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The £2m bat bridges that don’t work: Scientists say the walkways for flying mammals are ineffective

The £2m bridges for bats that don’t work: Walkways designed to stop flying mammals getting killed by traffic are ineffective, scientists say

  •  Experts say bridges designed to stop bats getting killed by traffic are ‘ineffective’
  • There were 15 bat bridges built in the UK from Cumbria to Cornwall for a cost of £2million
  • The structures are meant to trick the bats into thinking a tree is in their way, making them fly higher


They’re designed to make sure bats don’t get killed by the traffic rushing along busy new roads.

But the 15 ‘bat bridges’ that have been built across the UK from Cumbria to Cornwall at a cost of £2million simply don’t work, say scientists.

The wire structures, or gantries, are supposed to trick the bats, which navigate using echo location, into thinking there is a tree canopy in their way, making them fly higher.

But Dr Anna Berthinussen, a bat ecologist commissioned by the Government to study the bridges said: ‘The evidence suggests that actually no, these structures are not effective, they’re not meeting their purpose.’

Dr Anna Berthinussen, a bat ecologist commissioned by the Government to study the bridges said: ‘The evidence suggests that actually no, these structures are not effective, they’re not meeting their purpose.’ Pictured: A bat bridge in Norwich

Dr William Sutherland, who runs the National Conservation Evidence Database at Cambridge University, added: ‘Wire bat bridges, or gantries, have been created in many locations costing about £2million. Pictured: A bat bridge over the A590 dual carriageway in Cumbria

Dr William Sutherland, who runs the National Conservation Evidence Database at Cambridge University, added: ‘Wire bat bridges, or gantries, have been created in many locations costing about £2million. Pictured: A bat bridge over the A590 dual carriageway in Cumbria

Dr William Sutherland, who runs the National Conservation Evidence Database at Cambridge University, added: ‘Wire bat bridges, or gantries, have been created in many locations costing about £2million. Before and after tests showed they were ineffective.’ He told BBC’s Countryfile: ‘We have good ideas, but the good ideas get turned into best practice without there being testing in between.

‘And that’s where the problem is. It’s just based on faith rather than science.’

Dr Berthinussen’s study focused on seven of the bridges which were built across the Norwich Northern Distributor Road at a cost of around £1million to prevent disturbance to ‘nationally significant’ populations of Barbastelle bats – the UK’s rarest species.

Ninety per cent of bats should have been flying at a safe height within five metres of the bat bridge. Pictured: Lesser horseshoe bat (file image)

Ninety per cent of bats should have been flying at a safe height within five metres of the bat bridge. Pictured: Lesser horseshoe bat (file image)

Ninety per cent of bats should have been flying at a safe height within five metres of the bat bridge. But the study found more than 40 per cent were crossing at unsafe heights.

Norfolk County Council said: ‘Until several more survey seasons have been completed it is not appropriate to draw any conclusions about the effectiveness of the gantries.’

The Environment Act requires builders of new roads to mitigate effects on wildlife. Bats are disorientated by traffic noise and lights on country roads.

A spokesman for the Bat Conservation Trust said: ‘The available evidence suggests that the impacts of the proposed NDR Western Link on this nationally significant barbastelle population cannot be adequately mitigated or compensated for and we have significant concerns about this scheme if taken forwards as proposed.’

Councillor Martin Wilby, Cabinet Member for Highways, Infrastructure and Transport at Norfolk County Council, added: ‘It’s too early to say how the bat mitigation measures on Broadland Northway are working. 

‘Ecologists conducting monitoring surveys have stated that “until several more survey seasons have been completed it is not appropriate to draw any conclusions about the effectiveness of the gantries and crossing features”. 

‘National advice on environmental mitigation has moved on in recent years and, as a result, we are not planning to install bat gantries on the Norwich Western Link.

‘Instead, we plan to use green bridges and wildlife underpasses which were mentioned in the Countryfile feature as being effective mitigation measures. 

‘Broadland Northway has been hugely successful in taking traffic out of the city of Norwich and cutting journey times. Once built, we expect the Norwich Western Link to create similar benefits for the people living in and travelling through the area west of the city.’ 

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