Insect And Arthropod Biomass In Rapid Decline In Europe, North America, SE Asia
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The same year that Wilson published his article in Scientific American, a group of insect fanciers installed what are known as malaise traps in several nature reserves in Germany. Malaise traps look like tents that have blown over on their sides, and they’re designed to capture virtually anything that flies into them. The group, the Krefeld Entomological Society, was interested in how insects were faring in different types of parks and protected areas. Every summer from then on, society members set out new traps, usually in different preserves. In 2013, they resampled some of the sites they’d originally sampled back in 1989. The contents of the traps were a fraction of what they’d been the first time around.
Over the next three summers, the group members resampled more sites. The results were similar. In 2017, with the help of some outside experts, they published a paper documenting a seventy-five-per-cent decline in “total flying insect biomass” in the areas surveyed. These areas were exactly the sort of habitat fragments that, according to Wilson’s theory, were destined to lose species. Nevertheless, the findings were shocking. In 2019, a second group of researchers published a more rigorous and extensive study, and its findings were even more dire. In the course of just the previous decade, grasslands in Germany had, on average, lost a third of their arthropod species and two-thirds of their arthropod biomass. (Terrestrial arthropods include spiders and centipedes in addition to insects.) In woodlands, the number of arthropod species had dropped by more than a third, and biomass by forty per cent. “This is frightening” is how one of the paper’s authors, Wolfgang Weisser, a biologist at the Technical University of Munich, put it.
In the years since, many more papers have appeared with comparable findings. Significant drops have been found in mayfly populations in the American Midwest, butterfly numbers in the Sierra Nevadas, and caterpillar diversity in northern Costa Rica. While many species appear to be doing just fine—for instance, the spotted lanternfly, an invasive species from Asia, which was first detected in Pennsylvania around 2014, and has since spread to at least ten other states, including New York—there is, as was noted in the introduction to a recent special issue of the Proceedings of the National Academy of Sciences devoted to the state of the insect world, “ample cause for concern.”
Dave Goulson, an entomologist at the University of Sussex, is one of the experts the Krefeld group contacted to help make sense of its data. Like Wilson, Goulson could be described as a naturalist turned post-naturalist; he decided to study insects because he found them enthralling, and now he studies why they’re in trouble. “I have watched clouds of birdwing butterflies sipping minerals from the muddy banks of a river in Borneo, and thousands of fireflies flashing their luminous bottoms in synchrony at night in the swamps of Thailand,” he writes in “Silent Earth: Averting the Insect Apocalypse” (Vintage). “I have had enormous fun. But I have been haunted by the knowledge that these creatures are in decline.”
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https://www.newyorker.com/magazine/2021/11/01/where-have-all-the-insects-gone-e-o-wilson-silent-earth
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