The primary driver behind the global drop in insect numbers is the loss of the most common species. Yet researchers found that this decrease is not counterbalanced by a rise in rare insects, at least not yet. A study published in a major journal examined insect populations and looked at terrestrial insects like beetles, moths, and grasshoppers. The team pooled data from 106 long-term studies, tracking populations for periods ranging from nine to sixty-four years.
Across these observations, the total count of terrestrial insects showed a steady decline of about 1.5 percent each year. The decline was even more pronounced among common species, which dropped by roughly 8 percent annually. By common species, scientists mean those species that dominate in numbers within a given area. The results challenge the notion that shifts in insect biodiversity are solely driven by the loss of rare species, suggesting that the most abundant groups are fading faster than the less common ones.
What stands out is that the loss of species that dominate ecosystems did not get offset by a compensatory increase in rare species. This imbalance has broad consequences: many birds and other animals rely on these abundant insects as a primary food source. With fewer of the common insects, there could be a reshaping of food webs and, ultimately, wider ecological restructuring across multiple habitats.
The broader implications extend beyond simple counts. Insects play vital roles in pollination, nutrient cycling, and serving as a crucial food link within ecosystems. When the dominant insects decline, plants may experience reduced pollination in some regions, and predators may have to adapt to changing prey availability. The cumulative effect of ongoing losses can cascade through ecosystems, altering plant community composition and the stability of food chains over time.
In related ecological news, researchers note that discoveries in other regions continue to illuminate biodiversity patterns. For instance, recent fieldwork in Russia identified four new species of pea clams, underscoring that freshwater invertebrate diversity remains incompletely understood and still rising in some areas as sampling and taxonomic methods improve.