Meeting Europe's renewable energy targets in harmony with - RSPB

RENEWABLE ENERGY TECHNOLOGIES AND ECOLOGICAL SUSTAINABILITY 21
Tidal range power. Tidal range power is risky from
a conservation perspective.”High head” shore-toshore
barrages, in particular, are likely to result in
significant losses of important intertidal habitats to
submersion and erosion (Box 8).
BOX 8
Potential impacts of a tidal power barrage
on the UK’s Severn Estuary
The Severn estuary and the rivers that feed into it contain
a wealth of biodiversity, supporting over 60,000 wintering
waders and wildfowl and several rare or scarce fish
species. This wildlife wealth has been recognised in a
series of national and international designations. The
Severn Estuary Special Protection Area (SPA) supports
internationally important numbers of Bewick’s swan,
gadwall, dunlin and redshank. The Severn Estuary Special
Area of Conservation (SAC) is important for a range of
habitats including sandbanks, mudflats, salt meadows and
reefs. SACs on the Severn’s major tributaries are important
for fish such as salmon, bullhead, lamprey and twaite shad.
Tidal power could make a significant contribution to the
urgent task of decarbonising the UK’s electricity supply.
However, the impacts on wildlife and the natural
environment could be very severe, depending on the way
the energy is harnessed. Tidal power barrages can
submerge and erode intertidal areas, harming wildlife and
potentially leading to increased flood risk. The 2008–10
Severn Tidal Power Feasibility Study showed that any
structure in the Severn is likely to cause harm to wildlife.
In particular, the so-called “Cardiff-Weston barrage” would
lead to 80% loss of internationally protected intertidal
habitat and cause 100% mortality of migrating fish
populations such as shad and sea lamprey in the Severn.
The study also noted that a Severn barrage would cause
changes to sediment erosion and deposition, resulting in
erosion of existing flood defences. The cost of revetment
works to address this for the Cardiff-Weston barrage
option was estimated at between £672 million and £2,015
million. The erosion problem is most acute in wide
estuaries with high sediment loads. The Eastern Scheldt
storm surge barrier in the Netherlands provides some
alarming lessons, revealed in a report iii by the
Rijkswaterstaat – part of the Dutch Ministry of
Infrastructure and the Environment. There the barrier has
had massive negative implications for wildlife and flood
risk management. By around 2050 the area of intertidal will
have halved. As intertidal areas in front of flood defences
are lost to erosion, flood risk increases, resulting in a need
for additional flood risk investment. As tidal flats are
eroded, the area and duration of their exposure for feeding
birds is reduced – Dutch Government calculations suggest
an 80% decline in oystercatchers by 2045.
New hydro power. Dams can have significant and
lasting impacts on wildlife if they disturb species
during construction, destroy habitat or create
dramatic changes in physical and hydrological
conditions. They can result in a permanent loss of
freshwater and terrestrial habitats, drainage of
wetlands and bogs, and subsequent loss of habitat
and species diversity. Large dams disrupt the
natural flows of rivers and migratory pathways of
fish such as salmon and eels. Dams and reservoirs
act as major sediment traps, interrupting natural
transport of sediments. Water level fluctuations in
reservoirs and the loss of habitat diversity can have
indirect impacts on birds by decreasing the
invertebrates and fish they eat or by flooding
or stranding their nests. However, some carefully
designed schemes, of appropriate scale and in
suitable locations, with fish-friendly turbines and
fish passes, may be able to avoid significant harm
to biodiversity.