Scientists may have vastly underestimated the number of insect species on Earth. A new study published in the journal Proceedings of the National Academy of Sciences estimates that the planet could hold between 14.2 million and 20.3 million insect species. That is more than double the long-accepted estimate of about 6 million species.
Researchers say the findings reveal how much of Earth’s biodiversity remains unknown and why documenting insect life has become more urgent as populations decline worldwide.
Massive survey in Costa Rica
The study drew on one of the largest insect surveys ever conducted. Researchers worked in the Área de Conservación Guanacaste, a 169,000-hectare reserve in northwestern Costa Rica that includes dry forests, cloud forests, and rainforests.
The team analyzed more than 1.6 million insects collected from 15 Malaise traps, tent-like structures designed to catch flying insects. DNA barcoding helped scientists identify 53,945 insect species from those samples alone.
The study focused on Microgastrinae, a highly diverse group of parasitoid wasps. These wasps lay their eggs inside caterpillars, and their larvae develop by feeding on the host.
Researchers selected the group because of its diversity and close links to other insect species, making it a useful indicator of broader insect richness.
How scientists estimated global diversity
The survey identified 1,414 Microgastrinae species across multiple sampling methods. Using statistical models, the researchers estimated that the conservation area itself may contain about 332,846 insect species, including many that have not yet been detected.
To scale those findings globally, the team compared the number of tree species in the reserve with the estimated number of tree species worldwide. That approach produced a preferred estimate of 20.3 million insect species globally. Alternative calculations based on mammals, amphibians, and moths yielded estimates ranging from 14.2 million to 20.3 million species.
“Our preferred upscaling reference group, trees, yielded an estimate of global insect richness of 20.3 million,” the researchers wrote in the study.
Far more species remain undiscovered
Scientists have formally described only about 1.2 million insect species so far. The new estimate suggests that most insect species remain unknown to science. The researchers argue that even their estimate is likely conservative because the survey did not fully capture insects living in forest canopies and other habitats that are difficult to sample.
The findings also challenge long-standing assumptions about global biodiversity. “For more than 40 years, entomologists have attempted to estimate the number of insect species on Earth, with the current consensus at about six million,” the study notes. The new analysis suggests that figure may be far too low.
The study arrives as scientists report declines in insect populations across many parts of the world due to habitat loss, climate change, pesticide use, and other human pressures. Researchers say a better understanding of insect diversity is critical for conservation planning.
The study concludes that Earth’s insect life is likely far richer than previously recognized. Yet much of it remains undocumented, leaving scientists racing to identify species before they disappear.
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