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