Global dark diversity study reveals hidden impact of human activities on nature
Natural vegetation often lacks many species that could be present, especially in regions heavily affected by human activities, according to a new study coordinated by researchers at the University of Tartu and published in Nature. Over 200 scientists from the research collaboration DarkDivNet, including researchers from the Biology Centre of the Czech Academy of Sciences, studied plants at nearly 5500 sites in 119 regions around the world. At each site, local researchers recorded all plant species and identified the dark diversity – native species that could live there but were absent.
Above: illustrative stock photo by RÜŞTÜ BOZKUŞ, Pixabay.
Identifying the dark diversity allowed them to understand the full potential of plant diversity at each site and measure how much of the potential diversity was actually present. This way of measuring biodiversity revealed the hidden impact of human activities on natural vegetation.
In regions with little human impact, ecosystems typically contain over a third of potentially suitable species, with other species remaining absent mainly due to natural reasons, such as limited dispersal. By contrast, in regions heavily impacted by human activities, ecosystems contain only one out of five suitable species. Traditional biodiversity measurements, like simply counting the number of recorded species, did not detect this impact because natural variation in biodiversity across regions and ecosystems hid the true extent of human impact.
Human activity can influence the plant diversity up to hundreds of kilometres away. Photo: Petr Macek, BC CAS
The DarkDivNet collaboration started in 2018, based on an idea by Prof. Meelis Pärtel, lead author of the study. Prof Pärtel recalls, “We had introduced the dark diversity theory and developed methods to study it, but to make global comparisons we needed consistent sampling in many regions. It felt like an impossible mission, but many colleagues from different continents joined us.” Despite the challenges posed by COVID-19 and global economic and political crises, data were gathered over the years. Prof Pärtel adds, “I am very grateful to all DarkDivNet participants for their hard field work and enthusiasm. Everybody found a way to contribute data without central funding. We only had a grant for my team at the University of Tartu in Estonia to coordinate the network and analyse the data.”
A map of study regions, scatterplot.
The level of human disturbance in each region was measured using the Human Footprint Index, which includes factors like human population density, land-use changes (such as urban development and agriculture), and infrastructure (roads and railways). The study found that plant diversity at a site is negatively influenced by the level of the Human Footprint Index and most of its components in a surrounding area, up to hundreds of kilometres away. Prof Pärtel summarises, “This result is alarming because it shows human disturbances have a much wider impact than previously thought, even reaching nature reserves. Pollution, logging, littering, trampling and human-caused fires can exclude plants from their habitats and prevent recolonization. We also found that the negative influence of human activity was less pronounced when at least one-third of the surrounding region remained pristine, supporting the global target to protect 30% of the land.”
The study highlights the importance of maintaining and improving ecosystem “health” beyond nature reserves. The concept of dark diversity provides a practical tool for conservationists to identify absent suitable species and track progress in restoring ecosystems.
Publication
Pärtel, M., R. Tamme, C. P. Carmona, K. Riibak, M. Moora, … , and M. Zobel (2025). Global impoverishment of natural vegetation revealed by dark diversity. Nature.
DOI: 10.1038/s41586-025-08814-5
https://www.nature.com/articles/s41586-025-08814-5
