How creating wildlife crossings can help reindeer, bears – and even crabs

Sweden's announcement this week that it is to build a series of animal bridges is the latest in global efforts to help wildlife navigate busy roads

Every April, Sweden's main highway comes to a periodic standstill. Hundreds of reindeer overseen by indigenous Sami herders shuffle across the asphalt on the E4 as they begin their journey west to the mountains after a winter gorging on the lichen near the city of Umea. As Sweden's main arterial road has become busier, the crossings have become increasingly fractious, especially if authorities do not arrive in time to close the road. Sometimes drivers try to overtake the reindeer as they cross - spooking the animals and causing long traffic jams as their Sami owners battle to regain control.

During difficult climate conditions, these lichen lands can be extra important for the reindeer," says Per Sandstrom, a landscape ecologist at the Swedish University of Agricultural Sciences who works as an intermediary between the Sami and authorities to improve the crossings.