A groundbreaking study has revealed that the number of insect species on Earth could be as high as 20 million—three times previous estimates. Researchers are sounding the alarm as they uncover alarming trends in insect populations, with nearly 40 percent in decline worldwide. This research highlights the urgent need for understanding and preserving biodiversity, particularly as climate change and habitat loss threaten these essential organisms.
A New Estimate for Insect Species
For decades, scientists have approximated the number of insect species at around six million, a figure that has now been dramatically revised. The latest findings suggest that the true number could range from 14 million to 20 million. This revelation underscores the critical role insects play in ecosystems and human life, such as pollination, pest control, and serving as a food source for various wildlife.
Laura Melissa Guzman, an assistant professor of entomology at Cornell University, emphasised the importance of this research: “We cannot protect species if we don’t know that they exist. To understand the biodiversity on our planet, it’s crucial to know how many species there are.”
Methodology Behind the Findings
The researchers conducted their study using the genetic data of 1.6 million tropical insects, alongside a comprehensive census of parasitoid wasps in Costa Rica. By employing insect traps in the Área de Conservación Guanacaste, they managed to capture over 1.6 million insects, successfully sequencing DNA to identify nearly 54,000 species.
Focusing on a specific subfamily of wasps known as Microgastrinae, the team calculated the ratio of known to unknown species. They identified 1,414 species of these wasps in the region, which are crucial for controlling butterfly and moth populations. This data was then extrapolated to suggest a staggering total of approximately 333,000 insect species in the protected area.
Further comparisons with other species, such as trees and mammals, allowed the researchers to estimate the global insect population more accurately. They found that the ratio of tree species in Costa Rica could provide a framework for estimating global insect diversity, leading to their revised figures.
The Decline of Insects
While the findings are significant, they come amidst a troubling backdrop of declining insect populations. Recent studies have shown that around 40 percent of the world’s insect species are facing population decreases, primarily driven by human activities such as habitat destruction, climate change, and the introduction of invasive species.
In the United States, approximately 91,000 insect species have been identified, but many remain unclassified. A 2025 study revealed that only 1.2 percent of these had been assessed for extinction risk, raising concerns about the timeline for these species as environmental pressures mount.
Charlotte Probst, a doctoral candidate at the University of Michigan, highlighted the urgent need to understand the interactions between climate change and biodiversity loss. “We really need to study how these two factors are interacting through time instead of just focusing on one or the other,” she stated.
The Bigger Picture
The implications of declining insect populations extend far beyond the creatures themselves. Insects are integral to the functioning of ecosystems, and their decline can lead to cascading effects on food supply, pollination, and even disease transmission. Recent research from Michigan has shown that diminished insect numbers are linked to the smaller size and lower reproductive success of tree swallows, illustrating the interconnectedness of these species.
Why it Matters
The stark increase in estimated insect diversity highlights the urgent need for conservation efforts. Understanding the true scale of insect populations is crucial for developing effective strategies to protect them from extinction. With insects at the foundation of global ecosystems, their decline threatens not only biodiversity but also human food security and health. In a rapidly changing world, the call to action is clear: we must prioritise the study and conservation of these vital organisms before it’s too late.
