Gerhard Klesen, a forester employed by the Ruhr Regional Association, spent a decade campaigning for an animal-only bridge to be built over a motorway in the town of Schermbeck in North Rhine-Westphalia.
Man-made barriers such as roads and canals restrict animals' natural movement, he said. That limits genetic diversity, which in turn leads to an increase in disease and shortened lifespans. The ‘Green Bridges' are designed to counteract this effect.
"The area of land east of the motorway at Schermbeck is much smaller than that on the western side," Klesen told The Local. That's led to a decrease in species diversity on the eastern side, prompting Klesen to launch his ten-year campaign, which culminated in the opening of the "green bridge" - Germany's 35th - exactly a year ago.
But it was not always an easy sell. "Bridges cost a lot of money," Klesen said. However the determined forester persisted in his campaign, which got a financial boost from the Netherlands in 2005, where such bridges are relatively commonplace. "They're way ahead of us there," Klesen told The Local.
Both federal and EU funding followed and in September 2012, the €4.5 million, 2,700 square-metre bridge opened to animals.
"It usually takes a year before an animal dares to cross the green bridge," Klesen said. But the animals of Schermbeck are a plucky bunch. "One red stag traversed the bridge just three days after it was opened," Klesen said. Others followed suit and within a few days, boars were making the journey too.
Cameras set up along the bridge have captured a variety of creatures, including rabbits, foxes and bats, making their way across the specially-designed terrain.
"There are strips of sand just for insects, as well as grass, shrubs and other vegetation providing food and shelter to some of the smaller creatures," said Klesen.
Some animals, like mice, take to life in transit so much that they set up their permanent homes on the bridge. Others travel back and forth. Stags in particular often make the journey in search of a mate.
Although it will take decades to assess whether the bridge is managing to promote genetic diversity and health among bigger animals, the effects on smaller animals with shorter lifespan could be studied soon.