Earth’s insect population – essential for the world’s food supply – decreases by 27% in 30 years

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The world has lost more than a quarter of its terrestrial insects in the past 30 years, according to researchers whose comprehensive study of the global decline of insects paints a worrying but more nuanced problem than previous research.

From bees and other pollinators essential to the global food supply to the butterflies that beautify places, insects are disappearing at a rate of just under 1% per year, with much variation from place to place, according to a study published Thursday in the journal Science.

This is a smaller population decline than that seen by some smaller localized studies, which had raised fears of a so-called insect apocalypse. But that always adds up to something “terribly alarming,” said entomologist Roel van Klink of the German Center for Integrative Biology, lead author of the study.

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“The decline in insect orders on earth is breathtaking,” said Nick Haddad, a butterfly expert at Michigan State University, who was not part of the study. “The continued decline of land at this rate will be catastrophic for ecological systems and for humans. Insects are pollinators, natural enemies of parasites, decomposers and in addition, they are essential for the functioning of all ecosystems on Earth.

The decline in insects is worst in North America, especially the Midwestern United States, and parts of Europe, but the decline appears to be leveling off in the United States in recent years, the study said. who gathered previous research on over 10,000 species with data. from 1676 locations.

The Midwest sheds 4% of its bugs per year. The big global losses appear to be in urban and suburban areas and cropland, where insects are losing their food and habitat, van Klink said.

University of Delaware entomologist Douglas Tallamy, who was not part of the study, said he would travel through the Midwest where there must be lots of butterflies and other insects, but he would not would see only corn and soybeans in a desert of insects.

Some outside scientists said the results made sense, but worried the study would lack research and data on some large regions, such as the tropics and Africa.

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Co-author Ann Swengel, a citizen scientist who has tracked butterflies for more than 30 years, recalled that while driving in Wisconsin a few decades ago, she “looked in a field and you would see all those Sulfur butterflies.” I can’t think of the last time I saw this.

The study detailed quite different losses from place to place and decade to decade. This tells scientists that “we are not looking for a single stressor or we are not looking for a global phenomenon that stresses insects in the same way,” said University of Connecticut insect expert David Wagner, which was not part of the study. . What is happening, he said, is “absolutely intolerable”.

Van Klink did not find a link to climate change in the loss of insects. But he saw a general theme of rampant urbanization, which absorbs the land where insects live and eat, and the general loss of habitat due to agriculture which removes the weeds and flowers that insects need.

While ground bugs have declined, freshwater insects, such as mayflies, dragonflies and mosquitoes, are increasing by more than 1% per year, according to the study. It’s faster than ground bugs go away. But these flourishing freshwater insects make up only a tiny percentage of insects in the world.

This improvement in freshwater species, likely because rivers and streams have become cleaner, shows hope, scientists said.

Swengel said she saw another sign of hope on a cloudy day last year in Wisconsin: She and her husband counted 3,848 monarchs, reflecting recent local efforts to improve the habitat of the colorful migratory butterfly.

“It was absolutely beautiful,” she said. “It is not too late.”


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