Using ecosystem engineers as tools in habitat restoration and rewilding: beaver and wetlands

Potential for habitat restoration is increasingly used as an argument for reintroducing ecosystem engineers. Beaver have well known effects on hydromorphology through dam construction, but their scope to restore wetland biodiversity in areas degraded by agriculture is largely inferred. Our study presents the first formal monitoring of a planned beaver-assisted restoration, focussing on changes in vegetation over 12 years within an agriculturally-degraded fen following beaver release, based on repeated sampling of fixed plots. Effects are compared to ungrazed exclosures which allowed the wider influence of waterlogging to be separated from disturbance through tree felling and herbivory. After 12 years of beaver presence mean plant species richness had increased on average by 46% per plot, while the cumulative number of species recorded increased on average by 148%. Heterogeneity, measured by dissimilarity of plot composition, increased on average by 71%. Plants associated with high moisture and light conditions increased significantly in coverage, whereas species indicative of high nitrogen decreased. Areas exposed to both grazing and waterlogging generally showed the most pronounced change in composition, with effects of grazing seemingly additive, but secondary, to those of waterlogging.  Our study illustrates that a well-known ecosystem engineer, the beaver, can with time transform agricultural land into a comparatively species-rich and heterogeneous wetland environment, thus meeting common restoration objectives. This offers a passive but innovative solution to the problems of wetland habitat loss that complements the role of beavers in water or sediment storage and flow attenuation. The role of larger herbivores has been significantly overlooked in our understanding of freshwater ecosystem function; the use of such species may yet emerge as the missing ingredient in successful restoration

Ecological effects of the feeding and construction activities of the Eurasian beaver (Castor fiber) in Scotland : implications for reintroduction

Beavers have been described as a “keystone species” and “ecosystem engineers”, and in this dual role have great potential to physically modify their environment through tree-felling, foraging and construction activities. The resultant change in habitat heterogeneity can affect the flora and fauna that share the habitat with them. There has been recent interest in reintroducing the Eurasian beaver to the United Kingdom after an absence of over 400 years. To date, no research (aside from this thesis) has focussed on beaver ecology and behaviour in Scotland. This study has investigated the ecological effects of a small number of beavers in two enclosed but semi-natural Scottish sites at Bamff in Perthshire. The research conducted over a three-year period, with particular emphasis on the effects of tree-felling, foraging and construction activities. Trees were felled for both dietary and construction purposes, with felling rates being influenced by habitat availability, quality and the degree of habitat modification required. Highest rates were evident during the initial colonisation period of marginal sites (c. >300 trees / beaver / calendar year), and lowest rates in later years of occupation of more optimal sites (c. 55 – 70 trees / beaver / calendar year). Preferences were generally for willow and aspen trees, with conifers almost entirely avoided, and smaller trees preferred over larger ones. Proximity of trees to waterbodies was also an important factor, with nearer trees favoured, and generally most felling occurred within 50 m of water. Such behaviour followed the principles of optimal central place foraging. These preferences were less predictable however when intense construction activity was undertaken, with larger trees preferred and generic preferences for deciduous trees apparently invalid. In such cases, close proximity to the construction site was of prime importance. Increased cover of herbaceous plant species was observed in beaver-created canopy gaps in riparian woodland, whilst macrophyte diversity within waterbodies increased slightly in areas of herbaceous grazing. The diversity of terrestrial ground invertebrates was highest in areas of heavy tree-felling, and invertebrate richness and abundance was greatest in areas of herbaceous grazing under an intact tree-canopy. Furthermore, the abundance, diversity and richness of macroinvertebrate communities were increased by beaver-generated woody debris in ponds and streams. Overall, 30% of all macroinvertebrate species collected were found only in beaver-affected areas, due to the refugia and food supply provided by beaver dams, caches and lodges, as well as hydrological effects of these structures. These results are discussed with reference to future plans to return the beaver to Scotland. The habitat usage and modification of riparian ecosystems in northern Britain is likely to be similar to that found in this study, and the results are believed to be relevant, applicable and transferable to many areas of Scotland.EThOS - Electronic Theses Online ServiceScottish Natural Heritage (CASE studentship)GBUnited Kingdo

Modelling Eurasian Beaver Foraging Habitat and Dam Suitability, for Predicting the Location and Number of Dams Throughout Catchments in Great Britain

Eurasian beaver (Castor fiber) populations are expanding across Europe. Depending on location, beaver dams bring multiple benefits and/or require management. Using nationally available data, we developed: a Beaver Forage Index (BFI), identifying beaver foraging habitat, and a Beaver Dam Capacity (BDC) model, classifying suitability of river reaches for dam construction, to estimate location and number of dams at catchment scales. Models were executed across three catchments, in Great Britain (GB), containing beaver. An area of 6747 km2 was analysed for BFI and 16,739 km of stream for BDC. Field surveys identified 258 km of channel containing beaver activity and 89 dams, providing data to test predictions. Models were evaluated using a categorical binomial Bayesian framework to calculate probability of foraging and dam construction. BFI and BDC models successfully categorised the use of reaches for foraging and damming, with higher scoring reaches being preferred. Highest scoring categories were ca. 31 and 79 times more likely to be used than the lowest for foraging and damming respectively. Zero-inflated negative binomial regression showed that modelled dam capacity was significantly related (p = 0.01) to observed damming and was used to predict numbers of dams that may occur. Estimated densities of dams, averaged across each catchment, ranged from 0.4 to 1.6 dams/km, though local densities may be up to 30 dams/km. These models provide fundamental information describing the distribution of beaver foraging habitat, where dams may be constructed and how many may occur. This supports the development of policy and management concerning the reintroduction and recolonisation of beaver

The response of a brown trout (Salmo trutta) population to reintroduced Eurasian beaver (Castor fiber) habitat modification

Globally, freshwaters are the most degraded and threatened of all ecosystems. In northern temperate regions, beaver (Castor spp.) reintroductions are increasingly used as a low-cost and self-sustaining means to restore river corridors. River modifications by beavers can increase availability of suitable habitat for fish, including salmonids. This study investigated the response of a population of brown trout (Salmo trutta) to reintroduced Eurasian beaver (Castor fiber) habitat modifications in northern Scotland. The field site comprised two streams entering a common loch; one modified by beavers, the other unaltered. Electrofishing and PIT telemetry surveys indicated abundance of post-young-of-the-year (post-YOY) trout was higher in the modified stream. Considering juvenile year groups (YOY and post-YOY) combined, abundance and density varied with year and season. In the modified stream, fork length and mass were greater, there was a greater variety of age classes, and mean growth was positive during all seasons. Beavers had profound effects on the local brown trout population that promoted higher abundances of larger size classes. This study provides important insight into the possible future effect of beavers on freshwater ecosystems

Intended Consequences Statement in Conservation Science and Practice

As the biodiversity crisis accelerates, the stakes are higher for threatened plants and animals. Rebuilding the health of our planet will require addressing underlying threats at many scales, including habitat loss and climate change. Conservation interventions such as habitat protection, management, restoration, predator control, trans location, genetic rescue, and biological control have the potential to help threatened or endangered species avert extinction. These existing, well-tested methods can be complemented and augmented by more frequent and faster adoption of new technologies, such as powerful new genetic tools. In addition, synthetic biology might offer solutions to currently intractable conservation problems. We believe that conservation needs to be bold and clear-eyed in this moment of great urgency

BHPR research: qualitative1. Complex reasoning determines patients' perception of outcome following foot surgery in rheumatoid arhtritis

Background: Foot surgery is common in patients with RA but research into surgical outcomes is limited and conceptually flawed as current outcome measures lack face validity: to date no one has asked patients what is important to them. This study aimed to determine which factors are important to patients when evaluating the success of foot surgery in RA Methods: Semi structured interviews of RA patients who had undergone foot surgery were conducted and transcribed verbatim. Thematic analysis of interviews was conducted to explore issues that were important to patients. Results: 11 RA patients (9 ♂, mean age 59, dis dur = 22yrs, mean of 3 yrs post op) with mixed experiences of foot surgery were interviewed. Patients interpreted outcome in respect to a multitude of factors, frequently positive change in one aspect contrasted with negative opinions about another. Overall, four major themes emerged. Function: Functional ability & participation in valued activities were very important to patients. Walking ability was a key concern but patients interpreted levels of activity in light of other aspects of their disease, reflecting on change in functional ability more than overall level. Positive feelings of improved mobility were often moderated by negative self perception ("I mean, I still walk like a waddling duck”). Appearance: Appearance was important to almost all patients but perhaps the most complex theme of all. Physical appearance, foot shape, and footwear were closely interlinked, yet patients saw these as distinct separate concepts. Patients need to legitimize these feelings was clear and they frequently entered into a defensive repertoire ("it's not cosmetic surgery; it's something that's more important than that, you know?”). Clinician opinion: Surgeons' post operative evaluation of the procedure was very influential. The impact of this appraisal continued to affect patients' lasting impression irrespective of how the outcome compared to their initial goals ("when he'd done it ... he said that hasn't worked as good as he'd wanted to ... but the pain has gone”). Pain: Whilst pain was important to almost all patients, it appeared to be less important than the other themes. Pain was predominately raised when it influenced other themes, such as function; many still felt the need to legitimize their foot pain in order for health professionals to take it seriously ("in the end I went to my GP because it had happened a few times and I went to an orthopaedic surgeon who was quite dismissive of it, it was like what are you complaining about”). Conclusions: Patients interpret the outcome of foot surgery using a multitude of interrelated factors, particularly functional ability, appearance and surgeons' appraisal of the procedure. While pain was often noted, this appeared less important than other factors in the overall outcome of the surgery. Future research into foot surgery should incorporate the complexity of how patients determine their outcome Disclosure statement: All authors have declared no conflicts of interes

Increasing frailty is associated with higher prevalence and reduced recognition of delirium in older hospitalised inpatients: results of a multi-centre study

Purpose: Delirium is a neuropsychiatric disorder delineated by an acute change in cognition, attention, and consciousness. It is common, particularly in older adults, but poorly recognised. Frailty is the accumulation of deficits conferring an increased risk of adverse outcomes. We set out to determine how severity of frailty, as measured using the CFS, affected delirium rates, and recognition in hospitalised older people in the United Kingdom. Methods: Adults over 65 years were included in an observational multi-centre audit across UK hospitals, two prospective rounds, and one retrospective note review. Clinical Frailty Scale (CFS), delirium status, and 30-day outcomes were recorded. Results: The overall prevalence of delirium was 16.3% (483). Patients with delirium were more frail than patients without delirium (median CFS 6 vs 4). The risk of delirium was greater with increasing frailty [OR 2.9 (1.8–4.6) in CFS 4 vs 1–3; OR 12.4 (6.2–24.5) in CFS 8 vs 1–3]. Higher CFS was associated with reduced recognition of delirium (OR of 0.7 (0.3–1.9) in CFS 4 compared to 0.2 (0.1–0.7) in CFS 8). These risks were both independent of age and dementia. Conclusion: We have demonstrated an incremental increase in risk of delirium with increasing frailty. This has important clinical implications, suggesting that frailty may provide a more nuanced measure of vulnerability to delirium and poor outcomes. However, the most frail patients are least likely to have their delirium diagnosed and there is a significant lack of research into the underlying pathophysiology of both of these common geriatric syndromes

The impacts of beavers Castor spp. on biodiversity and the ecological basis for their reintroduction to Scotland, UK

In Scotland, UK, beavers became extinct about 400 years ago. Currently, two wild populations are present in Scotland on a trial basis, and the case for their full reintroduction is currently being considered by Scottish ministers. Beavers are widely considered ‘ecosystem engineers’. Indeed, beavers have large impacts on the environment, fundamentally change ecosystems, and create unusual habi-tats, often considered unique. In this review, we investigate the mechanisms by which beavers act as ecosystem engineers, and then discuss the possible impacts of beavers on the biodiversity of Scotland. A meta-analysis of published studies on beavers’ interactions with biodiversity was conducted, and the balance of positive and negative interactions with plants, invertebrates, amphibians, reptiles, birds, and mammals recorded. The meta-analysis showed that, overall, beavers have an overwhelmingly posi-tive influence on biodiversity. Beavers’ ability to modify the environment means that they fundamentally increase habitat heterogeneity. As beavers are central-place foragers that feed only in close proximity to watercourses, their herbivory is unevenly spread in the landscape. In addition, beaver ponds and their associated unique successional stages increase habitat heterogeneity both spatially and temporally. Beavers also influence the ecosystems through the creation of a variety of features such as dams and lodges, important habitat features such as standing dead wood (after inundation), an increase in woody debris, and a graded edge between terrestrial and aquatic habitats that is rich in structural complexity. In Scotland, a widespread positive influence on biodiversity is expected, if beavers are widely reintroduced. For instance, beaver activity should provide important habitat for the otter Lutra lutra, great crested newt Triturus cristatus and water vole Arvicola amphibious, all species of conservation importance. Beavers are most likely to have detrimental impacts on certain woodland habitats and species of conservation importance, such as the Atlantic hazelwood climax community and aspen Populus tremula woodland. A lack of woodland regeneration caused by high deer abundance could lead to habitat degradation or loss. These are also of particular importance due to the variety of associated dependent species of conservation interest, such as lichen communities in Atlantic hazelwoods

Willow (Salix spp.) and aspen (Populus tremula) regrowth after felling by the Eurasian beaver (Castor fiber): implications for riparian woodland conservation in Scotland

1. A proposed trial reintroduction of the Eurasian beaver (Castor fiber L.) to Scotland has recently been approved (May 2008). A previous proposal was turned down by the licensing authority, partly over the perceived risks to woodland within a Special Area of Conservation.2. This paper presents data on two years of willow (Salix spp.) and aspen (Populus tremula L.) regrowth following tree felling by captive beavers within two large semi-natural enclosures in eastern Scotland. Both willow and aspen are highly preferred by beavers.3. Regrowth of willow stems was quantified from cut stumps, felled logs and partially severed (‘incompletely felled') trees, and compared with growth of stems in the canopies of untouched willows.4. Maximum annual regrowth was observed in incompletely felled trees, followed by cut stumps and then unfelled control trees. Mean regrowth rates were ca 18 m regrowth per metre of measured tree section per year in incompletely felled trees. This was approximately 12 times more annual regrowth than that observed in unfelled trees, despite apparently selective browsing of the regrowth of incompletely felled trees by roe deer.5. Although incompletely felled willows represent a relatively small component of felling activity (9% of all felled willow), they contribute disproportionately to the biomass of beaver-engineered riparian woodlands, creating a more multi-layered habitat structure.6. Willow regrowth in inundated areas was avoided by deer, and harvesting of regrowth by beavers was rare.7. Significant regrowth from 11 stumps of aspen in 2 years post-felling occurred by suckering, with 85 suckers of mean height 2.1 m being recorded, all of which were subsequently avoided by browsing deer and beavers.8. These data suggest that rapid regeneration of willow and aspen will occur in riparian woodlands in the event of major felling activity by Eurasian beaver, even in the presence of low to moderate levels of roe deer browsing, and that the conservation status of both these trees or the wider habitats that they form would not be threatened by a well planned and managed reintroduction of beavers to Scotland