What’s Causing the Sharp Decline in Insects, and Why It Matters
e360.yale.edu
Insect populations are declining dramatically in many parts of the world, recent studies show. Researchers say various factors, from monoculture farming to habitat loss, are to blame for the plight of insects, which are essential to agriculture and ecosystems.

On three occasions from 1989 to 2014, entomologists set up tents in the meadows and woodlands of the Orbroicher Bruch nature reserve and 87 other areas in the western German state of North Rhine-Westphalia. The tents act as insect traps and enable the scientists to calculate how many bugs live in an area over a full summer period. Recently, researchers presented the results of their work to parliamentarians from the German Bundestag, and the findings were alarming: The average biomass of insects caught between May and October has steadily decreased from 1.6 kilograms (3.5 pounds) per trap in 1989 to just 300 grams (10.6 ounces) in 2014.

“The decline is dramatic and depressing and it affects all kinds of insects, including butterflies, wild bees, and hoverflies,” says Martin Sorg, an entomologist from the Krefeld Entomological Association involved in running the monitoring project.

Another recent study has added to this concern. Scientists from the Technical University of Munich and the Senckenberg Natural History Museum in Frankfurt have determined that in a nature reserve near the Bavarian city of Regensburg, the number of recorded butterfly and Burnet moth species has declined from 117 in 1840 to 71 in 2013. “Our study reveals, through one detailed example, that even official protection status can’t really prevent dramatic species loss,” says Thomas Schmitt, director of the Senckenberg Entomological Institute.

“The decline is dramatic and depressing and it affects all kinds of insects, including butterflies, wild bees, and hoverflies,” says Martin Sorg, an entomologist from the Krefeld Entomological Association involved in running the monitoring project.

Another recent study has added to this concern. Scientists from the Technical University of Munich and the Senckenberg Natural History Museum in Frankfurt have determined that in a nature reserve near the Bavarian city of Regensburg, the number of recorded butterfly and Burnet moth species has declined from 117 in 1840 to 71 in 2013. “Our study reveals, through one detailed example, that even official protection status can’t really prevent dramatic species loss,” says Thomas Schmitt, director of the Senckenberg Entomological Institute.