Among the authors of a landmark study published in the pages of the Nature included employees of the Botanical Garden of the Polish Academy of Sciences Prof. Arkadiusz Nowak and Dr. Sebastian Swierszcz. His participation in the international team of researchers underscores the importance of Polish science in global conservation efforts.

Natural vegetation often lacks many of the species that could be found in it - especially in regions heavily transformed by humans, according to a new study coordinated by researchers at the University of Tartu. More than 200 scientists from the international research network DarkDivNet analyzed vegetation at nearly 5,500 sites in 119 regions of the world. At each site, local researchers recorded all plant species present and identified so-called "dark diversity" - that is, native species that could grow there but are absent. This allowed the researchers to estimate the full potential of each site's plant diversity and compare it with the actual state. This method of measuring biodiversity revealed the hidden impact of human activity on natural vegetation.

In regions that have been little altered by humans, ecosystems typically contain more than a third of potentially suitable species, with the remainder absent mainly for natural reasons, such as limited dispersal. In contrast, only one in five suitable species is present in regions heavily transformed by humans. Traditional measures of biodiversity - such as simply counting recorded species - have failed to detect this impact, as natural variability between regions and ecosystem types has masked the true scale of anthropogenic impacts.

The DarkDivNet research network was launched in 2018 at the initiative of Professor Meelis Pärtel, the study's lead author. The professor recalls: "We had previously developed a theory of dark diversity and methods to study it, but in order to compare the results globally, we needed consistent sampling across multiple regions. This seemed impossible, but we were joined by many colleagues from different continents." Despite the challenges of the COVID-19 pandemic and the global economic and political crisis, the data was collected over several years. Prof. Pärtel adds, "I am very grateful to all DarkDivNet participants for their hard work in the field and enthusiasm. Everyone found a way to contribute data despite the lack of central funding. The only grant went to my team from the University of Tartu for network coordination and data analysis."

The level of transformation of a region was measured using the Human Footprint Index, which takes into account factors such as population density, land use changes (e.g., urbanization, agriculture) and infrastructure (roads, railroads). The study showed that plant diversity at a given site was negatively related to the level of the Human Footprint Index and most of its components - the impact extended even hundreds of kilometers around the study site. Prof. Pärtel concludes: "This is a disturbing result, because it shows that the impact of human activity is much broader than thought - it even extends to nature reserves. Pollution, logging, littering, trampling or human-induced fires can displace plant species from their habitats and prevent their return. We also noted that the negative impact of human activities was less severe when at least a third of the surrounding region was left intact - supporting the global goal of 30% land area protection."

The study underscores the importance of taking care of the "health" of ecosystems not only in reserves, but also outside them. The concept of dark diversity provides a practical tool for conservationists to identify absent but suitable species and monitor progress in ecosystem restoration.

Link to publication: https://www.researchgate.net/publication/390433337_Global_impoverishment_of_natural_vegetation_revealed_by_dark_diversity