exploration of impacts on forestry grants and herbivore management requirements and opportunities for beavers to promote riparian woodland restoration.
Material assets	Fisheries	+/-	Medium	High	As for salmon and lamprey.
Material assets	Agriculture	+/-	Medium	Low	Existing measures through the Beaver Management Framework to mitigate or consider the use of licensing approaches. Opportunity to work with farming interests to deliver environmental benefits that are supported by rural support mechanisms.
Infrastructure	Roads	Neutral/-	-	-	Existing measures through the Beaver Management Framework to mitigate or consider the use of licensing approaches.

Annexes and Maps (high resolution)