BY EARLY next century, three giant bridges will span the entrances to the Baltic Sea. They will give Sweden its first fixed link to the mainland of northwest Europe, and tie Denmark鈥檚 main islands to each other and to the continent鈥檚 road and rail networks. Both countries have worked hard to present the project as the greenest possible. But oceanographers appointed to review the scheme are not convinced. In particular, they fear that the hundreds of bridge piers and three or more artificial islands could disrupt the delicate flushing mechanism that keeps the heavily polluted Baltic alive (see Map).
Trade roots
The first link, which spans the 17-kilometre Great Belt, is currently Europe鈥檚 largest construction project. Due to be fully open to traffic by 1997, it joins two of Denmark鈥檚 islands: Zealand, on which Copenhagen stands, and F眉nen, which is already linked to the mainland. The second link, on which engineers hope to begin work this year, comprises 16 kilometres of tunnel and bridges across the 脴resund between Copenhagen and Sweden鈥檚 second city, Malm枚. And the third, which could be completed within a decade, is a 20-kilometre crossing of the Fehmarn Belt to Germany from the Danish island of Lolland, which already has rail and road links to Zealand.
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With work on the Great Belt link well advanced, concern about the effects on the environment of these huge civil engineering projects is being focused on plans for crossing the 脴resund. Construction of this link should have been well under way by now, following an agreement to build signed by Sweden and Denmark four years ago. But, due largely to Sweden鈥檚 passion for protecting the environment, it is now unlikely to be open before early next century.
At the heart of the Swedish concern over the 脴resund link is the Baltic itself, and a vital mechanism that periodically flushes it with salty, oxygen-rich water from the North Sea. About two-thirds of that water enters the Baltic through the Great Belt, the rest through the 脴resund. Anybody who has ever struggled to persuade a temperamental toilet cistern to flush can understand the hydrological difficulty: the water finds it hard to get round the bend.
The Baltic Sea is the world鈥檚 largest stretch of brackish water, a poorly mixed cocktail of freshwater from rivers that drain into it, pollution, and saltwater from the North Sea. The salt content of the North Sea is around 3.5 per cent, but within the Baltic it falls fast with distance from the open sea, to below 0.4 per cent in places.
On average, some 500 cubic kilometres of saltwater flows into the Baltic along the seabed each year, while half that volume of freshwater leaves on the surface; the difference is made up by the inflow from rivers, less the loss by evaporation. However, this flushing with salty seawater is irregular. A major topping up happens only every few years. Nature seems to have to pull the chain several times before achieving success in forcing water from the Kattegat, down the 脴resund and Great Belt and into the Baltic.
The flush works only when westerly winds and high pressure in the North Sea coincide with low pressure in the Baltic. Such a combination forces salt water over the sea鈥檚 shallow sills to the deep depressions in its farthest recesses, such as the Gulf of Finland and the Gulf of Bothnia. The most recent major infusion of saltwater, in January 1993, was the first for more than a decade, and followed the sea鈥檚 longest recorded period of stagnation. It was, says Jan Backhaus, a hydrologist from the Marine Science Institute in Hamburg, 鈥渁n enormous event with very positive effects, changing much of the sea bottom from anoxic to oxic鈥�.
Fragile youth
Such ecological instability reflects the Baltic鈥檚 extreme youth. Until around 7500 years ago, the sea was a freshwater lake. It is still in a state of transition, and has not had time to evolve a community of creatures that thrive in brackish water. Instead the Baltic has freshwater and marine species living side by side, and often close to their limits for survival. Only a few species can cope. Within the Baltic there are fewer than 150 marine species of plants and animals, against more than a thousand in the North Sea.
The 1991 agreement between Sweden and Denmark to build the 脴resund link stipulated that the crossing鈥檚 design should take account of what was 鈥渆cologically responsible, technically possible and financially viable鈥�. Since then, disagreements over the interpretation of ecological 鈥渞esponsibility鈥� have been the main cause of delay. An international panel of independent experts, backed by Sweden鈥檚 powerful Water Rights Court, insisted in late 1993 on a major redesign. After those changes, Sweden鈥檚 Prime Minister, Carl Bildt, called the project 鈥渢he greenest bridge you can build鈥�. But that did not stop Olof Johansson, Sweden鈥檚 environment minister and leader of the Centre Party in the coalition government, resigning last June, when his colleagues insisted on going ahead with the link.
The $2 billion 脰resund link, which will carry a four-lane motorway and a double railway track, will be a complex hybrid. First there is an artificial peninsula 400 metres long built onto the Danish coast at Kastrup, close to Copenhagen airport. Next comes a concrete tunnel extending for almost 4 kilometres beneath the Drogden Channel west of the low-lying island of Saltholm. It surfaces on the first of two artificial islands just south of Saltholm, which are joined to each other by a 600-metre bridge. After running for 4 kilometres across the islands, the link reaches the main bridge across the Flinterenden Channel. This is a two-deck steel structure that stretches for 7.5 kilometres from the artificial islands to the Swedish coast south of Malm枚.
Building the link will require close to 200 000 tonnes of steel and a million cubic metres of concrete, plus around 4 million cubic metres of fill and stone for the artificial islands. On the bridge across the Flinterenden Channel, the motorway will sit on a top deck with the railway below. This part of the link will have 64 main spans, each 100 metres long, leading to a 500-metre centre span suspended on cables across the channel鈥檚 shipping lane, providing a 57-metre clearance for shipping.
The siting and design of the artificial islands has changed substantially in the past four years as engineers have tried to address the fears of the oceanographers on the expert panel. Early designs called for a single large, round island. However, modelling studies revealed that this would have had a substantial 鈥渂locking effect鈥� on water passing into the Baltic, as it reduced the cross-sectional area of the 脴resund by 2.3 per cent. To maintain flow of water, engineers planned to offset this with a large programme of 鈥渃ompensation dredging鈥� in the main channels to restore the cross-sectional area. But in November 1993, on the advice of the independent experts, the Swedish Water Rights Court ruled that the dredging of roughly 12 million cubic metres from the 脴resund would itself cause too much environmental damage, and demanded a redesign to reduce the blocking effect of the link to below 1 per cent.
The resulting changes have put up the construction bill by more than $100 million. They turn the single island into two slender fingers of new land, each just 100 metres wide and 2 kilometres long, with half-moon hammerhead-shaped breakwaters at each end to ease the flow of water. Additionally, they lengthen the tunnel beneath the Drogden Channel by more than a kilometre. This allows the peninsula at Kastrup to be shortened by 600 metres and the islands to be repositioned further east, away from the Drogden Channel and into the lee of Saltholm.
The overall effect of these measures is to reduce the predicted blocking effect to 0.5 per cent, and the amount of compensation dredging to 2.3 million cubic metres. 鈥淭hat was a major victory for us,鈥� says John Gray, a marine biologist from the University of Oslo and chairman of the expert panel. But uncertainties remain, and may not be resolved until the expert panel next meets in April, if then. 鈥淭he big question is whether the models mimic the big salt fluxes into the Baltic,鈥� Gray says.
The stratification of the waters in the Baltic leads to another worry, as changes in the layering of saltwater and freshwater could have serious biological and commercial implications. 鈥淐od stocks are very dependent on salt levels,鈥� says Gray. For cod eggs to develop they must drift freely. If the water becomes too fresh, it also becomes less dense and the eggs, which cod lay on the seabed, will stay there. This came close to happening in the early 1990s.
The Great Belt link has already used compensation dredging with the aim of maintaining water flow into the Baltic, but it is not yet clear whether this goal has been achieved. 鈥淭hey say that nothing happened to inflow and salinity,鈥� Backhaus observes, 鈥渂ut I鈥檝e never seen any proof.鈥�
For both projects, there are fears that the dredging aimed at preserving water flows into the Baltic may cause unnecessary local environmental damage. The bilateral agreement for the 脴resund project imposes a 鈥渮ero solution鈥� on impacts to the Baltic hydrology, but says that 鈥減ermanent as well as temporary effects are accepted in a specified area around the construction and dredging areas鈥�. These local effects will be caused overwhelmingly by dredging.
The 脴resund consortium鈥檚 environment director, Claus Dynesen, says that dredging is 鈥渢he major environmental risk in this project 鈥� actually it is the only environmental risk I can see鈥�. Dredging will have four purposes: to provide construction materials; to excavate the tunnel beneath the Drogden Channel; to realign the Flinterenden shipping channel so that it takes a straight path beneath the bridge; and, as 鈥渃ompensation dredging鈥�, to maintain overall water flow into the Baltic.
Since the redesign, compensation dredging amounts to less than a third of the total, says Dynesen. Even so, the consortium鈥檚 environmental assessment recognises that plumes of sediment will cloud the waters of the 脴resund. 鈥淭he fine particles will be deposited gradually,鈥� it says, 鈥渂ut both the shadows of the sediment clouds and the sediment deposits can have a negative impact on the flora and fauna.鈥�
To minimise this impact, the expert panel has said that no more than 5 per cent of the dredged material should escape into the water. The rest must be contained, to be used in construction or dumped. 鈥淚 have never heard of such a target being met anywhere before on a project so large,鈥� says Dynesen. 鈥淲e hope to restrict loss to 5 per cent,鈥� he adds, 鈥渁t least until the contractors tell me they cannot do it.鈥� During dredging for the Great Belt link, between 10 and 15 per cent of the sediment escaped, and some parts of the project lost more than 30 per cent.
Dynesen insists that the 5 per cent target for the 脴resund link is an average. 鈥淒eviations will be allowed,鈥� he says. But Gray says that the experts have not agreed to this interpretation of their advice. He fears a repetition of the laxity seen during the Great Belt project where, he recalls, 鈥測ou could see the sediment plume 40 kilometres away鈥�.
One specific stipulation for the 脴resund link is that the creation and extension of the islands will not be done simply by dumping mounds of material on the seafloor. Instead, engineers will have to lay an impermeable barrier 鈥� a kind of bag on the seafloor 鈥� into which the material for the islands will be poured.
Sediment plumes matter because they can settle out on beds of seaweed, creating marine deserts as surely as sand dunes stifle life on land. Also, fish avoid plumes of sediment, so concentrated dredging activity might create a barrier of sediment across the 脴resund that would halt the seasonal migration of fish. To reduce the risk of this happening, the expert panel has insisted that dredging be confined to only one of the two main channels at a time, and that all dredging should cease during the main migratory season of spring and early summer.
For many environmentalists, the fate of Saltholm is critical. In theory, the island is protected under the European Union鈥檚 Birds Directive. It has 15 000 breeding eider ducks, the largest colony in Europe, and is visited by 9000 greylag geese, making it the species鈥� second most important moulting area in Europe. There are also 4000 moulting mute swans, up to 4000 teals, 3800 cormorants and annual visits from hundreds of thousands of migrating water birds.
These birds will be disturbed by construction, by having a major transport link roaring past their feeding grounds, and by losing some of those grounds altogether. According to the consortium鈥檚 environmental assessment, the artificial islands and extended peninsula will obliterate 30 hectares of dense eelgrass, and 2 per cent of Saltholm鈥檚 mussel banks, on which eider ducks feed. They could be further threatened if rats and even foxes get onto Saltholm, via the islands.
One casualty is likely to be the small seal colony of about a dozen animals on Saltholm. 鈥淭he noise will drive them away,鈥� says Gray. 鈥淲e doubt if they will return.鈥� This would be a further blow to declining stocks of seals in the Baltic, hit by disease and pollution. On the plus side, says Backthaus, bridge piers could provide new habitats for mussels, which would in turn provide food for the eider ducks.
The Danish Ornithological Society charges that the expert panellists have downplayed the impacts on Saltholm鈥檚 birds. In effect, ornithologists say, the local environment has been sacrificed to protect the wider Baltic, and the society has taken the Danish government to court for violation of the EU Birds Directive. For now the case is languishing in a technical dispute about whether the society has the right to bring it.
Tunnel vision
The wider question for the three links is whether they should include bridges at all. And this depends on whether you believe the era of expanding car use is over or not, and whether governments should be investing in railway tunnels rather than bridges carrying roads as well. Three years ago, Greenpeace in Denmark and Sweden established a company to press their case for digging a tunnel as 鈥渁 contribution to a more ecological traffic system throughout northern Europe鈥�.
Mats Abrahamsson of Greenpeace Sweden says the rocks beneath the 脴resund make for easy drilling. 鈥淥ur consultants say the tunnel would cost only a third as much as the bridge link, but would be just as profitable. Not only that, it would have none of the bad environmental impacts, on the local marine environment, the Baltic 鈥� or in increased air pollution from vehicle exhausts.鈥�
Nobody seriously doubts that the bridges will increase road traffic. But in Sweden, the government is at pains to play down the prospect. The 脴resund link has been costed on the basis of a forecast of 10 000 vehicle movements per day. It is widely reported that this figure is a deliberate underestimate, intended to keep at bay accusations that the bridge is inconsistent with Swedish promises to reduce emissions from vehicle exhausts.
There are few such inhibitions in Denmark. There, car traffic across the Great Belt is forecast to almost double when the fixed link takes over from the existing ferries. And the forecasts are going up. Early this year, the link鈥檚 owners upped their traffic projections for the bridge by 7 per cent to almost 16 000 vehicles a day, while forecasts of rail traffic were revised downwards by 20 per cent.
The 脴resund link shows every sign of generating similarly large amounts of traffic. The consortium building it claims that 鈥渢he fixed link will create the right conditions to turn the 脴resund region into an attractive growth region鈥�. The city of Malm枚 hopes the link will kick-start an economic revival after a decade of decline since the collapse of its shipbuilding industry. Its entire purpose is to generate trade and traffic.
For the moment, however, the forces promoting these bridges appear to have triumphed over the green dream that the l99Os would see an end to the era of mammoth construction projects. In the eyes of even the most progressive European governments, big remains beautiful.