As global biodiversity continues to decline, a new international study published in Nature presents a powerful framework for identifying the “missing” species from ecosystems, species that could exist in a habitat but are currently absent. Known as dark diversity, these absent species form an invisible frontier of ecological potential, offering a tool to better understand habitat degradation and inform conservation priorities.
Photo credit: Robert Lewis, NINA
Behind the study is a global research network of more than 200 researchers, called DarkDivNet, coordinated by the University of Tartu in Estonia, and advised by an international scientific committee, including Robert John Lewis, researcher at The Norwegian Institute for Nature Research (NINA).
“This isn’t just about what's visible. It's about what’s missing, silently and systemically,” says Lewis, who led NINA’s contribution to the study. “By identifying species that could thrive in a habitat but are absent, we gain a sharper lens for restoration planning and biodiversity assessments.”
Mapping dark diversity world wide
Dark diversity of vascular plants was assessed at nearly 5500 sites in 119 regions across all vegetated continents of the world, spanning a wide range of vegetation types and representative of most global climatic conditions. In Norway, contributions were made through coordinated sampling at sites in Nordhordland, Skjelingahaugen, and Ulvehaugen, spanning coastal to alpine grasslands.
Fieldwork at these locations was conducted by master’s students at the University of Bergen (UiB), Ruben Schelbred Thormodsæter and Kristine Birkeli, under the supervision of Vigdis Vanvik at UiB and Lewis, highlighting the vital role of student-led research in global ecological science.
“The success of global networks like DarkDivNet relies on meticulous fieldwork, Lewis noted. The dedication of Master students like Kristine and Ruben ensured the collection of high-quality data that now feeds into global ecological understanding.”
What is dark diversity and community completeness?
Dark diversity, defined as species that are ecologically suitable and present in a region but currently absent from a given site, allows estimation of community completeness, a biodiversity metric that represents the proportion of all suitable species in a region that are actually present at a site. According to the study, this metric is globally comparable because it accounts for natural variation in potential biodiversity.
The data showed a clear decline in community completeness as human impact increased (estimated using the human footprint index), with the strongest effect at distances of several hundred kilometers away. The strong relation with the human footprint index was not, however, found when assessing the number of species at a particular site nor all species found in the surrounding region.
Also, the study found that the negative impact of human activities on community completeness was less pronounced when at least 30% of the natural vegetation in a landscape remained intact. This further supports Target 3 of the Global Biodiversity Framework under the Convention of Biological Diversity, stating that “by 2030 at least 30 per cent of terrestrial, inland water, and of coastal and marine areas, especially areas of particular importance for biodiversity and ecosystem functions and services, are effectively conserved and managed”.
A powerful tool for conservation and restoration
In addition to revealing hidden threats to biodiversity, dark diversity offers valuable guidance for conservation and restoration efforts. As species in the dark diversity still remain present in a region, populations and their connectivity can be restored through appropriate measures, enhancing the long-term viability of species and populations.
“By integrating the concept of dark diversity into conservation and land-use planning, policymakers and ecologists can more effectively identify areas where restoration is possible and prioritize habitats that still retain ecological potential, a critical step toward addressing both visible and hidden biodiversity loss”, says Lewis.
Read the full article in Nature here: Global impoverishment of natural vegetation revealed by dark diversity
Contact: Robert Lewis