Old oak trees and semi-natural grasslands are very important for a large number of species that risk disappearing as habitats decline. In a new study, researchers at Linköping University in Sweden present their findings on the habitat amount needed. The results can help nature conservation agencies set scientifically based goals and take more precise action to ensure long term survival of threatened species.
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.
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.
“A sensitive species is more likely to be found in an oak-rich landscape than in a place where there are very few oaks. We’ve been able to calculate threshold values for different species. We can with relatively high confidence provide a target for how much habitat is needed,” says Karl-Olof Bergman, senior associate professor at Linköping University, who led the study published in the journal Landscape Ecology .
One of the most discerning species, which needs many old oaks in its vicinity, is the orange polypore Aurantiporus croceus ; a globally endangered fungus species that is critically endangered in Sweden. In their study, the researchers identified how much habitat is required for the species to be found in a particular location. And if the orange polypore can grow there, the requirements are also met for all other species dependent on old oaks. The results provide conservationists with concrete, science-based data to prioritise cost-effective interventions where they are most useful.
“It’s 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,” says Karl-Olof Bergman.
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.
“The 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,” 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: Identifying functional landscapes in Sweden for semi-natural grasslands and old-growth oaks ( Quercus robur ) based on habitat thresholds , Karl‑Olof Bergman, Leif Andersson, Markus Franzén, Victor Johansson and Lars Westerberg, (2026), Landscape Ecology , published online 22 May 2026, doi: https://doi.org/10.1007/s10980-026-02373-4
Landscape Ecology
Identifying functional landscapes in Sweden for semi-natural grasslands and old-growth oaks (Quercus robur) based on habitat thresholds
22-May-2026
The authors declare no competing interests.