CLM20-2 full issue-1 - Flipbook - Page 35
VIEWPOINT: Dams without beavers: could beaver dam analogues yield benefits in the UK?
they are not intended to be
permanent fixtures. They may
get breached or overtopped in
times of flood, and sometimes
they silt up to leave a ‘beaver
meadow’ which fosters particular
plant and animal communities.
Beavers abandon silted dams
and move on, and successions of
communities thrive through the
subsequent changes within the
system. Hence, BDAs should also
be seen as parts of a dynamic
system where collapse, repair or
replacement mimic what would
happen with natural beaver dams.
In the USA then, BDAs are
often used to quickly and
A beaver dam in Devon; natural dams and their associated habitats
cheaply initiate the restoration
are highly dynamic, which can add to their value to biodiversity.
of river ecosystems that have
Nick Upton/Alamy Stock Photo
been so badly degraded that
population, give a clue as to what the whole of
beavers may have difficulty recolonising them
the heavily farmed Radnor Valley must have once
even if they are present nearby. They are used to
been like.
reconnect the creek to its floodplain and to create
conditions that encourage the growth of riparian
Until recently, awareness of the historical
vegetation such that beavers may move in and
importance of beavers has, perhaps surprisingly,
take over.
been greatest in disciplines outside of ecology
and conservation science. The archaeologist
Bryony Coles, working on the Somerset Levels
River degradation in the UK
in the late 1970s, took an early interest in
The UK, by contrast with the USA, has been
beavers in the landscapes of prehistory (Coles
slow to recognise the impact that beavers
2006), while there has also been realisation
can – and historically did – have as ecosystem
among geologists that beavers are crucial to our
engineers, perhaps because much of the damage
understanding of naturally functioning river
was done in the more distant past. Although
systems. Worsley (2009), for example, states, ‘the
the changes to watercourses in the USA are not
importance of beavers in influencing geological
directly comparable with those in the UK, the
processes in floodplain environments is normally
North American experience alerts us to two
omitted in textbooks on fluvial geomorphology
critical realisations: the loss of the beaver and
and sedimentology; this is to the detriment of
the activities of humans have oversimplified our
a fuller and more realistic understanding of
waterways and, crucially, our watercourses have
fluvial environmental change in the Holocene
been disconnected from their floodplains, leaving
in particular’. As this kind of awareness has
our streams and rivers straighter, more deeply
developed, discoveries have been made that
incised and less complex (Bowles et al. 2021).
demonstrate the role of beavers centuries ago in
Beaver-mediated braided stream systems were
the creation of fertile land used for agriculture in
probably an important feature of our lowland
present-day Britain (e.g. Wells et al. 2000).
ecosystems but have since been entirely erased
Greater understanding of the influence of
by drainage and reclamation to make way for
beavers in Britain’s prehistoric landscapes
agriculture. Wetland fragments such as Burfa Bog
nature reserve in Radnorshire, for instance, which reinforces the view that their presence in the
UK should be expanded as soon as possible.
can safely be assumed to have once held a beaver
Conservation Land Management Summer 2022 | Vol. 20 No. 2 33
