A new international study has more than doubled scientific estimates of how many insect species exist on Earth, and the breakthrough came from right here in Área de Conservación Guanacaste. The research, led by senior author Mike Sharkey and co-author Laura Melissa Guzman, an associate professor of entomology at Cornell University, drew on more than 1.5 million specimens collected over decades from 15 Malaise traps, tent-like structures used to gather wasps and other flying insects, positioned across ACG’s three major ecosystems of dry, cloud, and rain forest.
Using DNA barcoding, a technique that identifies distinct genetic signatures far more precisely than examining physical features alone, the team catalogued over 50,000 insect species within these traps. They then turned to a highly diverse subfamily of parasitic wasps called Microgastrinae as a proxy for insect life more broadly. Sharkey, a taxonomist with years of firsthand experience studying these wasps in Costa Rica, believed they offered a more reliable baseline than beetles, which prior studies had traditionally used.
By comparing specimens from the 15 main traps, 15 peripheral traps, and wasps reared from roughly 1,500 species of caterpillars, the researchers calculated the ratio of known to unknown species within ACG. That analysis produced an estimate of nearly 333,000 insect species living within the conservation area alone. Cross-referencing that figure against four additional groups, trees, frogs, birds, and a specific moth family, allowed the team to extrapolate a global range of 14 to 20 million insect species, published Monday in the Proceedings of the National Academy of Sciences.
Guzman described the number as a conservative lower bound, noting the team took extensive steps to test their assumptions. She added that ACG’s decades-long trapping records give scientists a rare opportunity to track how tropical insect populations are shifting in response to climate change and land use over time. The findings reaffirm what long-term monitoring in this corner of Guanacaste has suggested for years: ACG remains one of the richest, least fully documented reservoirs of biodiversity on Earth.