Can rewilding reverse freshwater biodiversity loss?

Overview

Declines in biodiversity are occurring at an unparalleled rate, but particularly so in freshwaters due to their high connectivity to the surrounding landscape. There is a strong desire to reduce these losses through habitat creation and restoration but, despite the varied methods available for improving freshwater habitats, questions remain over their wider applicability and how the benefits observed compare with larger landscape level initiatives such as rewilding via species reintroductions.

Beavers were reintroduced to Britain after an absence of 400 years, and, as ecosystem engineers, have the potential to transform aquatic and riparian environments into heterogeneous wetlands, via dam building and selective foraging on trees and vegetation. Their effects on aquatic biodiversity are beginning to be documented (Law et al., 2016; Nummi et al., 2019), with positive effects demonstrated at the local and landscape scale based on selected species groups. With further beaver reintroductions being planned and carried out in Britain, alongside the expansion of current beaver populations, it is now imperative that evidence of their effects is contextualised within the toolbox of ecological restoration techniques. Individually, various restoration techniques have demonstrated improvements at the local and regional scales, but when all are combined with the aim of creating a heterogenous freshwater landscape, is the net effect on biodiversity and resilience greater than the sum of their parts?

This PhD project exploits the timely opportunities presented by the planned rewilding of 166 ha of an upland farm in Angus, Scotland. We have a history of working at this site extending for almost 20 years and excellent relationships with estate management. The site is extensively instrumented and the project can draw on a wealth of supporting data and knowledge assembled in our long-term research and a succession of PhD studentships. It also contains the highest density of beaver dams in the UK, following the release of animals in 2002 as part of a wetland restoration demonstration project and we have documented many of the changes since this time, e.g. Law et al. (2017). From 2021, beavers will be complemented by free-ranging herbivores used in conservation grazing, plus a suite of freshwater restoration techniques, including restoring old ponds and creating new ponds and scrapes, in addition to existing freshwater habitats such as streams, ditches, temporary ponds and a small lake. This site will be an exemplary demonstration of a freshwater landscape with restored ecological functions set within a naturalising agricultural landscape. As such it represents a pioneering project within the UK.

The overall aim of this PhD project is to quantify the effects of landscape rewilding on freshwater biodiversity. Specifically, the objectives of this project are to;
I. Assess the individual and landscape biodiversity value of multiple freshwater habitats.
II. Quantify the resilience, functional diversity and redundancy provided by disparate freshwater habitats and the restorative effects of interventions applied in different combinations.
III. Assess long-term changes in biodiversity associated with a cascade of beaver dams.

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Image Captions

An image of a beaver-created, highly heterogeneous wetland at the Bamff Estate. (C) Alan Law

Methodology

2020 is the final year of traditional farm management before significant restoration work is to be conducted during the winter and spring of 2021. The study will focus on spatial contrasts in biodiversity between new, restored and existing freshwater habitats situated in different landscape settings. Seasonal field campaigns will be conducted to collect samples from the full range of freshwater habitat types in Spring, Summer and Autumn.
In each campaign, the student will be expected to carry out quantitative biodiversity surveys for aquatic plants and freshwater macroinvertebrates. In addition, samples of water and aquatic plant biomass will be collected to estimate habitat productivity and quality. Standard survey techniques will be used to obtain biodiversity data (e.g. sweep netting) in addition to collecting relevant physico-chemical data e.g. age, shade, area, depth, velocity and water quality. The majority of samples will be analysed at the University of Stirling, but with bi-monthly trips to labs at UKCEH to learn specific lab techniques.
Once data are collated, the responses of landscape-level biodiversity, functional diversity and redundancy to habitat type and other variables will be assessed using several statistical techniques, including multivariate analysis, mixed models and variance partitioning.

Project Timeline

Year 1

Literature review; refine experimental and sampling design; stakeholder liaison, learn water and biological sampling methods including laboratory skills. Training needs assessment (e.g. statistical or identification courses).

Year 2

Sampling campaign. Processing of data in lab at Stirling and UKCEH. Collation with existing data.

Year 3

Data exploration, analysis and interpretation. Further statistical training. Conference attendance to present interim results.

Year 3.5

Refining data analysis. Paper and thesis writing. Conference attendance to present developed results.

Training
& Skills

The student will benefit from a mix of field, lab and computer skills all of which are professional transferable skills. Development here will be supported through IAPETUS specific provision and external courses. Example courses include; statistical analysis with R, Media Training; Insights to industry; Leadership skills; Conference skills (e.g., networking, poster and oral presentation skills); Geographic Information Systems; and Grant writing. The supervisory team are highly experienced in freshwater science and restoration ecology, with access to a breadth of facilities at University of Stirling and UK Centre for Ecology and Hydrology (Edinburgh), and also an inclusive and productive lab group and PhD cohort at Stirling and CEH. The student will also have the opportunity to engage with large research projects at Stirling and CEH involving their supervisors

References & further reading

Law, A., Gaywood, M.J., Jones, K.C., Ramsay, P., Willby, N.J., 2017. Using ecosystem engineers as tools in habitat restoration and rewilding: beaver and wetlands. Sci. Total Environ. 605-606, 1021-1030. https://doi.org/10.1016/j.scitotenv.2017.06.173

Law, A., McLean, F., Willby, N.J., 2016. Habitat engineering by beaver benefits aquatic biodiversity and ecosystem processes in agricultural streams. Freshw. Biol. 61, 486-499.

Nummi, P., Liao, W., Huet, O., Scarpulla, E., Sundell, J., 2019. The beaver facilitates species richness and abundance of terrestrial and semi-aquatic mammals. Glob. Ecol. Conserv. e00701. https://doi.org/10.1016/j.gecco.2019.e00701

Further Information

Serious applicants are strongly advised to make an informal enquiry about the PhD well before the final submission deadline.
For further information and informal enquires contact: Dr Alan Law, email: alan.law1@stir.ac.uk, telephone: 01786 467860.

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