severn barrage report

EnErgy at any pricE

Valuing the Severn as an international asset

Protecting Wildlife for the Future

What could happen to the Estuary? pp4/5

What’s at risk? pp6-15

How the Estuary works, pp16-19

The tidal power options, pp20-21

What’s the best way ahead? pp22/23

In this report

The Wildlife Trusts’ Severn Estuary report 32 The Wildlife Trusts’ Severn Estuary report

The vast tidal range of the Severn Estuary makes it one of the great natural wonders of the world. It has unique wildlife habitats shaped by the beautiful winding

rivers that run down from the Welsh hills to meet the sea of the Bristol Channel.

The Estuary provides a haven for the young of our commercial fish stocks, it is a means of transport and trade, it is the site of many recreational pursuits and by its very nature it brings enjoyment to people of all ages. It is all these things and more, and a glance through this report will provide the first-hand accounts of what the Estuary means to people who live their lives by its tides and nature.

The tidal range also makes it a huge potential source of energy. Proposals to use this potential, and concerns about the possible

Choose wiselyThe right tidal power solution must consider – and understand – the Estuary system as a whole

We believe the SETS options promise the best technology possible, with the least impact

Clevedon, eight miles up from the proposed Cardiff-Weston barrage. Intertidal habitat like this is the basis of the entire Estuary ecosystem, and contributes to other ecosystems in the UK and abroad

The

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impacts on the Estuary ecosystem, go back decades. So do warnings about the threat of climate change.

Now, quite suddenly, the need to reduce our greenhouse gas emissions has been recognised. What remains much less well recognised is the value of wildlife to people, and the urgency to restore our landscapes so that they are resilient to the impacts of climate change. The great risk is that the debate becomes one-dimensional.

This is why it is so vital that we make the right decision about harnessing the Severn: to capture the power of the water without blocking its full flow. In this way fish can still move and the tides can still ebb and flow for miles, creating huge mud flats and marshes.

There are five short-listed options currently under consideration – this report looks at each

in turn. The list includes three barrages and two lagoons which all look to impound seawater at high tide, letting it out again on the low tide. The Wildlife Trusts do not support any of these five options, and believe that a barrage from Cardiff to Weston would have a devastating impact.

More positively, there are also three more innovative options, known as the Severn Embryonic Technologies Scheme (SETS). These include a reef, fence and a new kind of barrage. None would block the flow of the

tide in such a devastating way. They therefore hold the most promise for the best technology possible, with the least impact. The Wildlife Trusts believe they must be researched further.

For decades, successive Governments ignored the pleas of environmentalists to address climate change. Now surely they must listen to us and ensure the right means of harnessing a fantastic resource without losing this wonder of the world.

Stephanie HilborneChief executive, The Wildlife Trusts

What could happen to the Estuary?The second biggest tidal range in the world makes it a strong candidate to supply renewable energy

The idea of harnessing the tidal power of the Severn Estuary is more than 100 years old, but it has never looked closer to becoming reality than today.

Under pressure to decarbonise energy production, the UK Government is considering a shortlist of five options.

There are three barrages (the huge Cardiff-Weston; the smaller Shoots Barrage; and the even smaller Beachley Barrage) and two lagoons (Bridgwater Bay and Fleming). For all five, the basic idea is the same: to build up a head of water at high tide behind a retaining

wall, and then let out the water through turbines to generate electricity. Some options have the potential to generate energy on the incoming tide too.

The Government is also investing in the Severn Embryonic Technologies Scheme (SETS). The SETS projects are less technically proven, but may create less environmental impact. They include a proposal for a tidal fence (essentially a line of marine turbines) and a tidal reef (using the rise and fall of the tides to generate power). There’s also a new kind of barrage, the Spectral Marine Energy Converter, that uses pillars rather than a solid

wall, thus allowing the water to flow in and out of the Estuary relatively freely.

Each of these schemes (see p20) comes with different costs, environmental impacts and energy outputs. Depending on the decisions made, harnessing the Estuary’s tidal energy could fundamentally change its ecology, affecting both people and wildlife.

It’s no exaggeration to say that the Severn Estuary is an irreplaceable part of the UK’s natural heritage. It boasts some of Europe’s finest natural habitats and wildlife, recognised and protected by international, European and UK laws and agreements.

It’s not just the sheer size of the place which makes it unique. Its fast-flowing, silty water has, over thousands of years, created an ecosystem unlike any other in the UK. Its workings are still only partly understood, (see pages 16-19), but that brown water and sticky mud are so productive that birds and fish migrate thousands of miles to feed there.

The Government’s job is to balance our energy needs against the Estuary’s ecological, recreational, social and cultural value. The Wildlife Trusts believe that any development should respect the intricate natural processes which have developed here over millennia.

Exmoor national park

n Minehead

n Bristol

n Barnstaple

n Weston-super-Mare

SHOrtLiSt OptiOnS

SEtS ScHEMES

1. Beachley Barrage2. Shoots barrage3. cardiff-Weston barrage4. Fleming lagoon5. Bridgwater Bay lagoon

6. tidal reef7. tidal fence (location a or b)8. SMEc (possibly a or b)

The Estuary is heavily protected by UK, international and European law. There are 228 Wildlife Trust nature reserves in the region, totalling 3,450ha, and 17 Living Landscape schemes covering 372,700ha, or 1,400 square miles. Up to 16 reserves

would be affected by construction of a barrage. Much of the Estuary is designated as a Site of Special Scientific Interest, a Ramsar site (a wetland of international importance), a Special Protection Area and a Special Area of Conservation.

Where are the proposed sites? Wildlife trust reserve

Wildlife trust Living Landscape Scheme

Sacs, Spas and ramsar sites (darker blue indicates multiple designations)

Heritage coast

proposed scheme location


A flock of curlew, fresh in from Russia, cross Bridgwater Bay National Nature Reserve as they wait for rich pickings at low tide

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The coastFar from bringing benefits, a tidal barrage is likely to make our coast less resilient against the effects of sea level rise

The end of archaeology in the Estuary?The Estuary’s interwoven layers of silt and peat have revealed evidence of human travel, settlements and trade dating back as far as the Stone Age. Much more could be discovered

Blocking the Estuary would dramatically alter the way the tides move silt around, leading to unexpected consequences

The Wildlife Trusts’ Severn Estuary report The Wildlife Trusts’ Severn Estuary report6 7

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Proposals for a barrage across the Estuary have been accompanied by considerable positive spin. The Estuary is claimed to have little ecological value, and local

communities have been convinced that there will also be major flood relief benefits. But are these assertions true? Evidence from barrages in silty estuaries in The Netherlands and Canada suggests otherwise.

It is argued that reducing tidal flow, and therefore the amount of sediment in the water, will lead to increased sediment deposition on foreshores. This deposition, combined with micro-algae blooming in the clearer water, is also presented as the solution to feeding displaced waterfowl.

the Estuary’s huge deposits of mud and silt are laid down upon one another and interleaved with peat bands very much like the rings of a tree. Every layer represents a particular episode in our past, from the fossilised footprints of Stone age hunter-gatherers walking across the muddy Estuary, through the complex wooden trackways built up until the Bronze age, to the roman-built ports along the coast that were further developed through Medieval times up until the present day. Uncovering this rich treasure-house of history within the

sediments is possible due to the natural waves and tides eroding small cliffs, allowing archaeologists access to the pages of time.

However, if the Estuary’s natural energy were to be blocked, foreshore erosion may initially increase and as water levels upstream of a barrage would be raised – caused by the deposition of sediments subtidally – these layers would become submerged and drowned. this wonderful window to the past would be shut tight.

Professor Simon HaslettUniversity of Wales, Newport

and influences the whole ecosystem. Technology that extracts some of this energy will inevitably affect the way the coast develops. The main impact will be to reduce sediment supply to the coast and to increase sedimentation in the subtidal area. This means that putting any structure in the Estuary will lead to some degree of erosion.

In the long term this process has important implications for flood defences and other coastal structures such as ports, railway lines and roads. Far from bringing flood defence benefits, tidal energy structures are likely to make our coast less resilient in the face of sea level rise.

Roger MorrisCoastal management consultant

These arguments are very attractive, but they overlook the lessons arising from relevant schemes elsewhere. Both the surge-tide barrage across the eastern Schelde in The Netherlands and the tidal power barrage at Annapolis Royal in Canada have resulted in foreshore erosion, rather than deposition. These examples show how removal of energy from coastlines has unexpected consequences. Flood defences are likely to be undermined in the long term and waterfowl populations can be expected to decline further, as foreshores become less muddy rather than muddier.

The ecology and the shape of the Estuary are constantly changing due to the complex interchange of water and sediment. This regime distinguishes it from other estuaries

In the long term, extracting energy from the Estuary

has implications for ports, railway lines and roads

David W

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The BoreThe Estuary is exceptional for fishing and birdwatching. And the Severn Bore is one of the UK’s greatest natural phenomena

As dawn breaks over Gloucestershire a strange scene unfolds in a pub car park. This is Arlingham on the banks of the Severn, but it is a sight more

commonly associated with the beaches of Devon and Cornwall. Men and women are donning wetsuits, waxing their surfboards and entering the waters of the river.

The opposite bank is already thronged with people holding video cameras and binoculars. Everyone is gazing downstream, straining to be the first to glimpse the oncoming tide. But it’s their ears that sense it first. Initially a dull

rumble, the sound intensifies until by the time the Severn Bore is visible, rounding the final bend, it sounds like an approaching train.

The surfers clamber onto their boards. For some, it will be the longest ride of their lives; a few have managed over six miles. The spectators are about to witness one of the UK’s most spectacular natural phenomena.

The Bore is born in the funnel-shaped, strongly tidal Estuary. The massive incoming tide is squeezed into a smaller and smaller space until the water has no choice but to pile up, forming a wave that travels upstream for more than 30 miles, at speeds of up to 15mph.

Over the ages the Bore has become part of the river’s ecosystem. But it’s also important to people. Many businesses benefit from the tourism the Bore creates, whilst salmon and elver fishermen rely on it for their livelihood.

The Bore is also incredibly important to the surfers that ride it. As well as the hundreds of coastal surfers who come for the largest tides there is a tight-knit group who organise their lives around the lunar cycle, so that they can be in the river the next time the Bore rounds that bend. But a device that reduces the river’s tidal range would eliminate all that.

Dave Butterton, Bore surfer

The Estuary provides many forms of recreation. Its landscape brings walkers and sightseers from all over Wales, the South West and the Midlands

It’s quite possible to spend a lifetime birdwatching in the Estuary (see page 14). Hundreds of species, some from half way round the world, pass through

More than 100 species of fish are found in the river Severn and its Estuary. Some of the most sought- after species migrate into its eight tributary rivers

About 80 times a year the incoming tide and

the Estuary’s funnel shape create the

Severn Bore – and the chance to surf for

miles in fresh water


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Mike Lane

Andrew

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Our fish stocksIt’s not just salmon. Eel, shad, lamprey and sea trout must all move between fresh and salt water to survive


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Nigel Mott and Dave Merrett are not your typical retired industrial chemist or civil engineer. They are modern day hunter-gatherers, fishing the

river day and night using ‘putchers’ – rows of conical baskets fixed to the river bed to trap unwary salmon. Although the baskets use modern-day stainless steel, their design and function are no different from the wicker structures that have caught salmon here sustainably since the Iron Age.

“We established the fishery here in 1975 with a National Rivers Authority licence,”

says Nigel. “It was the first time it had been done on this site since 1861, though there are about 20 other fishing stations in the Estuary. We installed the stainless steel baskets in 1985, with pilings driven into a concrete base.

“When the salmon enter the Estuary system, they swim up and return on average 15-20 times before finally working their way upriver. Higher temperatures and pollutant run-off can reduce the likelihood that the salmon will head upstream.”

Maintaining the fishery takes three or four hours twice a day, starting an hour after high water, clearing the 650 baskets of seaweed,

rubbish and (occasionally) fish. Salmon fishing might sound romantic, but it is hard work.

Both men support the need to move towards non-fossil energy generation, but are nervous of the effects of turbines on migratory fish. “If the salmon swam straight up the Estuary and entered fresh water straight away, then many might survive,” Nigel believes. “But if they swam through turbines a number of times it would increase the risk of mortality to an already depleted stock. Our fishing would be devastated in quite a short time.”

As would the sport of thousands of game fishermen along the Severn and its tributaries.

If the salmon swam through the turbines it would increase

the risk of mortality on an already depleted stock

Collecting fish and cleaning

off debris is an all-weather job

Around 20 fisheries in the

Estuary sell locally-caught

wild salmon

Atlantic salmon hatch in clear, clean gravel beds upstream before travelling downriver to the ocean to feed and grow. Two or three years later, they’ll return to breed in the same place

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The life sourceIt’s easy to overlook what mudflats really are. In fact they’re the Estuary’s power source, swarming with life, and sustaining... us!

In this picture alone there are countless millions of animals just below the surface – waiting to eat, or be eaten

From flotsam to protein


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Dig down an inch, scrape up a square metre of estuarine mud and you’ll be holding the calorific content of 13 Mars bars. So someone told me once

and, while I’m not sure it’s true, it certainly goes some way to pointing out just how important that mud is!

You see, mud is all the best bits of the land, donated via our rivers and then dropping out of suspension as the water flow slows. This nutrient-rich soup then feeds the system which we all need – whether we realise it or not.

If you’re a doubter, you need to (safely) access some of the glorious stuff – to scoop up a cupful and sort through it in a tray of sea

diatoms (microscopic plants) and algae. And that’s why countless visiting or resident birds frequent the exposed flats betwixt the tides, and why these estuarine habitats are a vital nursery ground for many fish – including commercially valuable ones.

water. Let it settle out for a few minutes, and soon you’ll notice mysterious animations: wriggling and writhing bodies, limbs and gills all etch their hieroglyphics in the silt.

From the more obvious worms of the rag and lug variety (I think they look like miniature Chinese dragon dancers) to small clams, Corophium shrimp and my favourite (and that of the shelduck) the miniscule laver spire shell. All these creatures add up to a sum greater than its parts.

The mud may not look like much from a human perspective, just a monotonous plain. It is actually one of the most productive habitats on Earth, thanks to the activities of the above characters, plus the even smaller plant lives being lived out in there – the

A mudflat may look like a monotonous plain, but it is

actually one of the most productive habitats on Earth

Nick Baker is a zoologist best known for his wildlife programmes with the BBC, Channel 5, Granada and Animal Planet. He is also a vice president of The Wildlife Trusts

A pile of estuarine debris: recently deceased crab mixed up with freshwater reed stems. It’ll all be eaten in the end by the mud-dwelling worms, shellfish and prawns...

...who in turn must take their chances with the feathered

predators who want to eat them. High tide

provides no relief: it just means the fish

are moving in where the birds left off

David W

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David S

later

Refuge for birdsThey arrive by the thousand, from Canada, Africa and Russia. And they come to the Estuary for food, rest and shelter

Like many visiting waders, knot gather

in the Estuary in huge flocks


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I have watched birds on the Gloucestershire sector of the Severn Estuary since I was ten, when I made the 50-mile round trip by bicycle every weekend. Some early highlights arouse

fond memories: that snow bunting in October 1953, or the red-throated diver at high tide in January 1956. But it’s the regular visitors which leave the lasting impression.

For example, Slimbridge is a winter refuge for white-fronted geese and thousands of wigeon, teal and pintail, which migrate every year from Russian breeding grounds to the terminus at the westernmost end of their 3,000 mile flyway. In the cold winter of 1962 they were joined by a massive arrival of Russian Bewick’s swans, which have

hatch their young; within a few days the adults leave, arriving on the Severn in late July or August before moving on to places such as the Banc d’Aguin in Mauritania, or even South Africa. Their young find their own way a month or so later.

Quite apart from the navigational feat, the physiological performance is exceptional; both young and adults put on half their body weight in fat to enable them to make these

continued to come ever since, though like the whitefronts their numbers have decreased.

The Severn is also an essential refuelling stop for long distance migrants that winter in sub-Saharan Africa and pass through the UK twice: in spring, on their way to Arctic breeding grounds in Canada and the Russian tundra; then again in early autumn on their way back. Waders like bar-tailed godwit or little stint use the short tundra summer to

The adults leave their young in the Arctic, arriving on the Severn in July before moving on to Africa

flights. They use up this extra fat in migration, so stops in biologically rich estuaries are vital. Then, having wintered in warmer climes, they are back on the Estuary the following spring, together with other waders like whimbrel which gather in the western UK to refuel, en route to their Icelandic nesting grounds.

In cold snaps the Estuary’s brackish water remains ice free, attracting birds from inland sites like the Somerset Levels or the Severn Vale. Waders such as lapwing or golden plover, together with ducks from riverside marshes, flock to the Estuary at these times.

In every way, then, the Severn Estuary is a bird site for all seasons.

Mike Smart, TrusteeGloucestershire Wildlife Trust

Besides the huge flocks, the rarities. This is a

pomarine skua, pausing half way between the far

North and the tropics

David S

later

How the Estuary ecosystem worksIt all begins with washed-in organic debris. Then the mud dwellers get to work

WiLDLiFEHaBitatS

tUrn tHE pagE FOr tHE Main EFFEctS

On OtHEr EcOSyStEMS

Large tidal range

Large intertidal area

Lots of suspended material

nutrient rich

Strong currents

Highly productive habitats

Saltmarsh

Sandbanks

Mudflats rich in wildlife

rock and shingle shoreline habitats

Low and high salinity water

Shallow sandbanks

Silt laden currents

Muddy seabed rich in wildlife

Shallow water-churned seabed

cHaractEriSticS

EXpO

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rtiD

aLSU

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ZOnES

the key feeding zone: birds at low tide, fish at high tide

the humble lugworm. Estuary mud and sand contains relatively few species, but in huge numbers

the silty water looks lifeless but, as this salmon trap shows, is a corridor and food supply

plant plankton Mid-waterfish

wormsSand-dwelling

animal plankton

plant communitiesalgal and

The Severn Estuary is a hugely productive place, but that productivity isn’t driven directly by green plants and the sun. Instead the Estuary acts like a gigantic reprocessing plant, using as its raw material plankton and flotsam washed in from the sea and tributary rivers, plus churned-up sand-dwelling microscopic plants. In the mud and silt of the intertidal zone (between high and low tide), billions of invertebrates and bacteria convert this debris into protein.

With fast, silt-laden currents in the central channel, most of the predation happens in the intertidal zone. The fish grab the worms and shellfish at high tide, with the prawns and crustaceans hoovering up the bits; six hours later it’s the birds’ turn.

Most of the Estuary’s ecology happens in the intertidal zone. Reduce its extent, and you lose most of that huge productivity, with knock-on effects to ecosystems elsewhere. Overleaf shows where they are.


David Chapman

David Chapman

Rick Park

Paul Naylor

crustaceansPaul Naylor

Bottom-dwellingfish

Paul Hobson

Sand-dwellinginvertebrates

Hans Hillewaert

Fish

Paul Naylor

Birds

David Slater

David Slater

Anson MacKay

Rick Park

Shellfish

Neil Hepworth

David W

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avid Woodfall

Sea mammalsFlorian Graner

Nature PL

VITAL STATISTICS OF THE ESTUARy ECOSySTEMestimated tonnes of sediment carried up and down the Estuary on a spring tide

visiting birds, either sheltering from the arctic winter or refuelling during their spring/autumn migration between north and south hemispheres

hectares of the Severn Estuary in total, making it one of the largest in Europe

hectares of mud and sand flats – the fourth largest expanse in the UK

years of sedimentation evidence in the Estuary – a valuable geomorphological and archaeological history

hectares of rock, boulder, mussel/cobble scars, rocky pools and shingle

hectares of salt marsh – the largest expanse in the South West

species of fish found in the Estuary

species of commercial fish use the Estuary in their life cycle: herring, cod, plaice, sole, whiting, blue whiting, hake, horse mackerel, ling and saithe

10,000,00069,00024,70020,9585,0001,5001,400

100+10

David Chapman

Otherinvertebrates

Sand-dwellingdiatoms

The local effectAnimal movements disperse large quantities of energy and material from the Severn Estuary to neighbouring systems in the region. The key areas to benefit are the rivers Parrett in Somerset, Usk in Wales, the Wye either side of the border, and the Gwent and Somerset Levels

Eels After maturing in fresh water, adults swim across the Atlantic to spawn and die in the Sargasso Sea. The larvae are thought to return on North Atlantic currents. Numbers of eels have declined hugely in recent years, for reasons which are not fully understood.

Birds With several dozen species and sub-populations involved, the routes shown here are hugely simplified. But essentially there are three sorts of bird migration through the Estuary.

The spring passage from Africa, branching west to breeding grounds in Iceland and Greenland, or east to northern Europe and Russia.

The return journey, from late June to October, by adults and young.

The winter visitors, which don’t go further south than the Estuary, and return north in spring to breed.

Salmon Principal feeding grounds are north of the Faeroes; adults are at sea for up to four years. Most populations are in decline. The sea trout, another migrant, is thought to stay near the UK coast, as do the allis and twaite shad (the Severn shad is a genetically distinct species).

Bar-tailed godwits: 300 grams of pure energy

Little is known of the eel’s migration routes

Reasons for salmon declines are complex

1918 The Wildlife Trusts’ Severn Estuary report The Wildlife Trusts’ Severn Estuary report

Dispersal happens across the UK too

The global impactBirds and fish disperse the Estuary’s energy and productivity to ecosystems across the globe

The previous pages explain how the Estuary generates very large amounts of biomass (the sheer weight of living things), most of it from the intertidal zone.

Because most of the Estuary’s predators are highly mobile fish and birds, they effectively transport the energy and material they pick up in the mud to other places. This energy and material is carried in these animals’ body tissues and guts, and transmitted via their participation in other ecosystems where they feed, are fed on, and eventually die and decompose. Millions of fish and birds moving around is impressive enough, but they keep up

these movements year after year, and the cumulative effect is astronomical. Without the Severn’s effect as a stopover and refuel facility, for example, the Arctic tundra couldn’t support so many migratory waders. Without its effect as a huge fish nursery, the Celtic Sea (and the Atlantic Ocean beyond) could not support so many salmon, sprats or mackerel.

This extreme interconnectedness is what makes altering the Severn’s intertidal habitat so risky. Does the Estuary’s energy prize justify severing these global wildlife links, with their benefits to people which are not yet fully understood?

The Gwent LevelsHabitat for a huge diversity of birds. Many are reliant on the Estuary’s mudflats for their source of food

Repro please change

“Weston-Super-Mare: to

‘Weston-super-Mare”

The Severn’s tributaries The rivers are fine habitats for resident and migratory fish which feed in (and pass through) the Estuary

The Somerset LevelsThe Levels and the River Parrett are excellent habitats for resident and migratory birds, many of which feed in the Estuary

iStock Photo

Colin Varndell

Laurie Cam

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Habitat loss 3500ha% within protected area 100%Claimed power 0.625 GWConstruction cost £2.3bnCO2 savings per year 0.7mtCost per unit of energy 12.6p/kWh

Beachley BarrageHabitat loss same or less than Fleming, but no fish passage to the upper Severn and the Wye SAC. Wholly within the cSAC, SPA and Ramsar, so significant loss of habitat and disturbance during construction.

Shoots BarrageSmallest barrage, lowest adverse impact, but lowest energy potential too. Located above the Wye, so fish passage to SAC rivers still possible. Wholly within the cSAC, SPA and Ramsar, so significant loss of habitat.

Habitat loss 5000ha% within protected area 100%Claimed power 1.05 GWConstruction costs £3.2bnCO2 savings per year 1.2mtCost per unit of energy 10.4p/kWh

Cardiff-Weston Barrage

SHORTLISTED

SHORTLISTED SETS OPTION SETS OPTION SETS OPTION

SHORTLISTED SHORTLISTED SHORTLISTED

Habitat loss 20,000ha% within protected area >95%Claimed power 8.64 GWConstruction costs £20.9bnCO2 savings per year 7.2mtCost per unit of energy 12.9p/kWh

Highest energy and overall impact, with far more intertidal habitat loss than any other option. Fish passage to all tributary rivers impeded, leading to likely regional extinction of Atlantic salmon and twaite shad.

Fleming LagoonHabitat loss 6500ha% within protected area 100%Claimed power 1.36 GWConstruction costs £4bnCO2 savings per year 1.0mtCost per unit of energy 15.5p/kWh

The longest structure, all of it in cSAC. Impacts to migratory fish and freshwater habitats likely to be less than barrages, but would greatly affect erosion and sediment movements around the wall.

Habitat loss 5000ha% within protected area 100%Claimed power 1.36 GWConstruction costs £3.8bnCO2 savings per year 1.1mtCost per unit of energy 13p/kWh

Bridgwater LagoonExtends across smaller proportion of Estuary than Fleming Lagoon, so likely to have less impact on erosion and siltation. Impedes fish migration to Rivers Parrett, Cary and Brue. Relatively low carbon saving.

Habitat loss 8600ha% within protected area 0%Claimed power 5 GWConstruction costs £18.7-19.8bnCO2 savings per year 5.6mtCost per unit of energy 20.3p/kWh

Tidal ReefLeast technically developed option, so estimate for intertidal loss likely to be less accurate. Turbines likely to turn more slowly than in barrages and lagoons, posing a lower risk to fish. Large footprint is outside cSAC.

Habitat loss 2800ha% within protected area 0%Claimed power 1.2 GWConstruction costs £6.5-6.9bnCO2 savings per year 1.4mtCost per unit of energy 22.72p/kWh

Tidal FenceRelatively low impact over a wide area. Partial barrier and low turbine speed less harmful to migratory fish. Less impact on siltation/erosion too, due to constant flow. Large construction footprint, outside cSAC.

Habitat loss not known% within protected area not knownClaimed power not knownConstruction costs not knownCO2 savings per year not knownCost per unit of energy not known

Spectral Marine Energy ConverterA series of pillars supporting a causeway road. Structures in the pillars use very high speed turbines to generate electricity. Tidal flow is only partly impeded. Data and location not yet available.

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The optionsThere are five on the shortlist, with three SETS options needing further research. Here are their environmental, energetic and cost analyses

20 21The Wildlife Trusts’ Severn Estuary reportThe Wildlife Trusts’ Severn Estuary report

These are the choices facing the UK Government as it tackles our climate change targets. Each options will affect the Estuary’s protected species and habitats.

However, The Wildlife Trusts believe the decision should be taken on the basis of least environmental damage and best cost effectiveness.

2. Change the way sediment moves around. Different erosion and deposition patterns are likely to greatly alter the quality and extent of marine habitats, and of the surrounding coast, but the Estuary’s physical processes remain largely unstudied.

3. Threaten populations of migratory fish.Estimates of what the impacts might be are hampered by a lack of baseline data.

In general the proposals create three adverse impacts, none of them well understood:

1. Reduce upstream tidal range. This is likely to depress the productivity of the mud-based food webs, affecting everything higher up the food chain – including people. Estimates of intertidal habitat loss vary hugely, from 2,800ha (Tidal Fence) to 20,000ha (Cardiff-Weston barrage).

Despite these uncertainties the Cardiff-Weston Barrage would, without question, have by far the highest environmental impact. The smaller barrages and two lagoon schemes (in their various forms) would be likely to have an intermediate impact. The SETS options (labelled in green below) would have the lowest impact.

The Government’s own environmental report expresses low confidence in the possibility of minimising the impacts of a barrage or lagoon development, and in creating compensatory habitat. In fact it describes the chance of finding like-for-like habitat elsewhere as ‘impossible’. Any habitat creation, it admits, would have to be on an ‘unprecedented’ scale.

The Wildlife Trusts want to ensure the chosen option will not be something that society regrets in decades to come.

twenty miles from the sea, the Severn Bore

sweeps upstream. But for how much longer?

WHat tHE acrOnyMS MEanSAC = Special Area of Conservation cSAC = candidate Special Area of ConservationSPA = Special Protection Area Ramsar = internationally important wetland

What kind of a world do we want to live in?It is time to understand that we are part of nature, not outside of it

Starlings at sunset, second

Severn crossing

It is self-defeating to view our energy needs in isolation from our natural environment

22 23The Wildlife Trusts’ Severn Estuary reportThe Wildlife Trusts’ Severn Estuary report

We are becoming more and more aware of the impacts which our everyday lives have on the environment in which we find ourselves.

We must now take the next step: to realise that yes, we are part of our ecosystem – not some separate entity existing apart from the fish, the birds, the worms and the mud.

This understanding changes our idea of the world we want to live in. Of course we need energy – and the Severn Estuary presents an exciting and all too tempting option to provide a large slice of the UK’s renewables. But we cannot view our energy needs in isolation from our environment. To do so could easily be self-defeating. Why should this be so?

wrong decisions are taken in the Severn – the wrong technology selected, in the wrong places – then renewable energy has the potential to destroy all that we rely upon.

That destruction would not only affect the Estuary’s internationally recognised wildlife and habitats. The shape and structure of the Estuary itself would change, and this could have serious consequences for our flood defences. Then there are the ‘silent’ impacts –

As climate change takes hold, the changes in our environment are becoming ever more apparent. We must therefore ensure that our environment is one that can adapt to these global changes, not decline under growing pressure. For this to happen we need to create both a Living Landscape and Living Seas – our vision for the future.

We often think of renewable energy as being environmentally-friendly. But if the

those which will take time to become evident, some of which we simply cannot foresee.

The Wildlife Trusts believe that none of the shortlisted options is cost effective, and all five could destroy one of the most prized natural resources in the country. Whilst we recognise that the SETS options are still in their infancy we believe they demonstrate the most promise.

We have a moral and ethical obligation to ensure that the least environmentally-damaging, most cost-effective option is selected. So we need to fully investigate all the options, to make sure that the technology is right for the job. Most of all we need to ensure that decisions we take now, in the face of climate change, are not ones that we will live to regret in years in come.

The Wildlife Trusts believe that a sustainable future can

only come from working with natural processes, not

against them

David S

later

Andrew

Kerr

Editor Rupert Paul. Layout editor Phil Long. Researcher Liz Walker. Project co-ordinator Dr Lissa Goodwin. Printed by Warners Printers, Lincs.Cover picture David Slater. Back page picture David Woodfall. Copyright The Wildlife Trusts 2010.

References: P5: Location of options based on Department for Energy and Climate Change (DECC) data. P16/17: Ecosystem flow information by Dr Rick Park, Gwent Wildlife Trust. Severn facts: British Geological Survey 1996; Dargie, 2000. P18/19: bird migration routes supplied by Mark Ward, RSPB. Salmon migration route: CEFAS, also Tony Andrews, Atlantic Salmon Trust, www.nasco.int/sas/salseamerge.htm. P20/21: Shortlisted and

SETS option performance data from DECC report.

Email or write to your MpExpress your concerns about taking the right decision, for the Estuary and people

alike. You can find out who your local MP is by visiting theyworkforyou.com

Join our campaignKeep an eye on wildlifetrusts.org for further news and developments, and specific

details of how to help.

VolunteerIf you would like to give your time to help The Wildlife Trusts’ campaign, please

contact your local Wildlife Trust (if you’re in Wales or the South West) or visit our volunteering pages on wildlifetrusts.org.

Enjoy the Estuary!Visit your local Wildlife Trust’s reserves in the area, or simply get out and about in

the natural wonder that is the Severn Estuary

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