Scientists Say Roughly 90% of Earth's Species Remain Unknown, Driven by Tiny, Overlooked Organisms
Researchers warn that the bulk of biodiversity — microscopic and small invertebrate life — remains undescribed, complicating efforts to protect ecosystems and understand planetary life
Scientists studying global biodiversity say a large majority of Earth's species remain unidentified, a reality that undercuts assumptions that the planet's life is largely cataloged. New assessments suggest that for every species formally described, there may be roughly nine more that have yet to be discovered or given scientific names, meaning around 90% of life on Earth is effectively unknown to science.
The gap is concentrated not in whales or eagles but in the vast diversity of small organisms — insects, mites, nematodes, small crustaceans and other invertebrates — that make up ecosystems' foundational processes. These organisms, often measured in millimeters, help produce soil, pollinate crops, recycle nutrients and form the base of food webs supporting larger animals.
Taxonomists and biodiversity scientists use the term "dark taxa" to describe groups that appear in genetic databases or museum collections but lack formal scientific names or descriptions. Dark taxa proliferate in DNA barcode datasets and bulk sequencing results, where many unique genetic signatures have no corresponding described species. That disconnect highlights a growing mismatch between the raw data of biodiversity and the capacity to translate it into named, described species that can enter conservation planning and ecological research.
The problem is illustrated within seemingly familiar insect groups. Some fly families, for example, contain vast numbers of species that remain undescribed; one family, Cecidomyiidae, is thought to include thousands of species that taxonomists have not yet formally cataloged. The consequence is a skewed scientific picture in which charismatic and large-bodied organisms are well known while the smaller taxa that determine much ecosystem function remain obscure.
Experts say multiple factors combine to produce the large backlog of undescribed species. Traditional taxonomy is time-intensive and depends on a shrinking pool of specialists with the training to identify and describe taxa. Collecting and curating specimens across remote and understudied habitats is logistically challenging and costly. Meanwhile, modern molecular methods and mass-sequencing projects are producing a flood of genetic data that outpaces the capacity to link sequences to formal species descriptions.
The implications reach beyond academic completeness. Conservation prioritization, environmental monitoring, agricultural planning and disease ecology all rely on accurate inventories of species and their ecological roles. When the majority of taxa in an ecosystem are unknown, estimates of species richness, ecosystem services and vulnerability can be substantially off. That uncertainty complicates efforts to measure biodiversity loss, enforce protections, restore habitats and predict how ecosystems will respond to climate change.
Researchers and institutions are responding with a mix of approaches intended to accelerate discovery and description. Large-scale digitization of museum collections makes specimens more accessible to taxonomists worldwide. New molecular techniques, including DNA barcoding and environmental DNA sampling, allow scientists to detect and approximate the diversity of organisms that are difficult to observe directly. Citizen-science initiatives and coordinated specimen-sampling campaigns are expanding geographic and taxonomic coverage.
Despite these advances, scientists caution that rapid molecular identification does not fully substitute for the taxonomic work required to assign formal names, describe species' morphology and place them within scientific classification. Formal descriptions remain crucial for legal protections, ecological study and communication across disciplines.
The emerging portrait of Earth as home to overwhelmingly undocumented biodiversity reframes long-standing assumptions about exploration and knowledge. Centuries of expeditions and field work established the scientific names and natural-history accounts of many large and conspicuous species, but the bulk of life's diversity operates at scales that have historically attracted less attention and less funding. As scientists continue to document the planet's smaller inhabitants, they expect to revise estimates of total species richness, reassess conservation priorities, and deepen understanding of the biological networks that sustain ecosystems.
Addressing the dark taxa gap will require sustained investment in taxonomic training, international collaboration to broaden geographic sampling, and integration of molecular and morphological methods. Until those steps scale up, large portions of Earth's biodiversity will remain on the margins of scientific knowledge despite their centrality to ecological function and human well-being.