A British conservationist is taking to the skies next year for a daring and uncomfortable 4,500-mile journey across the Russian Arctic to help save the UK’s smallest and shyest swan.

Sacha Dench plans to use a paramotor – a kind of parachute propelled by a motor – to brave temperatures of -9C (15.8F) as she mirrors the Bewick’s swan’s yearly migration route. The swans migrate as the northern Russian winter turns inhospitable and birds travel west to Britain and other milder climes.

There are an estimated 16,000 of the species left in the world, and their number has halved in the last two decades.

Wildlife experts do not know exactly why the population is falling so dramatically – other swan species have not suffered similar declines – but shooting by hunters, habitat loss and climate change are all believed to be factors.

In late 2016, Dench who works for the Wildfowl & Wetlands Trust (WWT) at Slimbridge in Gloucestershire, will take flight to find out why, and push governments along her epic route to adopt an action plan that so far only Estonia has agreed to.

Her journey through some of the remotest parts of Europe, about 370 miles (600km), has no roads and will be undertaken in gruelling conditions.

The expedition will uncover new science about the Bewick’s swans, whose numbers have halved in the last 20 years. Photograph: Angharad Barlow/WWT

“We have to get used to flying in the cold, it could be -9C. Taking off [with the paramotor] is one thing, it’s energetic, but once you’re flying you’re reasonably static, you’re just moving your arms,” said Dench.

“If you get too cold, your decision-making gets sloppy. If your feet get too cold, you can’t land on them, because you need to land running.”

Including her kit, fuel and the paramotor itself, Dench will have to be capable of running with 35-40kg of weight on her back. “I can carry that at the moment, but the thing is being able to run with it, to take off.”

She will also have to cope with extremely early starts, sometimes waking at 3am to take off at dawn when winds – which will regularly be blowing against her – are relatively light. Each flight could last up to three hours, depending on the cold and the winds.

“The chances of being stopped by weather are really, really high,” Dench said, adding that her team – which will include an as-yet-unnamed pilot and a Russian national, Alexander Bogdanov – will have several backup plans in place.

Bogdanov will help her communicate with remote communities when they land. Dench is learning Russian but said she doubts it will be perfect by the time she leaves.

The expedition’s biggest achievement, she said, would be if countries along the way take up an action plan to stem the species’ decline. She will traverse 11 countries in 10 weeks, including Finland, Germany, Poland and the Netherlands.

“We know that there are multiple impacts [causing the swan’s decline]. Shooting is a considerable one. About a quarter of Bewick’s have shot in them, when we x-ray them at Slimbridge,” she said. “But even at that high rate is doesn’t seem to be solely responsible for their decline.”

Flock of Bewick’s swans flying at Slimbridge. Photograph: James Lees/WWT

A loss of wetlands, disturbance of habitats along the route and more predation by Arctic foxes are all considered further factors. The Bewick is smaller than the larger and more aggressive whooper swans that migrate west to Slimbridge each year and are known for having particularly close family relationships.

The WWT team will train through 2016 to prepare for the expedition, before starting their journey at Nar’Yan Mar in the Arctic tundra. They plan to head west until they finish by flying over the Thames and ultimately landing at Slimbridge, approximately in November.