No less than 1,800 species are associated with the oak. This makes the oak the most biodiversity-rich tree in Sweden. Together with semi-natural grasslands, oak landscapes play an important role in enabling species to form viable populations that survive in the long term. But how much of these types of habitat is needed?
It would be practically impossible for researchers to physically count every animal and plant at each site. Instead, they used a combination of private databases, various species projects and the digital reporting system Artportalen, a platform for open public reporting of species sightings. The researchers behind the study combined millions of reported species data with data on habitat distribution, such as inventories of large oaks made by county administrative boards, and other openly available geodata on grasslands. By combining data on species found with habitat data, the researchers were able to search for patterns.
Threshold values identified
The researchers show that the amount of habitat is linked to whether different species occur at a given location. They were also able to identify thresholds for how much habitat is needed for a species to persist.
Charlotte Perhammar
鈥淎 sensitive species is more likely to be found in an oak-rich landscape than in a place where there are very few oaks. We鈥檝e been able to calculate threshold values for different species. We can with relatively high confidence provide a target for how much habitat is needed,鈥� says Karl-Olof Bergman, senior associate professor at Link枚ping University, who led the study published in the journal Landscape Ecology.
Where restoration make the greatest difference
鈥淚t鈥檚 particularly important that we can identify areas where endangered species occur today, but where habitats are too small or fragmented for the species to survive long-term. Species richness in these places exists on borrowed time. We have a time window now when we can act and restore these environments to save species that will otherwise disappear from there,鈥� says Karl-Olof Bergman.
Biodiversity for the future
But why does it matter if we lose species such as the orange polypore? The answer lies in how deeply interwoven biodiversity is with our own everyday lives. Functional, species-rich ecosystems are a prerequisite for the existence of clean water, clean air and productive soils. Some fruits and vegetables are highly dependent on pollination by various insects to provide good harvests. Many pharmaceuticals are based on substances found in plants and animals, and even today new discoveries are being made that may come to benefit humans in the future.
Charlotte Perhammar
鈥淭he utility perspective is important, but everything in nature has an intrinsic value. What right do we have to eradicate species that have millions of years of evolution behind them? The species that disappear during our lifetime are also lost for all future generations,鈥� says Karl-Olof Bergman.
The study was conducted in collaboration with the Pro Natura enterprise foundation and was funded by WWF Sweden and Formas.
Article: , Karl鈥慜lof Bergman, Leif Andersson, Markus Franz茅n, Victor Johansson and Lars Westerberg, (2026), Landscape Ecology, published online 22 May 2026, doi: https://doi.org/10.1007/s10980-026-02373-4
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