New mapping approach shows wolverine population spreading in Finland
The study introduces a new approach to mapping the occurrence and distribution of animal species.
Finland’s smallest large carnivore seeks new forests – remote sensing supports wolverine conservation
Satellite data and snow track surveys reveal that wolverines have returned to Southern Finland. While the national population is growing, the species remains endangered. A new study sheds light on the forest environments that support its survival.
The wolverine is making a comeback in Southern Finland. Previously eradicated by hunting, today around 400 members of the species live in Finland, mostly in the coniferous forests of Eastern Finland and the fell regions of northern Lapland.
Researchers at Aalto University have, for the first time, mapped the wolverine’s distribution across all of Finland by combining satellite imagery, field data and snow track surveys. This kind of integrated mapping method is globally unique in wildlife research.
‘The population in Eastern Finland is doing well enough that wolverines are beginning to spread southward in search of suitable habitats. Traditionally, they inhabit coniferous forests, but our research found that they also thrive in mixed and broadleaf-dominated forests, especially in large, unfragmented woodland areas,’ says Pinja-Emilia Lämsä, a doctoral researcher at Aalto University.
Solitary and wide-ranging, wolverines avoid recently logged areas but may use forests that were harvested a decade or more ago. They also prefer areas with mature but not overly dense tree cover.
The study, conducted in collaboration with the Natural Resources Institute Finland (Luke), combined national forest inventory data based on remote sensing and fieldwork with snow track surveys carried out by hunters and nature enthusiasts along wildlife triangle routes. The researchers compared wolverine habitat use between 2009–2010 and 2018–2021.
Finland is known for its extensive and long-standing environmental monitoring data. Systematic forest inventories have been conducted for over a century, and there is a long tradition of citizen science-based wildlife surveys.
‘Remote sensing is a powerful tool for tracking animal distributions across large areas. The data used in this study covers the entire country, with forests divided into 16-by-16 metre squares, allowing us to closely analyse their structure,’ says Miina Rautiainen, a professor of remote sensing at Aalto. Remote sensing refers to collecting data from a distance – via satellites, aircraft or drones – by measuring how different surfaces reflect electromagnetic radiation across various wavelengths. Field observations remain a key part of interpreting remote sensing data in natural environments.
Adapting to snowless winters
While the study confirms that Finland’s wolverine population is growing, the species – the largest mustelid in Europe – remains at risk. It is critically endangered because of its low genetic diversity and fragmented distribution. Understanding its habitat preferences is crucial for developing effective conservation strategies.
‘Forestry significantly affects forest structure. To safeguard wolverine habitats, we should favour mixed forests and preserve large, continuous forest areas. Our findings suggest that Finland’s broadleaf-dominated mixed forests may be more important to the wolverine than previously assumed,’ Lämsä notes. Lämsä is a wildlife ecologist whose doctoral research focuses on studying the habitats of Finnish mustelids via remote sensing. After the wolverine, she will study the pine marten, stoat and least weasel.
‘Before my PhD, I worked as a field biologist identifying species in the wild. Now, using remote sensing, I can monitor habitat changes from my computer – while also challenging myself with mathematical problems,’ she says.
To researchers, the wolverine is a fascinating subject. Curious and intelligent, it adapts to changing environmental conditions and a wide range of food sources. Finland’s smallest large carnivore scavenges moose carcasses left by wolves and hunts small animals, from hares to frogs. It also preys on reindeer. A thick snowpack helps this broad-pawed hunter move easily across deep snow when stalking prey.
But climate change and snowless winters pose serious threats. Wolverines often give birth in dens dug into snow and use snow to store food.
‘In southern Finland, the diverse forest structure can help wolverines adapt – for instance, by allowing them to den in coarse woody debris. In the absence of snow, they may also hide their food in cool bogs,’ Lämsä explains.
Monitoring based on snow tracks is becoming increasingly difficult due to shorter snowy periods and thinning snow cover. New methods are needed, especially in coastal areas where winters are already typically snow-poor.
Satellites and the future of ecosystem monitoring
Animal tracking is a new direction for Rautiainen’s remote sensing research group, which has previously focused on vegetation and forest structure in peatlands and forest ecosystems.
‘Remote sensing provides essential tools for monitoring the impacts of climate change and biodiversity loss. It also helps us assess the success of nature restoration efforts. In the coming years, large peatland restoration projects will be carried out in Finland to meet EU requirements,’ Rautiainen says.
She is pleased with the increasing availability of open-access satellite data for climate and nature monitoring. Satellite imaging technology is also developing rapidly. Traditional multispectral sensors use fewer than ten wavelength bands, while hyperspectral instruments can measure hundreds.
‘Hyperspectral satellite imaging will allow even more precise tracking of biodiversity. It’s truly fascinating how satellites orbiting hundreds of kilometres above Earth can give us such detailed insights into the state of nature,’ Rautiainen says.
The study, Wolverines on the Move: A Multi-Scale Analysis of Forest and Landscape Factors Influencing Wolverine Occurrence in Finland, was published in Ecology and Evolution on 21 April 2025.
Text: Marjukka Puolakka.
This article has been published in the Aalto University Magazine issue 36 (issuu.com) September 2025.
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