Page 13 - Natural World Spring 2017

Stephen said the adult beavers The beaver effect
were around the size of a cocker
spaniel but, looking at David’s cocker These three maps span 2011 Lodge
spaniel, Willow, I decided this was an five years of the Tamar
underestimation. The adult female beaver study. Their Fence Watercourse
beaver looked a fair match on the three hectare enclosure
scales for his labrador, Bracken. consisted of culm 2012 Pond
grassland encroached
As dark fell and the kits returned to by willow, birch and New pond Dam
the lodge, David and I walked back gorse, with a trickle of a
along the river in the direction of my stream. The beavers
car. David, who clearly had more quickly felled trees and
finely tuned hearing than me, built dams to create the
stopped abruptly every minute or deep water they prefer.
two to investigate a distant splash or Within a year there
a rustle in the reeds. I had to remind were eight ponds with a
myself not to get complacent about combined area of
this: in less than a week I had seen 900m2. The knock-on
three examples of an animal that, just e ects (see graphs
a few years ago, I’d assumed I’d below) were
never see here in during my lifetime. remarkable.

One of the dams The female had 2016 Marshy area
in made by the kits in 2013
Tamar beavers

MIKE SYMES Foraging channels
ELLIOTT, M., BLYTHE, C., BRAZIER, R., BURGESS, P., KING, S., PUTTOCK, A., TURNER,C., (2016) BEAVERS – NATURE’S WATER ENGINEERS. DEVON WILDLIFE TRUST.
More wildlife Frog spawn 600
Rainfall (mm/hour)clumps on site500
From mosses to 400
NICK UPTON/NATUREPL invertebrates to bats, a 300
wider range of species 200
used the site once the 100
beavers had got to
work. Particularly 2011 2012 2013 2014 2015 2016
impressive was the
dramatic yearly increase
in frog spawn clumps

Slower flow Flow (m3/sec) 0.12 Flow in and out of beaver site 00
0.10 10
Scientists measured I Rainfall 20
flows into and out of 0.08 I Flow above site 30
the beaver enclosure. 0.06 I Flow below site 40
The results showed how 50
the dams and ponds 0.04
hold water back. Across
a catchment, beavers 0.02
might be able to stop
floods being so severe. 3.45pm 4.15am 4.45pm

Less pollution I Above the site I Below the site

Intensively managed 200 4 0.1
farmland above the site
produced soil, nitrogen 100 2 0.1
and phosphate runo .
As the water slowed Mg/litre 0
through the ponds, Mg/litre Phosphate
a high proportion of Mg/litre
these pollutants were 0 0
filtered out. Sediment Nitrogen

SPRING 2017 NATURAL WORLD 13