Greening the Desert - Feral: Rewilding the Land, the Sea, and Human Life - page 82

than those in Europe, streams where beavers live harbour seventy-ive
times as many waterbirds as those without. 20
In both Sweden and Poland (where European beavers live), the
trout in beaver ponds are on average larger than those in the other
parts of the streams: the ponds provide them with habitats and shelter
they cannot find elsewhere. 21 Young salmon grow faster and are in
better condition where beavers make their dams than in other
stretches. 22 The total weight of all the creatures living in the water
may be between two and five times greater in beaver ponds than in
the undammed sections. 23 In Poland, beavers increase the number of
bats hunting around the rivers, both because the population of flying
insects increases as a result of their dams and their creation of swampy
ground, and because they make gaps among the riverside trees in
which the bats can hunt. 24 The trees they eat tend to be those which
coppice or sucker well, such as aspen, willow and ash. The scrub this
creates beside the rivers provides shelter for birds and mammals.
Our rivers, like the land, have suffered from intensive management.
They have been straightened and canalized, dredged and cleared. The
results have hurt both wildlife and people: by reducing the amount of
time that water takes to flow from the tributaries into the lower
reaches, we have ensured that the rivers are more likely to flood.
These policies often appear to have been informed by the same
impulse that has driven some farmers to destroy lone trees and archae-
ological traces: a desire for tidiness. In the catchment of the River Wye,
for example, the authorities spent large amounts of public money until
the late 1990s on the pointless task of dragging what they called 'tim-
ber blockages' out of the tributaries. These great nests of branches
took hundreds of years to accumulate. They were the prime habitat
for a wide range of species, including the young of the salmon for
which the river is renowned. Four hundred logjams were destroyed
before someone realized that the policy resulted in nothing but harm. 25
The programme is likely to have helped cause the continuing fall in
salmon numbers and the continuing rise in the number and intensity
of the floods plaguing the towns around the river's lower course. 26
Now the policy is being reversed. 'Let sleeping logs lie', the Wildlife
Trusts advise. 27 They point out that woody debris in rivers helps to
stabilize their banks and beds, that it traps sediments and provides