Can rewilding reverse freshwater biodiversity loss?

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