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 Umeå. 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 Sandström, a landscape ecologist at the Swedish University of Agricultural Sciences who works as an intermediary between the Sami and authorities to improve the crossings.

This week, Swedish authorities announced they would build up to a dozen “renoducts” (reindeer viaducts) to aid the crossings and allow reindeer herds to reach grazing more easily.

It is hoped the crossings will allow herders to find fresh grazing lands and alleviate traffic jams, and also help moose and lynx to move around the landscape. The country’s 4,500 Sami herders and 250,000 reindeer have been hit hard by the climate crisis, battling forest fires in the summer and freezing rain in the winter that hides lichen below impenetrable sheets of ice.

“The animals that will really benefit from this system are long-ranging mammals that are really not meant to survive in these small, isolated pockets,” says Sandström, who started his career in the US helping to create ecological corridors in Montana for grizzly bears.

The renoducts are part of a growing number of wildlife bridges and underpasses around the world that aim to connect fractured habitats. On the Yucatán peninsula in Mexico, underpasses have been used to shield jaguars from traffic. Natural canopy bridges in the Peruvian Amazon have helped porcupines, monkeys and kinkajous pass over natural gas pipelines. On Christmas Island, bridges have been built over roads to allow millions of red crabs to pass from the forest to the beaches on their annual migration.

The wildlife bridges help avert some of the billions of animal deaths that happen on the roads every year around the world and counteract unintended consequences of human infrastructure.

In southern California, there have been signs of inbreeding among lions in the Santa Monica Mountains because busy freeways around Los Angeles have isolated populations with low genetic diversity. To help save the mountain lion population from local extinction, an $87m (£63m) wildlife bridge is planned over the 101 highway north of LA, which would be the largest in the world.

“When habitat is isolated, we can have impact on individual animals where they might not be able to find water or food. We can also have impact on the genetic diversity of populations,” says Mark Benson, a member of the human-wildlife coexistence team for Lake Louise, Yoho and Kootenay at Parks Canada.

The agency has overseen one of the most successful uses of wildlife bridges in the world in Banff national park, Alberta, installing seven overpasses and 41 underpasses on the section bisected by the Trans-Canada Highway. A 2014 study found that fencing off the road and installing wildlife passes had maintained high genetic diversity in black and grizzly bear populations. Benson credits the passes with a big fall in roadkill along the highway, also significantly reducing human mortality from animal collision.

“We can go all the way back to 1983. There was an underpass that was put in place as part of twinning improvements [widening the highway] in the park. The first overpasses were put in place in 1996 and the twinning of the highway was completed in 2016,” he says.

“It’s very effective in terms of allowing wildlife to move across the landscape.”

In the UK, wildlife bridges are likely to form part of the government’s nature recovery network which aims to link together biodiverse areas under a 25-year environment plan. A 2015 review by Natural England acknowledged the benefits for nature and cited the example of the Netherlands, which is developing a network of “ecoducts” to help animals move around the country.

Highways England is increasingly building wildlife bridges as part of schemes around the country, with more planned for future infrastructure work. But some conservationists warn not enough is being done in the UK.

“We’re woefully behind the rest of the world. In Europe, it’s become second nature in some areas,” says Martin​ de Retuerto, director of conservation at Hampshire & Isle of Wight Wildlife Trust.

The trust is advocating the creation of a green bridge across the M3 at Twyford Down, one of the most controversial road schemes in English history, built in the 90s. The motorway severed the link between the South Downs national park and St Catherine’s Hill, an iron age fort and nature reserve home to rare butterflies and wildflowers.

Major protests against the scheme might have failed to stop construction but De Retuerto says they marked a shift in attitudes to environmental issues in the UK. For that reason alone, he says, a green bridge at Twyford Down should be made to kickstart the nature recovery network.

“It’s been heralded as the best bad example of how to do a road scheme. It’s symbolic and deserves to be the one where, politically, prioritisation is centred,” he said.

“If the Romanians can build them for bison, then we can build them for butterflies.”

Find more age of extinction coverage here, and follow biodiversity reporters Phoebe Weston and Patrick Greenfield on Twitter for all the latest news and features

Contributor

Patrick Greenfield

The GuardianTramp

Related Content

Article image
Animal crossings: the ecoducts helping wildlife navigate busy roads across the world
India’s tiger corridor and Australia’s possum ‘tunnel of love’ are among the myiad infrastructure projects providing safe passage

Patrick Greenfield

29, Dec, 2021 @10:15 AM

Article image
Rewilding: should we bring the lynx back to Britain?
Reintroducing the big cats could control deer numbers and enrich ecosystems but farmers and the public need reassurance, say experts

Phoebe Weston

16, Aug, 2021 @11:47 AM

Article image
Natural England 'cut to the bone' and unable to protect wildlife, say staff
Report warns of ‘yawning gap’ between government rhetoric on environment and reality of years of underfunding

Phoebe Weston

10, Nov, 2020 @7:00 AM

Article image
Hot houses: the race to save bats from overheating as temperatures rise
Chimneys for bat boxes and a flying fox heat stress forecaster are among efforts to prevent deaths from effects of climate crisis

Isabelle Groc

24, Feb, 2021 @10:30 AM

Article image
‘Crabs everywhere’: off Canada’s Pacific coast, Indigenous Haida fight a host of invasive species
The unique wildlife of Haida Gwaii’s 150 islands is under attack by invasive crabs, rats and deer – echoing how local people also became vulnerable to outside forces

Leyland Cecco in Haida Gwaii. Photographs by Cole Burston

23, Oct, 2023 @5:30 AM

Article image
Gardeners urged to ‘keep it local’ when creating a wildflower meadow
Experts say neighbourhood varieties will suit an area’s pollinators, and that caution is needed when buying generic seed mixes

Phoebe Weston

07, May, 2023 @9:00 AM

Article image
‘Zombie deer disease’ epidemic spreads in Yellowstone as scientists raise fears it may jump to humans
Warnings that ‘slow-moving disaster’ in North America raises chances of fatal mad cow-type disease jumping species barrier

Todd Wilkinson in Bozeman, Montana

22, Dec, 2023 @2:00 PM

Article image
Nature calling: how can Sweden's success story help rewild London?
The transformation of a Swedish shipyard into a haven for biodiversity inspired the UK capital’s ‘urban greening factor’ plan

Matthew Ponsford

05, Feb, 2021 @11:15 AM

Article image
Collecting ‘gourmet’ eggs from black-headed gulls should be banned, says RSPB
Conservationists say government must stop licensing ‘unsustainable’ harvest of eggs from amber-listed birds

Phoebe Weston

03, May, 2023 @7:00 AM

Article image
Wildlife rescue centres struggle to treat endangered species in coronavirus outbreak
Shortages in funds, medicines and masks threaten charities across the globe

Gloria Dickie

28, Mar, 2020 @8:00 AM