Habitats Regulation Appraisal (HRA) of Possible Beaver Translocations in Scotland: River Leven and River Forth Catchments
November 2022
Introduction
In November 2021 Scottish Government announced that they would support the expansion of the Eurasian beaver Castor fiber population into new areas outside their current range in Scotland. Spatial analysis by NatureScot combined with an awareness of where there is existing interest in translocations has led to an initial focus on four possible river catchments for future beaver releases; The Rivers Forth and Leven (Loch Lomond), Beauly and Spey. It is anticipated that licence applications for beaver translocations will be forthcoming within these catchments. However before NatureScot (SNH), as competent authority for the issuing of any licences, can approve an application, we first need to ensure that any such proposal will not adversely affect the integrity of a European site (Special Areas of Conservation (SACs) and Special Protection Areas (SPAs)). Rather than waiting until individual licence applications are received it is proposed the impact of introducing beavers to specific river catchments is first assessed at a strategic or catchment level. This approach also allows for the assessment of impacts not just specific to a given release site. This HRA focuses on the Rivers Forth and Leven (Loch Lomond) catchments. Further assessments will be carried out for other prioritised catchments.
Background
In 2017 SNH provided information to inform the Habitats Regulations Appraisal (HRA) of the Scottish Government decision to allow Eurasian beavers to remain in Scotland (hereafter referred to as the “2017 Beaver HRA”). The appraisal considered the impact of both allowing the existing beaver populations in Argyll and Tayside to remain in Scotland and whether they should be allowed to expand their range naturally.
SNH’s appraisal concluded that with the identified mitigation in place it was possible to conclude that the proposal would not adversely affect the integrity of a European site. The appraisal included a buffer zone of 10km around the river catchments based on research by Newcastle University in their Commissioned Report 814 on beaver population modelling. It also concluded that an updated HRA should be carried out after 10 to 12 years, or at any point any new release site or other reinforcement is considered (whichever comes first).
We have produced an Addendum to the 2017 SEA which summarises any new information we have gained since that assessment was carried out in terms of the population, expansion, the monitoring carried out, the use of licensing and mitigation approaches to address negative impacts in Tayside and Knapdale, beaver research and the changes to the policy context.
Methodology
As outlined above rather than waiting until individual licence applications are received it is proposed that a strategic approach is first taken to consider the impact of introducing beavers to specific river catchments.
Parts of the river Forth catchment were considered within the scope of the 2017 Beaver HRA. This assessment covers the whole Forth catchment and the adjacent River Leven (Loch Lomond) catchment. The HRA will look at the European sites that overlap with these catchments and the possible impacts beaver could have on their qualifying interests. Table 1 lists the European sites that overlap with the River Leven (Loch Lomond) and the River Forth catchments.
Table 1: European sites that overlap with the River Leven (Loch Lomond) and River Forth catchments
| River catchment | European site | Designation |
|---|---|---|
| River Leven | Ben Lui | SAC |
| River Leven | Endrick Water | SAC |
| River Leven | Loch Lomond Woods | SAC |
| River Leven | Glen Etive and Glen Fyne | SPA |
| River Leven | Loch Lomond | SPA |
| River Forth | Trossachs Woods | SAC |
| River Forth | Flanders Mosses | SAC |
| River Forth | River Teith | SAC |
The 2017 beaver HRA used a pre-existing ‘Potential Core Beaver Woodland’ GIS layer, developed during 2015 and described in NatureScot Commissioned Report 875: A geospatial analysis of potential Eurasian beaver (Castor fiber) colonisation following reintroduction to Scotland. and the ‘Beavers in Scotland’ report to help determine possible impacts to European sites. This showed the locations of suitable riparian woodland (Suitable’ woodland means the presence of broadleaf woodland and shrub within approximately 50m of a freshwater edge. See Beavers in Scotland report. Section 3.2) buffered to suitable freshwater habitat (Suitable’ freshwater habitat means within 50m of broadleaf woodland and shrub, with streams of less than 15% gradient, and in sections not affected by tides. See ‘Beavers in Scotland’ report. Section 3.2) that are expected are able to support viable beaver territories (core habitat). There is also a GIS map identifying ‘Beaver habitat’ (i.e. non-core) which is similar, but includes habitat fragments of any size, including very small ones likely to be unable to support beaver territories – but which might be used on occasion by, for example, dispersing individuals etc. Combined, these maps show the entire potential existing habitat that beavers could be expected to inhabit (these combined GIS layers can be seen in Annex A of the 2017 Beaver HRA). In reality, beavers are unlikely to inhabit all this habitat at the same time, and habitats could change over time. These habitat layers continue to be valid as the base mapping on which they are based has not changed substantially, but will be reviewed and updated as appropriate.
This work in 2017 provided a list of all the European sites where there is at least some overlap with predicted beaver habitat (see Annex B of the 2017 Beaver HRA). When comparing this with Table 1 it can be seen that some sites are not considered to overlap with predicted beaver habitat (e.g. Ben Lui SAC).
The sites identified in Table 1 will be considered as part of the Habitats Regulations Appraisal. The current approach aims to assess whole catchments and is not specific to existing beaver populations as was the case for the 2017 assessment which used a buffer zone to define the detailed zone of appraisal. Future beaver monitoring will indicate any need for HRA for other catchments colonised by natural dispersal from these catchments
Appraisal in relation to regulation 48 of the Conservation (Natural Habitats, &c.) Regulations 1994 as amended (Habitats Regulations Appraisal) for the River Leven (Loch Lomond) and the River Forth catchments
Is the plan or project directly connected with or necessary to site management for nature conservation?
While beaver are considered to have a number of positive effects on biodiversity the proposal is not considered to be directly connected with or necessary to site management for nature conservation and the potential impact on the qualifying features of European sites needs to be considered.
Is the plan or project (either alone or in combination with other plans or projects) likely to have a significant effect on a European site?
There is connectivity between many of the qualifying features of the European sites listed in Table 1 and the proposal to allow beaver translocations into the River Leven (Loch Lomond) and the River Forth catchments. The proposal could therefore have a likely significant effect (LSE) on the qualifying features of the European sites. The possible impacts on the qualifying features are considered below in an appropriate assessment.
In the 2017 beaver HRA a number of SAC features were identified as having no ecological connectivity with beavers. These features, that are also qualifying features of SACs within the River Leven (Loch Lomond) and River Forth catchments, are identified below in Table 2 and are not considered further within the appropriate assessment.
Table 2: Habitats that are qualifying features of European sites within the River Leven (Loch Lomond) and River Forth catchments initially identified in the 2017 Beaver HRA as having some overlap with GIS beaver habitat maps, but which were advised to have no LSE due to a lack of connectivity with beavers.
| Acidic scree | Dry heaths | Montane acid grasslands | Plants in crevices on base-rich rocks | Mountain willow scrub |
|---|---|---|---|---|
| Alpine and subalpine calcareous grasslands | Species-rich grassland with mat-grass in upland areas | Plants in crevices on acid rocks | Tall herb communities | Wet heathland with cross-leaved heath |
| Alpine and subalpine heaths |
Appropriate assessment
Appraisal
The following is a summary of how beaver could potentially impact some of the qualifying features of European sites that occur in more than one SAC within the River Leven (Loch Lomond), and River Forth catchments. An appraisal against the conservation objectives for individual SACs then follows. Further details about the HRA process can be found on the NatureScot website.
Woodland
As outlined in the 2017 Beaver HRA the main factor causing unfavourable condition in Scottish woodlands is grazing / browsing pressure from herbivores (largely deer and sheep). At present, saplings can be considered ‘safe’ from further browsing once they get to a certain size (the specific size varies with the species). However, since beavers are able to fell quite large trees, this will no longer be the case in areas colonised by beavers for a reasonable length of time. In the absence of natural regeneration from seed, continuation of woodland will depend on coppice regrowth from the felled stumps or suckering from roots. Whilst all native Scottish broadleaves are able to coppice or sucker to some extent, if the regrowth is subsequently eaten by deer, sheep, or other large herbivores, there could be a simplification in the structure of the woodland, and possibly loss or deterioration of the woodland habitat.
Where grazing/ browsing are within target levels within these SACs, changes in structure are more likely than a deterioration of structure. It is not possible to be absolutely precise about what this will involve because it depends upon many factors and will vary from site to site; but it is likely to include an increase in young tree growth from coppicing, and changes in deadwood volume - either an increase if beavers leave it lying around, or a decrease if they remove it for food or dam construction. However, where woodland is already in unfavourable condition because of grazing/ browsing levels, it is probable that a further decline in condition (structure and extent) will occur in areas used by beavers, as they fell trees that are then unable to regenerate.
The Knapdale Beaver Trial monitoring suggested that beavers rarely moved more than 30m from waterbodies, so loss of habitat and decline in condition is likely to be confined to a small proportion of most sites, although this will be particularly problematic for riparian and wet woodland, where severe declines are possible.
Fish
Lamprey
Three species of lamprey are found in Scotland: brook (Lampetra planeri), river (L. fluviatilis), and sea (Petromyzon marinus). Lamprey are a primitive species of jawless fish that are eel-like in shape.
Larval lamprey (also termed ammocoetes) are filter feeders that trap water-borne fine organic matter. They are negatively phototactic (i.e. they move away from light) and positively thigmotactic (i.e. they seek contact with other objects) and as a result they commonly burrow into soft sediment in the margins of streams and rivers. They may also be found in detritus overlying coarse substrate, among submerged tree roots, emergent vegetation rooted in silt, shallow patches of fine sediment among coarser substratum, or submerged branches or twigs that have trapped fine sediment. Habitat degradation is one of the key factors that can affect lamprey which require clean, well oxygenated water and suitable substrates to use as spawning and nursery habitats. The quantity, location, and quality of juvenile lamprey habitat will vary naturally in response to changes in flow, geomorphology, and the availability of material to burrow into. Some patches will persist for years whilst others will be ephemeral. Lamprey require migration routes that are free of obstacles. Impassable man-made structures, e.g. dams and weirs, and natural obstacles e.g. waterfalls, will restrict their distribution across a catchment.
Brook lamprey are the most abundant, widespread, and smallest of the species found in Scotland. It spends its entire life in fresh water. Little is known about their movements within river systems, although it is clear that the species is mobile enough to use all of the habitat available. Research in Denmark suggests that whilst dams are a complete barrier to brook lamprey, they do not have an overall negative effect on the species (see Table 3.13, page 84, Beavers in Scotland). Lamprey surveys usually focus on catching juveniles, but as it is nearly impossible to differentiate between the young of brook and river lamprey in the field reports are for Lampetra, i.e. the two species are combined; information about the catchment distribution of river lamprey is therefore limited.
River and sea lamprey are anadromous, i.e. the adults spend some time in the marine (sea lamprey) or estuarine (river lamprey) environment before returning to fresh water to spawn. Unlike other species of anadromous fish, river and sea lamprey do not exhibit complete fidelity to their natal river (Genner et al., 2012; Bracken et al., 2015).
Beaver activity (e.g. burrowing, damming) has the potential to initiate changes in the quantity, location, and quality of lamprey nursery and spawning habitat. Beaver dams may, for example, trap fine sediment and so reduce the amount transported downstream and available to replenish juvenile lamprey habitat. But beaver dams might also, for example, benefit spawning areas by limiting the availability of fine material that could clog otherwise suitable habitat. There is however little if any empirical evidence of the actual effects that beaver dams might have on Scottish fish populations, notably including upon migration. Stringer et al. (2015) state:
Lamprey are thought to be poor at ascending river obstacles and their migration may be impeded by beaver dams (Maitland, 2003). There is a single observation of a brook lamprey passing a 70 cm high beaver dam (Jensen & Olsen, 2004). However, the degree to which migrations may be hampered remains unclear, and this is particularly important for the anadromous river and sea lamprey.
Kemp et al. (2010) state that the findings presented in their report (A critical review of the effects of beavers upon fish and fish stocks) indicate that:
Beavers can have both positive and negative impacts on fish populations; that response can be complex and spatially and temporally variable, and that perceived overall effects tend to be positive when viewed from the perspective of productivity. Nevertheless, potential for negative impacts of beaver activity on fish passage, particularly in tributary streams under low flows, and quality of spawning habitat must be appreciated, and management strategies developed.
Atlantic Salmon
The potential (positive and negative) impact of Eurasian beaver on freshwater fish, and the fisheries that they support, is extensively reviewed within the Beavers in Scotland report to the Scottish Government. Additional material, for Atlantic salmon only, is provided also within the Final Report of the Beaver Salmonid Working Group (2015).
Atlantic salmon are widely distributed across Scotland and within the network of Atlantic salmon SACs. However, when considering the viability of individual populations it is important to consider the complex nature of Atlantic salmon populations within UK rivers. Stock structure can, for example, incorporate a variety of discrete populations each of which are adapted to complete their life history within certain geographical areas of a catchment. The time taken to smolt, the timing and duration of the smolt migration, time spent at sea and timing of return may all have a genetic basis. In terms of location, it is widely accepted that early running multi-sea-winter fish (known as the Spring stock component) tend to spawn in the upper catchments of rivers, and that late-running fish (Autumn stock component) may ultimately spawn in the lower reaches of river systems. Whilst this may be a simplistic view, it demonstrates that Atlantic salmon can, and often do, utilise the entire catchment during spawning time and for the production of juvenile fish.
The Spring stock component typically spawns in the upper reaches of rivers, and damming activity in areas downstream of such areas may have a negative impact on this portion of the Atlantic salmon stock. This life history type, which is included as a reason for selection in many Atlantic salmon SACs, has undergone a long-term national decline and remains a key issue for those involved in the maintenance of Atlantic salmon fisheries, as well as for NatureScot. The resilience of migratory Atlantic salmon populations to new pressures is an issue that must be considered in respect of how beaver–salmon interactions are managed.
Otter
Otter could potentially be impacted by beavers through their grazing activities and also by altering of water levels. However information from Europe indicates that the presence of beaver does not appear to be detrimental to otter, and indeed may be beneficial (see section 18.6 of the 2017 Beaver HRA). The Eurasian beaver is a natural component of freshwater ecosystems in Europe, and beaver and otter are often recorded in the same areas.
Section 1 - River Leven Catchment
The Environmental Report includes a general description of the catchment.
Loch Lomond Woods SAC
Qualifying features
Western acidic oak woodland
Otter (Lutra lutra)
Conservation objectives
The conservation objectives for Loch Lomond Woods SAC can be found in full in the Conservation Advice Package along with other information about the site. The key elements to consider are as follows:
To ensure that the integrity of Loch Lomond Woods SAC is restored by meeting objectives 2a, 2b and 2c for each qualifying feature
Western acidic oak woodland
2a. Maintain the extent and distribution of the habitat within the site
2b. Restore the structure, function and supporting processes of the habitat
2c. Restore the distribution and viability of typical species of the habitat
Otter
2a. Maintain the population of the species as a viable component of the site
2b. Maintain the distribution of the species throughout the site
2c. Maintain the habitats supporting the species within the site and availability of food
Appraisal
Western acidic oak woodland
2a. Maintain the extent and distribution of the habitat within the site
Beaver foraging activity in combination with grazing and browsing pressure from other herbivores could lead to a loss of qualifying habitat. Grazing / browsing by herbivores is one of the pressures currently causing unfavourable condition at this site, and the added impacts of beavers could potentially exacerbate this, leading to the deterioration and / or loss of qualifying habitat.
The Knapdale Beaver Trial monitoring suggested that beavers rarely moved more than 30m from waterbodies, so any loss of habitat is likely to be confined to a small proportion of the site overall. However, given the nature of the site, including wooded islands and riparian woodland, loss or deterioration of qualifying woodland near waterbodies is possible due to the combined impacts of beaver and other herbivores, leading to a change in the distribution of the habitat. This particularly applies to the component SSSIs Endrick Mouth and Islands, Inchtavannach and Inchconnachan, Inchlonaig, and possibly the flatter parts of Rowardennan Woodlands around Cashell. Other areas are probably too steep and rocky for beavers to have a significant impact.
2b. Restore the structure, function and supporting processes of the habitat
In areas with high herbivore impact such as on some of the islands, Pollochro Wood, Craig Royston Wood and Rowardennan Wood there is a lack of woodland structure. There is little ground flora made up of palatable species, almost no shrub layer and mostly only mature and dying trees. Most of the grazing impacts are due to fallow, red and roe deer or goats, but on Inchtavannach they are due to high levels of livestock grazing in the woodland and here beavers could present an additional pressure. The impact of beavers will be more restricted to riparian and lochside habitats than that of other herbivores, the majority of the woodland on these sites is too steep and rocky for beavers to have a major impact, although parts of Rowardennan could also experience beaver impacts.
Only a small proportion of this habitat, close to waterbodies, is likely to be used by beavers although, on flatter land, they may alter the terrain resulting in an increase in the area accessible to them. Change in the structure of accessible woodland areas is likely, but is difficult to predict with accuracy at this point in time. Possible impacts include changes in the volume of deadwood, increases in dense young growth or in open space. Provided regeneration of felled trees and shrubs is able to take place, these changes are most likely to be beneficial, contributing to the dynamism which is an important feature of this habitat. However, where regeneration is restricted by other herbivores, a negative impact on site integrity is possible.
Short, medium or long-term changes in the vegetative structure, and / or hydrology of localised areas of accessible woodland, as a result of beaver activity, is likely to increase the dynamism of woodland processes. Provided regeneration of felled trees and shrubs is able to take place, this is likely to increase the overall conservation value of the site (for example, by increasing the amount of standing dead wood resulting from flooding, thereby increasing habitat for dead wood ‘typical species’). Such changes would be compatible with this conservation objective.
2c. Restore the distribution and viability of typical species of the habitat
The key tree species found in this habitat are oak (Quercus robur and/or Q. petraea) and birch (Betula pendula and/or B. pubescens). There is significant variation between individual stands of the habitat dominated by either oak or birch. Inchconnachan and Inchlonaig are dominated by birch rather than oak. Parts of Rowardennan and Craig Royston are mosaics with wet and ash woodland and Pollochro is a mosaic of wet woodland and oak birch woodland. Holly and hazel are also important components of the habitat. At Rowardennan there are large areas of pure stands of hazel. Whilst beaver may use any of these tree species, their palatability to other herbivores (and thus their ability to re-sprout after felling) varies. In general, birch is the least palatable to deer and sheep, with hazel and ash the most palatable. Selective browsing by any of the herbivore species has the potential to affect the future composition, by limiting regeneration of the more palatable species.
The ground flora is variable but key species may include dominant grasses such as Agrostis capillaris/canina bent grass, Anthoxanthum odoratum sweet vernal grass in less acidic soils and Deschampsia flexuosa wavy hair grass in more acidic soils. There is also a diverse fern assemblage including several Dryopteris spp buckler ferns, Blechnum spicant hard fern and the Oceanic Wilson’s filmy fern Hymenophyllum wilsonii. Key bryophytes species include hypnoid mosses such as Dicranium majus, Pleurozium schreberi, Rhytidiadelphus loreus and Polytricum formosum. The scrub layer may be absent or often dominated by ericoid scrubs such as Calluna vulgaris heather and Vaccinium myrtillis blaeberry along with Rubus fruticosus, Oxalis acetosella, Potentilla erecta and Galium saxatile. The restriction of beaver activity to within 30m of water is likely to limit the impact on these typical species, with herbivory likely to focus on the aquatic and streamside vegetation, with occasional tracking into these types from water-bodies.
Natural regeneration of the typical species of the habitat is being prevented in many parts of the SAC by the presence of non-native species, especially rhododendron and non-native conifers. Neither of these species are likely to be used by beavers. Removal of these non-native species is needed to ensure that the distribution of the typical oakwood species throughout the SAC is not compromised.
Conclusion
The above appraisal suggests that the conservation objectives for the western acidic oak woodland feature of the Loch Lomond Woods SAC could potentially be undermined by beaver translocation to the River Leven catchment without any appropriate management measures to mitigate impacts being in place. Impacts are possible in areas of qualifying habitat likely to be used by beavers (i.e. within c.30m of water-bodies), as a result of the cumulative impacts of beavers and other herbivores.
However if beavers begin to colonise the SAC, impacts could be monitored using the Woodland Herbivore Impact Assessment (WHIA) methodology and incorporating monitoring of beaver signs. The methods allow for some heterogeneity, but generally ‘low’ impacts are desirable for woodland restoration, although it is recognised they are not currently “low” in many of the woodlands within the SAC. Where herbivore impacts are already too high, the woodland will already be in an unfavourable condition. Beaver presence could exacerbate this – but management of other herbivores may allow any beaver coppiced trees to regenerate. Herbivore management in the case of wild deer and goats is generally by a deer/herbivore management plan and of livestock via consents and management agreements. For beavers, licenced intervention could be considered where there is serious risk of damage to a conservation interest, but proactive mitigation in the form of selective tree protection is more likely, but is unlikely to be appropriate on a large scale. Hence the focus would be on ensuring the impact of other herbivores are sufficiently low to allow beaver presence. It is advised that annual site checks would be necessary to ensure appropriate levels of herbivore impacts are maintained where beavers are present.
With the appropriate monitoring and herbivore management in place it would be possible to ensure that any translocations of beaver into the River Leven catchment would not adversely affect the integrity of the western acidic oak woodland feature of the Loch Lomond Woods SAC.
Otter
2a. Maintain the population of the species as a viable component of the site
Otter were assessed as being in favourable condition at the site during the last Site Condition Monitoring in 2012.
Eurasian beavers and otters do not compete directly for resources. The otter is a predatory species, and the beaver is herbivorous. Otter and beaver territories will overlap. There are occasional records of otter predation on beaver.
Information from Europe indicates that the presence of beavers does not appear to be detrimental to otters, and indeed may be beneficial. This is supported by the findings of the monitoring undertaken during the Scottish Beaver Trial (Harrington, L.A., Feber, R., Raynor, R. and Macdonald, D.W. 2015. The Scottish Beaver Trial: Ecological monitoring of the Eurasian beaver Castor fiber and other riparian mammals 2009-2014, final report. Scottish Natural Heritage Commissioned Report No. 685.). This is believed to be linked to the habitats that are created where beavers have been active, such as ponds, localised wetland areas which are also good quality habitat for otters and otter prey.
There will therefore be no adverse impact on the population of the species as a viable component of the site.
2b. Maintain the distribution of the species throughout the site
As described above, European information and the results of the Scottish Beaver Trial monitoring programme conclude that the presence of beavers will not affect otter distribution adversely. It is possible that an increase in wetland habitat may result in some localised increases in the overall area where otters are most likely to actively forage. However, beaver dams may sometimes have adverse impacts on migratory fish species which are one of the many prey species for otter. There is potential, therefore, for consequent localised impacts on otters and therefore this conservation objective could be undermined.
2c. Maintain the habitats supporting the species within the site and availability of food
Beaver activities can result in increased wetland habitat suitable for amphibians and some localised changes to fish populations. Amphibians may be an important seasonal source of prey for otter populations. A net benefit to otters, in terms of provision of foraging habitat, is expected as a result of beaver activities.
Conclusion
The above appraisal suggests that the conservation objectives for the otter feature of the Loch Lomond Woods SAC will not be undermined by any beaver translocations to the River Leven catchment, and it will not adversely affect the integrity of the SAC provided the following mitigation condition is put in place.
Where beaver dams are constructed that impede the movement of migratory fish to such a degree that there might be an adverse effect on site integrity via impacts to otter, all appropriate mitigation measures to facilitate fish passage are put in place to avoid this. This mitigation will require that proactive monitoring of beaver dams in areas important for fish passage is carried out. Although the appropriate assessment is specific to the Loch Lomond Woodlands SAC, this mitigation applies more widely to all the rivers and streams that are important for fish passage where beavers are present.
Ben Lui SAC
Qualifying features
Wet heathland with cross-leaved heath
Mountain willow scrub
Montane acid grasslands
Alpine and subalpine calcareous grasslands
Species-rich grassland with mat-grass in upland areas *
Tall herb communities
Base-rich fens
High-altitude plant communities associated with areas of water seepage *
Acidic scree
Plants in crevices on acid rocks
Plants in crevices on base-rich rocks
*denotes a Habitats Directive priority habitat
Conservation objectives
The conservation objectives for Ben Lui SAC can be found in full in the Conservation Advice Package along with other information about the site.
Appraisal
There is considered to be no ecological connectivity between beavers and the qualifying features of Ben Lui SAC as there is no overlap with predicted beaver habitat. The conservation objectives for these qualifying features will therefore not be undermined by any beaver translocations into the River Leven catchment and it can be concluded that any beaver translocations will not adversely affect the integrity of the Ben Lui SAC.
Endrick Water SAC
Qualifying features
Atlantic salmon
Brook lamprey
River lamprey
Conservation objectives
To avoid deterioration of the habitats of the qualifying species or significant disturbance to the qualifying species, thus ensuring that the integrity of the site is maintained and the site makes an appropriate contribution to achieving favourable conservation status for each of the qualifying features; and
To ensure for the qualifying species that the following are maintained in the long term:
- Population of the species, including range of genetic types for salmon, as a viable component of the site
- Distribution of the species within site
- Distribution and extent of habitats supporting the species
- Structure, function and supporting processes of habitats supporting the species
- No significant disturbance of the species
Appraisal
Brook and river lamprey
The 2012 Site Condition Monitoring (SCM) survey of brook and river lamprey showed that the populations were in favourable condition. Due to the similar effects beavers could have on either species they are considered together here to avoid repetition.
Population of the species as a viable component of the site
Distribution of the species within site
Beaver activity that alters the flow or morphology of the streams and rivers that contain brook and river lamprey habitat could affect both the viability and distribution of the species. Beaver activity could lead to changes in the populations and distribution of lamprey by altering the quantity, location or quality of their nursery or spawning habitat, or the ease with which they can migrate. River lamprey usually migrate to an estuary as juveniles before returning to spawn as adults. However the population in the Endrick Water SAC is of particular interest as the adults remain in the fresh water of Loch Lomond where they feed on freshwater fish before returning to the Endrick Water to spawn; this is the only river system in Great Britain where the river lamprey population exhibits this unusual behavioural trait.
Lamprey require migration routes that are free of obstacles. Beaver dams could affect lamprey movements within the SAC. According to the Beavers in Scotland report (Scottish Natural Heritage, 2015), Although there is an extensive literature describing dam-building by beavers, it is not always predictable where or in what physical conditions beavers will build dams. One detailed study in Sweden reported that the mean width of streams on which beavers built dams was 2.5 m, up to a maximum of 6 m. Presuming that this maximum width is appropriate here it seems unlikely that beaver would establish barriers in the Endrick Water itself; the channel width in the upper reaches of the SAC appears to be approximately 5 m at its narrowest. However, beaver dams in tributaries of the Endrick Water SAC could impede or prevent lamprey movements.
Distribution and extent of habitats supporting the species
Dam building and other in-stream or riparian beaver activity might affect sediment transport in rivers and streams, either directly or by influencing the hydrology of the affected watercourses. The changes might negatively affect nursery or spawning habitat. By trapping fine material that would have moved downstream to replenish nursery habitat beaver dams might lead to changes in the quantity, quality, and distribution of it. However, accumulations of fine material upstream of beaver dams might provide new nursery habitat. Similarly, accumulations of fine material upstream of beaver dams might smother spawning areas, but the reduction in fine material moving downstream might lead to the development of or improve spawning habitat which comprises clean, well-oxygenated gravel.
Structure, function and supporting processes of habitats supporting the species
As outlined above, beaver could affect sediment transport and hydrology and therefore the structure, functioning and supporting processes of habitats supporting lamprey
No significant disturbance of the species
There is potential for beaver activity to negatively affect the life history of lamprey. For migrating adults, the severity of this impact may be significant if it impedes access to spawning habitat. Note that although they are not anadromous, even brook lamprey may undertake significant migrations upstream from nursery areas to spawning grounds (Maitland, 2003). The severity of impact may be less for juvenile lamprey if for example additional habitat is created through the in-stream and riparian activities of beaver.
Conclusion
This appraisal suggests that the conservation objectives for brook and river lamprey could be undermined by the translocation of beaver to the River Leven catchment. While much remains unknown about these lamprey species, including their distribution throughout the SAC, impacts are possible through changes to their habitat and also through barriers to movement. Until more is known about the potential effects on lamprey of beaver activity the following mitigation would need to be employed to ensure that the integrity of the SAC would not be adversely affected:
- Monitoring to alert to beaver dam presence within the SAC and its tributaries.
- Measures to ensure that juveniles and adults can move upstream and downstream freely. These movements include both within the SAC and into and out of it. The measures are likely to include the partial or complete removal of beaver dams. Further testing of flow device designs incorporating fish passes should be carried out before they can be routinely used.
- Actions to halt the beaver activity related deterioration of spawning habitat, e.g. through the accumulation of fine sediment upstream of a dam.
- Appropriate mitigation must be agreed and included in a beaver management plan before a reintroduction or translocation licence is approved.
If further research is undertaken to better understand how lamprey use the Endrick Water SAC and its tributaries (e.g. an intensive, catchment-wide assessment of the distribution of juveniles, or an extensive adult trapping programme), and how lamprey could be affected by beaver activity, more targeted mitigation could be developed.
Atlantic salmon
Atlantic salmon were assessed as being in unfavourable recovering condition during monitoring in 2011. More recent monitoring of the adult and juvenile stock components through the annual reporting of the likelihood of the site reaching its egg deposition targets for Atlantic salmon (Grade 2 for 2022), and through data gathered via the National Electrofishing Programme for Scotland, also suggests the population is in an unfavourable condition.
Population of the species, including range of genetic types for salmon, as a viable component of the site
Distribution of the species within site
Eurasian beaver have the potential to impact Atlantic salmon populations within the SAC. Beaver activity may be restricted to certain areas of the catchment (with river width <6 m and presence of potential core beaver woodland) but the locations of impacts may be coincident with vulnerable life history types of Atlantic salmon (the ‘Spring’ stock component). An adverse effect on site integrity cannot be ruled-out due to the potential undermining of this conservation objective.
The building of dams in areas where river widths are <6m may have a particularly significant impact on the Spring stock component or other fish which spawn in river tributaries which are narrow (i.e. <6m). Although Atlantic salmon are assessed for the Endrick Water SAC for the purposes of reporting on the likelihood that egg deposition targets will be achieved in any given year, these data are not divided into specific stock components. Any Spring fish data is only available at the Clyde Fishery District level. This is too coarse to be used at the scale of the Endrick Water.
Even if a dam does not form a complete barrier to upstream Atlantic salmon movement, delays caused by such an obstruction can increase the probability of predation, result in a loss of fish condition, and delay movement to a point where low water temperature becomes a physiological constraint. Juvenile Atlantic salmon occupy all areas of suitable habitat and barriers may slow or prevent their movement, or impact specifically on the downstream movement of smolts.
To maintain the distribution of Atlantic salmon in such areas it is important to ensure that the passage of fish past barriers is assured. This may be achieved through the easement or removal of barriers at certain times of year (e.g. during spawning time) or through the installation of measures such as flow management devices. However it is unclear whether such a device could be used to assist the upstream migration of large Atlantic salmon (which is typical of ‘Spring’ fish) as it has not yet been scientifically evaluated in Scotland in this regard and further trials are required.
Much of the Endrick Water SAC will not be suitable for beaver dam construction, either because it is too wide (beaver dams are generally built across stretches of water that are less than 6m wide), or because much of the lower and middle catchment lacks suitable woodland habitat. One area where greater vigilance may be required on the main stem of the river is the weir and fish pass at Gartness. Beaver dams within tributaries of the Endrick, where Atlantic salmon are found (e.g. Boquhan Burn, Catter Burn, Burn of Mar and Walton Burn and the Blane Water), could also impede fish movement to and from the SAC.
Distribution and extent of habitats supporting the species
In addition to potentially impacting movement within watercourses, barriers and other in-stream/riparian beaver activities may impact sediment transport within rivers and streams, either directly or by influencing the hydrology of affected watercourses. This can negatively impact the replenishment of Atlantic salmon spawning areas.
Structure, function and supporting processes of habitats supporting the species
As above, by impacting issues such as sediment transport and hydrology, Eurasian beaver may affect the structure, function and supporting processes of habitats in which Atlantic salmon live.
No significant disturbance of the species
There is potential for dam building and feeding-related activities of Eurasian beaver to impact on the life history of Atlantic salmon. The location, nature and degree of these impacts could be considered to be a significant disturbance to Atlantic salmon. This impact on their life history can also occur in man-made structures where facilities such as fish passes can be partially or wholly blocked by in-stream structures created by Eurasian beaver. The only significant man-made structure within the Endrick Water is the weir and fish pass at Gartness. This structure is currently in disrepair and the fish pass needs to be refurbished.
Conclusion
This appraisal suggests that the conservation objectives for Atlantic salmon could be undermined by the translocation of beaver to the Endrick Water SAC. Much remains unknown about the actual impacts of beaver activity on Atlantic salmon, in particular the passability and impact of dams on fish movement. Until more is known about the potential effects of beaver activity on Atlantic salmon the following mitigation would need to be employed to ensure that the integrity of the SAC would not be adversely affected:
- Monitoring to alert to beaver dam presence within the SAC and its tributaries.
- Measures to ensure that juvenile and adult Atlantic salmon can move upstream and downstream freely. These movements include both within the SAC and into and out of it. The measures are likely to include the partial or complete removal of beaver dams. The use of flow device designs incorporating fish passes remains untested and would require further testing before they could be used with confidence as a means of ensuring fish passage.
- Actions to halt the beaver activity related deterioration of spawning habitat, e.g. through sediment or gravel starvation below dams. Measures should ensure spawning areas can be recharged with new gravels from upstream.
- Appropriate mitigation must be agreed and included in a beaver management plan before a reintroduction or translocation licence is approved.
Further research to assess the actual impact of beaver dams on Atlantic salmon movement will further inform the need for, and scale of, future management interventions.
Glen Etive and Glen Fyne SPA
Qualifying features
Golden eagle (Aquila chrysaetos)
Conservation objectives
To avoid deterioration of the habitats of the qualifying species or significant disturbance to the qualifying species, thus ensuring that the integrity of the site is maintained; and
To ensure for the qualifying species that the following are maintained in the long term:
- Population of the species as a viable component of the site
- Distribution of the species within site
- Distribution and extent of habitats supporting the species
- Structure, function and supporting processes of habitats supporting the species
- No significant disturbance of the species
Appraisal
The Glen Etive and Glen Fyne SPA stretches over 81,372 ha. Potential beaver woodland habitat (as detailed in Annex B of the 2017 beaver HRA) makes up just over 309 ha of this. There is very limited connectivity between beaver and golden eagle due to their feeding and nesting habits and the conservation objectives for the site will not be undermined. It can therefore be concluded that beaver translocations to the River Leven catchment will not adversely affect the integrity of the Glen Etive and Glen Fyne SPA.
Loch Lomond SPA
Qualifying features
Capercaillie (Tetrao urogallus)
Greenland white-fronted goose (Anser albifrons flavirostris)
Conservation objectives
To avoid deterioration of the habitats of the qualifying species or significant disturbance to the qualifying species, thus ensuring that the integrity of the site is maintained; and
To ensure for the qualifying species that the following are maintained in the long term:
- Population of the species as a viable component of the site
- Distribution of the species within site
- Distribution and extent of habitats supporting the species
- Structure, function and supporting processes of habitats supporting the species
- No significant disturbance of the species
Appraisal
Capercaillie (Tetrao urogallus)
Capercaillie are no longer present in the Loch Lomond SPA, where they previously bred on the islands within the Loch. The UK capercaillie population is now almost entirely restricted to the Cairngorms National Park, and other than an extremely small population in Perthshire, all the other remaining small populations are north of the National Park. Based on this there seems little likelihood of the SPA being recolonised naturally in the near future.
As capercaillie are no longer present in the SPA any beaver translocations to the area will have no effect on the conservation objectives relating to maintaining the population as a viable component of the site, distribution of capercaillie within the site or significant disturbance of the species. However any beaver translocations should not prevent these conservation objectives from being maintained should capercaillie become re-established within the SPA in the future. To allow any future recolonisation/reintroduction of capercaillie to the SPA we need to ensure the 3rd and 4th conservation objectives are still met.
- Distribution and extent of habitats supporting the species
- Structure, function and supporting processes of habitats supporting the species
Beaver foraging activity in combination with grazing and browsing pressure from other herbivores could lead to a loss of supporting habitat on the islands. Grazing / browsing by herbivores is one of the pressures currently causing unfavourable condition of the Loch Lomond Woods SAC that covers the capercaillie habitat in the SPA. The added impacts of beavers could potentially exacerbate this, leading to the deterioration and / or loss of supporting habitat.
The Knapdale Beaver Trial monitoring suggested that beavers rarely moved more than 30m from waterbodies, so any loss of habitat is likely to be confined to a small proportion of the site. Therefore some loss or deterioration of supporting habitat on the margins of the islands is possible due to the combined impacts of beaver and other herbivores, leading to a change in the distribution of the habitat.
However the potential habitat loss/deterioration is likely to be low on the islands. It is also possible that the increased wetland areas created by beavers will provide improved brood feeding habitat.
Conclusion
The future recolonisation/re-introduction of capercaillie to the Loch Lomond SPA could potentially be undermined by any beaver translocations to the River Leven catchment without mitigation in place. Impacts are possible in areas of supporting habitat likely to be used by beavers (i.e. within c.30m of water-bodies), as a result of the cumulative impacts of beavers and other herbivores. Mitigation methods suggested to protect the woodland features of the Loch Lomond Woods SAC should also protect the supporting habitat of the capercaillie and avoid an adverse impact to the SPA conservation objectives.
Greenland white-fronted goose (Anser albifrons flavirostris)
This species was considered to be in favourable condition when last monitored in 2017 as part of NatureScot’s Site Condition Monitoring programme. The population at the time of notification was 237 individuals and counts by the Greenland White-Fronted Goose Study Group from 2017/18 to 2020/21 averaged 264 so the population is still in favourable condition.
Population of the species as a viable component of the site & Distribution of the species within site
Feeding sites: The geese feed in the marshes and on the rough rushy grassland within the Loch Lomond SPA, but more frequently range over adjacent farmland e.g. on wet and flooded pasture. Flooding caused by beaver dams in the SPA is unlikely to reduce the available feeding habitat for Greenland white fronted geese (Gw-fG) to a significant degree as they feed over a wider area outside the SPA. As this species feeds more often on semi-natural rushy pastures than most other geese species in Scotland, the creation of ‘beaver lawns’ and wetter pastures along the River Endrick within the SPA might actually increase the potential feeding areas for the geese.
Roosting sites: The geese roost on Loch Lomond, or on adjacent floodwaters near the mouth of the River Endrick. Increased flooding of habitats adjacent to the River Endrick is therefore unlikely to have any impact on roosting sites for GW-fG.
The conservation objectives for maintaining the population of the species as a viable component of the SPA, and distribution of the species within the SPA, will therefore not be undermined by the proposal.
Distribution and extent of habitats supporting the species & Structure, function and supporting processes of habitats supporting the species
A fairly broad range of habitats support the wintering population of GW-fG in the SPA and the geese are not dependent on any specific habitat or combination of habitats. They also use agricultural land outside the SPA.
No significant disturbance of the species –
Any beaver translocations will not cause significant disturbance for this species. However any proposals to increase or enhance visitor access to the area will need to consider whether there could be any potential impacts for this species.
Conclusion
Any changes in the distribution and extent of habitats within the Endrick Mouth area of the SPA caused by beaver activity are unlikely to undermine the conservation objectives for the site or have an adverse impact on the integrity of the SPA.
Can it be ascertained that the proposal will not adversely affect the integrity of a European site?
Beaver translocations to the River Leven (Loch Lomond) catchment will not adversely affect the integrity of the following European sites:
| European site | Qualifying feature |
|---|---|
| Glen Etive and Glen Fyne SPA | Golden eagle (Aquila chrysaetos) |
| Ben Lui SAC | Wet heathland with cross-leaved heath; Mountain willow scrub; Montane acid grasslands; Alpine and subalpine calcareous grasslands; Species-rich grassland with mat-grass in upland areas; Tall herb communities; Base-rich fens; High-altitude plant communities associated with areas of water seepage; Acidic scree; Plants in crevices on acid rocks; Plants in crevices on base-rich rocks |
Beaver translocations to the River Leven (Loch Lomond) catchment will also not undermine the conservation objectives for the following qualifying features:
| European site | Qualifying feature |
|---|---|
| Loch Lomond SPA | Greenland white-fronted geese |
The conservation objectives of the following European sites could be undermined by beaver translocations to the River Leven (Loch Lomond) catchment without any mitigation in place:
| European site | Qualifying feature | Mitigation needed |
|---|---|---|
| Endrick Water SAC | Atlantic salmon
| Monitoring to alert to beaver dam presence within the SAC and its tributaries. Measures to ensure that juvenile and adult Atlantic salmon can move upstream and downstream freely. These movements include both within the SAC and into and out of it. The measures are likely to include the partial or complete removal of beaver dams. Actions to halt the beaver activity related deterioration of spawning habitat, e.g. through sediment or gravel starvation below dams. Measures should ensure spawning areas can be recharged with new gravels from upstream. Appropriate mitigation must be agreed and included in a beaver management plan before a reintroduction or translocation licence is approved. |
| Endrick water SAC | Brook and river lamprey | Monitoring to locate beaver dam presence within the SAC and its tributaries. Measures to ensure that juveniles and adults can move upstream and downstream freely. These movements include both within the SAC and into and out of it. The measures are likely to include the partial or complete removal of beaver dams. Further testing of flow device designs incorporating fish passes should be carried out before they can be routinely used. Actions to halt the beaver activity related deterioration of spawning habitat, e.g. through the accumulation of fines upstream of a dam. Appropriate mitigation must be agreed and included in a beaver management plan before a reintroduction or translocation licence is approved. |
| Loch Lomond Woods SAC | Otter | Ensure any beaver dams do not impact on the passage of fish and so provide sufficient prey for otters. |
| Loch Lomond Woods SAC | Western acidic oak woodland | Monitoring should be carried out using the Woodland Herbivore Impact Assessment (WHIA) methodology and incorporating monitoring of beaver signs. This should be done through annual site checks and the results used to inform deer/livestock management. Where herbivore impacts are higher than ‘low’ further action is required. For beavers, licenced intervention could be considered where there is serious risk of damage to a conservation interest, but proactive mitigation in the form of selective tree protection is more likely, but is unlikely to be appropriate on a large scale. Hence the focus would be on ensuring the impact of other herbivores are sufficiently low to allow beaver presence. |
| Loch Lomond SPA | Capercaillie | As per Loch Lomond Woods SAC. |
With the appropriate mitigation in place beaver translocations to the River Leven (Loch Lomond) catchment will not adversely affect the integrity of a European site. This mitigation will need to be considered and secured as part of the consenting process for any applications to translocate beavers to the River Leven (Loch Lomond) catchment.
Section 2 - River Forth Catchment
The Environmental Report includes a description of the catchment.
Flanders Mosses SAC
Qualifying features
Active Raised Bog (priority habitat)
Degraded Raised Bog
Conservation Objectives
The conservation objectives for Flanders Mosses SAC can be found in full in the Conservation Advice Package along with other information about the site. The key elements to consider are as follows:
To ensure that the integrity of Flanders Mosses SAC is restored by meeting objectives 2a, 2b and 2c
2a. Maintain the extent and distribution of the habitat within the site
2b. Restore the structure, function and supporting processes of the habitat
2c. Restore the distribution and viability of typical species of the habitat
Appraisal
Although there is some overlap with potential habitat for beavers at Flanders Mosses SAC, lowland raised bogs (Active and Degraded) are unlikely to be significantly affected by beavers in a negative way as they are domed in structure and become isolated from the influence of surrounding groundwater sources. As they are entirely rainwater-fed, and typically higher than surrounding land they are therefore not impacted by beaver activity.
Some raised bogs also have scrub and willow growing on them, and although beavers would be likely to feed on some if they spent much time in their vicinity, neither the scale nor nature of the impacts would undermine the conservation objectives. Active and degraded raised bog at Flanders Mosses SAC are in unfavourable condition due to the cover of non-desirable woody species on the rand and margins of the bog. Tree felling and removal, particularly from the bog rand, is an active part of the current management of the site. The activities of beavers in felling trees, particularly broadleaves, would be complimentary to current management.
The conservation objectives for active and degraded raised bog will therefore not be undermined by any beaver translocations into the River Forth catchment and it can be concluded that any beaver translocations will not adversely affect the integrity of Flanders Mosses SAC.
Trossachs Woods SAC
Qualifying features
Western acidic oak woodland
Conservation objectives
The conservation objectives for Trossachs Woods SAC can be found in full in the Conservation Advice Package along with other information about the site. The key elements to consider are as follows:
To ensure that the integrity of the SAC is restored by meeting objectives 2a, 2b and 2c
2a. Maintain the extent and distribution of the habitat within the site
2b. Restore the structure, function and supporting processes of the habitat
2c. Restore the distribution and viability of typical species of the habitat
Appraisal
2a. Maintain the extent and distribution of the habitat within the site
The woodland is made up of a mosaic of woodland habitat types including wet woodland, possible wood pasture, upland ash woodland, scrub and open spaces. These habitats are closely associated with the oak woodland and are considered an interdependent part of the qualifying habitat. Grazing / browsing by herbivores is one of the pressures currently causing unfavourable condition at this site, and the added impacts of beavers could potentially exacerbate this, leading to the deterioration and / or loss of qualifying habitat.
The Knapdale Beaver Trial monitoring suggested that beavers rarely moved more than 30m from waterbodies, so any loss of habitat is likely to be confined to a small proportion of the site overall. However, given the nature of the site, including wooded islands and lochside woodland, loss or deterioration of qualifying woodland near waterbodies is possible due to the combined impacts of beaver and other herbivores, leading to a change in the distribution of the habitat.
2b. Restore the structure, function and supporting processes of the habitat
Younger age classes of the tree species characteristic of this site e.g. oak, birch, hazel ash and rowan are rare, due to long term grazing pressure. Palatable shrubs and palatable ground flora species are not found in the abundance that would be expected for this habitat type, due to long-term grazing pressure. Reduced shrub layer and increasingly sparse canopy cover caused by overgrazing could compromise the conditions required by some moss and lichen species.
Only a small proportion of this habitat, close to waterbodies, is likely to be used by beavers although, on flatter land, they may alter the terrain resulting in an increase in the area accessible to them. Change in the structure of accessible woodland areas is likely, but difficult to predict with accuracy at this point in time. Possible impacts include changes in the volume of deadwood, increases in dense young growth or in open space. Where regeneration of felled trees and shrubs is able to take place, these changes are most likely to be beneficial, contributing to the dynamism which is an important feature of this habitat. However, where regeneration is restricted by other herbivores, a negative impact on site integrity is possible.
Short, medium or long-term changes in the vegetative structure, and / or hydrology of localised areas of accessible woodland, as a result of beaver activity, is likely to increase the dynamism of woodland processes. Where regeneration of felled trees and shrubs is able to take place, this is likely to increase the overall conservation value of the site (for example, by increasing the amount of standing dead wood resulting from flooding, thereby increasing habitat for dead wood ‘typical species’). Such changes would be compatible with this conservation objective.
2c. Restore the distribution and viability of typical species of the habitat
The key tree species found in this habitat are oak (Quercus robur and/or Q. petraea) and birch (Betula pendula and/or B. pubescens). There is significant variation between individual stands whether they are dominated by oak or birch. Holly and hazel are also important components of the habitat. More fertile areas have ash trees, with a rich understorey, including dog’s mercury, broad buckler fern, wild garlic and wood sedge. Where ground water flushing occurs, alder dominates with sharp-flowered rush, marsh violet and yellow pimpernel. Whilst beaver may use any of these tree species, their palatability to other herbivores (and thus their ability to re-sprout after felling) varies. In general, birch is the least palatable to deer and sheep, with hazel and ash the most palatable.
Conclusion
The above appraisal suggests that the conservation objectives for the western acidic oak woodland feature of the Trossachs Woods SAC could potentially be undermined by beaver translocation to the River Forth catchment without any mitigation being in place. Impacts are possible in areas of qualifying habitat likely to be used by beavers (i.e. within c.30m of water-bodies), as a result of the cumulative impacts of beavers and other herbivores.
However if beavers begin to colonise the SAC, impacts could be monitored using the Woodland Herbivore Impact Assessment (WHIA) methodology and incorporating monitoring of beaver signs. The methods allow for some heterogeneity, but generally ‘low’ impacts are desirable for woodland restoration, although it is recognised they are not currently ‘low’ in many of the woodlands within the SAC. Where herbivore impacts are already too high, the woodland will already be in an unfavourable condition. Beaver presence could exacerbate this – but management of other herbivores may allow any beaver coppiced trees to regenerate. Herbivore management in the case of wild deer and goats is generally by a deer/herbivore management plan and of livestock via consents and management agreements. For beavers, licenced intervention could be considered where there is serious risk of damage to a conservation interest, but proactive mitigation in the form of selective tree protection is more likely, but is unlikely to be appropriate on a large scale. Hence the focus would be on ensuring the impact of other herbivores are sufficiently low allow beaver presence. It is advised that annual site checks would be necessary to ensure appropriate levels of herbivore impacts are maintained where beavers are present.
With the appropriate monitoring and herbivore management in place it would be possible to ensure that any translocations of beaver into the River Forth catchment would not adversely affect the integrity of the western acidic oak woodland feature of the Trossachs Woods SAC.
River Teith SAC
Qualifying features
Atlantic salmon
Brook lamprey
River Lamprey
Sea Lamprey
Conservation Objectives
The conservation objectives for the River Teith SAC can be found here. The key elements to consider are as follows:
- To ensure for the qualifying species that the following are maintained in the long term:
- Population of the species, including range of genetic types for salmon, as a viable component of the site
- Distribution of the species within site
- Distribution and extent of habitats supporting the species
- Structure, function and supporting processes of habitats supporting the species
- No significant disturbance of the species
Appraisal
Atlantic salmon
Atlantic salmon were assessed as being in unfavourable recovering condition during monitoring in 2011. More recent monitoring of the adult and juvenile stock components through the annual reporting of the likelihood of the site reaching its egg deposition targets for Atlantic salmon (Grade 2 for 2022), and through data gathered via the National Electrofishing Programme for Scotland (where it falls below the national benchmark) also suggests the population is in an unfavourable condition.
Population of the species, including range of genetic types for salmon as a viable component of the site
Eurasian beaver have the potential to impact Atlantic salmon populations. Beaver activity may be restricted to certain areas of the catchment (with river width <6 m and presence of potential core beaver woodland) but the locations of impacts may be coincident with vulnerable life history types of Atlantic salmon (the ‘Spring’ stock component). An adverse effect on site integrity cannot be ruled-out due to the potential undermining of this conservation objective.
Distribution of the species within site
The building of dams in areas where river widths are <6m may have a particularly significant impact on the Spring stock component or other fish which spawn in river tributaries which are narrow (i.e. <6m). Key Spring salmon spawning areas include the rivers Larig, Balvaig and Calair, although fish may also be found in other locations. The River Teith SAC is extensive, extending from the Forth catchment in the east to Loch Katrine in the west. It includes a wide range of river, streams and standing waters. In addition to the main stem of the River Teith SAC it includes Loch Lubnaig, Loch Voil, Loch Doine, Loch Venechar and Loch Achray. Smaller systems include Ardoch Burn, Annet Burn, Calair Burn River laig, Keltie Water, Collechat Burn, Garbh Uisge, Eas Ghobhain, Leny Burn, Allt a’ Ghlinne Dhuibh, Allt Fathan Glinne, Invernenty Burn, Allt Sgionie, Ishag Burn, Milton Glen Burn, Drunkie Burn, River Turk and Achray Water. All of these sites contribute to the Atlantic salmon feature of the River Teith SAC.
Even if a dam does not form a complete barrier to upstream Atlantic salmon movement, delays caused by such an obstruction can increase the probability of predation, result in a loss of fish condition, and delay movement to a point where low water temperature becomes a physiological constraint. Juvenile Atlantic salmon occupy all areas of suitable habitat and barriers may slow or prevent their movement, or impact specifically on the downstream movement of smolts.
To maintain the distribution of Atlantic salmon in such areas it is important to ensure that the passage of fish past any barrier is assured. This may be achieved through the easement or removal of barriers at certain times of year (e.g. during spawning time) or through the installation of measures such as flow management devices. However; it is unclear whether such a device could be used to assist the upstream migration of large Atlantic salmon (which is typical of ‘Spring’ fish) as it has not yet been scientifically tested in Scotland in this regard.
Distribution and extent of habitats supporting the species
Barriers and other in-stream/riparian beaver activities may impact sediment transport within rivers and streams, either directly or by influencing the hydrology of affected watercourses. This can negatively impact the replenishment of Atlantic salmon spawning areas.
Structure, function and supporting processes of habitats supporting the species
As above, by impacting issues such as sediment transport and hydrology, Eurasian beaver may affect the structure, function and supporting processes of habitats in which Atlantic salmon live.
No significant disturbance of the species
There is potential for dam building and feeding-related activities of Eurasian beaver to impact on the life history of Atlantic salmon, particularly in small upland waterbodies where woodland habitat is suitable for beaver. The location, nature and degree of these impacts could be considered to be a significant disturbance to the salmon. This impact on their life history can also occur in man-made structures where facilities such as fish passes can be partially or wholly blocked by in-stream structures created by Eurasian beaver.
Brook, river and sea lamprey
The 2016 Site Condition Monitoring (SCM) survey of brook, river and sea lamprey showed that the populations were in favourable condition. Due to the similar effects beavers could have on each of the species they are considered here together to avoid repetition.
Population of the species as a viable component of the site
Distribution of the species within site
Beaver activity that alters the flow or morphology of the streams and rivers that contain brook, river or sea lamprey habitat could affect both the viability and distribution of the species. Beaver activity could lead to changes in the populations and distribution of lamprey by altering the quantity, location or quality of their nursery or spawning habitat, or the ease with which they can undertake within-river or between river and estuary or sea migrations.
During surveys juvenile sea lamprey are ordinarily found in the lower, wider reaches of rivers; it may therefore be reasonable to presume that beaver activity is unlikely to affect them as it will generally occur in narrower stretches. However, there is some uncertainty about the true distribution of anadromous lampreys; the markedly low numbers caught suggest that the juveniles may occupy areas that are not included in assessments. Although surveys show that brook lamprey is more widely distributed than either of the anadromous species the same precautionary approach should be taken to protecting its distribution and density.
Distribution and extent of habitats supporting the species
Dam building and other in-stream or riparian beaver activity might affect sediment transport in rivers and streams, either directly or by influencing the hydrology of the affected watercourses. The changes might negatively affect nursery or spawning habitat. By trapping fine material that would have moved downstream to replenish nursery habitat beaver dams might lead to changes in the quantity, quality, and distribution of it. However, accumulations of fine material upstream of beaver dams might provide new nursery habitat. Similarly, accumulations of fine material upstream of beaver dams might smother spawning areas, but the reduction in fine material moving downstream might lead to the development of or improve spawning habitat which comprises clean, well-oxygenated gravel.
Structure, function and supporting processes of habitats supporting the species
As outlined above, beaver could affect sediment transport and hydrology and therefore the structure, functioning and supporting processes of habitats supporting lamprey.
No significant disturbance of the species
There is potential for beaver activity to negatively affect the life history of lamprey. For migrating adults, the severity of this impact may be significant if it impedes access to spawning habitat. Note that although they are not anadromous, even brook lamprey may undertake significant migrations upstream from nursery areas to spawning grounds (Maitland, 2003). The severity of impact may be less for juvenile lamprey if for example additional habitat is created through the in-stream and riparian activities of beaver.
Conclusion
This appraisal suggests that the conservation objectives for Atlantic salmon, and brook, river and sea lamprey, could be undermined by the translocation of beaver to the catchment of the River Teith SAC. Much remains unknown about the actual impacts of beaver activity on Atlantic salmon, in particular the passability and impact of dams on fish movement. Similarly while much remains unknown about brook, river and sea lamprey, including their distribution throughout the SAC, impacts are possible through changes to their habitat and also through barriers to movement. Until more is known about the potential effects of beaver activity on Atlantic salmon and lamprey the following mitigation would need to be employed to ensure that the integrity of the SAC would not be adversely affected:
- Monitoring to alert to beaver dam presence within the SAC and its tributaries. For Atlantic salmon particular attention should be focussed on those streams utilised by the Spring stock component (such as, but not exclusively, the rivers Larig, Balvaig and Calair).
- Measures to ensure that juvenile and adult Atlantic salmon and lamprey can move upstream and downstream freely. These movements include both within the SAC and into and out of it. The measures are likely to include the partial or complete removal of beaver dams. The use of flow device designs incorporating fish passes remains untested and would require further testing before they could be used with confidence as a means of ensuring fish passage.
- Actions to halt the beaver activity related deterioration of spawning habitat, e.g. through sediment or gravel starvation below dams. Measures should ensure spawning areas are maintained and can be recharged with new gravels from upstream.
- Appropriate mitigation must be agreed and included in a beaver management plan before a reintroduction or translocation licence is approved.
If further research is undertaken to better understand how lamprey use the River Teith SAC and its tributaries (e.g. an intensive, catchment-wide assessment of the distribution of juveniles, or an extensive adult trapping programme), and how lamprey could be affected by beaver activity, more targeted mitigation could be developed. Similarly further research to assess the actual impact of beaver dams on Atlantic salmon movement will further inform the need for, and scale of, future management interventions.
Can it be ascertained that the proposal will not adversely affect the integrity of a European site?
Beaver translocations to the River Forth catchment will not adversely affect the integrity of the following European sites:
| European site | Qualifying feature |
|---|---|
| Flanders Mosses SAC | Active raised bog Degraded raised bog |
The conservation objectives of the following European sites could be undermined by beaver translocations to the River Forth catchment without any mitigation in place:
| European site | Qualifying feature | Mitigation needed |
|---|---|---|
| River Teith SAC | Atlantic salmon Brook lamprey River lamprey Sea lamprey
| Monitoring to alert to the presence of beaver dams within the SAC and its tributaries. For Atlantic salmon particular attention should be focussed on those streams utilised by the Spring stock component (such as, but not exclusively, the rivers Larig, Balvaig and Calair). Measures to ensure that juvenile and adult Atlantic salmon and lamprey can move upstream and downstream freely. These movements include both within the SAC and into and out of it. The measures are likely to include the partial or complete removal of beaver dams. The use of flow device designs incorporating fish passes remains untested and would require further testing before they could be used with confidence as a means of ensuring fish passage. Actions to halt the beaver activity related deterioration of spawning habitat, e.g. through sediment or gravel starvation below dams. Measures should ensure spawning areas are maintained and can be recharged with new gravels from upstream. Appropriate mitigation must be agreed and included in a beaver management plan before a reintroduction or translocation licence is approved. |
| Trossachs Woods SAC | Western acidic oak woodland | Monitoring should be carried out using the Woodland Herbivore Impact Assessment (WHIA) methodology and incorporating monitoring of beaver signs. This should be done through annual site checks and the results used to inform deer/livestock management. Where herbivore impacts are higher than ‘low’ further management actions will be required. For beavers, licenced intervention could be considered where there is serious risk of damage to a conservation interest, but proactive mitigation in the form of selective tree protection is more likely, but is unlikely to be appropriate on a large scale. Hence the focus would be on ensuring the impact of other herbivores are sufficiently low to allow beaver presence. |
With the appropriate mitigation in place beaver translocations to the River Forth catchment will not adversely affect the integrity of a European site. This mitigation will need to be considered and secured as part of the consenting process for any applications to translocate beavers to the River Forth catchment.
References
Harrington, L.A., Feber, R., Raynor, R. and Macdonald, D.W. 2015. The Scottish Beaver
Trial: Ecological monitoring of the Eurasian beaver Castor fiber and other riparian mammals
2009-2014, final report. Scottish Natural Heritage Commissioned Report No. 685
Hartman G & Tornlov S (2006) Influence of watercourse depth and width on dam-building behaviour by Eurasian beaver (Castor fiber). Journal of Zoology (London) 268(2):127–131.
Jensen JK & Olsen OG (2004) Observations of the ability of brook lamprey Lampetra planari planeri to pass small dams in streams. Flora og Fauna, 110, 56-57.
Kemp PS, Worthington TA & Langford TEL (2010) A critical review of the effects of beavers upon fish and fish stocks. Scottish Natural Heritage Commissioned Report No. 349 (iBids No. 8770).
Maitland PS (2003) Ecology of the River, Brook and Sea Lamprey. Peterborough: Conserving Natura 2000 Rivers Ecology Series No. 5. English Nature.
Scottish Natural Heritage (2015) Beavers in Scotland: A report to the Scottish Government.
Shirley, M.D.F., Harrington, L.A. & Mill, A.C. 2015. A model simulating potential colonisation by Eurasian beaver (Castor fiber) following reintroduction to Scotland. Scottish Natural Heritage Commissioned Report No. 814.
Stringer, A.P., Blake, D. & Gaywood, M.J. 2015. A geospatial analysis of potential Eurasian beaver (Castor fiber) colonisation following reintroduction to Scotland. Scottish Natural Heritage Commissioned Report No. 875.
Stringer AP, Blake D & Gaywood MJ (2015) A review of beaver (Castor spp.) impacts on biodiversity, and potential impacts following a reintroduction to Scotland. Scottish Natural Heritage Commissioned Report No. 815.
Approval
This is subject to the mitigation identified in this appraisal being secured and effective before any adverse effects on the habitats and species listed are found.
John Kerr
Operations Manager Protected Areas, Innovation & Data (PAID) Activity
5 December 2022
